Cell-free DNA concentration as a biomarker of response and recurrence in HER2-negative breast cancer receiving neoadjuvant chemotherapy

PURPOSE

We previously demonstrated the clinical significance of circulating tumor DNA (ctDNA) in patients with HER2-negative breast cancer receiving neoadjuvant chemotherapy (NAC). Here, we compared its predictive and prognostic value with cell-free DNA (cfDNA) concentration measured in the same samples from the same patients.

EXPERIMENTAL DESIGN

145 hormone receptor (HR)-positive/HER2-negative and 138 triple-negative breast cancer (TNBC) patients with ctDNA data from a previous study were included in the analysis. Associations of serial cfDNA concentration with residual cancer burden (RCB) and distant recurrence-free survival (DRFS) were examined.

RESULTS

In TNBC, we observed a modest negative correlation between cfDNA concentration 3 weeks after treatment initiation and RCB, but none of the other timepoints showed significant correlation. In contrast, ctDNA was significantly positively correlated with RCB at all timepoints (all R>0.3 and p<0.05). In the HR-positive/HER2-negative group, cfDNA concentration did not associate with response to NAC, but survival analysis showed that high cfDNA-shedders at pretreatment had a significantly worse DRFS than low shedders (hazard ratio 2.12, p=0.037). In TNBC, the difference in survival between high vs. low cfDNA-shedders at all timepoints was not statistically significant. In contrast, as previously reported, ctDNA at all timepoints was significantly correlated with DRFS in both subtypes.

CONCLUSIONS

In TNBC, cfDNA concentrations during therapy were not strongly correlated with response or prognosis. In the HR-positive/HER2-negative group, pretreatment cfDNA concentration was prognostic for DRFS. Overall, the predictive and prognostic value of cfDNA concentration was more limited than that of ctDNA.

A dedicated structured data set for reporting of invasive carcinoma of the breast in the setting of neoadjuvant therapy: recommendations from the International Collaboration on Cancer Reporting (ICCR)

AIMS

The International Collaboration on Cancer Reporting (ICCR), a global alliance of major (inter-)national pathology and cancer organisations, is an initiative aimed at providing a unified international approach to reporting cancer. ICCR recently published new data sets for the reporting of invasive breast carcinoma, surgically removed lymph nodes for breast tumours and ductal carcinoma in situ, variants of lobular carcinoma in situ and low-grade lesions. The data set in this paper addresses the neoadjuvant setting. The aim is to promote high-quality, standardised reporting of tumour response and residual disease after neoadjuvant treatment that can be used for subsequent management decisions for each patient.

METHODS

The ICCR convened expert panels of breast pathologists with a representative surgeon and oncologist to critically review and discuss current evidence. Feedback from the international public consultation was critical in the development of this data set.

RESULTS

The expert panel concluded that a dedicated data set was required for reporting of breast specimens post-neoadjuvant therapy with inclusion of data elements specific to the neoadjuvant setting as core or non-core elements. This data set proposes a practical approach for handling and reporting breast resection specimens following neoadjuvant therapy. The comments for each data element clarify terminology, discuss available evidence and highlight areas with limited evidence that need further study. This data set overlaps with, and should be used in conjunction with, the data sets for the reporting of invasive breast carcinoma and surgically removed lymph nodes from patients with breast tumours, as appropriate. Key issues specific to the neoadjuvant setting are included in this paper. The entire data set is freely available on the ICCR website.

CONCLUSIONS

High-quality, standardised reporting of tumour response and residual disease after neoadjuvant treatment are critical for subsequent management decisions for each patient.

Neoadjuvant Trebananib plus Paclitaxel-based Chemotherapy for Stage II/III Breast Cancer in the Adaptively Randomized I-SPY2 Trial-Efficacy and Biomarker Discovery

PURPOSE

The neutralizing peptibody trebananib prevents angiopoietin-1 and angiopoietin-2 from binding with Tie2 receptors, inhibiting angiogenesis and proliferation. Trebananib was combined with paclitaxel±trastuzumab in the I-SPY2 breast cancer trial.

PATIENTS AND METHODS

I-SPY2, a phase II neoadjuvant trial, adaptively randomizes patients with high-risk, early-stage breast cancer to one of several experimental therapies or control based on receptor subtypes as defined by hormone receptor (HR) and HER2 status and MammaPrint risk (MP1, MP2). The primary endpoint is pathologic complete response (pCR). A therapy "graduates" if/when it achieves 85% Bayesian probability of success in a phase III trial within a given subtype. Patients received weekly paclitaxel (plus trastuzumab if HER2-positive) without (control) or with weekly intravenous trebananib, followed by doxorubicin/cyclophosphamide and surgery. Pathway-specific biomarkers were assessed for response prediction.

RESULTS

There were 134 participants randomized to trebananib and 133 to control. Although trebananib did not graduate in any signature [phase III probabilities: Hazard ratio (HR)-negative (78%), HR-negative/HER2-positive (74%), HR-negative/HER2-negative (77%), and MP2 (79%)], it demonstrated high probability of superior pCR rates over control (92%-99%) among these subtypes. Trebananib improved 3-year event-free survival (HR 0.67), with no significant increase in adverse events. Activation levels of the Tie2 receptor and downstream signaling partners predicted trebananib response in HER2-positive disease; high expression of a CD8 T-cell gene signature predicted response in HR-negative/HER2-negative disease.

CONCLUSIONS

The angiopoietin (Ang)/Tie2 axis inhibitor trebananib combined with standard neoadjuvant therapy increased estimated pCR rates across HR-negative and MP2 subtypes, with probabilities of superiority >90%. Further study of Ang/Tie2 receptor axis inhibitors in validated, biomarker-predicted sensitive subtypes is warranted.

Protein signaling and drug target activation signatures to guide therapy prioritization: Therapeutic resistance and sensitivity in the I-SPY 2 Trial

Molecular subtyping of breast cancer is based mostly on HR/HER2 and gene expression-based immune, DNA repair deficiency, and luminal signatures. We extend this description via functional protein pathway activation mapping using pre-treatment, quantitative expression data from 139 proteins/phosphoproteins from 736 patients across 8 treatment arms of the I-SPY 2 Trial (ClinicalTrials.gov: NCT01042379). We identify predictive fit-for-purpose, mechanism-of-action-based signatures and individual predictive protein biomarker candidates by evaluating associations with pathologic complete response. Elevated levels of cyclin D1, estrogen receptor alpha, and androgen receptor S650 associate with non-response and are biomarkers for global resistance. We uncover protein/phosphoprotein-based signatures that can be utilized both for molecularly rationalized therapeutic selection and for response prediction. We introduce a dichotomous HER2 activation response predictive signature for stratifying triple-negative breast cancer patients to either HER2 or immune checkpoint therapy response as a model for how protein activation signatures provide a different lens to view the molecular landscape of breast cancer and synergize with transcriptomic-defined signatures.

Quantifying hormone receptor status in lobular breast cancer in an institutional series: the relationship between estrogen and progesterone receptor status and outcomes

PURPOSE

Recent guidelines defined a new reporting category of ER-low-positive breast cancer based on immunohistochemistry (IHC). While low positivity of either hormone receptor is uncommon in invasive lobular carcinoma (ILC), we sought to investigate whether relatively low hormone receptor positivity was associated with tumor characteristics and patient outcomes in a single institutional cohort.

METHODS

We searched an institutional database for cases of stage I-III ILC with available IHC reports. Based on prior published categories in ILC, ER was classified as low, medium, or high as defined by ER staining of 10-69%, 70-89%, and ≥ 90% respectively. PR low and high tumors were defined by < 20%, or ≥ 20% staining respectively. We used chi-squared tests, t-tests, and Cox proportional hazards models to evaluate associations between ER/PR categories and tumor characteristics or disease-free survival (DFS).

RESULTS

The cohort consisted of 707 ILC cases, with 11% of cases categorized as ER low, 15.1% as medium, and 73.8% as high. The majority (67.6%) were PR high. Patients with ER low/medium expression were significantly younger, and more likely to also have PR low and/or HER2 positive tumors compared to those that were ER high. In a Cox proportional hazards model adjusting for age, stage, grade, pleomorphic histology, and treatment, ER category was not prognostic for DFS, but PR negative and PR low status each had significantly worse DFS compared to PR high status (HR 3.5, 95% CI 1.8-6.7, p < 0.001; and HR 2.0, 95% CI 1.1-3.5, p = 0.015, respectively).

CONCLUSION

These findings highlight the relevance of quantifying ER and PR within ILC.

Pre-analytical effects on whole transcriptome and targeted RNA sequencing analysis in cytology: The effects of prolonged time in storage of effusion specimens prior to preservation

OBJECTIVES

To investigate the pre-analytics of the molecular testing of cytology specimens, we studied the effects of time in refrigerator storage (4°C) of malignant effusions on RNA sequencing (RNAseq) results.

METHODS

Ten effusion specimens were stored in a refrigerator (4°C) for different durations (day 0, 1, 4, and 7). All specimens were prepared as cytospins fixed in either Carnoy's solution or 95% ethanol (EtOH) and in an RNA preservative for a fresh frozen (FF) high-quality reference. Whole transcriptome (wt) and targeted (t)RNAseq of two multigene expression signatures were performed. We then compared transcript expression levels (including mutant allele fraction) according to pre-analytical variables using a concordance correlation coefficient (CCC) and a mixed effect model.

RESULTS

Sequencing results were mostly stable over increasing time in storage. Cytospins fixed in Carnoy's solution were more concordant with FF samples than cytospins fixed in 95% EtOH at all timepoints. This finding was consistent for both wtRNAseq (averages: day 0 CCC = 0.98 vs 0.91; day 7 CCC = 0.88 vs 0.78) and tRNAseq methods (averages: day 0 CCC = 0.98 vs 0.81; day 7 CCC = 0.98 vs 0.90). Cytospins fixed in Carnoy's solution did not show significant changes in expression over timepoints or between expression signatures, whereas 95% EtOH did.

CONCLUSION

RNAseq can be accurately performed on effusion specimens after prolonged refrigerator storage. RNA extracted from scraped cytospin slides fixed in Carnoy's solution was marginally superior to 95% EtOH fixation, but either method had comparable analytic performance to high-quality FF RNA samples.

Clinical significance and biology of circulating tumor DNA in high-risk early-stage HER2-negative breast cancer receiving neoadjuvant chemotherapy

Circulating tumor DNA (ctDNA) analysis may improve early-stage breast cancer treatment via non-invasive tumor burden assessment. To investigate subtype-specific differences in the clinical significance and biology of ctDNA shedding, we perform serial personalized ctDNA analysis in hormone receptor (HR)-positive/HER2-negative breast cancer and triple-negative breast cancer (TNBC) patients receiving neoadjuvant chemotherapy (NAC) in the I-SPY2 trial. ctDNA positivity rates before, during, and after NAC are higher in TNBC than in HR-positive/HER2-negative breast cancer patients. Early clearance of ctDNA 3 weeks after treatment initiation predicts a favorable response to NAC in TNBC only. Whereas ctDNA positivity associates with reduced distant recurrence-free survival in both subtypes. Conversely, ctDNA negativity after NAC correlates with improved outcomes, even in patients with extensive residual cancer. Pretreatment tumor mRNA profiling reveals associations between ctDNA shedding and cell cycle and immune-associated signaling. On the basis of these findings, the I-SPY2 trial will prospectively test ctDNA for utility in redirecting therapy to improve response and prognosis.

