Outcomes in Nonmetastatic Hormone Receptor-Positive HER2-Negative Pure Mucinous Breast Cancer: A Multicenter Cohort Study

BACKGROUND

Although considered a favorable subtype, pure mucinous breast cancer (PMBC) can recur, and evidence for adjuvant therapy is limited. We aimed to compare outcomes of nonmetastatic PMBC with invasive ductal carcinoma (IDC) and invasive lobular carcinoma (ILC) to address these uncertainties.

METHODS

Individual patient-level data from 6 centers on stage I-III hormone receptor-positive and HER2-negative PMBC, IDC, and ILC were used to analyze recurrence-free interval (RFI), recurrence-free survival (RFS), and overall survival (OS), and to identify prognostic factors for PMBC.

RESULTS

Data from 20,684 IDC cases, 1,475 ILC cases, and 943 PMBC cases were used. Median follow-up was 6.6 years. Five-year RFI, RFS, and OS for PMBC were 96.1%, 94.9%, and 98.1%, respectively. On multivariable Cox regression, PMBC demonstrated superior RFI (hazard ratio [HR], 0.59; 95% CI, 0.43-0.80), RFS (HR, 0.70; 95% CI, 0.56-0.89), and OS (HR, 0.71; 95% CI, 0.53-0.96) compared with IDC. ILC showed comparable outcomes to IDC. Fewer than half (48.7%) of recurrences in PMBC were distant, which was a lower rate than for IDC (67.3%) and ILC (80.6%). In contrast to RFI, RFS events were driven more by non-breast cancer deaths in older patients. Significant prognostic factors for RFI among PMBC included positive lymph node(s) (HR, 2.42; 95% CI, 1.08-5.40), radiotherapy (HR, 0.44; 95% CI, 0.23-0.85), and endocrine therapy (HR, 0.25; 95% CI, 0.09-0.70). No differential chemotherapy associations with outcomes were detected across PMBC subgroups by nodal stage, tumor size, and age. A separate SEER database analysis also did not find any association of improved survival with adjuvant chemotherapy in these subgroups.

CONCLUSIONS

Compared with IDC, PMBC demonstrated superior RFI, RFS, and OS. Lymph node negativity, adjuvant radiotherapy, and endocrine therapy were associated with superior RFI. Adjuvant chemotherapy was not associated with better outcomes.

A 10-Gene Signature to Predict the Prognosis of Early-Stage Triple-Negative Breast Cancer

Purpose

Triple-negative breast cancer (TNBC) is a particularly challenging subtype of breast cancer, with a poorer prognosis compared to other subtypes. Unfortunately, unlike luminal type cancers, there is no validated biomarker to predict the prognosis of patients with early-stage TNBC. Accurate biomarkers are needed to establish effective therapeutic strategies.

Materials and Methods

In this study, we analyzed gene expression profiles of tumor samples from 184 TNBC patients (training cohort, n=76; validation cohort, n=108) using RNA sequencing.

Results

By combining weighted gene expression, we identified a 10-gene signature (DGKH, GADD45B, KLF7, LYST, NR6A1, PYCARD, ROBO1, SLC22A20P, SLC24A3, and SLC45A4) that stratified patients by risk score with high sensitivity (92.31%), specificity (92.06%), and accuracy (92.11%) for invasive disease-free survival. The 10-gene signature was validated in a separate institution cohort and supported by meta-analysis for biological relevance to well-known driving pathways in TNBC. Furthermore, the 10-gene signature was the only independent factor for invasive disease-free survival in multivariate analysis when compared to other potential biomarkers of TNBC molecular subtypes and T-cell receptor β diversity. 10-gene signature also further categorized patients classified as molecular subtypes according to risk scores.

Conclusion

Our novel findings may help address the prognostic challenges in TNBC and the 10-gene signature could serve as a novel biomarker for risk-based patient care.

IMpassion132 double-blind randomised phase III trial of chemotherapy with or without atezolizumab for early relapsing unresectable locally advanced or metastatic triple-negative breast cancer

BACKGROUND

Immune checkpoint inhibitors improve the efficacy of first-line chemotherapy for patients with programmed death-ligand 1 (PD-L1)-positive unresectable locally advanced/metastatic triple-negative breast cancer (aTNBC), but randomised data in rapidly relapsing aTNBC are scarce.

PATIENTS AND METHODS

IMpassion132 (NCT03371017) enrolled patients with aTNBC relapsing <12 months after last chemotherapy dose (anthracycline and taxane required) or surgery for early TNBC. PD-L1 status was centrally assessed using SP142 before randomisation. Initially patients were enrolled irrespective of PD-L1 status. From August 2019, enrolment was restricted to PD-L1-positive (tumour immune cell ≥1%) aTNBC. Patients were randomised 1:1 to placebo or atezolizumab 1200 mg every 21 days with investigator-selected chemotherapy until disease progression or unacceptable toxicity. Stratification factors were chemotherapy regimen (carboplatin plus gemcitabine or capecitabine monotherapy), visceral (lung and/or liver) metastases and (initially) PD-L1 status. The primary endpoint was overall survival (OS), tested hierarchically in patients with PD-L1-positive tumours and then, if positive, in the modified intent-to-treat (mITT) population (all-comer patients randomised pre-August 2019). Secondary endpoints included progression-free survival (PFS), objective response rate (ORR) and safety.

RESULTS

Among 354 patients with rapidly relapsing PD-L1-positive aTNBC, 68% had a disease-free interval of <6 months and 73% received carboplatin/gemcitabine. The OS hazard ratio was 0.93 (95% confidence interval 0.73-1.20, P = 0.59; median 11.2 months with placebo versus 12.1 months with atezolizumab). mITT and subgroup results were consistent. Median PFS was 4 months across treatment arms and populations. ORRs were 28% with placebo versus 40% with atezolizumab. Adverse events (predominantly haematological) were similar between arms and as expected with atezolizumab plus carboplatin/gemcitabine or capecitabine following recent chemotherapy exposure.

CONCLUSIONS

OS, which is dismal in patients with TNBC relapsing within <12 months, was not improved by adding atezolizumab to chemotherapy. A biology-based definition of intrinsic resistance to immunotherapy in aTNBC is urgently needed to develop novel therapies for these patients in next-generation clinical trials.

Event-free survival by residual cancer burden with pembrolizumab in early-stage TNBC: exploratory analysis from KEYNOTE-522

BACKGROUND

KEYNOTE-522 demonstrated statistically significant improvements in pathological complete response (pCR) with neoadjuvant pembrolizumab plus chemotherapy and event-free survival (EFS) with neoadjuvant pembrolizumab plus chemotherapy followed by adjuvant pembrolizumab in patients with high-risk, early-stage triple-negative breast cancer (TNBC). Prior studies have shown the prognostic value of the residual cancer burden (RCB) index to quantify the extent of residual disease after neoadjuvant chemotherapy. In this preplanned exploratory analysis, we assessed RCB distribution and EFS within RCB categories by treatment group.

PATIENTS AND METHODS

A total of 1174 patients with stage T1c/N1-2 or T2-4/N0-2 TNBC were randomized 2 : 1 to pembrolizumab 200 mg or placebo every 3 weeks given with four cycles of paclitaxel + carboplatin, followed by four cycles of doxorubicin or epirubicin + cyclophosphamide. After surgery, patients received pembrolizumab or placebo for nine cycles or until recurrence or unacceptable toxicity. Primary endpoints are pCR and EFS. RCB is a prespecified exploratory endpoint. The association between EFS and RCB was assessed using a Cox regression model.

RESULTS

Pembrolizumab shifted patients into lower RCB categories across the entire spectrum compared with placebo. There were more patients in the pembrolizumab group with RCB-0 (pCR), and fewer patients in the pembrolizumab group with RCB-1, RCB-2, and RCB-3. The corresponding hazard ratios (95% confidence intervals) for EFS were 0.70 (0.38-1.31), 0.92 (0.39-2.20), 0.52 (0.32-0.82), and 1.24 (0.69-2.23). The most common first EFS events were distant recurrences, with fewer in the pembrolizumab group across all RCB categories. Among patients with RCB-0/1, more than half [21/38 (55.3%)] of all events were central nervous system recurrences, with 13/22 (59.1%) in the pembrolizumab group and 8/16 (50.0%) in the placebo group.

CONCLUSIONS

Addition of pembrolizumab to chemotherapy resulted in fewer EFS events in the RCB-0, RCB-1, and RCB-2 categories, with the greatest benefit in RCB-2. These findings demonstrate that pembrolizumab not only increased pCR rates, but also improved EFS among most patients who do not have a pCR.

Trastuzumab deruxtecan versus treatment of physician's choice in patients with HER2-positive metastatic breast cancer (DESTINY-Breast02): patient-reported outcomes from a randomised, open-label, multicentre, phase 3 trial

BACKGROUND

In DESTINY-Breast02, patients with HER2-positive unresectable or metastatic breast cancer who received trastuzumab deruxtecan demonstrated superior progression-free and overall survival compared with those receiving treatment of physician's choice. We present the patient-reported outcomes (PROs) and hospitalisation data.

METHODS

In this randomised, open-label, phase 3 trial conducted at 227 clinical sites globally, enrolled patients had to be aged 18 years or older with HER2-positive unresectable or metastatic breast cancer that had progressed on trastuzumab emtansine and had an Eastern Cooperative Oncology Group performance status of 0 or 1. Patients were randomly assigned (2:1) using block randomisation (block size of 3) to receive trastuzumab deruxtecan (5·4 mg/kg intravenously once every 21 days) or treatment of physician's choice by an independent biostatistician using an interactive web-based system. Patients and investigators remained unmasked to treatment. Treatment of physician's choice was either capecitabine (1250 mg/m2 orally twice per day on days 1-14) plus trastuzumab (8 mg/kg intravenously on day 1 then 6 mg/kg once per day) or capecitabine (1000 mg/m2) plus lapatinib (1250 mg orally once per day on days 1-21), with a 21-day schedule. The primary endpoint, which was progression-free survival based on blinded independent central review, has previously been reported. PROs were assessed in the full analysis set (all patients randomly assigned to the study) using the oncology-specific European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30), breast cancer-specific EORTC Quality of Life Questionnaire Breast 45 (QLQ-BR45), and the generic HRQoL EQ-5D-5L questionnaire. Analyses included change from baseline and time to definitive deterioration for PRO variables of interest and hospitalisation-related endpoints. This study is registered with ClinicalTrials.gov, NCT03523585, and is closed to recruitment.

FINDINGS

Between Sept 6, 2018, and Dec 31, 2020, 608 patients were randomly assigned to receive either trastuzumab deruxtecan (n=406; two did not receive treatment) or treatment of physician's choice (n=202; seven did not receive treatment). Overall, 603 patients (99%) were female and five (<1%) were male. The median follow-up was 21·5 months (IQR 15·2-28·4) in the trastuzumab deruxtecan group and 18·6 months (IQR 8·8-26·0) in the treatment of physician's choice group. Median treatment duration was 11·3 months (IQR 6·2-20·5) in the trastuzumab deruxtecan group and approximately 4·5 months in the treatment of physician's choice group (4·4 months [IQR 2·5-8·7] with trastuzumab; 4·6 months [2·1-8·9] with capecitabine; and 4·5 months [2·1-10·6] with lapatinib). Baseline EORTC QLQ-C30 global health status (GHS) scores were similar with trastuzumab deruxtecan (n=393) and treatment of physician's choice (n=187), and remained stable with no clinically meaningful change (defined as ≥10-point change from baseline) over time. Median time to definitive deterioration was delayed with trastuzumab deruxtecan compared with treatment of physician's choice for the primary PRO variable EORTC QLQ-C30 GHS (14·1 months [95% CI 10·4-18·7] vs 5·9 months [4·3-7·9]; HR 0·5573 [0·4376-0·7099], p<0·0001) and all other prespecified PROs (EORTC QLQ-C30 subscales, EORTC QLQ-BR45 arm and breast symptoms, and EQ-5D-5L visual analogue scale). Patient hospitalisation rates were similar in the trastuzumab deruxtecan (92 [23%] of 406) and treatment of physician's choice (41 [20%] of 202) groups; however, median time to hospitalisation was 133 days (IQR 56-237) with trastuzumab deruxtecan versus 83 days (30-152) with treatment of physician's choice.

INTERPRETATION

Overall, GHS and quality of life were maintained for both treatment groups, with prespecified PRO variables favouring trastuzumab deruxtecan over treatment of physician's choice, suggesting that despite a longer treatment duration, there was no detrimental impact on patient health-related quality of life with trastuzumab deruxtecan. When considered with efficacy and safety data from DESTINY-Breast02, these results support the overall benefit of trastuzumab deruxtecan for patients with HER2-positive unresectable or metastatic breast cancer previously treated with trastuzumab emtansine.

FUNDING

Daiichi Sankyo and AstraZeneca.

Comprehensive Young Age Breast Cancer registry from clinical, genomics, and patient-reported outcomes measured with 15 years follow-up: the CHARM cohort profile

BACKGROUND

In recognition of the distinct clinical challenges and research gaps in young breast cancer (YBC) patients, we established the Comprehensive Young Age Breast Cancer (CHARM) registry to collect prospective data.

METHODS

This prospective cohort included patients who were newly diagnosed with histologically confirmed breast cancer without prior treatment at the Samsung Medical Center (SMC) in April 2013. We included patients who were either 40 years old or younger at the time of diagnosis, pregnant at breast cancer diagnosis or diagnosed with breast cancer within 1 year of delivery. All data were collected using Medidata's Rave Electronic Data. Clinical data were obtained from electronic medical records. Two experienced pathologists reviewed the pathologic data. Bone mineral densitometry tests have been conducted annually. To obtain multi-omics data, tumor tissues and blood samples were prospectively collected from consenting patients in the registry during surgery. The fertility-related factor also collected collaborated with the Department of Obstetrics and Gynecology. Anti-Müllerian hormone, estradiol, follicle-stimulating hormone, and luteinizing hormone levels were measured using an additional blood sample from baseline to last follow-up. Patient-reported outcomes were assessed using mobile questionnaires.

RESULTS

A total of 1868 participants were included in the SMC YBC study. The average (standard deviation) age was 35.57 (3.79) and 99.8% of the participants were premenopausal. Among them, 1062 participants completed the PRO questionnaires.

CONCLUSIONS

The SMC YBC cohort serves as a comprehensive registry for YBC to optimize care and improve knowledge regarding the management of YBC.

Clinical effectiveness and safety of olaparib in BRCA-mutated, HER2-negative metastatic breast cancer in a real-world setting: final analysis of LUCY

PURPOSE

The interim analysis of the phase IIIb LUCY trial demonstrated the clinical effectiveness of olaparib in patients with germline BRCA-mutated (gBRCAm), human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer (mBC), with median progression-free survival (PFS) of 8.11 months, which was similar to that in the olaparib arm of the phase III OlympiAD trial (7.03 months). This prespecified analysis provides final overall survival (OS) and safety data.

METHODS

The open-label, single-arm LUCY trial of olaparib (300 mg, twice daily) enrolled adults with gBRCAm or somatic BRCA-mutated (sBRCAm), HER2-negative mBC. Patients had previously received a taxane or anthracycline for neoadjuvant/adjuvant or metastatic disease and up to two lines of chemotherapy for mBC.

RESULTS

Of 563 patients screened, 256 (gBRCAm, n = 253; sBRCAm, n = 3) were enrolled. In the gBRCAm cohort, median investigator-assessed PFS (primary endpoint) was 8.18 months and median OS was 24.94 months. Olaparib was clinically effective in all prespecified subgroups: hormone receptor status, previous chemotherapy for mBC, previous platinum-based chemotherapy (including by line of therapy), and previous cyclin-dependent kinase 4/6 inhibitor use. The most frequent treatment-emergent adverse events (TEAEs) were nausea (55.3%) and anemia (39.2%). Few patients (6.3%) discontinued olaparib owing to a TEAE. No deaths associated with AEs occurred during the study treatment or 30-day follow-up.

CONCLUSION

The LUCY patient population reflects a real-world population in line with the licensed indication of olaparib in mBC. These findings support the clinical effectiveness and safety of olaparib in patients with gBRCAm, HER2-negative mBC.

CLINICAL TRIAL REGISTRATION

Clinical trials registration number: NCT03286842.

Trastuzumab deruxtecan in previously treated patients with HER2-positive metastatic breast cancer: updated survival results from a phase II trial (DESTINY-Breast01)

BACKGROUND

Primary analysis of the multicenter, open-label, single-arm, phase II DESTINY-Breast01 trial (median follow-up 11.1 months) demonstrated durable antitumor activity with trastuzumab deruxtecan (T-DXd) in patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (mBC) previously treated with trastuzumab emtansine (T-DM1). We report updated cumulative survival outcomes with a median follow-up of 26.5 months (data cut-off 26 March 2021).

PATIENTS AND METHODS

Patients with HER2-positive mBC resistant or refractory to T-DM1 received T-DXd 5.4 mg/kg intravenously every 3 weeks until disease progression, unacceptable adverse events, or withdrawal of consent. The primary endpoint was confirmed objective response rate (ORR) by independent central review (ICR). Secondary endpoints included overall survival (OS), duration of response (DoR), progression-free survival (PFS), and safety.

RESULTS

The ORR by ICR was 62.0% [95% confidence interval (CI) 54.5% to 69.0%] in patients who received T-DXd 5.4 mg/kg every 3 weeks (n = 184). Median OS was 29.1 months (95% CI 24.6-36.1 months). Median PFS and DoR were 19.4 months (95% CI 14.1-25.0 months) and 18.2 months (95% CI 15.0 months-not evaluable), respectively. Drug-related treatment-emergent adverse events (TEAEs) were observed in 183 patients (99.5%), and 99 patients (53.8%) had one or more grade ≥3 TEAEs. Adjudicated drug-related interstitial lung disease/pneumonitis occurred in 15.8% of patients (n = 29), of which 2.7% (n = 5) were grade 5.

CONCLUSIONS

These updated results provide further evidence of sustained antitumor activity of T-DXd with a consistent safety profile in heavily pretreated patients with HER2-positive mBC.

A nationwide real-world study for evaluation of effectiveness and safety of T-DM1 in patients with HER2-positive metastatic breast cancer in Korea (KCSG BR19-15)

Purpose

This study aimed to investigate clinical practices and factors related to the outcomes of T-DM1 use in patients with HER2-positive metastatic breast cancer (mBC).

Methods

We included patients with HER2-positive mBC who received T-DM1 as a palliative therapy between August 2017 and December 2018. The safety and outcomes of T-DM1, including overall response rate (ORR), progression-free survival (PFS), and overall survival (OS), were evaluated. A Cox proportional hazards model was used to estimate the hazard ratio and 95% confidence interval (CI) for mortality or progression to HER2-positive mBC.

Results

In total, 824 patients were enrolled during the study period. The mean age of patients was 58 years, and 516 (62.6%) patients relapsed after curative treatment. Excluding a history of endocrine therapy, 341 (41.4%) patients previously received none or first-line chemotherapy, 179 (21.7%) received second-line therapy, and 303 (36.9%) received third-or later-line chemotherapy before T-DM1 therapy. During a median follow-up of 16.8 months, the ORR was 35%, the median PFS was 6.6 months, and the median OS was not reached. The clinical factors associated with the hazard of progression were age (<65 years), poor performance status (⩾2), advanced line of palliative chemotherapy (⩾2), prior pertuzumab use, and treatment duration of palliative trastuzumab (<10 months). Common grade 3-4 adverse events were thrombocytopenia (n = 107, 13.2%), neutropenia (n = 23, 2.8%), anemia (n = 21, 2.6%), and elevated liver enzyme (n = 20, 2.5%). Hypokalemia (⩽3.0 mmol/L) and any-grade bleeding events occurred in 25 (3.1%) and 94 (22.6%) patients, respectively.

Conclusion

This is the first nationwide real-world study of T-DM1 use in patients with HER2-positive mBC in Korea. The effectiveness and toxicity profiles of T-DM1 in real-world practice were comparable to those in randomized trials. Moreover, patient factors and previous anti-HER2 therapy could predict the outcomes of T-DM1 therapy.

Traffic Exposure and Breast Cancer Mortality by Area of Residence: Incorporating Clinical and Socioeconomic Data

Incorporating clinical and environmental data holds promise for monitoring vulnerable populations at the community level. This spatial epidemiology study explores the link between traffic-related air pollution and breast cancer mortality in Seoul, using public socioeconomic and clinical data from Samsung Medical Center's registry (N=6,089). Traffic and socioeconomic status were collected from official sources and integrated for spatial analysis. The findings revealed a significant association between adult breast cancer mortality and districts with high road density, NO2 emissions, and family income (p<0.05). Significant spatial autocorrelation of residuals was observed (Moran's I test p<0.001).

c-MET-positive circulating tumor cells and cell-free DNA as independent prognostic factors in hormone receptor-positive/HER2-negative metastatic breast cancer

BACKGROUND

Endocrine therapy resistance in hormone receptor-positive/HER2-negative (HR+/HER2-) breast cancer (BC) is a significant clinical challenge that poses several unmet needs in the management of the disease. This study aimed to investigate the prognostic value of c-MET-positive circulating tumor cells (cMET+ CTCs), ESR1/PIK3CA mutations, and cell-free DNA (cfDNA) concentrations in patients with hormone receptor-positive (HR+) metastatic breast cancer (mBC).

METHODS

Ninety-seven patients with HR+ mBC were prospectively enrolled during standard treatment at Samsung Medical Center. CTCs were isolated from blood using GenoCTC® and EpCAM or c-MET CTC isolation kits. PIK3CA and ESR1 hotspot mutations were analyzed using droplet digital PCR. CfDNA concentrations were calculated using internal control copies from the ESR1 mutation test. Immunocytochemistry was performed to compare c-MET overexpression between primary and metastatic sites.

RESULTS

The proportion of c-MET overexpression was significantly higher in metastatic sites than in primary sites (p = 0.00002). Survival analysis showed that c-MET+ CTC, cfDNA concentration, and ESR1 mutations were significantly associated with poor prognosis (p = 0.0026, 0.0021, and 0.0064, respectively) in HR+/HER2- mBC. By contrast, EpCAM-positive CTC (EpCAM+ CTC) and PIK3CA mutations were not associated with progression-free survival (PFS) in HR+/HER2- mBC. Multivariate analyses revealed that c-MET+ CTCs and cfDNA concentration were independent predictors of PFS in HR+/HER2- mBC.

CONCLUSIONS

Monitoring c-MET+ CTC, rather than assessing c-MET expression in the primary BC site, could provide valuable information for predicting disease progression, as c-MET expression can change during treatment. The c-MET+ CTC count and cfDNA concentration could provide complementary information on disease progression in HR+ /HER2- mBC, highlighting the importance of integrated liquid biopsy.

Impact of Social Support during Diagnosis and Treatment on Disease Progression in Young Patients with Breast Cancer: A Prospective Cohort Study

PURPOSE

We evaluated the association between changes in social support after cancer treatment and recurrence-free survival (RFS) in such patients using a prospective cohort study.

MATERIALS AND METHODS

Data were obtained from a prospective cohort study (NCT03131089) conducted at Samsung Medical Center (2013-2021). The primary outcome measure was RFS. Social support was measured using the social and family well-being (SFWB) domain of the Functional Assessment of Cancer Therapy-General. We calculated the changes in SFWB scores before and during treatment and the hazard ratio for RFS by comparing such changes.

RESULTS

The mean±standard deviation (SD) age of the patients was 35±3.9 years, and 71.5% and 64.8% of the patients were married and had children, respectively. The mean±SD SFWB score at baseline was 20.5±5.0 out of 26. After cancer treatment, 35.9%, 10.3%, and 53.8% of the participants had increasing, unchanged, and decreasing SFWB scores, respectively. The decreasing SFWB score group had a higher risk of mortality or recurrence than the increasing group. Risk factors for the decreasing score were the presence of children during diagnosis.

CONCLUSION

In this cohort, changes in social support after treatment were associated with RFS in young patients with breast cancer. Health professionals should develop family interventions to help them receive proper social support.

Pemetrexed plus vinorelbine versus vinorelbine monotherapy in patients with metastatic breast cancer (KCSG-BR15-17): A randomized, open-label, multicenter, phase II trial

INTRODUCTION

Metastatic breast cancer refractory to anthracycline and taxanes often shows rapid progression. The development of effective and tolerable combination regimens for these patients is needed. This phase II trial investigated the efficacy of pemetrexed plus vinorelbine in patients with metastatic breast cancer.

METHODS

This randomized, open-label, phase II trial was conducted in 17 centers in Korea. Patients with advanced breast cancer who had previously been treated with anthracyclines and taxanes were randomly assigned in a 1:1 ratio to receive either vinorelbine or pemetrexed plus vinorelbine. Randomization was stratified by prior capecitabine treatment and hormone receptor status. The primary endpoint was investigator-assessed progression-free survival (PFS). Secondary endpoints included the objective response rate, overall survival, safety, and quality of life.

RESULTS

Between March 2017 and August 2019, a total of 125 patients were enrolled. After a median follow-up duration of 14.1 months, 118 progression events and 88 death events had occurred. Sixty-two patients were assigned to the pemetrexed plus vinorelbine arm, and 63 were assigned to the vinorelbine arm. Pemetrexed plus vinorelbine significantly prolonged PFS compared to vinorelbine (5.7 vs. 1.5 months, p < 0.001). The combination arm had higher disease control rate (76.8% vs. 45.9%, p = 0.001) and a tendency toward longer overall survival (16.8 vs. 10.5 months, p = 0.102). Anemia was more frequent in the pemetrexed plus vinorelbine arm per cycle compared with vinorelbine (7.9% vs. 1.9%, p < 0.001), but there was no difference in the incidence of grade 3-4 neutropenia per cycle between the pemetrexed plus vinorelbine arm and the vinorelbine single arm (14.7% vs. 19.5%, p = 0.066).

CONCLUSIONS

This phase II study showed that pemetrexed plus vinorelbine led to a longer PFS than vinorelbine. Adverse events of pemetrexed plus vinorelbine were generally manageable.

A Survey of Practice Patterns for Clinical Nodal Staging Prior to Neoadjuvant Chemotherapy in Breast Cancer

BACKGROUND

The importance of clinical staging in breast cancer has increased owing to the wide use of neoadjuvant systemic therapy (NST). This study aimed to investigate the current practice patterns regarding clinical nodal staging in breast cancer in real-world settings.

MATERIALS AND METHODS

A web-based survey was administered to board-certified oncologists in Korea, including breast surgical, medical, and radiation oncologists, from January to April 2022. The survey included 19 general questions and 4 case-based questions.

RESULTS

In total, 122 oncologists (45 radiation, 44 surgical, and 33 medical oncologists) completed the survey. Among them, 108 (88%) responded that clinical staging before NST was primarily performed by breast surgeons. All the respondents referred to imaging studies during nodal staging. Overall, 64 (52.5%) responders determined the stage strictly based on the radiology reports, whereas 58 (47.5%) made their own decision while noting radiology reports. Of those who made their own decisions, 88% referred to the number or size of the suspicious node. Of the 75 respondents involved in prescribing regimens for neoadjuvant chemotherapy, 58 (77.3%) responded that the reimbursement regulations in the selection of NST regimens affected nodal staging in clinical practice. In the case-based questions, high variability was observed among the clinicians in the same cases.

CONCLUSIONS

Diverse assessments by specialists owing to the lack of a clear, harmonized staging system for the clinical nodal staging of breast cancer can lead to diverse practice patterns. Thus, practical, harmonized, and objective methods for clinical nodal staging and for the outcomes of post-NST response are warranted for appropriate treatment decisions and accurate outcome evaluation.

Incidence of and Influencing Factors for Arm Lymphedema After Salvage Treatment for an Isolated Locoregional Recurrence of Breast Cancer

PURPOSE

Data on subsequent arm lymphedema (SAL) after salvage treatment for locoregional recurrence (LRR) of breast cancer are limited. We conducted a study to evaluate the risk of SAL in patients with LRR.