HER-2 low status in early-stage invasive lobular carcinoma of the breast: associated factors and outcomes in an institutional series

PURPOSE

HER2 overexpression has a central role in breast cancer carcinogenesis and is associated with poor prognosis if untreated. Lately, identification of HER2-low breast cancer has been proposed to select patients for novel HER2-directed chemotherapy and includes cancers with immunohistochemistry 1 + or 2 + with negative FISH, encompassing approximately 55-60% of all breast carcinomas. In early-stage breast cancer, the prognostic significance of HER2 low-disease is less well understood, with a particular paucity of data evaluating the prevalence and implications of HER2-low status in invasive lobular carcinoma (ILC).

METHODS

We evaluated 666 stage I-III ILC tumors from a prospectively maintained institutional database, comparing clinicopathologic features and disease-free survival (DFS) using a multivariable Cox proportional hazards model.

RESULTS

HER2-low status was common in this cohort of patients with ILC, but most clinicopathologic features did not differ between HER2-low and HER2-negative cases. However, when adjusting for tumor size, number of positive nodes, ER/PR status, and local therapy received, patients with HER2-low status had worse disease-free survival (DFS) than those with HER2-negative tumors (hazard ratio 2.0, 95% confidence interval 1.0-4.1, p = 0.05).

CONCLUSION

This difference in DFS supports the notion that HER2-low and HER2-negative early stage ILC may differ clinically, despite similar clinicopathologic features. Further investigation into the potential benefit of HER2 targeted therapy in HER2-low early-stage breast cancer, and specifically lobular cancer, is warranted to ensure optimal outcomes in this distinct tumor subtype.

Simple combination of multiple somatic variant callers to increase accuracy

Publications comparing variant caller algorithms present discordant results with contradictory rankings. Caller performances are inconsistent and wide ranging, and dependent upon input data, application, parameter settings, and evaluation metric. With no single variant caller emerging as a superior standard, combinations or ensembles of variant callers have appeared in the literature. In this study, a whole genome somatic reference standard was used to derive principles to guide strategies for combining variant calls. Then, manually annotated variants called from the whole exome sequencing of a tumor were used to corroborate these general principles. Finally, we examined the ability of these principles to reduce noise in targeted sequencing.

A phase II study of neoadjuvant atezolizumab and nab-paclitaxel in patients with anthracycline-resistant early-stage triple-negative breast cancer

PURPOSE

Neoadjuvant anti-PD-(L)1 therapy improves the pathological complete response (pCR) rate in unselected triple-negative breast cancer (TNBC). Given the potential for long-term morbidity from immune-related adverse events (irAEs), optimizing the risk-benefit ratio for these agents in the curative neoadjuvant setting is important. Suboptimal clinical response to initial neoadjuvant therapy (NAT) is associated with low rates of pCR (2-5%) and may define a patient selection strategy for neoadjuvant immune checkpoint blockade. We conducted a single-arm phase II study of atezolizumab and nab-paclitaxel as the second phase of NAT in patients with doxorubicin and cyclophosphamide (AC)-resistant TNBC (NCT02530489).

METHODS

Patients with stage I-III, AC-resistant TNBC, defined as disease progression or a < 80% reduction in tumor volume after 4 cycles of AC, were eligible. Patients received atezolizumab (1200 mg IV, Q3weeks × 4) and nab-paclitaxel (100 mg/m² IV,Q1 week × 12) as the second phase of NAT before undergoing surgery followed by adjuvant atezolizumab (1200 mg IV, Q3 weeks, × 4). A two-stage Gehan-type design was employed to detect an improvement in pCR/residual cancer burden class I (RCB-I) rate from 5 to 20%.

RESULTS

From 2/15/2016 through 1/29/2021, 37 patients with AC-resistant TNBC were enrolled. The pCR/RCB-I rate was 46%. No new safety signals were observed. Seven patients (19%) discontinued atezolizumab due to irAEs.

CONCLUSION

This study met its primary endpoint, demonstrating a promising signal of activity in this high-risk population (pCR/RCB-I = 46% vs 5% in historical controls), suggesting that a response-adapted approach to the utilization of neoadjuvant immunotherapy should be considered for further evaluation in a randomized clinical trial.

Response to Neoadjuvant Therapy and Long-Term Survival in Patients With Triple-Negative Breast Cancer

PURPOSE

Triple-negative breast cancer (TNBC) is defined by the lack of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER-2) expression. In this study, we compared response to neoadjuvant chemotherapy and survival between patients with TNBC and non-TNBC.

PATIENTS AND METHODS

Analysis of a prospectively collected clinical database was performed. We included 1,118 patients who received neoadjuvant chemotherapy at M.D. Anderson Cancer Center for stage I-III breast cancer from 1985 to 2004 and for whom complete receptor information were available. Clinical and pathologic parameters, pathologic complete response rates (pCR), survival measurements, and organ-specific relapse rates were compared between patients with TNBC and non-TNBC.

RESULTS

Two hundred fifty-five patients (23%) had TNBC. Patients with TNBC compared with non-TNBC had significantly higher pCR rates (22% v 11%; P = .034), but decreased 3-year progression-free survival rates (P < .0001) and 3-year overall survival (OS) rates (P < .0001). TNBC was associated with increased risk for visceral metastases (P = .0005), lower risk for bone recurrence (P = .027), and shorter postrecurrence survival (P < .0001). Recurrence and death rates were higher for TNBC only in the first 3 years. If pCR was achieved, patients with TNBC and non-TNBC had similar survival (P = .24). In contrast, patients with residual disease (RD) had worse OS if they had TNBC compared with non-TNBC (P < .0001).

CONCLUSION

Patients with TNBC have increased pCR rates compared with non-TNBC, and those with pCR have excellent survival. However, patients with RD after neoadjuvant chemotherapy have significantly worse survival if they have TNBC compared with non-TNBC, particularly in the first 3 years.

Evaluation of the Sensitivity to Endocrine Therapy Index and 21-Gene Breast Recurrence Score in the SWOG S8814 Trial

PURPOSE

Chemotherapy has not demonstrated benefit over adjuvant endocrine therapy alone for postmenopausal patients with node-positive breast cancer with a 21-gene breast recurrence score (RS) of 25 or below (RS ≤ 25). We tested whether combined results from RS and the sensitivity to endocrine therapy (SET2,3) index of endocrine-related transcription (SETER/PR) adjusted for baseline prognostic index (BPI) improve prognostic assessment, and whether SET2,3 predicted benefit from anthracycline-based chemotherapy.

METHODS

A blinded retrospective clinical validation of SET2,3 in two randomized treatment arms from the SWOG S8814 trial comparing adjuvant anthracycline-based chemotherapy followed by tamoxifen endocrine therapy for 5 years, versus tamoxifen alone. SET2,3 assay was calibrated and measured using whole-transcriptome RNA sequence of tumor samples already tested for RS. The primary end point was disease-free survival (DFS).

RESULTS

There were 106 events in 283 patients over a median follow-up of 8.99 years. Proportional hazards assumptions were met during the first 5 years only. SET2,3 index and RS were not correlated (r = -0.04) and were independently prognostic (SET2,3: hazard ratio [HR], 0.48 per unit; 95% CI, 0.34 to 0.68; P < .001; RS: HR, 1.28 per 10 units; 95% CI, 1.14 to 1.44; P < .001). SET2,3 index did not predict chemotherapy benefit (interaction P = .77). SET2,3 was high in 93/175 (53%) patients with RS ≤ 25 (concordant low-risk), with 5-year DFS 97%. SET2,3 was low in 55/108 (51%) patients with RS > 25 (concordant high-risk), with 5-year DFS 53%. Both components of SET2,3 index were prognostic after adjustment for RS: SETER/PR (HR, 0.65; 95% CI, 0.46 to 0.92) and BPI (HR, 0.45; 95% CI, 0.31 to 0.64).

CONCLUSION

SET2,3 index was not correlated with RS, demonstrated additive prognostic performance, and was not chemopredictive in this subset of patients from S8814. The SETER/PR and BPI components of SET2,3 each added prognostic information to RS.

Abstract PD11-01: PD11-01 Evaluation of the PD-1 Inhibitor Cemiplimab in early-stage, high-risk HER2-negative breast cancer: Results from the neoadjuvant I-SPY 2 TRIAL

Background: I-SPY2 is a multicenter, phase 2 trial using response-adaptive randomization within biomarker subtypes defined by hormone-receptor (HR), HER2, and MammaPrint (MP) status to evaluate novel agents as neoadjuvant therapy for high-risk breast cancer. The primary endpoint is pathologic complete response (pCR). Cemiplimab (Cemi) is a PD-1 inhibitor approved for the treatment of NSCLC, cutaneous basal, and squamous cell cancer. Here, we report current efficacy rates of Cemi in combination with paclitaxel followed by AC.

Methods: Women with tumors ≥ 2.5cm were eligible for screening. Only HER2 negative (HER2-) patients were eligible for this treatment; HR positive (HR+) patients had to be MP high risk. Treatment included paclitaxel 80 mg/m2 IV weekly x 12 and Cemi 350 mg IV given q3weeks x 4, followed by doxorubicin/cyclophosphamide (AC) every 2 weeks x 4. The control arm was weekly paclitaxel x 12 followed by AC every 2-3 weeks x 4. All patients undergo serial MRI imaging; and imaging response (at 3 weeks, 12 weeks and prior to surgery) were used along with accumulating pCR data to continuously update and estimate pCR rates for trial arms. Analysis was modified intent to treat. Patients who switched to non-protocol therapy count as non-pCR. The goal is to identify (graduate) regimens with ≥85% Bayesian predictive probability of success (i.e. demonstrating superiority to control) in a future 300-patient phase 3 neoadjuvant trial with a pCR endpoint within responsive signatures. Cemi was eligible to graduate in 3 pre-defined signatures: HER2-, HR-HER2-, and HR+HER2-. To adapt to changing standard of care, we constructed “dynamic controls” comprising ‘best’ alternative therapies using I-SPY 2 and external data and estimated the probability of Cemi being superior to the dynamic control.

Results: 60 HER2- patients (28 HR+ and 32 HR-) received Cemi arm treatment. The control group included 357 patients with HER2- tumors (201 HR+ and 156 HR-) enrolled since March 2010. Cemi graduated in HR-/HER2- signature. Estimated pCR rates (as of June 2022) are summarized in the table.