METHODS

We reviewed the data of patients with breast cancer who had LRR and were initially diagnosed between January 2003 and December 2017. Among the 214 patients who received curative salvage treatment, most had local (n = 125, 57.9%), followed by regional (n = 73, 34.1%), and locoregional (n = 16, 7.9%) recurrences. A competing risk analysis considering the factors of death and a second LRR were performed to exclude potential malignant lymphedema. We used the Fine-Gray subdistribution hazards model to estimate the hazard ratio (HR) for comparing the risk of SAL.

RESULTS

With a median follow-up duration of 41.4 months (interquartile range, 25.6-65.1), 51 patients (23.8%) experienced SAL with a median interval of 9.9 months after treatment. The two-year cumulative incidence of SAL was 12.7%. Among the 18 patients with initial lymphedema, nine (50.0%) developed SAL. Multivariate analysis revealed that a history of lymphedema (HR, 4.61; p < 0.001) and taxane-based salvage chemotherapy (HR, 2.38; p = 0.009) were significantly associated with SAL development.

CONCLUSION

Salvage treatment for LRR-induced SAL was performed in 24% of the patients. A history of initial lymphedema and salvage taxane-based chemotherapy increases the risk of developing SAL. Therefore, close surveillance for the incidence of SAL is required in patients opting for salvage treatment for LRR.

Clinical activity of nivolumab in combination with eribulin in HER2-negative metastatic breast cancer: A phase IB/II study (KCSG BR18-16)

AIM

We evaluated the efficacy and safety of nivolumab and eribulin combination therapy for metastatic breast cancer (BC) in Asian populations.

METHODS

In this parallel phase II study, adult patients with histologically confirmed recurrent/metastatic hormone receptor-positive/HER2-negative (HR+HER2-) or triple-negative BC (TNBC) were prospectively enroled from 10 academic hospitals in Korea (ClinicalTrials.gov Identifier: NCT04061863). They received nivolumab (360 mg) on day 1 plus eribulin (1.4 mg/m2) on days 1 and 8 every 3 weeks until disease progression or intolerable toxicity. The primary endpoint was the investigator-assessed 6-month progression-free survival (PFS) rate in each subtype. Secondary endpoints included investigator-assessed objective response rate (ORR) as per Response Evaluation Criteria in Advanced Solid Tumors version 1.1, disease control rate, overall survival, and treatment toxicity. The association between PD-L1 expression and efficacy was investigated.

RESULTS

Forty-five patients with HR+HER2- BC and 45 with TNBC were enroled. Their median age was 51 (range, 31-71) years, and 74 (82.2%) received one or two prior treatments before enrolment. Six-month PFS was 47.2% and 25.1% in the HR+HER2- and TNBC cohorts, respectively. Median PFS was 5.6 (95% confidence interval [CI]: 5.3-7.4) and 3.0 (95% CI: 2.1-5.2) months in the HR+HER2- and TNBC groups, respectively. ORRs were 53.3% (complete response [CR]: 0, partial response [PR]: 24) and 28.9% (CR: 1, PR: 12). Patients with PD-L1+ tumours (PD-L1 expression ≥1%) and PD-L1- tumours (ORR 50% versus 53.8% in HR+HER2-, 30.8% versus 29.0% in TNBC) had similar ORRs. Neutropenia was the most common grade 3/4 adverse event; the most common immune-related adverse events (AEs) were grades 1/2 hypothyroidism and pruritus. Five patients discontinued therapy because of immune-related AEs.

CONCLUSION

Nivolumab plus eribulin showed promising efficacy and tolerable safety in previously treated HER2- metastatic BC.

TRIAL REGISTRATION

NCT04061863.

Benefit of postoperative regional nodal irradiation in patients receiving preoperative systemic therapy with docetaxel/carboplatin/trastuzumab/pertuzumab for HER2-positive breast cancer

AIM

The role of regional nodal irradiation (RNI) after preoperative systemic treatment (PST) with targeted therapy for HER2-positive breast cancer remains uncertain. This study aimed to investigate the impact of RNI on locoregional recurrence (LRR) and disease-free survival (DFS) outcomes after docetaxel/carboplatin/trastuzumab/pertuzumab (TCHP) for PST.

METHODS

We retrospectively analyzed 255 patients who were treated with six cycles of TCHP between 2016 and 2019. The patients were divided into four groups based on clinical nodal involvement: group A, with no nodal disease; group B, with axillary lymph node (AXL) level I; group C, with AXL level I with II/III; and group D, with supraclavicular or internal mammary nodes.

RESULTS

The RNI group had more advanced nodal disease (C/D) than the no RNI group (56.9 % vs. 6.8 %). With a median follow-up of 51.3 months, there were two (0.8 %), three (1.2 %), and 15 (5.9 %) local, regional, and distant metastases, respectively. LRR did not differ significantly according to the RNI (2.6 % vs. 1.0 %, p = 0.651). Group D had the most frequent distant metastases (17.5 %; p = 0.005). The 4-year DFS rate was 92.7 %, and DFS did not improve significantly after RNI (p = 0.074). When stratified by clinical nodal groups and pathological axillary response, RNI had no effect on LRR/DFS outcomes.

CONCLUSION

With a rare incidence of LRR, RNI did not significantly affect LRR or DFS in patients with HER2-positive breast cancer after with PST-TCHP. However, intensive systemic treatment is required for advanced diseases (C/D). Selective de-intensified RNI and intensified systemic treatment should be investigated in future studies.

Pembrolizumab Plus Chemotherapy Followed by Pembrolizumab in Patients With Early Triple-Negative Breast Cancer: A Secondary Analysis of a Randomized Clinical Trial

Importance

In the phase 3 KEYNOTE-522 study, addition of pembrolizumab to neoadjuvant chemotherapy followed by adjuvant pembrolizumab significantly increased pathologic complete response (pCR) and event-free survival (EFS) vs neoadjuvant chemotherapy in patients with early triple-negative breast cancer.

Objective

To evaluate efficacy and safety outcomes for patients enrolled in East/Southeast Asia (Asia) in KEYNOTE-522.

Design, Setting, and Participants

KEYNOTE-522, a multicenter, double-blind, randomized clinical trial, enrolled 1174 patients between March 7, 2017, and September 13, 2018. For interim EFS and overall survival (OS) analyses (data cutoff, March 23, 2021), median follow-up was 39.8 months (range, 30.4-46.9 months) for pembrolizumab plus chemotherapy and 40.8 months (range, 30.1-46.9 months) for placebo plus chemotherapy. Data cutoff for pCR analysis was September 24, 2018. This secondary analysis included adults enrolled in Asia with newly diagnosed, previously untreated, nonmetastatic triple-negative breast cancer (tumor stage T1c and nodal stage N1-2 or tumor stage T2-4 and nodal stage N0-2) and Eastern Cooperative Oncology Group performance status of 0 to 1, regardless of programmed cell death ligand 1 (PD-L1) status.

Intervention

Patients were randomized 2:1 to 4 cycles of pembrolizumab (200 mg every 3 weeks) or placebo plus carboplatin and paclitaxel and another 4 cycles of pembrolizumab or placebo plus doxorubicin or epirubicin and cyclophosphamide before surgery. After definitive surgery, patients received pembrolizumab or placebo every 3 weeks for 9 cycles or until recurrence or unacceptable toxic effects.

Main Outcomes and Measures

The main outcome was pCR (no evidence of primary tumor after neoadjuvant therapy or carcinoma in situ after neoadjuvant therapy and no regional lymph node involvement after neoadjuvant therapy) at the time of definitive surgery and EFS.

Results

A total of 216 of 1174 randomized patients (all female; median [range] age, 46.0 [24.0-71.0] years) were from Korea, Japan, Taiwan, and Singapore (136 in the pembrolizumab plus chemotherapy group and 80 in the placebo plus chemotherapy group). Of these patients, 104 (76.5%) in the pembrolizumab plus chemotherapy group and 60 (75.0%) in the placebo plus chemotherapy group had a tumor PD-L1 combined positive score of 1 or greater. Pathologic complete response was 58.7% (95% CI, 46.7%-69.9%) with pembrolizumab plus chemotherapy and 40.0% (95% CI, 26.4%-54.8%) with placebo plus chemotherapy; benefit was observed regardless of PD-L1 status. Thirteen patients (9.6%) in the pembrolizumab plus chemotherapy group and 20 patients (25.0%) in the placebo plus chemotherapy group had EFS events (hazard ratio, 0.35; 95% CI, 0.17-0.71). The 36-month EFS rate was 91.2% (95% CI, 85.0%-94.9%) with pembrolizumab plus chemotherapy and 77.2% (95% CI, 66.3%-85.0%) with placebo plus chemotherapy. Grade 3 to 4 treatment-related adverse events occurred in 109 patients (80.1%) receiving pembrolizumab plus chemotherapy and 64 patients (81.0%) receiving placebo plus chemotherapy.

Conclusions and Relevance

In this subgroup analysis of patients enrolled in Asia in KEYNOTE-522, neoadjuvant pembrolizumab plus chemotherapy followed by adjuvant pembrolizumab led to clinically meaningful improvements in pCR and EFS vs neoadjuvant chemotherapy alone. These findings support the use of neoadjuvant pembrolizumab plus chemotherapy followed by adjuvant pembrolizumab as a standard-of-care therapy for patients in Asian countries with early triple-negative breast cancer.

Trial Registration

ClinicalTrials.gov Identifier: NCT03036488.

A Retrospective Exploratory Analysis for Serum Extracellular Vesicles Reveals APRIL (TNFSF13), CXCL13, and VEGF-A as Prognostic Biomarkers for Neoadjuvant Chemotherapy in Triple-Negative Breast Cancer

Neoadjuvant chemotherapy (NAC) is widely used as a standard treatment for early-stage triple-negative breast cancer (TNBC). While patients who achieve pathologic complete response (pCR) have a highly favorable outcome, patients who do not achieve pCR have variable prognoses. It is important to identify patients who are most likely to have poor survival outcomes to identify candidates for more aggressive therapeutic approaches after NAC. Many studies have demonstrated that cytokines and growth factors packaged into extracellular vesicles (EVs) have an essential role in tumor progression and drug resistance. In this study, we examined the role of serum-derived EV-associated cytokines as prognostic biomarkers for long-term outcomes in patients who underwent anthracycline-taxane-based NAC. We isolated extracellular vesicles from the serum of 190 TNBC patients who underwent NAC between 2015 and 2018 at Samsung Medical Center. EV-associated cytokine concentrations were measured with ProcartaPlex Immune Monitoring 65-plex panels. The prognostic value of EV-associated cytokines was studied. We found that patients with high EV_APRIL, EV_CXCL13, and EV_VEGF-A levels had shorter overall survival (OS). We further evaluated the role of these selected biomarkers as prognostic factors in patients with residual disease (RD) after NAC. Even in patients with RD, high levels of EV_APRIL, EV_CXCL13, and EV_VEGF-A were correlated with poor OS. In all subgroup analyses, EV_CXCL13 overexpression was significantly associated with poor overall survival. Moreover, multivariate analysis indicated that a high level of EV_CXCL13 was an independent predictor of poor OS. Correlation analysis between biomarker levels in EVs and serum showed that EV_VEGF-A positively correlated with soluble VEGF-A but not CXCL13. An elevated level of soluble VEGF-A was also associated with poor OS. These findings suggest that EV_APRIL, EV_CXCL13, and EV_VEGF-A may be useful in identifying TNBC patients at risk of poor survival outcomes after NAC.

Impact of high dose radiotherapy for breast tumor in locoregionally uncontrolled stage IV breast cancer: a need for a risk-stratified approach

AIM

Patients with locoregionally uncontrolled breast tumors are frequently referred for breast palliative radiotherapy (PRT) to mitigate symptoms. We analyzed the outcomes following breast PRT to optimize PRT according to risk groups.

METHODS

We reviewed 133 patients who underwent breast PRT. A median total dose of 45 Gy was prescribed with an equivalent dose in 2 Gy fractions (EQD2, α/β = 3.5) of 53 Gy. The Cox proportional hazards model was used to analyze the prognostic factors of local control (LC).

RESULTS

Most (90.2%) had polymetastatic disease (> 5 lesions), and 48.9% had bone metastasis. With a median follow-up of 17.2 months, the 2-year LC and overall survival (OS) rates were 49.4%, and 48.3%, respectively. Multivariable analyses demonstrated progressive or mixed responses outside the breast and > 2 lines of previous therapy as adverse features for clinical outcomes. Group 1 (0 risk factors) showed favorable 2-year LC and OS of 63.9%, and 72.8%, respectively, whereas group 3 (2 risk factors) showed the worst outcomes of 0%, and 6.8%, respectively. Breast PRT with EQD2 ≥ 63 Gy showed a significant benefit in LC for group 1 and marginal benefit (p = 0.055) for group 2, but no improvement for group 3 (p = 0.300).

CONCLUSION

Breast PRT showed favorable LC outcomes in patients with stable disease outside the breast and treated with ≤ 2 lines of systemic treatment. Our findings warrant future clinical trials investigating the role of higher than palliative dose and early intervention of PRT in stage IV patients.

Safety and Tolerability of a Novel Anti-HER2 Antibody-Drug Conjugate (PF-06804103) in Patients with HER2-Expressing Solid Tumors: A Phase 1 Dose-Escalation Study

PF-06804103 is an anti-HER2 antibody-drug conjugate with auristatin payload. We evaluated its safety, tolerability, and antitumor activity in patients with advanced/unresectable or metastatic breast and gastric cancers. This multicenter, open-label, first-in-human, phase 1 study (NCT03284723) comprised dose escalation (P1) and dose expansion (P2). In P1, adults with HER2+ breast or gastric cancer received PF-06804103 0.15-5.0 mg/kg intravenously once/21 days (Q3W); in P2, patients with HER2+ or HER2-low (IHC 1+ or IHC 2+/ISH-) breast cancer received 3.0 or 4.0 mg/kg Q3W. The primary endpoints were dose-limiting toxicities (DLT) and safety (P1), and objective response rate (ORR) assessed using RECIST v1.1 (P2). Ninety-three patients enrolled in P1 (n = 47: HER2+ gastric cancer = 22, HER2+ breast cancer = 25) and P2 [n = 46: HER2+ breast cancer = 19, hormone receptor (HR)+ HER2-low breast cancer = 27] received PF-06804103. Four patients (3.0- and 4.0-mg/kg groups, n = 2 each) had DLTs (mostly Grade 3). Safety and efficacy results showed a dose-response relationship. Adverse events (AE) leading to treatment discontinuation (44/93, 47.3%) included neuropathy (11/93, 11.8%), skin toxicity (9/93, 9.7%), myalgia (5/93, 5.4%), keratitis (3/93, 3.2%), and arthralgia (2/93, 2.2%). Two (2/79, 2.5%) patients (P1, 4.0- and 5.0-mg/kg groups, n = 1 each) achieved complete response; 21 (21/79, 26.6%) achieved partial response. In P2, ORR was higher in HER2+ compared with HR+ HER2-low breast cancer [3.0 mg/kg: 16.7% (2/12) vs. 10.0% (1/10); 4.0 mg/kg: 47.4% (9/19) vs. 27.3% (3/11)]. PF-06804103 demonstrated antitumor activity; however, AEs led to discontinuation in 47.3% of patients. Safety and efficacy were dose-dependent.