Immune-related endocrine disorders include: hypothyroid (14.5%), adrenal insufficiency (10%), hyperthyroid (4.8%),) and thyroiditis (3.2%). Only one grade 3 adrenal insufficiency was observed. All immune related AE’s were manageable. Additional biomarker analyses are ongoing and will be presented at the meeting. Response predictive subtypes (Immune+ vs Immune-) and additional predictive biomarkers were assessed. Associations with pCR will be presented at SABCS.

Conclusion: The I-SPY 2 study aims to assess the probability that investigational regimens will be successful in a phase 3 neoadjuvant trial. Anti-PD-1 therapy with Cemi resulted in a higher predicted pCR rate in HR-/HER2- 55 rate% disease compared to control at 29%. Immune-mediated AE’s were observed. This data is consistent with previously published data using check point inhibitors in early-stage HR-/HER2- breast cancer.

Estimated pCR rates

Citation Format: Erica Stringer-Reasor, Rebecca A. Shatsky, Jo Chien, Anne Wallace, Judy C. Boughey, Kathy S. Albain, Hyo S. Han, Rita Nanda, Claudine Isaacs, Kevin Kalinsky, Zahi Mitri, Amy S. Clark, Christos Vaklavas, Alexandra Thomas, Meghna S. Trivedi, Janice Lu, Smita Asare, Ruixiao Lu, Maria Pitsouni, Amy Wilson, Jane Perlmutter, Hope Rugo, Richard Schwab, W. Fraser Symmans, Nola M. Hylton, Laura Van ’t Veer, Douglas Yee, Angela DeMichele, Donald Berry, Laura J. Esserman, I-SPY Investigators. PD11-01 Evaluation of the PD-1 Inhibitor Cemiplimab in early-stage, high-risk HER2-negative breast cancer: Results from the neoadjuvant I-SPY 2 TRIAL [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 PD11-01.

Abstract HER2-14: HER2-14 HER-2 low status in early stage invasive lobular carcinoma of the breast: associated factors and outcomes in an institutional series

Objectives: The concept of human epidermal growth factor receptor 2 (HER2)-low status has been proposed as a potential treatment target for breast cancers previously considered to be HER2-negative. Defined by an immunohistochemistry (IHC) score of 1+ or 2+ and negative fluorescent in situ hybridization (FISH) for HER2, HER2-low status predicts significant clinical benefit from novel therapeutic compounds in recent clinical trials. The prevalence and clinical implications of HER2-low status in patients with early stage invasive lobular carcinoma (ILC) has not been described. We aimed to describe the clinicopathologic features and prevalence of HER2-low status in ILC, and identify any potential differences in clinical outcome. Methods: We evaluated stage I-III ILC tumors from a prospectively maintained institutional database of patients where both IHC and FISH testing for HER2 status was performed as standard clinical care. Tumors were classified as HER2 negative (IHC=0), HER2-low (IHC=1+ or 2+ and negative FISH), or HER2 positive (IHC=3+ or FISH ratio ⇒2). Data were analyzed in Stata 16.1 using chi-squared tests, t-tests, and Cox proportional hazards models for disease free survival (DFS). Results: 666 ILC tumors with available HER2 status were available for analysis. The mean age at diagnosis was 59.8 years (range 21-91). The majority of patients had stage I disease (63.1%) with an average follow up time of 6.7 years (standard deviation [5.4]). Overall, 184 (27.6%) tumors were HER2 negative, 434 (65.1%) were HER2-low, and 48 (7.2%) were HER2 positive. There were no associations between HER2 status and age, menopausal status, body mass index, tumor stage, grade, presence of lymphovascular invasion, or molecular assay results. Hormone receptor status was significantly associated with HER2 status, with HER2 positive tumors significantly less likely to be estrogen receptor (ER) positive than both HER2 negative and HER2-low tumors (89.6% versus 97.3% and 96.8% respectively, p=0.03). HER2-low tumors were also significantly more likely to have progesterone receptor (PR) positivity (86.6% compared to 79.9% of HER2 negative and 72.9% of HER2 positive tumors, p = 0.01). This difference remained significant when comparing just HER2-low to HER2 negative cases (p=0.034). While there were no differences in use of neoadjuvant or adjuvant chemotherapy by HER2 status, HER2-low patients were significantly more likely to undergo mastectomy versus lumpectomy when compared to HER2 negative and HER2 positive patients (53.7% versus 38.0% and 43.8% respectively, p= 0.001). In a multivariable Cox proportional hazards model adjusting for tumor size, number of positive nodes, ER/PR status, and local therapy received, patients with HER2-low status had worse DFS than those with HER2 negative tumors (hazard ratio 2.0, 95% confidence interval 1.0 - 4.1, p=0.05). Conclusions: In this analysis of 666 early stage ILC cases, we found that most tumors were HER2-low, and that those with HER2-low disease were significantly more likely to have PR positive tumors and to undergo mastectomy. When adjusting for these variables, we identified a difference in DFS between HER2 negative and HER2-low early stage ILC. These findings support the contention that HER2-low and HER2 negative disease represent two different clinical entities. Further investigation of the potential benefit of HER2 targeted therapy in ILC, which predominately lacks HER2-amplified disease, is needed to ensure optimal outcomes in this understudied tumor type.

Citation Format: Harriet T. Rothschild, Elle Clelland, Anne Patterson, Julissa Molina-Vega, Mandeep Kaur, Mary Kathryn Abel, W. Fraser Symmans, Christopher J. Schwartz, Rita Mukhtar. HER2-14 HER-2 low status in early stage invasive lobular carcinoma of the breast: associated factors and outcomes in an institutional series [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 HER2-14.

Abstract PD17-05: Development and Validation of a Composite Biomarker Predictive of Palbociclib + Endocrine Treatment Benefit in Early Breast Cancer: PENELOPE-B and PALLAS Trials

Background: The PENELOPE-B (NCT01864746) and PALLAS (NCT02513394) trials are large prospective, randomized, phase III trials that evaluated adjuvant palbociclib (PAL) + endocrine treatment (ET) vs ET in patients with hormone receptor–positive/human epidermal growth factor receptor 2–negative (HER2–) early breast cancer (EBC). Both studies did not meet the primary endpoint of improving invasive disease-free survival (iDFS). We conducted biomarker analyses to identify patients who might benefit from PAL + ET in EBC. Methods: Resected tumor tissue was collected from consenting patients. Gene expression analyses were conducted using the HTG EdgeSeq Oncology Biomarker Panel including 2549 genes. Based on 91 genes from the HTG panel, the intrinsic molecular subtypes were calculated using Absolute Intrinsic Molecular Subtyping (AIMS). Potential predictive treatment biomarkers were established in PENELOPE-B (n=906 with resected tissue) as the development set using an outcome-oriented approach based on iDFS with a selection procedure that maximized the log-rank statistic to estimate a standard Z score–based optimal cutoff. Independent validation was conducted on PALLAS (n=2085; PENELOPE-B-like with resected tissue and HTG data). Hazard ratios and corresponding 95% CIs were calculated using the Cox proportional hazards model, and iDFS distributions between treatment arms were compared using the log-rank test. Interaction between treatment and biomarker status was assessed. Results: Patient baseline characteristics were well balanced, with no differences in iDFS between the intent-to-treat set and the biomarker set for both trials. Approximately 73% of patients (PENELOPE-B [n=663] and PALLAS [n=1516]) had luminal A subtypes whereas only 7.1 % (PENELOPE-B [n=64]) and 8.3 % (PALLAS [n=172]) had a luminal B subtype. AIMS subtypes showed overall similar prognostic patterns for iDFS between PENELOPE-B and PALLAS. The biomarker-defined subgroup found in PENELOPE-B with optimal cutoff demonstrated a preferential benefit from PAL + ET (n=364 [96 events]; hazard ratio [95% CI], 0.63 [0.42, 0.95]; P=0.025). Independent validation of the PALLAS subgroup using the pre-defined optimal cutoff confirmed a significant benefit from PAL + ET (n=916 [70 events]; 0.55 [0.34–0.90]; P=0.015) while not in the rest of the patients (interaction p=0.0025). Significant treatment effects remained (0.55 [0.34–0.89]; P=0.015) after adjusting for the randomization stratification factors of PALLAS. Conclusions: The composite predictive biomarker defined from PENELOPE-B was independently validated in a prospectively defined retrospective analysis of a subset of patients selected from PALLAS. The composite biomarker identified a subset of EBC patients deriving benefit from the addition of PAL to ET. This patient stratification approach can potentially be applied to future adjuvant clinical trials for treatment of hormone receptor–positive/HER2– EBC.

Citation Format: Sibylle Loibl, Carsten Denkert, Yuan Liu, Erik S. Knudsen, Angela DeMichele, Zhe Zhang, Julia Teply-Szymanski, Martin Filipits, Peter A. Fasching, Michael Gnant, Shibing Deng, Marija Balic, Federico Rojo, Mark Watson, Chetan Deshpande, Nicholas Turner, Otto Metzger, Kathy Puyana Theall, Agnieszka Witkiewicz, Olga Valota, W. Fraser Symmans, Erica L. Mayer. Development and Validation of a Composite Biomarker Predictive of Palbociclib + Endocrine Treatment Benefit in Early Breast Cancer: PENELOPE-B and PALLAS Trials [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 PD17-05.

Abstract PD6-11: PD6-11 Evaluation of the Sensitivity to Endocrine Therapy Index (SET2,3) in Early Male Breast Cancer: Results from an analysis in the EORTC 10085/TBCRC/BIG/NCTN International Male Breast Cancer Program

Introduction Breast cancer is uncommon in men. Almost all male breast cancers are hormone receptor-positive, HER2-negative, although the pathogenesis is not always attributable to an endocrine condition. A few studies have compared biological characteristics or molecular signatures with breast cancers in women. We sought to evaluate whether hormone receptor-related gene expression is different in cancers from men compared to equivalent cancers from women. SET2,3 index measures non-proliferative hormone receptor-related transcriptional activity in the cancer (SET-ER/PR index) and adjusts this for a Baseline Prognosis Index (BPI) that combines the measurements of tumor and nodal stage with a 4-gene molecular subtype (ESR1, PGR, ERBB2, and AURKA). Methods We received aliquots of total RNA from male patients with breast cancer included in the retrospective cohort study of the EORTC 10085/BCG/TBCRC/BIG/NCTN International Male Breast Cancer Program (NCT01101425). SET2,3 assay was performed using the QuantiGene assay (Thermo Fisher) using bead-based hybridization and laser spectroscopy (Luminex). The statistical analyses were performed by the EORTC statistician. The primary objective of the study was the assessment of the prognostic value of the SET2,3 index score in patients with early-stage hormone receptor-positive, HER2-negative male breast cancer, treated with endocrine therapy. Clinical outcomes (recurrence-free survival – RFS; overall survival – OS) were estimated by Kaplan-Meier curves and secondarily compared using multivariable Cox models adjusted for continuous SET2,3 index, tumor size, nodal status, age, and chemotherapy and radiotherapy use. An exploratory analysis to compare the SET2,3 index scores distribution in female and male breast cancer patients was also performed using results from the same assay performed on cancers from women selected on the same inclusion criteria. Due to the low numbers of male patients treated with neoadjuvant treatment (N=6), this analysis was restricted to patients treated with adjuvant treatment (n=315 male and 660 female). Results Of the 321 male patients with breast cancer analyzed, treated between 1990 and 2010, 211 (65.7%) were categorized as high SET2,3 index score, reflecting a high endocrine activity in the cancer and low risk of recurrence, and 110 patients (34.3%) categorized as being low score, reflecting low endocrine activity and high risk of recurrence. At 5 years, the RFS was 75.0% (95% CI, 67.4-81.1) in the high SET2,3 group versus 60.7% (95% CI, 49.1-70.5) in the low SET2,3 group (HR univariate, 0.49; 95% CI, 0.34-0.70; P&lt; 0.0001). The 5-year OS rate among patients with a high SET2,3 index was 84.3% (95% CI, 45.5-73.8), in contrast of 67.8% (95% CI, 56.6-76.7) in the low SET2,3 group (HR univariate, 0.44; 95% CI, 0.30-0.65; P&lt; 0.0001). SET2,3 was independently prognostic for OS, but not RFS in multivariable Cox models. In patients classified as low SET2,3, the addition of neo/adjuvant chemotherapy to adjuvant endocrine therapy was associated with 5-year OS of 76.0% (95% CI, 59.5-86.4) and in patients who received endocrine therapy alone the 5-year OS was 61.3% (95% CI, 45.5-73.8), an absolute difference of 14.7 percentage points. Overall, we did not observe a difference in the distributions (median, interquartile range) of SET2,3 index between men (2.4, 1.9–2.6) and women (2.3, 2.0–2.7). Conclusion SET2,3 index measurements of endocrine-related transcriptional activity in male patients with breast cancer were not different from measurements in female patients with breast cancer. SET2,3 was prognostic in male breast cancer and our exploratory analysis suggests that chemotherapy might improve the poor prognosis for men with breast cancer that has low SET2,3 index. This study was funded by the Breast Cancer Research Foundation (BCRF).

Citation Format: Danielle B. Zakon, Coralie Poncet, Fatima Cardoso, Neven Anouk, Vicente Valero, Stefan Aebi, Kim Benstead, Oliver Bogler, Lissandra Dal Lago, Judith Fraser, Carmela Caballero, Ingrid A. Hedenfalk, Larissa A. Korde, Barbro Linderholm, John WM Martens, Lavinia P. Middleton, Melissa Murray, Catherine M. Kelly, Cecilia Nilsson, Monika Nowaczyk, Stephanie Peeters, Melanie Beauvois, Peggy Porter, Carolien P. Schroder, Isabel T. Rubio, Kathryn Ruddy, Christi van Asperen, Danielle Van Den Weyngaert, Carolien HM van Deurzen, Elise van Leeuwen-Stok, Joanna M. Vermeij, John MS Bartlett, Antonio C. Wolff, Sharon H. Giordano, W. Fraser Symmans. PD6-11 Evaluation of the Sensitivity to Endocrine Therapy Index (SET2,3) in Early Male Breast Cancer: Results from an analysis in the EORTC 10085/TBCRC/BIG/NCTN International Male Breast Cancer Program [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 PD6-11.

Abstract GS5-03: Evaluation of anti-PD-1 Cemiplimab plus anti-LAG-3 REGN3767 in early-stage, high-risk HER2-negative breast cancer: Results from the neoadjuvant I-SPY 2 TRIAL

Background: I-SPY2 is a multicenter, phase 2 trial using response-adaptive randomization within biomarker subtypes defined by hormone-receptor (HR), HER2, and MammaPrint (MP) status to evaluate novel agents as neoadjuvant therapy for high-risk breast cancer. The primary endpoint is pathologic complete response (pCR). Cemiplimab is an anti-PD-1 inhibitor approved for the treatment of NSCLC and cutaneous basal and squamous cell CA. Lymphocyte activation gene 3 (LAG-3) binds MHC class II leading to inhibition of T-cell proliferation and activation and is often co-expressed with PD-1. REGN3767 is a fully humanized mAb that binds to LAG-3 and blocks inhibitory T-cell signaling. Concurrent blockade of LAG-3 with an anti-PD-1 may enhance efficacy of an anti-PD-1.

Methods: Women with tumors ≥ 2.5cm were eligible for screening. Only HER2 negative (HER2-) patients were eligible for this treatment; HR positive (HR+) patients had to be MP high risk. Treatment included Paclitaxel 80 mg/m2 IV weekly x 12 and Cemiplimab 350 mg and REGN3767 1600 mg both given q3weeks x 4, followed by doxorubicin/cyclophosphamide (AC) every 2 weeks x 4. The control arm was weekly paclitaxel x 12 followed by AC every 2-3 weeks x 4. Cemiplimab/REGN3767 was eligible to graduate in 3 of 10 pre-defined signatures: HER2-, HR-HER2-, and HR+HER2-. The statistical methods for evaluating I-SPY 2 agents has been previously described. To adapt to changing standard of care, we constructed “dynamic controls” comprising ‘best’ alternative therapies using I-SPY 2 and external data and estimated the probability of Cemiplimab/REGN3767 being superior to the dynamic control. Response predictive subtypes (Immune+ vs Immune-) were assessed using pre-treatment gene expression data and the ImPrint signature.

Results: 73 HER2- patients (40 HR+ and 33 HR-) received Cemiplimab/REGN3767 treatment. The control group included [357 patients with HER2- tumors (201 HR+ and 156 HR-) enrolled since March 2010. Cemiplimab/REGN3767 graduated in both HR-/HER2- and HR+/HER2- groups; estimated pCR rates (as of June 2022) are summarized in the table. Safety events of note for Cemiplimab/REGN3767 include hypothyroidism 30.8%, adrenal insufficiency (AI) 19.2%, hyperthyroidism 14.1%, pneumonitis 1.3%, and hepatitis 3.8%. All were G1/2 except for 6 (7.7%) G3 AI and 3 (3.8%) G3 colitis. Rash occurred in 62.8%, 9% G3 and 2 pts (2.6%) had pulmonary embolism. X% of adrenal insufficiency cases required replacement therapy. 40 patients (11 HR+ and 29 HR-) in Cemiplimab/REGN3767 were predicted Immune+; 32 (29 HR+ and 3 HR-) were predicted Immune-. In the HR+ group pCR was achieved in 10/11 (91%) patients with Immune+ subtype compared with 8/29 (28%) with Immune- subtype. Additional biomarker analyses are ongoing and will be presented at the meeting.

Conclusion: The I-SPY 2 study aims to assess the probability that investigational regimens will be successful in a phase 3 neoadjuvant trial. Dual immune blockade with a LAG-3 inhibitor and anti-PD1 therapy resulted in a high predicted pCR rate both in HR-/HER2- (60%) and HR+/HER2- (37%) disease. The novel Imprint signature identified a group of HR+ patients most likely to benefit from this active regimen.

Table 1: Estimated pCR rates

Citation Format: Claudine Isaacs, Rita Nanda, Jo Chien, Meghna S. Trivedi, Erica Stringer-Reasor, Christos Vaklavas, Judy C. Boughey, Amy Sanford, Anne Wallace, Amy S. Clark, Alexandra Thomas, Kathy S. Albain, Laura C. Kennedy, Tara B. Sanft, Kevin Kalinsky, Hyo S. Han, Nicole Williams, Mili Arora, Anthony Elias, Carla Falkson, Smita Asare, Ruixiao Lu, Maria Pitsouni, Amy Wilson, Jane Perlmutter, Hope Rugo, Richard Schwab, W. Fraser Symmans, Nola M. Hylton, Laura Van’t Veer, Douglas Yee, Angela DeMichele, Donald Berry, Laura J. Esserman, I-SPY Investigators. Evaluation of anti-PD-1 Cemiplimab plus anti-LAG-3 REGN3767 in early-stage, high-risk HER2-negative breast cancer: Results from the neoadjuvant I-SPY 2 TRIAL [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 GS5-03.

Abstract P2-03-16: Quantifying estrogen and progesterone receptor status in early-stage invasive lobular carcinoma of the breast: associated factors and outcomes in an institutional series

Background: Recent guidelines regarding estrogen (ER) and progesterone (PR) receptor testing from the American Society of Clinical Oncology and College of American Pathologists defined a new reporting category of ER-low positive breast cancer for tumors with 1-10% ER expression by immunohistochemistry (IHC). The clinical implications of ER-low positivity are incompletely understood, especially in invasive lobular carcinoma (ILC), the second most common type of breast cancer. Given the rarity of low-ER positivity in ILC, we evaluated tumor features and outcomes associated with a spectrum of ER/PR positivity in a monoinstitutional ILC cohort. Methods: We analyzed cases of stage I-III ILC with available IHC reports. Based on prior published categories in ILC, we classified ER as low, medium, or high as defined by ER staining of 10–69%, 70–89%, and ≥90% respectively. PR negative, low, and high tumors were defined by 0%, &lt; 20%, or ≥20% staining respectively. We used chi-squared tests, t-tests, and Cox proportional hazards models in Stata 16.1 to evaluate associations between ER/PR categories including clinicopathologic variables and event-free survival (EFS). Results: Of 744 cases, 24 (3.2%) were ER negative and 10 (1.3%) were ER-low positive as defined by 1-10% positive staining. 713 remaining cases had ER positivity ≥ 10% and comprised the cohort categories of ER low, medium, and high for this study (11.2%, 15.0%, and 73.8% respectively). In 751 cases with PR data, 122 (16.2%) were PR negative, 145 (19.4%) were PR low and 483 (64.3%) were PR high. ER high status was significantly associated with older age (mean 56.7, 56.7, and 60.6 years in ER low, medium, and high respectively, p=0.0005). ER low was associated with PR negative and low status (42.3% were PR neg/low and ER low, versus 37.4% with ER medium and 29.9% in ER high, p=0.045), and more likely to have overexpression of HER2 (9.7%, 9.0%, and 2.9% ER low, medium, high, respectively, p=0.002). ER low tumors were more likely to be grade 1 than ER medium or high (41.8%, 29.8% and 24.5% respectively, p=0.025), and have positive surgical margins (39.4%, 35.9% and 23.9% respectively, p=0.002). ER status was not associated with Ki67, stage, body mass index (BMI), lymphovascular invasion, lobular carcinoma in situ (LCIS), pleomorphic histology, local therapy, or chemotherapy use. In contrast, PR high was significantly associated with younger age (57.6 versus 63.5 years in PR low, p&lt; 0.0001). PR low was associated with HER2 overexpression (8.6% versus 3.2% in PR high, p=0.002). PR low cases were more likely to present at higher stages (15.8% stage III versus 10.1% stage III in PR high, p=0.032), to be pleomorphic (16.8% versus 8.2%, p&lt; 0.001), and to receive chemotherapy (30.8% versus 23.1%, p=0.022) but were less likely to have associated LCIS (64.0 versus 74.2%, p=0.004). PR status was not associated with Ki67, BMI, lymphovascular invasion, local therapy, or surgical margins. In a Cox proportional hazards model adjusting for age, stage, grade, pleomorphic histology, and chemotherapy use, ER category was not associated with EFS but both PR negative and PR low status each had significantly worse EFS compared to PR ≥20% (HR 3.5, 95% CI 1.8-6.7, p&lt; 0.001 for PR negative, and HR 2.0, 95% CI 1.1-3.5, p=0.015 for PR low). The estimated cumulative 5-year EFS for patients with ER low, medium, and high tumors was 87.1%, 93.4%, and 90.1% respectively. The estimated cumulative 5-year EFS for patients with PR negative, low, and high tumors was 78.9%, 90.2%, and 92.7% respectively. Conclusions: Using ILC-specific categories for ER expression, we found associations between ER category and clinicopathologic variables but not with EFS. In contrast, PR negative and low status was associated with worse EFS. These findings highlight the importance of exploring the spectrum of ER/PR activity within ILC, a classically strongly hormone receptor-positive tumor type, using more quantitative methods.