Clinical Guidance on the Monitoring and Management of Trastuzumab Deruxtecan (T-DXd)-Related Adverse Events: Insights from an Asia-Pacific Multidisciplinary Panel

Trastuzumab deruxtecan (T-DXd)-an antibody-drug conjugate targeting the human epidermal growth factor receptor 2 (HER2)-improved outcomes of patients with HER2-positive and HER2-low metastatic breast cancer. Guidance on monitoring and managing T-DXd-related adverse events (AEs) is an emerging unmet need as translating clinical trial experience into real-world practice may be difficult due to practical and cultural considerations and differences in health care infrastructure. Thus, 13 experts including oncologists, pulmonologists and a radiologist from the Asia-Pacific region gathered to provide recommendations for T-DXd-related AE monitoring and management by using the latest evidence from the DESTINY-Breast trials, our own clinical trial experience and loco-regional health care considerations. While subgroup analysis of Asian (excluding Japanese) versus overall population in the DESTINY-Breast03 uncovered no major differences in the AE profile, we concluded that proactive monitoring and management are essential in maximising the benefits with T-DXd. As interstitial lung disease (ILD)/pneumonitis is a serious AE, patients should undergo regular computed tomography scans, but the frequency may have to account for the median time of ILD/pneumonitis onset and access. Trastuzumab deruxtecan appears to be a highly emetic regimen, and prophylaxis with serotonin receptor antagonists and dexamethasone (with or without neurokinin-1 receptor antagonist) should be considered. Health care professionals should be vigilant for treatable causes of fatigue, and patients should be encouraged to use support groups and practice low-intensity exercises. To increase treatment acceptance, patients should be made aware of alopecia risk prior to starting T-DXd. Detailed monitoring and management recommendations for T-DXd-related AEs are discussed further.

Comprehensive Clinical Characterization of Decade-Long Survivors of Metastatic Breast Cancer

BACKGROUND

Elucidating the clinical features of metastatic breast cancer (MBC) patients with an exceptionally favorable prognosis may offer insights to improve the survival of more typical patients.

METHODS

We collected comprehensive real-world data on clinicopathologic characteristics, treatments, and outcomes of 110 consecutive MBC patients who survived for over ten years from the clinical data warehouse of Samsung Medical Center.

RESULTS

The cohort included 54 hormone receptor (HR)-positive/HER2-negative (HR+/HER2-), 21 HR+/HER2+, 16 HR-/HER2+, and 14 triple-negative breast cancer (TNBC) patients. The median age at MBC diagnosis was 48.5 years. Approximately 70% of patients initially had a single-organ metastasis. The most common site of metastasis was the lung (46.4%), followed by distant lymph nodes (37.3%). During a median follow-up of 14.6 years, the median duration of systemic therapy was 11, 8.4, 7.3, and 0.8 years in the HR+/HER2-, HR+/HER2+, HR-/HER2+, and TNBC subgroups, respectively. Seven HER2+ and ten TNBC patients received systemic treatment for less than two years and remained treatment-free for most of the follow-up period, suggesting a potential chance of cure. The TNBC subtype (p < 0.001) and local treatment with curative intent within 1 year of MBC diagnosis (p = 0.002) were significantly associated with long-term treatment-free survival. The survival of HER2+ MBC and TNBC patients, but not that of HR+/HER2- patients, plateaued approximately 13 years after MBC diagnosis.

CONCLUSIONS

A small subset of patients with HER2+ MBC and metastatic TNBC may be curable with multimodality therapy. Prospective studies integrating clinical and genomic data may identify unique clinicogenomic features of MBC patients who can achieve durable disease control without prolonged chemotherapy.

Neoadjuvant palbociclib plus either giredestrant or anastrozole in oestrogen receptor-positive, HER2-negative, early breast cancer (coopERA Breast Cancer): an open-label, randomised, controlled, phase 2 study

BACKGROUND

The development of more potent selective oestrogen receptor antagonists and degraders (SERDs) that can be orally administered could help to address the limitations of current endocrine therapies. We report the primary and final analyses of the coopERA Breast Cancer study, designed to test whether giredestrant, a highly potent, non-steroidal, oral SERD, would show a stronger anti-proliferative effect than anastrozole after 2 weeks for oestrogen receptor-positive, HER2-negative, untreated early breast cancer.

METHODS

In this open-label, randomised, controlled, phase 2 study, postmenopausal women were eligible if they were aged 18 years or older; had clinical T stage (cT)1c to cT4a-c (≥1·5 cm within cT1c) oestrogen receptor-positive, HER2-negative, untreated early breast cancer; an Eastern Cooperative Oncology Group performance status of 0-1; and baseline Ki67 score of at least 5%. The study was conducted at 59 hospital or clinic sites in 11 countries globally. Participants were randomly assigned (1:1) to giredestrant 30 mg oral daily or anastrozole 1 mg oral daily on days 1-14 (window-of-opportunity phase) via an interactive web-based system with permuted-block randomisation with block size of four. Randomisation was stratified by cT stage, baseline Ki67 score, and progesterone receptor status. A 16-week neoadjuvant phase comprised the same regimen plus palbociclib 125 mg oral daily on days 1-21 of a 28-day cycle, for four cycles. The primary endpoint was geometric mean relative Ki67 score change from baseline to week 2 in patients with complete central Ki67 scores at baseline and week 2 (window-of-opportunity phase). Safety was assessed in all patients who received at least one dose of study drug. The study is registered with ClinicalTrials.gov (NCT04436744) and is complete.

FINDINGS

Between Sept 4, 2020, and June 22, 2021, 221 patients were enrolled and randomly assigned to the giredestrant plus palbociclib group (n=112; median age 62·0 years [IQR 57·0-68·5]) or anastrozole plus palbociclib group (n=109; median age 62·0 [57·0-67·0] years). 15 (7%) of 221 patients were Asian, three (1%) were Black or African American, 194 (88%) were White, and nine (4%) were unknown races. At data cutoff for the primary analysis (July 19, 2021), the geometric mean relative reduction of Ki67 from baseline to week 2 was -75% (95% CI -80 to -70) with giredestrant and -67% (-73 to -59) with anastrozole (p=0·043), meeting the primary endpoint. At the final analysis (data cutoff Nov 24, 2021), the most common grade 3-4 adverse events were neutropenia (29 [26%] of 112 in the giredestrant plus palbociclib group vs 29 [27%] of 109 in the anastrozole plus palbociclib group) and decreased neutrophil count (17 [15%] vs 16 [15%]). Serious adverse events occurred in five (4%) patients in the giredestrant plus palbociclib group and in two (2%) patients in the anastrozole plus palbociclib group. There were no treatment-related deaths. One patient died due to an adverse event in the giredestrant plus palbociclib group (myocardial infarction).

INTERPRETATION

Giredestrant offers encouraging anti-proliferative and anti-tumour activity and was well tolerated, both as a single agent and in combination with palbociclib. Results justify further investigation in ongoing trials.

FUNDING

F Hoffmann-La Roche.

Pretreatment endocrine symptoms and recurrence-free survival among young premenopausal patients with breast cancer: a prospective cohort study

Background

Pretreatment endocrine symptoms in premenopausal patients might be considered as a potential marker of poor prognosis. We conducted a cohort study to evaluate the association between endocrine symptoms prior to treatment and recurrence-free survival (RFS) among premenopausal patients with breast cancer aged ⩽40 years.

Methods

Data were obtained from a prospective cohort study (NCT03131089) conducted at the Samsung Medical Center from 2013 to 2021. We included patients aged ⩽40 years who had been diagnosed with breast cancer. The primary outcome measure was RFS. Endocrine symptoms were measured using the Functional Assessment of Cancer Therapy - Endocrine Symptoms (FACT-ES). We also calculated the hazard ratio (HR) for recurrence or all-cause mortality by comparing the tertiles of the FACT-ES score at diagnosis.

Results

Among the 977 participants, the mean (standard deviation) age was 35.3 (3.9) years. At diagnosis, 17.2% of the patients had at least one severe endocrine symptom. During 3512 person-years of follow-up, the high symptom group had a worse RFS than the low-symptom group [HR = 2.05; 95% confidence interval (CI) = 1.19-3.54]. In particular, hot flashes (HR = 5.59; 95% CI = 1.96-15.93) and breast sensitivity (HR = 1.82; 95% CI = 1.00-3.32) were associated with reduced RFS.

Conclusion

Close monitoring of pretreatment endocrine symptoms may be important in patients diagnosed with breast cancer at a young age.

Longitudinal multi-omics study of palbociclib resistance in HR-positive/HER2-negative metastatic breast cancer

BACKGROUND

Cyclin-dependent kinase 4/6 inhibitor (CDK4/6) therapy plus endocrine therapy (ET) is an effective treatment for patients with hormone receptor-positive/human epidermal receptor 2-negative metastatic breast cancer (HR+/HER2- MBC); however, resistance is common and poorly understood. A comprehensive genomic and transcriptomic analysis of pretreatment and post-treatment tumors from patients receiving palbociclib plus ET was performed to delineate molecular mechanisms of drug resistance.

METHODS

Tissue was collected from 89 patients with HR+/HER2- MBC, including those with recurrent and/or metastatic disease, receiving palbociclib plus an aromatase inhibitor or fulvestrant at Samsung Medical Center and Seoul National University Hospital from 2017 to 2020. Tumor biopsy and blood samples obtained at pretreatment, on-treatment (6 weeks and/or 12 weeks), and post-progression underwent RNA sequencing and whole-exome sequencing. Cox regression analysis was performed to identify the clinical and genomic variables associated with progression-free survival.

RESULTS

Novel markers associated with poor prognosis, including genomic scar features caused by homologous repair deficiency (HRD), estrogen response signatures, and four prognostic clusters with distinct molecular features were identified. Tumors with TP53 mutations co-occurring with a unique HRD-high cluster responded poorly to palbociclib plus ET. Comparisons of paired pre- and post-treatment samples revealed that tumors became enriched in APOBEC mutation signatures, and many switched to aggressive molecular subtypes with estrogen-independent characteristics. We identified frequent genomic alterations upon disease progression in RB1, ESR1, PTEN, and KMT2C.

CONCLUSIONS

We identified novel molecular features associated with poor prognosis and molecular mechanisms that could be targeted to overcome resistance to CKD4/6 plus ET.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03401359. The trial was posted on 18 January 2018 and registered prospectively.

Genomic characteristics of triple negative apocrine carcinoma: a comparison to triple negative breast cancer

Apocrine carcinoma is a rare breast cancer subtype. As such, the genomic characteristics of apocrine carcinoma with triple negative immunohistochemical results (TNAC), which has been treated as triple negative breast cancer (TNBC), have not been revealed. In this study, we evaluated the genomic characteristics of TNAC compared to TNBC with low Ki-67 (LK-TNBC). In the genetic analysis of 73 TNACs and 32 LK-TNBCs, the most frequently mutated driver gene in TNAC was TP53 (16/56, 28.6%), followed by PIK3CA (9/56, 16.1%), ZNF717 (8/56, 14.3%), and PIK3R1 (6/56, 10.71%). Mutational signature analysis showed enrichment of defective DNA mismatch repair (MMR)-related signatures (SBS6 and SBS21) and the SBS5 signature in TNAC, whereas an APOBEC activity-associated mutational signature (SBS13) was more prominent in LK-TNBC (Student's t test, p < 0.05). In intrinsic subtyping, 38.4% of TNACs were classified as luminal A, 27.4% as luminal B, 26.0% as HER2-enriched (HER2-E), 2.7% as basal, and 5.5% as normal-like. The basal subtype was the most dominant subtype (43.8%) in LK-TNBC (p < 0.001), followed by luminal B (21.9%), HER2-E (21.9%), and luminal A (12.5%). In the survival analysis, TNAC had a five-year disease-free survival (DFS) rate of 92.2% compared to 59.1% for LK-TNBC (P = 0.001) and a five-year overall survival (OS) rate of 95.3% compared to 74.6% for LK-TNBC (P = 0.0099). TNAC has different genetic characteristics and better survival outcomes than LK-TNBC. In particular, normal-like and luminal A subtypes in TNAC have much better DFS and OS than other intrinsic subtypes. Our findings are expected to impact medical practice for patients diagnosed with TNAC.

Real World Experience of Second-Line Treatment Strategies after Palbociclib and Letrozole: Overall Survival in Metastatic Hormone Receptor-Positive Human Epidermal Growth Factor Receptor 2-Negative Breast Cancer

BACKGROUND

We analyzed real-world practice of second-line treatment in hormone receptor (HR)+ human epidermal growth factor receptor-2 (HER2)- metastatic breast cancer (MBC) following the first-line CDK4/6 inhibitor with letrozole. In addition, we evaluated the relationship between second-line treatment strategies and survival outcome.

METHODS

Using the clinical data warehouse, clinical information including MBC diagnosis, treatment and survival outcomes were collected.