Citation Format: Elle Clelland, Harriet T. Rothschild, Anne Patterson, Julissa Molina-Vega, Mandeep Kaur, Mary Kathryn Abel, W. Fraser Symmans, Jo Chien, Christopher J. Schwartz, Rita Mukhtar. Quantifying estrogen and progesterone receptor status in early-stage invasive lobular carcinoma of the breast: associated factors and outcomes in an institutional series [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 P2-03-16.

Predictors of success in establishing orthotopic patient-derived xenograft models of triple negative breast cancer

Patient-derived xenograft (PDX) models of breast cancer are an effective discovery platform and tool for preclinical pharmacologic testing and biomarker identification. We established orthotopic PDX models of triple negative breast cancer (TNBC) from the primary breast tumors of patients prior to and following neoadjuvant chemotherapy (NACT) while they were enrolled in the ARTEMIS trial (NCT02276443). Serial biopsies were obtained from patients prior to treatment (pre-NACT), from poorly responsive disease after four cycles of Adriamycin and cyclophosphamide (AC, mid-NACT), and in cases of AC-resistance, after a 3-month course of different experimental therapies and/or additional chemotherapy (post-NACT). Our study cohort includes a total of 269 fine needle aspirates (FNAs) from 217 women, generating a total of 62 PDX models (overall success-rate = 23%). Success of PDX engraftment was generally higher from those cancers that proved to be treatment-resistant, whether poorly responsive to AC as determined by ultrasound measurements mid-NACT (p = 0.063), RCB II/III status after NACT (p = 0.046), or metastatic relapse within 2 years of surgery (p = 0.008). TNBC molecular subtype determined from gene expression microarrays of pre-NACT tumors revealed no significant association with PDX engraftment rate (p = 0.877). Finally, we developed a statistical model predictive of PDX engraftment using percent Ki67 positive cells in the patient's diagnostic biopsy, positive lymph node status at diagnosis, and low volumetric reduction of the patient's tumor following AC treatment. This novel bank of 62 PDX models of TNBC provides a valuable resource for biomarker discovery and preclinical therapeutic trials aimed at improving neoadjuvant response rates for patients with TNBC.

Molecular testing opportunities on cytology effusion specimens: the pre-analytic effects of various body fluid cytology preparation methods on RNA extraction quality and targeted sequencing

INTRODUCTION

RNA sequencing (RNAseq) analysis is emerging as a clinical research or diagnostic approach for cytologic samples, but there is need for formal comparison of different sample preparation methods in the cytology laboratory to identify which pre-analytic methods could provide alternatives to formalin-fixed paraffin-embedded (FFPE) sections.

MATERIALS AND METHODS

We prepared 13 malignant effusions (metastatic estrogen receptor-positive breast cancer) in the cytology laboratory using 6 routine cytologic methods: FFPE cell block, Carnoy's solution, 95% ethanol (EtOH), air-dried and Diff-Quik, ThinPrep, and SurePath preparations. Measurements of RNA quality, expression of 2 multigene expression signatures, molecular subtype, and 4 common activating mutation sites in each preparation were compared with fresh frozen (FF) cell pellet in RNA preservative using distribution of fragment length and concordance correlation coefficient (CCC).

RESULTS

The fraction of RNA fragments measuring 200 bases or more (DV200) were 24% higher from cytospins fixed in Carnoy's solution or 95% EtOH than DV200 from FFPE cell blocks. SurePath samples failed RNAseq quality control. There was high concordance of gene expression measurements with FF samples using cytospins fixed in Carnoy's solution, 95% EtOH, Diff-Quik (CCC = 0.829, 0.812, 0.760, respectively), or ThinPrep (CCC = 0.736), but lower using FFPE cell block (CCC = 0.564). The proportion of mutant transcripts was concordant between FF and any cytologic preparation methods.

CONCLUSIONS

Cytospin preparations fixed with Carnoy's or 95% ETOH then Papanicolaou stained produced RNAseq results that were equivalent to FF samples and superior to FFPE cell block sections.

Multiomics in primary and metastatic breast tumors from the AURORA US network finds microenvironment and epigenetic drivers of metastasis

The AURORA US Metastasis Project was established with the goal to identify molecular features associated with metastasis. We assayed 55 females with metastatic breast cancer (51 primary cancers and 102 metastases) by RNA sequencing, tumor/germline DNA exome and low-pass whole-genome sequencing and global DNA methylation microarrays. Expression subtype changes were observed in ~30% of samples and were coincident with DNA clonality shifts, especially involving HER2. Downregulation of estrogen receptor (ER)-mediated cell-cell adhesion genes through DNA methylation mechanisms was observed in metastases. Microenvironment differences varied according to tumor subtype; the ER+/luminal subtype had lower fibroblast and endothelial content, while triple-negative breast cancer/basal metastases showed a decrease in B and T cells. In 17% of metastases, DNA hypermethylation and/or focal deletions were identified near HLA-A and were associated with reduced expression and lower immune cell infiltrates, especially in brain and liver metastases. These findings could have implications for treating individuals with metastatic breast cancer with immune- and HER2-targeting therapies.

Safety and efficacy of HSP90 inhibitor ganetespib for neoadjuvant treatment of stage II/III breast cancer

HSP90 inhibitors destabilize oncoproteins associated with cell cycle, angiogenesis, RAS-MAPK activity, histone modification, kinases and growth factors. We evaluated the HSP90-inhibitor ganetespib in combination with standard chemotherapy in patients with high-risk early-stage breast cancer. I-SPY2 is a multicenter, phase II adaptively randomized neoadjuvant (NAC) clinical trial enrolling patients with stage II-III breast cancer with tumors 2.5 cm or larger on the basis of hormone receptors (HR), HER2 and Mammaprint status. Multiple novel investigational agents plus standard chemotherapy are evaluated in parallel for the primary endpoint of pathologic complete response (pCR). Patients with HER2-negative breast cancer were eligible for randomization to ganetespib from October 2014 to October 2015. Of 233 women included in the final analysis, 140 were randomized to the standard NAC control; 93 were randomized to receive 150 mg/m2 ganetespib every 3 weeks with weekly paclitaxel over 12 weeks, followed by AC. Arms were balanced for hormone receptor status (51-52% HR-positive). Ganetespib did not graduate in any of the biomarker signatures studied before reaching maximum enrollment. Final estimated pCR rates were 26% vs. 18% HER2-negative, 38% vs. 22% HR-negative/HER2-negative, and 15% vs. 14% HR-positive/HER2-negative for ganetespib vs control, respectively. The predicted probability of success in phase 3 testing was 47% HER2-negative, 72% HR-negative/HER2-negative, and 19% HR-positive/HER2-negative. Ganetespib added to standard therapy is unlikely to yield substantially higher pCR rates in HER2-negative breast cancer compared to standard NAC, and neither HSP90 pathway nor replicative stress expression markers predicted response. HSP90 inhibitors remain of limited clinical interest in breast cancer, potentially in other clinical settings such as HER2-positive disease or in combination with anti-PD1 neoadjuvant chemotherapy in triple negative breast cancer.Trial registration: www.clinicaltrials.gov/ct2/show/NCT01042379.

Association of Residual Ductal Carcinoma In Situ With Breast Cancer Recurrence in the Neoadjuvant I-SPY2 Trial

Importance

Pathologic complete response (pCR) after neoadjuvant chemotherapy (NAC) in breast cancer strongly correlates with overall survival and has become the standard end point in neoadjuvant trials. However, there is controversy regarding whether the definition of pCR should exclude or permit the presence of residual ductal carcinoma in situ (DCIS).

Objective

To examine the association of residual DCIS in surgical specimens after neoadjuvant chemotherapy for breast cancer with survival end points to inform standards for the assessment of pathologic complete response.

Design, Setting, and Participants

The study team analyzed the association of residual DCIS after NAC with 3-year event-free survival (EFS), distant recurrence-free survival (DRFS), and local-regional recurrence (LRR) in the I-SPY2 trial, an adaptive neoadjuvant platform trial for patients with breast cancer at high risk of recurrence. This is a retrospective analysis of clinical specimens and data from the ongoing I-SPY2 adaptive platform trial of novel therapeutics on a background of standard of care for early breast cancer. I-SPY2 participants are adult women diagnosed with stage II/III breast cancer at high risk of recurrence.

Interventions

Participants were randomized to receive taxane and anthracycline-based neoadjuvant therapy with or without 1 of 10 investigational agents, followed by definitive surgery.

Main Outcomes and Measures

The presence of DCIS and EFS, DRFS, and LRR.

Results

The study team identified 933 I-SPY2 participants (aged 24 to 77 years) with complete pathology and follow-up data. Median follow-up time was 3.9 years; 337 participants (36%) had no residual invasive disease (residual cancer burden 0, or pCR). Of the 337 participants with pCR, 70 (21%) had residual DCIS, which varied significantly by tumor-receptor subtype; residual DCIS was present in 8.5% of triple negative tumors, 15.6% of hormone-receptor positive tumors, and 36.6% of ERBB2-positive tumors. Among those participants with pCR, there was no significant difference in EFS, DRFS, or LRR based on presence or absence of residual DCIS.

Conclusions and Relevance

The analysis supports the definition of pCR as the absence of invasive disease after NAC regardless of the presence or absence of DCIS.

Trial Registration

ClinicalTrials.gov Identifier NCT01042379.

Standardizing Pathologic Evaluation of Breast Carcinoma After Neoadjuvant Chemotherapy

CONTEXT.—

Neoadjuvant systemic therapy refers to the use of systemic agent(s) for malignancy prior to surgical treatment and has recently emerged as an option for most breast cancer patients eligible for adjuvant systemic therapy. Consequently, treated breast carcinomas have become routine specimens in pathology practices. A standard protocol has not yet been universally adopted for the evaluation and reporting of these specimens. The American Joint Committee on Cancer staging system recognizes the challenges in staging breast carcinomas after neoadjuvant treatment and provides important data points but does not currently provide detailed guidance in estimating the residual tumor burden in the breast and lymph nodes. The Residual Cancer Burden system is the only Web-based system that quantifies treatment response as a continuous variable using residual tumor burden in the breast and the lymph nodes.

OBJECTIVE.—

To provide clarifications and guidance for evaluation and reporting of postneoadjuvant breast specimens, discuss issues with the current staging and reporting systems, and provide specific suggestions for future modifications to the American Joint Committee on Cancer system and the Residual Cancer Burden calculator.

DATA SOURCES.—

English-language literature on the subject and the data from the I-SPY 2, a multicenter, adaptive randomization phase 2 neoadjuvant platform trial for early-stage, high-risk breast cancer patients.

CONCLUSIONS.—

This article highlights challenges in the pathologic evaluation and reporting of treated breast carcinomas and provides recommendations and clarifications for pathologists and clinicians. It also provides specific recommendations for staging and discusses future directions.

Evaluation of Sensitivity to Endocrine Therapy Index (SET2,3) for Response to Neoadjuvant Endocrine Therapy and Longer-Term Breast Cancer Patient Outcomes (Alliance Z1031)

PURPOSE

To evaluate prediction of response and event-free survival (EFS) following neoadjuvant endocrine therapy by SET2,3 index of nonproliferation gene expression related to estrogen and progesterone receptors adjusted for baseline prognosis.

EXPERIMENTAL DESIGN

A correlative study was conducted of SET2,3 measured from gene expression profiles of diagnostic tumor (Agilent microarrays) in 379 women with cStage II-III breast cancer from the American College of Surgeons Oncology Group Z1031 neoadjuvant aromatase inhibitor trial SET2,3 was dichotomized using the previously published cutoff. Fisher exact test was used to assess the association between SET2,3 and low proliferation at week 2-4 [Ki67 ≤ 10% or complete cell-cycle arrest (CCCA; Ki67 ≤ 2.7%)] and PEPI-0 rate in cohort B, and the association between SET2,3 and ypStage 0/I in all patients. Cox models were used to assess EFS with respect to SET2,3 excluding cohort B patients who switched to chemotherapy.

RESULTS

Patients with high SET2,3 had higher rate of pharmacodynamic response than patients with low SET2,3 (Ki67 ≤ 10% in 88.2% vs. 56.9%, P < 0.0001; CCCA in 50.0% vs. 26.2%, P = 0.0054), but rate of ypStage 0/I (24.0% vs. 20.4%, P = 0.4580) or PEPI = 0 (28.4% vs. 20.6%, P = 0.3419) was not different. Patients with high SET2,3 had longer EFS than patients with low SET2,3 (HR, 0.52, 95% confidence interval: 0.34-0.80; P = 0.0026).

CONCLUSIONS

This exploratory analysis of Z1031 data demonstrated a higher rate of pharmacodynamic suppression of proliferation and longer EFS in high SET2,3 disease relative to low SET2,3 disease. The ypStage 0/I rate and PEPI = 0 rate were similar with respect to SET2,3.

Abstract 1595: Analysis of spatiotemporal phenotypic heterogeneity in chemoresistant triple negative breast cancer using imaging mass cytometry

Shifts in tumor cell phenotype in response to selective pressures (i.e. changing microenvironments, drug treatments) pose one of the biggest obstacles to successful breast cancer therapies. Phenotypically diverse breast tumor and stroma subpopulations, and interactions between them that alter tumor cell biology, represent unique and spatially distinct niches. We hypothesize that localized neighborhoods of breast tumor cells possess specialized phenotypes that mediate chemoresistance and represent novel therapeutic vulnerabilities. In order to assess these potential phenotypes, we utilized imaging mass cytometry (IMC), a highly multiplexed imaging modality that allows simultaneous measurement of 30-40 antigens while retaining the spatial architecture of the cancer tissue. We constructed an IMC antibody panel that combines markers for tissue architecture, tumor and stromal cell phenotyping, and signaling pathway activation. IMC was applied to patient-derived xenograft (PDX) models of triple negative breast cancer (TNBC).Our TNBC PDX collection was established from tumors obtained before and after neoadjuvant Adriamycin and cyclophosphamide (AC). IMC analysis of 18 PDX models representing eight patients revealed that stromal cell phenotypes were generally shared between all models, but tumor cell phenotypes were largely patient-specific. While every model was comprised primarily of a few major tumor cell phenotypes, we noted that each case also harbored several minor, unique populations, suggesting that specialized neighborhoods may exist within the tumor mass. Comparison of paired PDX models showed a wide range of phenotypic responses to chemotherapy, ranging from stable tumor composition to widespread changes in tumor phenotypes. These phenotypic changes arose despite relatively consistent genomic architecture. Vimentinhi fibroblasts were present more often in post-AC models, while SMAhi fibroblasts were unchanged after treatment. Comparison of pre-/post-AC PDX pairs revealed spatially constrained MAPK activation emerged after treatment. To capture acute changes in tumor phenotype, we treated treatment-naïve PDX models with AC and evaluated tumors by IMC. As tumors regressed and then regrew, we identified novel phenotypic shifts, again including increased MAPK signaling localized to discrete neighborhoods, suggesting this property may be a common feature of chemoresistant TNBC. Analysis of adjacent cells revealed seven distinct neighborhoods, and ongoing work is aimed at determining whether these neighborhoods are altered in response to chemotherapy treatment. Taken together, our findings suggest that distinct tumor phenotypes arise following treatment. Our goal is to determine whether these unique phenotypic niches functionally contribute to chemoresistance and if disruption of these niches enhances chemosensitivity.

Citation Format: Amanda L. Rinkenbaugh, Vidya C. Sinha, Pankaj Singh, Yuan Qi, Jiansu Shao, Xiaomei Zhang, Gloria V. Echeverria, W. Fraser Symmans, Stacy L. Moulder, Helen Piwnica-Worms. Analysis of spatiotemporal phenotypic heterogeneity in chemoresistant triple negative breast cancer using imaging mass cytometry [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1595.

Redefining breast cancer subtypes to guide treatment prioritization and maximize response: Predictive biomarkers across 10 cancer therapies

Using pre-treatment gene expression, protein/phosphoprotein, and clinical data from the I-SPY2 neoadjuvant platform trial (NCT01042379), we create alternative breast cancer subtypes incorporating tumor biology beyond clinical hormone receptor (HR) and human epidermal growth factor receptor-2 (HER2) status to better predict drug responses. We assess the predictive performance of mechanism-of-action biomarkers from ∼990 patients treated with 10 regimens targeting diverse biology. We explore >11 subtyping schemas and identify treatment-subtype pairs maximizing the pathologic complete response (pCR) rate over the population. The best performing schemas incorporate Immune, DNA repair, and HER2/Luminal phenotypes. Subsequent treatment allocation increases the overall pCR rate to 63% from 51% using HR/HER2-based treatment selection. pCR gains from reclassification and improved patient selection are highest in HR+ subsets (>15%). As new treatments are introduced, the subtyping schema determines the minimum response needed to show efficacy. This data platform provides an unprecedented resource and supports the usage of response-based subtypes to guide future treatment prioritization.

Abstract PD9-06: Evaluation of the predicted sensitivity to endocrine therapy (SET2,3 index) and the 21-gene Breast Recurrence Score® assay in node-positive postmenopausal breast cancer: Results from an analysis in the SWOG S8814 trial

Background. SWOG trial S8814 randomized postmenopausal patients with pathologic lymph node-positive (N+) breast cancer that was hormone receptor-positive to receive adjuvant anthracycline-based chemotherapy (cyclophosphamide, doxorubicin, fluorouracil) followed by tamoxifen endocrine therapy for 5 years (CAF-T), versus tamoxifen alone (TAM). The 21-gene Breast Recurrence Score® assay was prognostic in S8814 and predicted chemotherapy benefit in patients with higher Recurrence Score® (RS) (Albain et al, Lancet Oncol 2009). Other prognostic signatures have yet to be evaluated in this cohort. The sensitivity to endocrine therapy index (SET2,3) measures non-proliferative hormone receptor-related transcription (SETER/PR) adjusted for a baseline prognosis index derived from tumor size, nodes involved and a 4-gene molecular subtype (RNA4) (Du et al, Ann Oncol 2021). SET2,3 has been shown to provide prognostic information independent from neoadjuvant chemotherapy response. We sought to evaluate the predictive and prognostic value of SET2,3 in SWOG 8814. Methods. Independently, the SET2,3 index and cut point were calibrated from their diagnostic platform to the whole transcriptome RNA sequencing (RNAseq) platform in 85 sample pairs. Expression of the 31 transcripts used for SET2,3 were provided from RNAseq data of 283 tumors in S8814 (all previously tested for RS). Blinded calculated results of SET2,3 were then merged with outcome data. The planned analysis tested whether SET2,3 (continuous index, dichotomized high/low) provided additional prognostic information to RS (overall and in pts. with RS≤25) by treatment arm, and whether low SET2,3 was associated with chemo benefit. Cox proportional hazards models of disease-free survival (DFS) included SET2,3; RS; treatment arm; and (where relevant) interaction term and reported hazard ratios (HR) and 95% confidence intervals (95%CI). Results. There were 106 events over median follow-up of 9.1 years in 283 patients. 175 patients had RS ≤25, 108 had RS &gt;25. Distribution of the SET2,3 low was similar in both RS high (51%) and low groups (47%), reflecting minimal correlation between the two. As proportional hazards assumptions were met during the first 5 years only the analysis was restricted to 5 years. Adjusting for treatment arm, high SET2,3 category was highly prognostic in this randomized trial (HR 0.27, 95% CI 0.15-0.49, p&lt;0.0001). High SET2,3 was not predictive of chemotherapy response (interaction p=0.83). In multivariable Cox models (Table), continuous RS and SET2,3 were independently prognostic in the overall population for each treatment arm (p≤0.01), whereas only SET2,3 was prognostic for patients with RS≤25 (N=175, p&lt;0.001). In patients with RS≤25, continuous SET2,3 was prognostic within the CAF-T arm (HR 0.34, p=0.006) with similar results in the TAM alone arm (HR 0.38, p=0.062). Conclusions. SET2,3 added independent prognostic information to RS results in the S8814 trial for patients with N+ disease treated with tamoxifen, though it was not predictive of benefit from adjuvant chemotherapy. When RS result ≤25, SET2,3 remained independently prognostic. Hence, SET2,3 provided independent information complementary to RS, possibly because it incorporates tumor size and number of positive nodes. SET2,3 warrants further evaluation in patients with N+ breast cancer.