RESULTS

In total, 305 patients were treated with the first-line palbociclib plus letrozole, and we evaluated 166 patients who were treated with second-line treatment. Of the 166 patients, 28.5% were treated with capecitabine (C), followed by exemestane with everolimus (EE) (27.3%) or cytotoxic chemotherapy other than capecitabine (T) (18.8%) and fulvestrant-based treatment or endocrine monotherapy (F) (12.7%). Eighteen patients (10.9%) were enrolled in clinical trials (CT). With regard to treatment strategies, and the median progression-free survival of second-line treatment in a metastatic setting (PFS2) was 7.4 months with C, 5.2 months with EE, 4.8 months with T, 3.6 months with F, and 3.6 months with CT (p = 0.066). In patients with visceral organ disease progression, C (31.3%) or T(31.3%) was the most common second-line treatment followed by EE (21.9%). Most of the 47 patients with bone metastasis alone were treated with EE (38.2%), followed by C (23.4%) and F (21.3%) (p = 0.008). The median overall survival of second-line treatment in a metastatic setting (OS2) was 42.3 months with C, 35.7 months with F, 30.7 months with EE, and 23.1 months with T. The median OS2 for those in CT was not reached (p = 0.064). ER driven BC, disease progression site and PFS2 were associated with OS and OS2 in HR+HER2- MBC (ps < 0.05).

CONCLUSIONS

We suggested the second line treatment strategy was important to improve prognosis in patients with HR+/HER2- MBC, especially given the recent standardization of first-line treatment and the many available second-line options.

Progesterone Receptor Expression Level Predicts Prognosis of Estrogen Receptor-Positive/HER2-Negative Young Breast Cancer: A Single-Center Prospective Cohort Study

BACKGROUND

Although estrogen receptor (ER) expression levels affect the prognosis of breast cancer, studies about progesterone receptor (PR) expression levels are insufficient, especially in young breast cancer (YBC). The purpose of this study was to compare clinical characteristics and prognosis according to PR expression levels in invasive breast cancer patients.

METHODS

A prospective cohort study was conducted to identify YBC patients with invasive carcinoma diagnosed at an age of less than 40 years old between 2013 and 2018. Clinicopathologic features and prognosis of ER-positive and human epidermal growth factor receptor 2 (HER2)-negative patients were investigated. Patients were stratified into strong PR (PR-positive cell proportion > 10%), low PR (PR-positive cell proportion = 1~10%), and PR-negative (PR-positive cell proportion < 1%).

RESULTS

Among 458 patients enrolled, 386 (84.3%), 26 (5.7%), and 46 (10.0%) were categorized into strong PR, low PR, and PR-negative groups, respectively. The median follow-up duration was 58.6 months. Compared with the strong PR group, low PR and PR-negative groups were more likely to have high Ki-67 and a high nuclear grade. Low R and PR-negative groups had significantly worse disease-free survival (DFS) and distant metastasis-free survival (DMFS) than the strong PR group (p = 0.0033, p = 0007). Low PR group had an even higher risk of distant metastasis than PR-negative patients. Low PR patients and PR-negative had significantly lower overall survival (OS) rates than strong PR.

CONCLUSION

Low PR might be a prognostic factor of ER-positive/HER2-negative in YBC.

Genomic analysis of plasma circulating tumor DNA in patients with heavily pretreated HER2 + metastatic breast cancer

We explored accumulated genomic alterations in patients with heavily treated HER2 + metastatic breast cancer enrolled in the KCSG BR18-14/KM10B trial. Targeted sequencing was performed with circulating tumor DNAs (ctDNAs) collected before the treatment of 92 patients. ctDNAs collected at the time of disease progression from seven patients who had a durable response for > 12 months were also analyzed. Sixty-five genes were identified as pathogenic alterations in 99 samples. The most frequently altered genes were TP53 (n = 48), PIKCA (n = 21) and ERBB3 (n = 19). TP53 and PIK3CA mutations were significantly related with shorter progression free survival (PFS), and patients with a higher ctDNA fraction showed a worse PFS. The frequency of homologous recombination deficiency (HRD)-related gene mutations was higher than that in matched tumor tissues, and these mutations tended to be associated with shorter PFS. New pathogenic variants were found at the end of treatment in all seven patients, including BRCA2, VHL, RAD50, RB1, BRIP1, ATM, FANCA, and PIK3CA mutations. In conclusion, TP53 and PIK3CA mutations, as well as a higher ctDNA fraction, were associated with worse PFS with trastuzumab and cytotoxic chemotherapy. The enrichment of HRD-related gene mutations and newly detected variants in ctDNA may be related to resistance to treatment.

Integrative analysis of risk factors for immune-related adverse events of checkpoint blockade therapy in cancer

Immune-related adverse events (irAEs) induced by checkpoint inhibitors involve a multitude of different risk factors. Here, to interrogate the multifaceted underlying mechanisms, we compiled germline exomes and blood transcriptomes with clinical data, before and after checkpoint inhibitor treatment, from 672 patients with cancer. Overall, irAE samples showed a substantially lower contribution of neutrophils in terms of baseline and on-therapy cell counts and gene expression markers related to neutrophil function. Allelic variation of HLA-B correlated with overall irAE risk. Analysis of germline coding variants identified a nonsense mutation in an immunoglobulin superfamily protein, TMEM162. In our cohort and the Cancer Genome Atlas (TCGA) data, TMEM162 alteration was associated with higher peripheral and tumor-infiltrating B cell counts and suppression of regulatory T cells in response to therapy. We developed machine learning models for irAE prediction, validated using additional data from 169 patients. Our results provide valuable insights into risk factors of irAE and their clinical utility.

Pan-Asian adapted ESMO Clinical Practice Guidelines for the diagnosis, staging and treatment of patients with metastatic breast cancer

The most recent version of the European Society for Medical Oncology (ESMO) Clinical Practice Guidelines for the diagnosis, staging and treatment of patients with metastatic breast cancer (MBC) was published in 2021. A special, hybrid guidelines meeting was convened by ESMO and the Korean Society of Medical Oncology (KSMO) in collaboration with nine other Asian national oncology societies in May 2022 in order to adapt the ESMO 2021 guidelines to take into account the differences associated with the treatment of MBC in Asia. These guidelines represent the consensus opinions reached by a panel of Asian experts in the treatment of patients with MBC representing the oncological societies of China (CSCO), India (ISMPO), Indonesia (ISHMO), Japan (JSMO), Korea (KSMO), Malaysia (MOS), the Philippines (PSMO), Singapore (SSO), Taiwan (TOS) and Thailand (TSCO). The voting was based on the best available scientific evidence and was independent of drug access or practice restrictions in the different Asian countries. The latter were discussed when appropriate. The aim of these guidelines is to provide guidance for the harmonisation of the management of patients with MBC across the different regions of Asia, drawing from data provided by global and Asian trials whilst at the same time integrating the differences in genetics, demographics and scientific evidence, together with restricted access to certain therapeutic strategies.

Capivasertib in Hormone Receptor-Positive Advanced Breast Cancer

BACKGROUND

AKT pathway activation is implicated in endocrine-therapy resistance. Data on the efficacy and safety of the AKT inhibitor capivasertib, as an addition to fulvestrant therapy, in patients with hormone receptor-positive advanced breast cancer are limited.

METHODS

In a phase 3, randomized, double-blind trial, we enrolled eligible pre-, peri-, and postmenopausal women and men with hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer who had had a relapse or disease progression during or after treatment with an aromatase inhibitor, with or without previous cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitor therapy. Patients were randomly assigned in a 1:1 ratio to receive capivasertib plus fulvestrant or placebo plus fulvestrant. The dual primary end point was investigator-assessed progression-free survival assessed both in the overall population and among patients with AKT pathway-altered (PIK3CA, AKT1, or PTEN) tumors. Safety was assessed.

RESULTS

Overall, 708 patients underwent randomization; 289 patients (40.8%) had AKT pathway alterations, and 489 (69.1%) had received a CDK4/6 inhibitor previously for advanced breast cancer. In the overall population, the median progression-free survival was 7.2 months in the capivasertib-fulvestrant group, as compared with 3.6 months in the placebo-fulvestrant group (hazard ratio for progression or death, 0.60; 95% confidence interval [CI], 0.51 to 0.71; P<0.001). In the AKT pathway-altered population, the median progression-free survival was 7.3 months in the capivasertib-fulvestrant group, as compared with 3.1 months in the placebo-fulvestrant group (hazard ratio, 0.50; 95% CI, 0.38 to 0.65; P<0.001). The most frequent adverse events of grade 3 or higher in patients receiving capivasertib-fulvestrant were rash (in 12.1% of patients, vs. in 0.3% of those receiving placebo-fulvestrant) and diarrhea (in 9.3% vs. 0.3%). Adverse events leading to discontinuation were reported in 13.0% of the patients receiving capivasertib and in 2.3% of those receiving placebo.

CONCLUSIONS

Capivasertib-fulvestrant therapy resulted in significantly longer progression-free survival than treatment with fulvestrant alone among patients with hormone receptor-positive advanced breast cancer whose disease had progressed during or after previous aromatase inhibitor therapy with or without a CDK4/6 inhibitor. (Funded by AstraZeneca and the National Cancer Institute; CAPItello-291 ClinicalTrials.gov number, NCT04305496.).

Trastuzumab deruxtecan versus treatment of physician's choice in patients with HER2-positive metastatic breast cancer (DESTINY-Breast02): a randomised, open-label, multicentre, phase 3 trial

BACKGROUND

In the single-arm, phase 2 DESTINY-Breast01 trial, trastuzumab deruxtecan showed robust activity in patients with HER2-positive metastatic breast cancer who were refractory or resistant to trastuzumab emtansine; a population with scarce effective treatments. In DESTINY-Breast02, we aimed to compare the efficacy and safety of trastuzumab deruxtecan with treatment of physician's choice in this patient population.

METHODS

This randomised, open-label, multicentre, phase 3 trial was conducted at 227 sites (hospitals, university hospitals, clinics, community centres, and private oncology centres) in North America, Europe, Asia, Australia, Brazil, Israel, and Türkiye. Eligible patients were aged 18 years or older, had unresectable or HER2-positive metastatic breast cancer, previously received trastuzumab emtansine, disease progression, an Eastern Cooperative Oncology Group performance status of 0 or 1, and adequate renal and hepatic function. Patients were randomly assigned (2:1) to receive trastuzumab deruxtecan (intravenously at 5·4 mg/kg once every 3 weeks) or treatment of physician's choice using block randomisation. Treatment of physician's choice was either capecitabine (1250 mg/m2; orally twice per day on days 1-14) plus trastuzumab (8 mg/kg intravenously on day 1 then 6 mg/kg once per day) or capecitabine (1000 mg/m2) plus lapatinib (1250 mg orally once per day on days 1-21), with a 21-day schedule. The primary endpoint was progression-free survival based on blinded independent central review in the full analysis set. This study is registered with ClinicalTrials.gov, NCT03523585.

FINDINGS

Between Sept 6, 2018, and Dec 31, 2020, 608 patients were randomly assigned to receive trastuzumab deruxtecan (n=406; two did not receive treatment) or treatment of physician's choice (n=202; seven did not receive treatment). 608 (100%) patients were included in the full analysis set. The median age was 54·2 years (IQR 45·5-63·4) in the trastuzumab deruxtecan group and 54·7 years (48·0-63·0) in the treatment of physician's choice group. 384 (63%) patients were White, 603 (99%) were female, and five (<1%) were male. The median follow-up was 21·5 months (IQR 15·2-28·4) in the trastuzumab deruxtecan group and 18·6 months (8·8-26·0) in the treatment of physician's choice group. Median progression-free survival by blinded independent central review was 17·8 months (95% CI 14·3-20·8) in the trastuzumab deruxtecan group versus 6·9 months (5·5-8·4) in the treatment of physician's choice group (HR 0·36 [0·28-0·45]; p<0·0001). The most common treatment-emergent adverse events were nausea (293 [73%] of 404 with trastuzumab deruxtecan vs 73 [37%] of 195 with treatment of physician's choice), vomiting (152 [38%] vs 25 [13%]), alopecia (150 [37%] vs eight [4%]), fatigue (147 [36%] vs 52 [27%]), diarrhoea (109 [27%] vs 105 [54%]), and palmar-plantar erythrodysaesthesia (seven [2%] vs 100 [51%]). Grade 3 or higher treatment-emergent adverse events occurred in 213 (53%) patients receiving trastuzumab deruxtecan versus 86 (44%) receiving treatment of physician's choice; whereas drug-related interstitial lung disease occurred in 42 (10%; including two grade 5 death events) versus one (<1%).

INTERPRETATION

DESTINY-Breast02 shows the favourable benefit-risk profile of trastuzumab deruxtecan in patients with HER2 positive metastatic breast cancer, as previously reported in DESTINY-Breast01, and is the first randomised study to show that one antibody-drug conjugate can overcome resistance to a previous one.

FUNDING

Daiichi Sankyo and AstraZeneca.

Diagnostic Value of FDG PET/CT in Surveillance after Curative Resection of Breast Cancer

With increasing incidence of breast cancer and improvement in treatment, the concern about surveillance management also has increased. This retrospective study was designed to evaluate the diagnostic value of routine surveillance FDG PET/CT in patients with breast cancer. The diagnostic performance of surveillance PET/CT was analyzed regarding sensitivity, specificity, positive predictive value, negative predictive value and accuracy. The diagnostic accuracy was defined as the ability to differentiate recurrence and no-disease correctly and the proportion of true results, either true positive or true negative, in the population. Findings from pathologic examination; other imaging modalities such as CT, MRI and bone scan; or clinical follow-up were used as the reference standard. In this study of 1681 consecutive patients with breast cancer who underwent curative surgery, surveillance fluorodeoxyglucose PET/CT showed good diagnostic performance in the detection of clinically unexpected recurrent breast cancer or other malignancy, with a sensitivity of 100%, specificity of 98.5%, positive predictive value of 70.5%, negative predictive value of 100% and accuracy of 98.5%. In conclusion, surveillance fluorodeoxyglucose PET/CT showed good diagnostic performance in the detection of clinically unexpected recurrent breast cancer after curative surgery.

Comparison of initial and sequential salvage brain-directed treatment in patients with 1-4 vs. 5-10 brain metastases from breast cancer (KROG 16-12)

PURPOSE

We aimed to compare the initial and salvage brain-directed treatment and overall survival (OS) between patients with 1-4 brain metastases (BMs) and those with 5-10 from breast cancer (BC). We also organized a decision tree to select the initial whole-brain radiotherapy (WBRT) for these patients.