Table: Multivariable Cox models in the overall population and subset with RS≤25 by treatment arm.CohortTreatment ArmContinuous Recurrence ScoreContinuous SET2,3HR (95%CI) per 10 unitsp-valueHR (95%CI)per 1 unitp-valueAll RS(N=283)CAF-TAM(N=166)1.21 (1.04-1.40)0.0120.48 (0.31-0.76)0.002TAM(N=117)1.44 (1.18-1.76)&lt; 0.0010.48 (0.27-0.88)0.017RS≤25 (N=175)CAF-TAM(N=99)1.43 (0.58-3.49)0.440.34 (0.15-0.73)0.006TAM(N=76)1.66 (0.46-5.93)0.440.38 (0.14-1.05)0.062

Citation Format: Corey W. Speers, W. Fraser Symmans, William E. Barlow, Alex Trevarton, Stephanie The, Lili Du, James M. Rae, Steven Shak, Frederick L. Baehner, Priyanka Sharma, Lajos Pusztai, Gabriel N. Hortobagyi, Daneil F Hayes, Kathy S. Albain, Andrew Godwin, Alastair Thompson. Evaluation of the predicted sensitivity to endocrine therapy (SET2,3 index) and the 21-gene Breast Recurrence Score® assay in node-positive postmenopausal breast cancer: Results from an analysis in the SWOG S8814 trial [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD9-06.

Abstract PD1-07: Mutant ESR1 receptors antagonize the tumor suppressor function of androgen receptors

Background: Acquired ESR1 mutations are a dominant driver of distant metastasis in metastatic breast cancer, inducing a basal-like phenotype that is relatively resistant to ER antagonists with decreased progression free survival. The majority of ER+ patients also express the androgen receptor (AR), and although AR expression is associated with better outcomes, high AR expression has also been associated with resistance to endocrine therapy (ET). Thus, there is currently a conundrum on how best to target AR, and to define when it is participating as a proliferative/metastatic driver, or when it may be a potential tumor suppressor associated with good prognosis. Methods: We generated ESR1 Y537S or D538G homozygous mutations in MCF-7 cells using CRISPR Cas-9 technology. ChIP-Seq, transcriptome analyses, and quantitative analysis of ER ChIP-Seq profiles from patient biopsies were integrated. Nuclear fractionation and immunoblot analyses were performed. Results: Correlation and gene set enrichment analyses demonstrated that the androgen response pathway was significantly reduced in ESR1 mutant, compared to wild-type (WT) ER cells. A dramatic redistribution in AR binding sites to heterochromatin was observed in ESR1 mutant cells. AR and ER co-occupied DNA binding sites were redistributed only to ERE motifs present in a restricted set of gene enhancer regions. Quantitative analysis of ER DNA binding profiles from ER+ patients showed that the highest recruitment of ER to AR/ER binding sites were in patients with metastatic breast cancer. Integration of AR/ER co-bound sites with the differentially-expressed mutant transcriptome identified a gene signature that predicted poor disease-free and overall survival in ER+ primary breast cancer patients from the METABRIC database. Elevated gene expression of these AR/ER co-regulated genes, including NCOA3, BMP7, N4BP3, and FOXA1, were validated in a cohort of metastatic tumors (N=97), compared to primary tumors (N=276). AR protein levels were elevated in ESR1 mutant tumors. Mechanistic studies demonstrated that elevated AR phosphorylation at specific sites (pS515, pS650) and decreased phosphorylation (pS308) occurs in mutant cells. These sites are known to affect AR transcriptional activity, protein stability, and nuclear export. Decreased K48-AR ubiquitination was observed, suggesting that elevated AR protein levels result from altered post-transcriptional modification of AR in mutant cells. Conclusions: We propose a two-prong genomic activation mechanism in ESR1 mutant tumors with AR redistribution to heterochromatin, and genomic co-activation of AR and ER. We hypothesize that the loss of AR tumor suppressor function may help drive metastasis in ESR1 mutant tumors via AR’s collaboration with ESR1 mutant oncogenic activity. Efficacious targeting of AR may require disruption of this driver AR/ER-regulated transcriptional program.

Citation Format: Sandra L. Grimm, Guowei Gu, Sarah K. Herzog, Thomas L. Gonzalez, Hangqing Lin, Amanda R. Beyer, Yassine Rechoum, Tasneem Bawa-Khalfe, Ashfia F. Khan, Lili Du, W. Fraser Symmans, Ralf Kittler, Cristian Coarfa, Suzanne A.W. Fuqua. Mutant ESR1 receptors antagonize the tumor suppressor function of androgen receptors [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD1-07.

Abstract PD8-07: Evaluation of Tucatinib + (Paclitaxel + Pertuzumab + Trastuzumab) followed by AC in high-risk HER2 positive (HER2+) stage II/III breast cancer: Results from the I-SPY 2 TRIAL

Background: I-SPY 2 is a multicenter, phase 2 trial using response-adaptive randomization within molecular subtypes defined by receptor status and MammaPrint (MP) risk to evaluate novel agents as neoadjuvant therapy for women with high-risk breast cancer. Tucatinib is a potent HER2 (ErbB2) tyrosine kinase inhibitor, selective for HER2 vs. epidermal growth factor receptor (EGFR) and is active vs. brain metastases. Safety and efficacy of tucatinib combined with paclitaxel, pertuzumab, and trastuzumab are unknown and were tested in a planned 10 patient (pt) safety run-in of the I-SPY 2 trial. Methods: Women with tumors ≥ 2.5cm were eligible for screening. Only pts with tumors that were HER2+ by FISH were eligible for this treatment. Treatment included tucatinib (max dose 300 mg) BID for 12 weeks with weekly paclitaxel 80 mg/m2 and trastuzumab (2 mg/kg weekly following loading), and pertuzumab (420 mg every 3 weeks following loading), followed by doxorubicin/cyclophosphamide (AC) every 2 weeks x 4. The control arm was weekly paclitaxel and trastuzumab with pertuzumab for 12 weeks followed by AC every 2 weeks x 4. All pts undergo serial MR imaging and response at 3 & 12 weeks is combined with real time pCR data to estimate, and continuously update, the predicted pCR rate for each trial arm. The goal of the trial is to identify/graduate regimens with ≥85.% Bayesian predictive probability of success (i.e. demonstrating superiority to control) in a future 300-patient phase 3 neoadjuvant trial with a pCR endpoint. This run-in arm was conducted to determine safety of combining tucatinib with paclitaxel/trastuzumab/pertuzumab, monitoring special adverse events of interest including LFT elevations and gastrointestinal toxicities.Methods: The I-SPY 2 methods have been previously published. Results: 20 pts were evaluable in tucatinib treatment arm. The control arm included 329 historical controls enrolled since April 2010. The initial tucatinib dose was 300 mg BID. After enrollment of the first 8 pts, there were 3 pts with grade 3 LFT elevations, 2 pts with grade 2/3 diarrhea, 1 pt with grade 2 neutropenia, and 1 pt with grade 3 nausea. After this safety review, the tucatinib dose was lowered to 250 mg BID. Among 5 additional pts enrolled, 3 developed grade 2/3 LFT abnormalities. The protocol was then modified to tucatinib 150 mg BID days 1-28 and then 250 mg BID days 29-84; 7 pts were treated. Safety data were reviewed after 20 pts were enrolled; the arm was then suspended due to similar LFT elevations regardless of tucatinib dose reduction or schedule. 7 of 20 pts (35%) had reversible Grade 3 or higher ALT/AST elevation (Table). No pt met criteria for Hy’s Law. In terms of efficacy, 12 of 14 evaluable pts had &gt; 80% reduction of tumor volume by 12 weeks, measured by MRI assessment of functional tumor volume (FTV). Conclusion: The goal of the run-in arm was to determine the safety of adding tucatinib to the combination of paclitaxel/trastuzumab/pertuzumab. The addition of tucatinib resulted in unacceptable but reversible LFT elevations despite tucatinib dose reduction. Tucatinib containing therapy resulted in &gt;80% decline in tumor volume at 12 weeks in 86% of pts. Tucatinib showed a high level of activity when combined with paclitaxel/trastuzumab/pertuzumab, but the combination is not feasible. Table: Number of pts with grade 2, 3, and 4 LFT elevations by treatment schedule (highest grade per patient per event, ALT or

Treatment scheduleGrade 2 LFT elevationGrade 3 LFT elevationGrade 4 LFT elevationTucatinib 300 mg BID030Tucatinib 250 mg BID210Tucatinib 150 mg BID days 1-28 followed by 250 mg BID days 29 to 84112

Citation Format: David A Potter, Erin Roesch, Christina Yau, Ruixiao Lu, Denise Wolf, Susan Samson, Debra Stafford, Kathy S Albain, Claudine Isaacs, Meghana Trivedi, Douglas Yee, Judy Boughey, Alexandra Thomas, A. Jo Chien, Nola Hylton, Wen Li, Angela DeMichele, Jane Perlmutter, W. Fraser Symmans, Dawn L Hershman, Michelle Melisko, Laura J van 't Veer, Amy Wilson, Smita M Asare, Donald A Berry, Richard Schwab, Hope S Rugo, Laura J Esserman. Evaluation of Tucatinib + (Paclitaxel + Pertuzumab + Trastuzumab) followed by AC in high-risk HER2 positive (HER2+) stage II/III breast cancer: Results from the I-SPY 2 TRIAL [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD8-07.

Long-term efficacy and safety of addition of carboplatin with or without veliparib to standard neoadjuvant chemotherapy in triple-negative breast cancer: 4-year follow-up data from BrighTNess, a randomized phase 3 trial

BACKGROUND

Primary analyses of the phase 3 BrighTNess trial showed addition of carboplatin with/without veliparib to neoadjuvant chemotherapy significantly improved pathological complete response (pCR) rates with manageable acute toxicity in patients with triple-negative breast cancer (TNBC). Here, we report 4.5-year follow-up data from the trial.

DESIGN

Women with untreated stage II-III TNBC were randomized (2:1:1) to paclitaxel (weekly for 12 doses) plus either: (a) carboplatin (every 3 weeks for four cycles) plus veliparib (twice daily); (b) carboplatin plus veliparib placebo; or (c) carboplatin placebo plus veliparib placebo. All patients then received doxorubicin and cyclophosphamide (AC) every 2‒3 weeks for four cycles. The primary endpoint was pCR. Secondary endpoints included event-free survival (EFS), overall survival (OS), and safety. Since the co-primary endpoint of increased pCR with carboplatin plus veliparib with paclitaxel versus carboplatin with paclitaxel was not met, secondary analyses are descriptive.

RESULTS

Of 634 patients, 316 were randomized to carboplatin plus veliparib with paclitaxel, 160 to carboplatin with paclitaxel, and 158 to paclitaxel. With median follow-up of 4.5 years, the hazard ratio [HR] for EFS for carboplatin plus veliparib with paclitaxel versus paclitaxel was 0.63 (95% confidence interval [CI] 0.43‒0.92, P=0.02), but 1.12 (95% CI 0.72‒1.72, P=0.62) for carboplatin plus veliparib with paclitaxel versus carboplatin with paclitaxel. In post hoc analysis, HR for EFS was 0.57 (95% CI 0.36‒0.91, P=0.02) for carboplatin with paclitaxel versus paclitaxel. OS did not differ significantly between treatment arms, nor did rates of myelodysplastic syndromes, acute myeloid leukemia, or other secondary malignancies.