METHODS

Between 2008 and 2014, 471 patients were diagnosed with 1-10 BMs. They were divided into two groups based on the number of BM: 1-4 BMs (n = 337) and 5-10 BMs (n = 134). Median follow-up duration was 14.0 months.

RESULTS

Stereotactic radiosurgery (SRS)/fractionated stereotactic radiotherapy (FSRT) was the most common treatment modality (n = 120, 36%) in the 1-4 BMs group. In contrast, 80% (n = 107) of patients with 5-10 BMs were treated with WBRT. The median OS of the entire cohort, 1-4 BMs, and 5-10 BMs was 18.0, 20.9, and 13.9 months, respectively. In the multivariate analysis, the number of BM and WBRT were not associated with OS, whereas triple-negative BC and extracranial metastasis decreased OS. Physicians determined the initial WBRT based on four variables in the following order: number and location of BM, primary tumor control, and performance status. Salvage brain-directed treatment (n = 184), mainly SRS/FSRT (n = 109, 59%), prolonged OS by a median of 14.3 months.

CONCLUSION

The initial brain-directed treatment differed notably according to the number of BM, which was chosen based on four clinical factors. In patients with ≤ 10 BMs, the number of BM and WBRT did not affect OS. The major salvage brain-directed treatment modality was SRS/FSRT and increased OS.

Prognostic Impact of Elevation of Cancer Antigen 15-3 (CA15-3) in Patients With Early Breast Cancer With Normal Serum CA15-3 Level

PURPOSE

Cancer antigen 15-3 (CA15-3) is a serum tumor marker for breast cancer (BC) extensively used in clinical practice. CA15-3 is non-invasive, easily available, and a cost-effective tumor marker for immediate diagnosis, monitoring and prediction of BC recurrence. We hypothesized that an elevation of CA15-3 may have prognostic impact in patients with early BC with normal serum CA15-3 level.

METHODS

This was a retrospective cohort study, which included patients with BC who received curative surgery at a comprehensive single institution between 2000 and 2016. CA15-3 levels from 0 to 30 U/mL were considered normal, and patients who had CA15-3 > 30 U/mL, were excluded from the study.

RESULTS

The mean age of study participants (n = 11,452) was 49.3 years. The proportion of participants with elevated CA15-3 ≥ 1 standard deviation (SD) compared with the previous examination during follow-up was 23.3% (n = 2,666). During the follow-up (median follow-up 5.8 years), 790 patients experienced recurrence. The fully-adjusted hazard ratio (HR) for recurrence comparing participants with stable CA15-3 level to subjects with elevated CA15-3 level was 1.76 (95% confidence interval [CI], 1.52-2.03). In addition, if the CA15-3 was elevated ≥ 1 SD, the risk was much higher (HR, 6.87; 95% CI, 5.81-8.11) than in patients without elevated CA15-3 ≥ 1 SD. In sensitivity analysis, the recurrence risk was consistently higher in participants with elevated CA15-3 levels than in participants without elevated CA15-3 levels. The association between elevated CA15-3 levels and incidence of recurrence was observed in all subtypes and the association was stronger in patients with N+ than in patients with N0 stage (p-value for interaction < 0.01).

CONCLUSION

The results of the present study demonstrated that elevation of CA15-3 in patients with early BC and initial normal serum CA15-3 levels has a prognostic impact.

Abstract 2054: Whole-genome sequencing based homologous recombination deficiency testing for precision oncology of breast cancers

Breast cancers (BCs) with defects in homologous recombination repair (HRR) pathway depend on the Poly (ADP-ribose) polymerase enzymes (PARP) for their survival and thus are sensitive to PARP inhibitors (PARPi). To screen out BCs with homologous recombination deficiency (HRD), germline mutations in BRCA genes have been tested, which constitute approximately 5% of unselected BC patients. However, a substantial proportion of BCs show HRD phenotypes despite the absence of BRCA inactivating mutations in germline. Herein, we apply whole-genome sequencing (WGS) and whole-transcriptome sequencing (WTS) in 332 samples from 325 BC patients for characterizing their HRD phenotypes for PARPi treatments. Of 325 BC patients, 75 cases (23.1%) showed remarkable HRD phenotypes, based on mutational signatures of HRR abrogation. Intriguingly, 51 cases do not harbor any germline mutations in HR-related genes including BRCA1 and BRCA2. The whole-genome portrait of these samples was similar to that of HRD-positive BCs with

germline mutation in HRR pathway, but showed markedly distinctive features from HRD-negative BCs. With a notable exception of BRCA1, the second most common somatic mutation in HRD-positive BCs without germline mutation, the mutational landscape of the whole study samples was primarily determined by hormone receptor and HER2 positivity, not by HRD status. Likewise, WTS-based clusters determined in an unsupervised manner were highly dependent on the histological subtype of BC, not on HRD status or germline mutations in the HRR pathway. Notably, differentially expressed gene and gene set enrichment analysis revealed that HRD-positive BCs had an increased inflammatory activity compared to BCs with proficient HR. Overall, our analysis demonstrate that WGS enables better classification of the HR status in BC than conventional BRCA germline testing, suggesting WGS as a rapid and sensitive tool for screening breast cancers for PARPi treatment.

Citation Format: Ryul Kim, Seongyeol Park, Joonoh Lim, Boram Yi, Jaemo Koo, Sangmoon Lee, Jeong Seok Lee, Yeon Hee Park, Young Seok Ju. Whole-genome sequencing based homologous recombination deficiency testing for precision oncology of breast cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2054.

Abstract 239: Whole-genome sequencing based homologous recombination deficiency testing for precision oncology of breast cancers

Breast cancers (BCs) with defects in homologous recombination repair (HRR) pathway depend on the Poly (ADP-ribose) polymerase enzymes (PARP) for their survival and thus are sensitive to PARP inhibitors (PARPi). To screen out BCs with homologous recombination deficiency (HRD), germline mutations in BRCA genes have been tested, which constitute approximately 5% of unselected BC patients. However, a substantial proportion of BCs show HRD phenotypes despite the absence of BRCA inactivating mutations in germline. Herein, we apply whole-genome sequencing (WGS) and whole-transcriptome sequencing (WTS) in 332 samples from 325 BC patients for characterizing their HRD phenotypes for PARPi treatments. Of 325 BC patients, 75 cases (23.1%) showed remarkable HRD phenotypes, based on mutational signatures of HRR abrogation. Intriguingly, 51 cases do not harbor any germline mutations in HR-related genes including BRCA1 and BRCA2. The whole-genome portrait of these samples was similar to that of HRD-positive BCs with germline mutation in HRR pathway, but showed markedly distinctive features from HRD-negative BCs. With a notable exception of BRCA1, the second most common somatic mutation in HRD-positive BCs without germline mutation, the mutational landscape of the whole study samples was primarily determined by hormone receptor and HER2 positivity, not by HRD status. Likewise, WTS-based clusters determined in an unsupervised manner were highly dependent on the histological subtype of BC, not on HRD status or germline mutations in the HRR pathway. Notably, differentially expressed gene and gene set enrichment analysis revealed that HRD-positive BCs had an increased inflammatory activity compared to BCs with proficient HR. Overall, our analysis demonstrate that WGS enables better classification of the HR status in BC than conventional BRCA germline testing, suggesting WGS as a rapid and sensitive tool for screening breast cancers for PARPi treatment.

Citation Format: Ryul Kim, Seongyeol Park, Joonoh Lim, Boram Yi, Jaemo Koo, Sangmoon Lee, Jeong Seok Lee, Yeon Hee Park, Young Seok Ju. Whole-genome sequencing based homologous recombination deficiency testing for precision oncology of breast cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 239.

Preliminary Attainability Assessment of Real-World Data for Answering Major Clinical Research Questions in Breast Cancer Brain Metastasis: Framework Development and Validation Study

BACKGROUND

In recent decades, real-world evidence (RWE) in oncology has rapidly gained traction for its potential to answer clinical questions that cannot be directly addressed by randomized clinical trials. Integrating real-world data (RWD) into clinical research promises to contribute to more sustainable research designs, including extension, augmentation, enrichment, and pragmatic designs. Nevertheless, clinical research using RWD is still limited because of concerns regarding the shortage of best practices for extracting, harmonizing, and analyzing RWD. In particular, pragmatic screening methods to determine whether the content of a data source is sufficient to answer the research questions before conducting the research with RWD have not yet been established.

OBJECTIVE

We examined the PAR (Preliminary Attainability Assessment of Real-World Data) framework and assessed its utility in breast cancer brain metastasis (BCBM), which has an unmet medical need for data attainability screening at the preliminary step of observational studies that use RWD.

METHODS

The PAR framework was proposed to assess data attainability from a particular data source during the early research process. The PAR framework has four sequential stages, starting with clinical question clarification: (1) operational definition of variables, (2) data matching (structural/semantic), (3) data screening and extraction, and (4) data attainability diagramming. We identified 5 clinical questions to be used for PAR framework evaluation through interviews and validated them with a survey of breast cancer experts. We used the Samsung Medical Center Breast Cancer Registry, a hospital-based real-time registry implemented in March 2021, leveraging the institution's anonymized and deidentified clinical data warehouse platform. The number of breast cancer patients in the registry was 45,129; it covered the period from June 1995 to December 2021. The registry consists of 24 base data marts that represent disease-specific breast cancer characteristics and care pathways. The outcomes included screening results of the clinical questions via the PAR framework and a procedural diagram of data attainability for each research question.

RESULTS

Data attainability was tested for study feasibility according to the PAR framework with 5 clinical questions for BCBM. We obtained data sets that were sufficient to conduct studies with 4 of 5 clinical questions. The research questions stratified into 3 types when we developed data fields for clearly defined research variables. In the first, only 1 question could be answered using direct data variables. In the second, the other 3 questions required surrogate definitions that combined data variables. In the third, the question turned out to be not feasible for conducting further analysis.

CONCLUSIONS

The adoption of the PAR framework was associated with more efficient preliminary clinical research using RWD from BCBM. Furthermore, this framework helped accelerate RWE generation through clinical research by enhancing transparency and reproducibility and lowering the entry barrier for clinical researchers.

Lymphocyte-activating gene 3 expression in tumor cells predicts immune checkpoint inhibitor response in triple negative breast cancer

Introduction

Immune checkpoint inhibitor (ICI) is one of the standard treatment strategies in triple negative breast cancer (TNBC). However, the benefit of ICI with chemotherapy is limited in metastatic TNBC. In this study, we evaluated the effect of PD-L1 and LAG-3 expression on tissue microenvironment of mTNBC treated with ICI.

Methods

We reviewed representative formalin-fixed paraffin embedded specimens from metastatic or archival tumor tissues of TNBCs who treated with PD-1/PD-L1 inhibitors in metastatic setting. We used the Opal multiplex Detection kit with six antibodies (anti-PD-L1, anti-LAG-3, anti-CD68, anti-panCK, anti-CD8, anti-CD107a/LAMP antibody).

Results

We evaluated the association between LAG-3+cells and survival outcome regarding CK expression. Stromal LAG-3+/CK+ and LAG-3+/CK- cells were not associated with ICI-progression free survival(PFS) (P=0.16). However, LAG-3+ cell distributions in the tumor area impacted on ICI-PFS. A high density of LAG-3+CK+ cells was associated with shorter ICI-PFS compared with low densities of both LAG-3+CK+ and LAG-3+CK- cells (1.9 vs. 3.5 months). In addition, a high density of LAG-3+CK- cells had a relatively longer ICI-PFS compared with other groups (P=0.01). In terms of total area, the pattern of densities of LAG-3+CK+ cells and LAG-3+CK- cells were similar to those in the tumor area In addition, ICI-PFS of LAG-3+CK- and LAG-3+CK+ cell densities in the total area was equal to that in the tumor area.

Discussion

In conclusion, our findings revealed tumor-intrinsic LAG-3 expression was the resistance mechanism toward PD-1/PD-L1 inhibitors in mTNBCs. Multivariate analysis also suggested that LAG-3 expression in tumor cells was an independent predictive biomarker.

Abstract P2-11-25: A 10-gene signature to predict the prognosis of early-stage triple-negative breast cancer

Background: Triple-negative breast cancer (TNBC) is highly heterogeneous cancer and the most challenging subtype of breast cancer. And its prognosis is poor compared to the other subtypes. Unlike luminal type cancers, there is no valid biomarker to predict the prognosis of patients with early TNBC. To establish an elaborate therapeutic strategy for TNBC, biomarkers that accurately predict the prognosis and response to treatment are needed. Method: 184 patients with early stage TNBC (training cohort, n = 76; validation cohort, n = 108) were enrolled. Median Follow-up period was 51.5 months (range: 4.6-230.8) for training cohort and 58.3 months (range: 6.6-99.8) for validation cohort. Of the patients in training cohort, 13 patients had recurrence or metastasis. Of the patients in validation cohort, 23 patients had recurrence or metastasis. Using a HiSeq sequencer, RNA sequencing was conducted to analyze the gene expression profiles of tumor samples from TNBC patients. Gene signature was analyzed by combination of DEGs which found in gene expression profiles. Cross validation and meta-analysis were conducted as pre-validation. Meta-analysis was conducted using CBS probePINGS. To compare gene signature and other methods, PAM 50 call and TCR diversity analysis were investigated. Statistical analyses were conducted using R language (v.3.4.3). Result: To predict prognosis of recurrence or metastasis for TNBC patients, we identified the 10-gene signature (DGKH, GADD45B, KLF7, LYST, NR6A1, PYCARD, ROBO1, SLC22A20P, SLC24A3 and SLC45A4) that stratified patients with TNBC by risk score (sensitivity = 92.31%; specificity = 92.06%; accuracy = 92.11%) and validated in a cohort of separate institutions. Meta-analysis supported the biological relevance of the 10-gene signature to well-known driving pathways in TNBC. When compared with other potential biomarkers like PAM 50 call and T-cell receptor β diversity, the 10-gene signature was the only independent factor that can predict prognosis for invasive disease-free survival in multivariate analysis. Conclusion: Our novel findings can contribute to solving the diagnostic challenges in TNBC and the 10-gene signature may serve as a novel biomarker for risk-based patient care.

Citation Format: Chang Min Kim, Kyong Hwa Park, Yun Suk Yu, Ju Won Kim, Jin Young Park, Jeong Eon Lee, Sung Hoon Sim, Bo Kyoung Seo, Jin Kyeoung Kim, Eun Sook Lee, Yeon Hee Park, Sun-Young Kong. A 10-gene signature to predict the prognosis of early-stage triple-negative breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-11-25.

Abstract PD3-01: Neoadjuvant pembrolizumab + chemotherapy vs placebo + chemotherapy followed by adjuvant pembrolizumab vs placebo for early TNBC: Post hoc analysis of adjuvant radiation therapy in the phase 3 KEYNOTE-522 study

Background: The phase 3 KEYNOTE-522 study (NCT03036488) showed that pembrolizumab (pembro) administered in combination with neoadjuvant chemotherapy (chemo) and then continued as adjuvant monotherapy resulted in statistically significant and clinically meaningful improvements in pathological complete response (pCR) and event-free survival (EFS) in patients with early triple-negative breast cancer (TNBC). In this post hoc analysis, we assessed outcomes by patterns of adjuvant radiation therapy (RT) administration.

Methods: Patients with previously untreated, nonmetastatic, stage T1c/N1-2 or T2-4/N0-2 TNBC were randomized 2:1 to pembro 200 mg Q3W or placebo, both given with 4 cycles of paclitaxel + carboplatin, then 4 cycles of doxorubicin or epirubicin + cyclophosphamide (neoadjuvant phase). After definitive surgery, patients received pembro or placebo for 9 cycles or until recurrence or unacceptable toxicity (adjuvant phase). Dual primary endpoints are pCR, defined as ypT0/Tis ypN0, and EFS. EFS and adverse events (AEs) that occurred during the adjuvant phase were examined in patient subgroups defined by receipt of adjuvant RT (yes or no) and the pattern of adjuvant RT and pembro administration, either concurrent (the last adjuvant RT exposure was after the first dose of adjuvant pembro or placebo) or sequential (the last adjuvant RT exposure was before the first dose of adjuvant pembro or placebo).

Results: Among 1174 randomized patients, 715 (60.9%) received adjuvant RT (n=454 pembro; n=261 placebo) and 459 (39.1%) did not (n=330 pembro; n=129 placebo). At data cutoff (March 23, 2021), median follow-up was similar (~38 months) in both subgroups. EFS was longer in the pembro arm compared to the placebo arm in patients who received adjuvant RT (either concurrently or sequentially) and those who did not (Table). Grade 3-5 treatment-related AE rates for pembro vs placebo were 5.9% vs 2.7% with adjuvant RT (4.9% vs 2.2% with concurrent RT; 6.8% vs 3.1% with sequential RT) and 7.5% vs 2.9% without adjuvant RT. Treatment-related AEs led to death in 2 patients (0.4%); both occurred in the pembro arm in patients who received adjuvant RT. Immune-mediated AE rates were 10.6% vs 5.0% with adjuvant RT (9.7% vs 4.4% with concurrent RT; 11.8% vs 5.7% with sequential RT) and 9.0% vs 10.0% without adjuvant RT in the two treatment arms, respectively.

Conclusion: In this post hoc analysis, the addition of pembro to neoadjuvant chemo followed by adjuvant pembro provided a clinically meaningful EFS benefit, independent of adjuvant RT administration. An EFS benefit was observed in patients who received pembro with either concurrent or sequential adjuvant RT. The addition of pembro to adjuvant RT was generally well tolerated. Similar rates of treatment-related AEs and immune-mediated AEs were seen in patients who received adjuvant RT and pembro either concurrently or sequentially, although the sample sizes are modest. These results are consistent with the therapeutic benefit seen with neoadjuvant pembro plus chemo followed by adjuvant pembro in the intention-to-treat population of patients with early TNBC randomized in KEYNOTE-522.

Table: EFS by Adjuvant RT in KEYNOTE-522

Citation Format: Heather McArthur, Javier Cortés, Rebecca Dent, Joyce O’Shaughnessy, Lajos Pusztai, Sherko Küemmel, Theodoros Foukakis, Yeon Hee Park, Rina Hui, Nadia Harbeck, Masato Takahashi, Michael Untch, Peter A. Fasching, Fatima Cardoso, Carsten Denkert, Yalin Zhu, Yu Ding, Wilbur Pan, Peter Schmid. Neoadjuvant pembrolizumab + chemotherapy vs placebo + chemotherapy followed by adjuvant pembrolizumab vs placebo for early TNBC: Post hoc analysis of adjuvant radiation therapy in the phase 3 KEYNOTE-522 study [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD3-01.

Abstract P6-01-37: Tumor microenvironment subtype influence the response of neoadjuvant chemotherapy in breast cancer

Introduction Recent transcriptome analysis developed a holistic tumor microenvironment (TME) classification platform based on immune and fibrotic markers. This TME classification had four categories, immune enriched, fibrotic (IE/F); immune enriched, non-fibrotic (IE); Fibrotic (F); and Immune Desert (D). And these four TME subtypes are a predictive biomarker to immunotherapy in multiple cancer and four subtypes have been changed during treatment. Previously our study suggested baseline immune features and dynamic immune response on-treatment were predictive of treatment outcome in BC with neoadjuvant chemotherapy (NAC). In this study, we evaluated the impact of TME classification and dynamic change of TME classification on treatment outcome in BC with NAC. Methods Early and locally advanced BCs which would be planned to receive standard NAC (four cycles of anthracycline plus cyclophosphamide and four cycles of docetaxel or docetaxel plus trastuzumab for human epidermal growth factor receptor 2[HER2+] disease or six cycles of docetaxel, carboplatin, trastuzumab and pertuzumab for HER2+ disease) followed by curative surgery. We prospectively collected tumor tissue and matched blood three times for each patients: at BC diagnosis (T1), three weeks after the first cycle of NAC (T2), and curative surgery (T3). RNASeq was performed to classify TME subtype. In terms of clinical variables, clinical stage and IHC subtype at diagnosis, pathologic complete response (pCR), distant recurrence free survival (DRFS) and overall survival (OS) were used. Generalized logistic regression was used for predicting RCB class and pCR with clinical and genomic characteristics at T1. Kaplan-Meier analysis were performed to analysis DRFS and OS. Results In total, 210 patients who were treated with scheduled NAC were enrolled. Finally, RNASeq in 240 BC tissues (T1:119, T2:91 and T3:30) were conducted from 142 patients. In 119 BCs which was performed RNASeq at T1, hormone receptor(HR)+, HER2- BC was 32 (26.9%), 29 of HR+HER2+ BC (24.4%), 18 of HR-HER2+ BC (15.1%) and 44 of triple negative BC (TNBC) (37.0%). In TME classification, immune desert (D) was most frequently observed (45.3%), followed by IE (35.3%), F (10.1%) and IE/F (9.2%). The association between BC subtype and TME subtype suggested that HR+HER2- BC was frequently categorized into D (22 of 32, 68.8%) whereas TNBC was into IE (24 of 44, 54.5%) (p&lt; 0.001). TME subtype has been dynamically changed during NAC. At T2, IE subtype was most frequently observed (27.5%) followed by D (25.3%), IE/F (24.2%) and F (23.1%). The inclination of TME change were different according to NAC response. In BC achieved pCR, IE/F subtype had increased (4 at T1 and 10 at T2) and decrease of D subtype (15 at T1 and 3 at T2). In BC with non-pCR, IE/F subtype had slightly increased at T2 (7 at T1 and 12 at T2) but there was no IE/F subtype at T3 point. Contrarily, D subtype had decreased at T2 but increased at T3 (39 at T1, 20 at T2 and 24 at T3). The impact of TME subtype was different according to pCR status. In BC with pCR, F subtype had poor prognosis in DRFS and OS compared to other subtype ([5year DRFS rate for F vs. others: 66.7% vs. 93.2%, p=0.028], [5year OS rate for F vs. others: 70.7% vs. 100%, p&lt; 0.001]). In BC without pCR, there was no different DRFS and OS according to TME subtypes. Conclusion Our data suggested that TME subtype has been changed during NAC and the subtype switching was affected by the NAC response. Moreover, TME subtype may have prognostic role in DRFS and OS according to pCR status.

Citation Format: ji-Yeon Kim, Kyunghee Park, woong-Yang Park, Jeong Eon Lee, Seok Won Kim, Seok Jin Nam, Se Kyung Lee, Yeon Hee Park. Tumor microenvironment subtype influence the response of neoadjuvant chemotherapy in breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P6-01-37.

Design of SERENA-6, a phase III switching trial of camizestrant in ESR1-mutant breast cancer during first-line treatment

ESR1 mutation (ESR1m) is a frequent cause of acquired resistance to aromatase inhibitor (AI) plus cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6i), which is a first-line therapy for hormone-receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancer (ABC). Camizestrant is a next-generation oral selective estrogen receptor degrader (SERD) that in a phase II study significantly improved progression-free survival (PFS) over fulvestrant (also a SERD) in ER+/HER2- ABC. SERENA-6 (NCT04964934) is a randomized, double-blind, phase III study evaluating the efficacy and safety of switching from an AI to camizestrant, while maintaining the same CDK4/6i, upon detection of ESR1m in circulating tumor DNA before clinical disease progression on first-line therapy for HR+/HER2- ABC. The aim is to treat ESR1m clones and extend the duration of control of ER-driven tumor growth, delaying the need for chemotherapy. The primary end point is PFS; secondary end points include chemotherapy-free survival, time to second progression event (PFS2), overall survival, patient-reported outcomes and safety.

Abstract P3-05-36: Prognostic factors in non-metastatic hormone receptor-positive HER2-negative mucinous breast cancer: an international multicentre cohort study

Background: Mucinous carcinoma is the third most common histological subtype of breast cancer after ductal and lobular carcinomas, accounting for approximately 3% of invasive breast cancers. Although considered a favourable subtype with de-escalation of treatment recommended in the National Comprehensive Cancer Network guidelines, recurrence can occur and supporting data is limited. We thus examined prognostic factors of pure mucinous breast cancer (PMBC) in an international multicentre cohort study. Methods: Patients diagnosed between January 2000 to December 2015 with hormone receptor-positive HER2-negative stage I to III PMBC, invasive ductal carcinoma (IDC) and invasive lobular carcinoma (ILC) at 6 centers in Singapore, Taiwan, Korea and Japan were evaluated. Cox proportional hazards regression analyses were used to compare relapse-free survival (RFS), distant relapse-free survival (DRFS) and overall survival (OS) by histological subtypes, and to identify prognostic factors for PMBC. Results: Of 23,105 women eligible for analysis, 20,684 had IDC, 1,475 had ILC and 946 had PMBC. The median follow-up was 6.6 years; 5-year RFS, DRFS and OS for PMBC were 94.6%, 96.5% and 98.1% respectively. On multivariable cox regression analyses, PMBC demonstrated superior RFS (hazard ratio [HR] = 0.70, 95% CI: 0.56 - 0.88), DRFS (HR = 0.69, 95% CI: 0.53 - 0.89) and OS (HR = 0.70, 95% CI: 0.52 - 0.93) compared to IDC, while ILC had comparable survival outcomes as IDC. When restricted to only PMBC, significant independent prognostic factors for RFS included ethnicity (vs Chinese, “Others” [non-Chinese/Japanese/Korean, mainly Malay and Indian]: HR = 2.62, 95% CI 1.23 – 5.57), older age (vs &lt; 40 years, &gt;70 years: HR = 3.53, 95% CI 1.67 – 7.46), tumor size (vs T1, T3-4: HR = 2.79, 95% CI 1.45 – 5.37), positive lymph nodes (HR = 2.04, 95% CI: 1.10 – 3.77), use of radiotherapy (HR = 0.54, 95% CI 0.33 – 0.91) and endocrine therapy (HR = 0.31, 95% CI 0.12 – 0.77). On further analysis, the inferior RFS, DRFS and OS in older patients (&gt;70 years) were driven largely by non-breast cancer deaths rather than relapses. Use of endocrine therapy was also associated with superior DRFS (HR = 0.26, 95% CI 0.09 – 0.73) but not OS. In a subgroup analysis, use of chemotherapy was associated with improved DRFS (HR = 0.25, 95% CI 0.08 – 0.82) and OS (HR = 0.07, 95% CI 0.01 – 0.37) with a trend in RFS (HR = 0.41, 95% CI 0.14 – 1.24) for lymph node-positive PMBC; no differences in outcomes were observed for the lymph node-negative subgroup. Conclusions: Larger tumor size, lymph node positivity and ethnicity were significant factors for RFS in PMBC. Use of endocrine therapy was associated with superior RFS and DRFS, while chemotherapy was associated with better DRFS and OS for lymph-node positive PMBC.

Citation Format: Ryan Tan, Whee Sze Ong, Kyung-Hun Lee, Seri Park, Jabed Iqbal, Yeon Hee Park, Jeong-Eon Lee, Jong Han Yu, Ching-Hung Lin, Yen-Shen Lu, Makiko Ono, Takayuki Ueno, Yoichi Naito, Tatsuya Onishi, Geok hoon Lim, Su-Ming Tan, Han-Byoel Lee, Jiwon Koh, Han Suk Ryu, Wonshik Han, Veronique Kiak Mien Tan, Fuh-Yong Wong, Seock-Ah Im, Puay Hoon Tan, Yoon-Sim Yap. Prognostic factors in non-metastatic hormone receptor-positive HER2-negative mucinous breast cancer: an international multicentre cohort study [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-05-36.

Abstract P5-06-04: The prognostic value of c-MET monitoring by using c-MET-enriched circulating tumor cells in HR-positive HER2-negative metastatic breast cancer

[Background] As the development of endocrine resistance and late recurrences are the major clinical concerns in hormone receptor (HR)-positive/HER2-negative metastatic breast cancer (MBC) patients, biomarkers to predict the occurrence of endocrine resistance or disease progression are crucial for improving patient outcomes. Aberrant HGF/c-MET signaling pathway has been reported to play a role in various cellular processes in cancer. Estrogen Receptor 1 (ESR1) mutations, encoding estrogen receptor α, are associated with endocrine resistance in HR+ breast cancer. PIK3CA hotspot mutations that induce hyperactivation of the PI3K are found in 30-40% of HR+ advanced breast cancers. In this context, we evaluated the prognostic values of c-MET-enriched CTC, ESR1 mutations, PIK3CA mutations, and cfDNA concentrations detected in the blood of HR+HER2- MBC patients. [Methods] MBC patients were prospectively enrolled during standard treatments at Samsung Medical Center (IRB No.2019-08-119). Circulating tumor cells (CTCs) were isolated using the GenoCTC® with c-MET-enriched or EpCAM-enriched CTC isolation kits (Genobio Corp., South Korea) from 4mL of blood each. PIK3CA and ESR1 hotspot mutations were analyzed by droplet digital PCR kits (Gencurix Inc., South Korea). cfDNA concentrations were calculated using ESR1 gene copy numbers from plasma. To compare the proportion of c-MET overexpression between primary breast tumors and metastatic sites in HR+HER2- breast cancer patients, primary breast (n=358) and metastatic sites (n=27) were independently collected. c-MET expression was evaluated by an immunohistochemistry assay using an anti-total c-MET (SP44) antibody with a Ventana Discovery XY automated system according to the manufacturer’s instruction. c-MET overexpression was defined if the staining was scored as 2+ or 3+. Progression-free survival (PFS) was defined as the time from blood draw to the first of either disease progression or death during standard therapy. [Results] Out of 93 patients with HR+ MBC, analysis was performed in 63 HR+HER2- MBC patients. Seventeen patients (27%) had one or more EpCAM-enriched CTCs, and fourteen patients (22%) had one or more c-MET-enriched CTCs detected in their blood. The median follow-up time and median time to censoring were 8.4 months and 18.7 months, respectively. According to the Kaplan-Meier survival analysis by log-rank test, c-MET-enriched CTCs, cfDNA concentrations, and ESR1 mutations were significantly associated with PFS (p=0.0026, 0.0064, and 0.011, respectively). However, PIK3CA mutations and EpCAM-enriched CTCs were not statistically significant with PFS (p=0.38 and 0.86, respectively). Multivariate analysis showed that both c-MET-enriched CTCs (HR=3.5, p=0.014) and cfDNA concentrations (HR=2.2, p=0.031) were independent predictors for PFS in HR+HER2- MBC. The proportion of c-MET overexpression was significantly higher in metastatic sites (22.2%) than in primary breast tumors (4.7%) in HR+HER2- breast cancer patients (p=0.00002). As c-MET-enriched CTCs and cfDNA concentrations were independent predictors of disease progression, patients were divided into two groups depending on the result of c-MET-enriched CTCs and cfDNA concentration. When patients with low c-MET-enriched CTC and cfDNA concentrations were classified as a low-risk group and other patients into a high-risk group, the high-risk group had a shorter PFS than the low-risk group (p=0.003). [Conclusion] This study provided c-MET-enriched CTCs and cfDNA concentrations calculated by ESR1 copy numbers in patient blood were significant independent predictors of disease progression in HR+HER2- MBC. The poor prognosis in the c-MET-enriched CTC-high group and the difference in the c-MET overexpression rate between the primary breast and metastatic sites suggested the importance of monitoring c-MET-enriched CTCs in the blood of HR+HER2- MBC patients.

Citation Format: Jieun Park, Eun Sol Chang, Ji-Yeon Kim, Chaithanya Chelakkot, Minjung Sung, Ji-Young Song, Kyungsoo Jung, Na Young Kim, Hyegyeong Lee, Mi-Ran Kang, Yeon Hee Park, Young Kee Shin, Yoon-La Choi. The prognostic value of c-MET monitoring by using c-MET-enriched circulating tumor cells in HR-positive HER2-negative metastatic breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-06-04.

Abstract P5-03-14: Prevalence of germline BRCA mutations in unselected Korean patients with HER2-negative breast cancer: A Prospective cohort study

Backgrounds Since OlympiAD study, National Comprehensive Cancer Network guideline recommends assessment of germline BRCA1/2 mutation in all patients with recurrent or metastatic breast cancer to identify candidates for PARP inhibitor therapy, which is not always possible in clinical practice due to limited resources for testing. Data on the prevalence of gBRCA mutation is still lacking, especially in patients with non-high risk for hereditary breast and ovarian cancer syndrome. In this study, we investigated prevalence of gBRCA mutation in unselected Korean patients with HER2-negative advanced BC in a prospective cohort and analyzed oncologic outcome. Methods Eligible patients were diagnosed with HER2-negative advanced BC and had initiated palliative systemic treatment. Peripheral blood was prospectively drawn from each patient and gBRCA mutation status was assessed by next generation sequencing using NGeneBio BRCAaccuTest®. In 100 patients, somatic mutations including BRCA1/2 from tumor tissue were investigated using targeted panel sequencing. To estimate the prevalence of gBRCA mutation with margin of error to be no more than ±4% at the 95% confidence interval in a population size of 20,000, 583 patients were to be enrolled. Results A total of 583 patients were enrolled between Oct 2019 and Mar 2022, and the prevalence of gBRCA mutation was analyzed in 570 patients, excluding ineligible patients. Median age was 54 years old (range 26-87) and 567 patients were female. 475 patients had HR+/HER2- BC and 94 patients had triple negative breast cancer (TNBC). The overall prevalence of gBRCA1/2 pathogenic mutation was 7.3% (42/570) in unselected patients. The prevalence of gBRCA1 mutation was 1.6%(9/570) overall, 0.8%(4/475) in HR+/HER2- BC, and 5.3%(5/94) in TNBC. The prevalence of gBRCA2 mutation was 5.8%(33/570) overall, 6.3%(30/475) in HR+/HER2- BC, 3.2%(3/94) in TNBC. Prevalence in low risk TNBC (&gt;60 years at first BC diagnosis, no known family history of relevant cancer and unilateral breast cancer) was 10.5% (2/19, all 2 patients had gBRCA2 mutation). Prevalence in low risk HR+/HER2- (&gt;40 years at first BC diagnosis, no known family history of relevant cancer and unilateral breast cancer) was 5.9% (18/307, 17 patients had gBRCA2 mutation). The overall prevalence of gBRCA1/2 pathogenic mutation in Korean patients with low risk HER2-negative advanced BC was 6.1%. The result of somatic mutation, treatment patterns and clinical outcome according to gBRCA1/2 mutation will be further analyzed. Conclusions The prevalence of gBRCA mutation among Korean patients with HER2-negative advanced BC classified as low risk (6.1%) in this study supports routine testing of gBRCA mutation in this population.

Citation Format: Hee Kyung Ahn, Jee Hung Kim, Mirae Kim, Seri Park, Su-Jin Koh, Joo Hyuk Sohn, Myoung Joo Kang, Kyung Hae Jung, Kyoung Eun Lee, Jieun Lee, Sung Ae Koh, Yee Soo Chae, Jae Ho Byun, In Hae Park, Hee-Jun Kim, Jee Hyun Kim, Han Jo Kim, Joo Young Jung, Jung Lim Lee, Yoon Young Cho, Kyong Hwa Park, Ji-Yeon Kim, Seock-Ah Im, Yeon Hee Park. Prevalence of germline BRCA mutations in unselected Korean patients with HER2-negative breast cancer: A Prospective cohort study [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-03-14.

Abstract P2-20-10: Prognostic impact of lymphocyte-Activation Gene-3 (LAG-3) expression in triple negative breast cancer

Introduction Recent advances in breast cancer treatment strategies have improved survival outcomes in metastatic breast cancer (mBC). Targeting immune checkpoint, especially programmed death 1 (PD-1)/programmed death ligand 1 (PD-L1), has made a breakthrough in treating advanced malignancies including breast cancer. Immune checkpoint inhibitors (ICIs), such as pembrolizumab and atezolizumab, in combination with chemotherapy have prolonged survival outcomes in mBC with triple negative subtype. However, the low response rate and resistance of ICIs with anti-PD 1/PDL-1 antibodies is a major limitation and a challenge. Lymphocyte Activation Gene-3 (LAG3; CD223) is a potential cancer immunotherapeutic target due to its negative regulatory role on T cells and cytokines, thereby ensuring immune homeostasis. Several studies suggested that combination immunotherapy of anti-LAG-3 and anti-PD-1 has shown promising efficacy in fighting PD-1 resistance. Therefore, we evaluated the prognostic role of LAG3 in metastatic TNBC (mTNBC) treated with ICIs to figure out resistance mechanism of ICIs. Methods mTNBC patients with available archival tumor tissues, who has received ICIs in Samsung Medical Center, were enrolled in this study. For the evaluation of LAG3 expression in tumor microenvironment, Vectra Polaris Multispectral Imaging and Whole Slide Scanning technique (PerkinElmer, Inc. Hopkinton, MA) was used. Results In total, 64 mTNBC patients were treated with ICI’s with or without cytotoxic chemotherapy between 2019.02- 2021.11. Of 70 mTNBC patients, 41 patients had archival tissues and finally 40 patients were included in this study. Median age was 43.0 years of age (range: 24.5 ~ 64.5). Recurrent mTNBC was 92.5% and only 7.5% was de novo mTNBC. Geremline BRCA1 pathogenic variants were detected in 4 (10.0%) patients. Among 37 recurrent mTNBC patients, 72.5% were treated with neoadjuvant chemotherapy with anthracycline (97.3%) and taxane(97.3%). Among ICI’s, 52.5% were treated with pembrolizumab and 47.5% of atezolizumab. LAG3 expression varies among mTNBC tissues (median cell density: 366, range: 48, 2861 cells/mm2). Among cells expressing LAG3, LAG3 was expressed more in CK+ cells compared with CK- cells (median:150 (20, 2503) cells/mm2 in CK+ cells, median: 88 (2, 806) cells/mm2 in CK- cells, p=0.005). Patients with high LAG3 expression in CK+ cells showed short progression free survival(PFS) compared to those with low LAG3 expression in CK+ cells (median PFS of high vs. low LAG3 expression [months]:1.9 vs. 4.2, p=0.01). On the contrary, patients with high LAG3 expression in CK- cells had 9.1 months of PFS compared to 3.1 months of PFS in patients with low LAG3 expression in CK- cells (p=0.10). In addition, patients with high LAG3 in CK- cells had longer overall survival(OS) compared to those with low LAG3 expression in CK- cells (median OS of high vs. low LAG3 expression [months]: not reached, 15.7, p=0.05). Conclusion LAG3 expression was associated with PFS in patients with mTNBC treated with ICI’s independent of PDL-1 expression. And the prognostic significance of LAG3 expression was different between CK+ cells and CK- cells. These findings need to be proved in large scale clinical trials.

Citation Format: ji-Yeon Kim, Jeehyun Kim, Hae Hyun Jung, eun Yoon Cho, Yeon Hee Park, Jin Seok Ahn, Kyoung-Mee Kim, Young-Hyuck Im. Prognostic impact of lymphocyte-Activation Gene-3 (LAG-3) expression in triple negative breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-20-10.

Abstract P4-02-27: Preliminary Attainability Assessment of Real-World Data for Answering Clinical Questions about Breast Cancer Brain Metastases

Background Brain metastases is one of breast cancer’s leading causes of death, and the incidence is increasing with advances in diagnosis and treatment techniques. Nevertheless, these patients have fewer opportunities to participate in prospective randomized clinical trials because of the design challenges of increasing target population heterogeneity or differentiating the definition of endpoints and how the endpoints are evaluated. Real-world data has the potential that reaches the information at a blinded area of RCT approaches. In recent years, observational studies using real-world data have gotten attention for their capability to enhance an understanding of hard-to-reach RCT approaches. However, the yet incomplete gold standard of the study protocol and the unpredictable ’hidden labor’ of secondary use of clinical data become barriers to clinical researchers. In the study, we demonstrate data attainability assessment focused on clinicians’ clinical unmet needs in breast cancer brain metastases (BCBM) as a preliminary step of the observational study for screening study feasibility on a certain data source.

Methods A breast cancer registry based on the clinical data warehouse (CDW) of Samsung Medical Center has been used as the data source (N=45,219, up to 31 Dec 2021). A total of 5 clinical questions (CQ) were presented as the result of the interview of two breast cancer experts about BCBM for the study (Table 1). Additionally, we conducted an attainability assessment for the population size and core variables constrained by a clinical question and a survey of 7 breast cancer clinicians for evaluation of the recognized clinical significance and research methods’ suitability for each CQ. A working group was formed for data attainability tests withal a person with experience in clinical research for at least several years across interdisciplinary areas, including clinical expertise, medical informatics, and epidemiology. For the first step, we declare the operational definition for the study population and core variables in which the research question is inherent conceptually. And appropriate data fields and value sets are figured out from the data set. Data attainability is examined via RWD extraction on the population size and availability of core variables.

Result The collected five CQs were mostly about the relationship between brain metastases, systemic metastases, and systemic treatments. Other CQs were related to the relationship between brain metastases incidence and the type of neoadjuvant treatment or patients’ described symptoms. Assessment of the importance of clinical questions aligned well, especially for the questions with higher scores. (r=- · 98) For CQ E, filtered out not to fit the SMC BCR dataset at the early stage of the data attainability screening process due to lack of explicit data field or semantically related value sets for one of the core variables, ‘neurological symptom.’ For CQ A, B, and D, we could confirm enough population size and dataset for conducting the study, but additional logical reconstruction of data elements had needed. For example, we used the ‘clinical subtype’ variable, which is provided from SMC BCR, as pre-processed feature variable using an expert-knowledge-based algorithm. For CQ C, we were able to obtain pertinent data for the study only with direct data field match and explicit code set definition.

Conclusion To effectively use CDW, the variables have to be interpreted and defined in a clinically meaningful way with the cooperation of clinicians and data science experts. For observational studies based on RWD, understanding the data source contents and clarifying the research question enough to translate to the data level is essential. The step-by-step protocol presented in the study could be applied to the other clinical researcher using RWD at preliminary feasibility screening.

Table 1. List of clinical questions from expert interviews

Citation Format: Min-Jeong Kim, Hyo Jung Kim, Danbee Kang, Hee Kyung Ahn, Soo-Yong Shin, Seri Park, Juhee Cho, Yeon Hee Park. Preliminary Attainability Assessment of Real-World Data for Answering Clinical Questions about Breast Cancer Brain Metastases [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-02-27.