CONCLUSION

Improvement in pCR with addition of carboplatin was associated with long-term EFS benefit with a manageable safety profile, and without increasing the risk of second malignancies, while adding veliparib did not impact EFS. These findings support the addition of carboplatin to weekly paclitaxel followed by AC neoadjuvant chemotherapy for early stage TNBC.

Residual cancer burden after neoadjuvant chemotherapy and long-term survival outcomes in breast cancer: a multicentre pooled analysis of 5161 patients

BACKGROUND

Previous studies have independently validated the prognostic relevance of residual cancer burden (RCB) after neoadjuvant chemotherapy. We used results from several independent cohorts in a pooled patient-level analysis to evaluate the relationship of RCB with long-term prognosis across different phenotypic subtypes of breast cancer, to assess generalisability in a broad range of practice settings.

METHODS

In this pooled analysis, 12 institutes and trials in Europe and the USA were identified by personal communications with site investigators. We obtained participant-level RCB results, and data on clinical and pathological stage, tumour subtype and grade, and treatment and follow-up in November, 2019, from patients (aged ≥18 years) with primary stage I-III breast cancer treated with neoadjuvant chemotherapy followed by surgery. We assessed the association between the continuous RCB score and the primary study outcome, event-free survival, using mixed-effects Cox models with the incorporation of random RCB and cohort effects to account for between-study heterogeneity, and stratification to account for differences in baseline hazard across cancer subtypes defined by hormone receptor status and HER2 status. The association was further evaluated within each breast cancer subtype in multivariable analyses incorporating random RCB and cohort effects and adjustments for age and pretreatment clinical T category, nodal status, and tumour grade. Kaplan-Meier estimates of event-free survival at 3, 5, and 10 years were computed for each RCB class within each subtype.

FINDINGS

We analysed participant-level data from 5161 patients treated with neoadjuvant chemotherapy between Sept 12, 1994, and Feb 11, 2019. Median age was 49 years (IQR 20-80). 1164 event-free survival events occurred during follow-up (median follow-up 56 months [IQR 0-186]). RCB score was prognostic within each breast cancer subtype, with higher RCB score significantly associated with worse event-free survival. The univariable hazard ratio (HR) associated with one unit increase in RCB ranged from 1·55 (95% CI 1·41-1·71) for hormone receptor-positive, HER2-negative patients to 2·16 (1·79-2·61) for the hormone receptor-negative, HER2-positive group (with or without HER2-targeted therapy; p<0·0001 for all subtypes). RCB score remained prognostic for event-free survival in multivariable models adjusted for age, grade, T category, and nodal status at baseline: the adjusted HR ranged from 1·52 (1·36-1·69) in the hormone receptor-positive, HER2-negative group to 2·09 (1·73-2·53) in the hormone receptor-negative, HER2-positive group (p<0·0001 for all subtypes).

INTERPRETATION

RCB score and class were independently prognostic in all subtypes of breast cancer, and generalisable to multiple practice settings. Although variability in hormone receptor subtype definitions and treatment across patients are likely to affect prognostic performance, the association we observed between RCB and a patient's residual risk suggests that prospective evaluation of RCB could be considered to become part of standard pathology reporting after neoadjuvant therapy.

FUNDING

National Cancer Institute at the US National Institutes of Health.

Matched cohort study of germline BRCA mutation carriers with triple negative breast cancer in brightness

In the BrighTNess trial, carboplatin added to neoadjuvant chemotherapy (NAC) was associated with increased pathologic complete response (pCR) rates in patients with stage II/III triple-negative breast cancer (TNBC). In this matched cohort study, cases with a germline BRCA1/2 mutation (gBRCA; n = 75) were matched 1:2 with non-gBRCA controls (n = 150) by treatment arm, lymph node status, and age to evaluate pCR rates and association of benefit from platinum/PARP inhibitors with validated RNA expression-based immune, proliferation, and genomic instability scores among gBRCA with the addition of carboplatin ± veliparib to NAC. Among the well-matched cohorts, odds of pCR were not higher in gBRCA cancers who received standard NAC with carboplatin (OR 0.24, 95% CI [0.04-1.24], p = 0.09) or with carboplatin/veliparib (OR 0.44, 95% CI [0.10-1.84], p = 0.26) compared to non-gBRCA cancers. Higher PAM50 proliferation, GeparSixto immune, and CIN70 genomic instability scores were each associated with higher pCR rate in the overall cohort, but not specifically in gBRCA cases. In this study, gBRCA carriers did not have higher odds of pCR than non-gBRCA controls when carboplatin ± veliparib was added to NAC, and showed no significant differences in molecular, immune, chromosomal instability, or proliferation gene expression metrics.

Neoadjuvant T-DM1/pertuzumab and paclitaxel/trastuzumab/pertuzumab for HER2+ breast cancer in the adaptively randomized I-SPY2 trial

HER2-targeted therapy dramatically improves outcomes in early breast cancer. Here we report the results of two HER2-targeted combinations in the neoadjuvant I-SPY2 phase 2 adaptive platform trial for early breast cancer at high risk of recurrence: ado-trastuzumab emtansine plus pertuzumab (T-DM1/P) and paclitaxel, trastuzumab and pertuzumab (THP). Eligible women have >2.5 cm clinical stage II/III HER2+ breast cancer, adaptively randomized to T-DM1/P, THP, or a common control arm of paclitaxel/trastuzumab (TH), followed by doxorubicin/cyclophosphamide, then surgery. Both T-DM1/P and THP arms 'graduate' in all subtypes: predicted pCR rates are 63%, 72% and 33% for T-DM1/P (n = 52), THP (n = 45) and TH (n = 31) respectively. Toxicity burden is similar between arms. Degree of HER2 pathway signaling and phosphorylation in pretreatment biopsy specimens are associated with response to both T-DM1/P and THP and can further identify highly responsive HER2+ tumors to HER2-directed therapy. This may help identify patients who can safely de-escalate cytotoxic chemotherapy without compromising excellent outcome.

Assessment of Residual Cancer Burden and Event-Free Survival in Neoadjuvant Treatment for High-risk Breast Cancer: An Analysis of Data From the I-SPY2 Randomized Clinical Trial

Importance

Residual cancer burden (RCB) distributions may improve the interpretation of efficacy in neoadjuvant breast cancer trials.

Objective

To compare RCB distributions between randomized control and investigational treatments within subtypes of breast cancer and explore the relationship with survival.

Design, Setting, and Participants

The I-SPY2 is a multicenter, platform adaptive, randomized clinical trial in the US that compares, by subtype, investigational agents in combination with chemotherapy vs chemotherapy alone in adult women with stage 2/3 breast cancer at high risk of early recurrence. Investigational treatments graduated in a prespecified subtype if there was 85% or greater predicted probability of higher rate of pathologic complete response (pCR) in a confirmatory, 300-patient, 1:1 randomized, neoadjuvant trial in that subtype. Evaluation of a secondary end point was reported from the 10 investigational agents tested in the I-SPY2 trial from March 200 through 2016, and analyzed as of September 9, 2020. The analysis plan included modeling of RCB within subtypes defined by hormone receptor (HR) and ERBB2 status and compared control treatments with investigational treatments that graduated and those that did not graduate.

Interventions

Neoadjuvant paclitaxel plus/minus 1 of several investigational agents for 12 weeks, then 12 weeks of cyclophosphamide/doxorubicin chemotherapy followed by surgery.

Main Outcomes and Measures

Residual cancer burden (pathological measure of residual disease) and event-free survival (EFS).

Results

A total of 938 women (mean [SD] age, 49 [11] years; 66 [7%] Asian, 103 [11%] Black, and 750 [80%] White individuals) from the first 10 investigational agents were included, with a median follow-up of 52 months (IQR, 29 months). Event-free survival worsened significantly per unit of RCB in every subtype of breast cancer (HR-positive/ERBB2-negative: hazard ratio [HZR], 1.75; 95% CI, 1.45-2.16; HR-positive/ERBB2-positive: HZR, 1.55; 95% CI, 1.18-2.05; HR-negative/ERBB2-positive: HZR, 2.39; 95% CI, 1.64-3.49; HR-negative/ERBB2-negative: HZR, 1.99; 95% CI, 1.71-2.31). Prognostic information from RCB was similar from treatments that graduated (HZR, 2.00; 95% CI, 1.57-2.55; 254 [27%]), did not graduate (HZR, 1.87; 95% CI, 1.61-2.17; 486 [52%]), or were control (HZR, 1.79; 95% CI, 1.42-2.26; 198 [21%]). Investigational treatments significantly lowered RCB in HR-negative/ERBB2-negative (graduated and nongraduated treatments) and ERBB2-positive subtypes (graduated treatments), with improved EFS (HZR, 0.61; 95% CI, 0.41-0.93) in the exploratory analysis.

Conclusions and Relevance

In this randomized clinical trial, the prognostic significance of RCB was consistent regardless of subtype and treatment. Effective neoadjuvant treatments shifted the distribution of RCB in addition to increasing pCR rate and appeared to improve EFS. Using a standardized quantitative method to measure response advances the interpretation of efficacy.

Trial Registration

ClinicalTrials.gov Identifier: NCT01042379.

Ganitumab and metformin plus standard neoadjuvant therapy in stage 2/3 breast cancer

I-SPY2 is an adaptively randomized phase 2 clinical trial evaluating novel agents in combination with standard-of-care paclitaxel followed by doxorubicin and cyclophosphamide in the neoadjuvant treatment of breast cancer. Ganitumab is a monoclonal antibody designed to bind and inhibit function of the type I insulin-like growth factor receptor (IGF-1R). Ganitumab was tested in combination with metformin and paclitaxel (PGM) followed by AC compared to standard-of-care alone. While pathologic complete response (pCR) rates were numerically higher in the PGM treatment arm for hormone receptor-negative, HER2-negative breast cancer (32% versus 21%), this small increase did not meet I-SPY's prespecified threshold for graduation. PGM was associated with increased hyperglycemia and elevated hemoglobin A1c (HbA1c), despite the use of metformin in combination with ganitumab. We evaluated several putative predictive biomarkers of ganitumab response (e.g., IGF-1 ligand score, IGF-1R signature, IGFBP5 expression, baseline HbA1c). None were specific predictors of response to PGM, although several signatures were associated with pCR in both arms. Any further development of anti-IGF-1R therapy will require better control of anti-IGF-1R drug-induced hyperglycemia and the development of more predictive biomarkers.

Interpreting the Complex Landscape of Immune-Tumor Interface

Predictive biomarkers for immune therapy must address a complex interface between the immune system and triple-negative breast cancer and still be technically reliable for diagnostic use. Two recent papers describe the assessment of spatial heterogeneity using digital methods that promise to improve the quantification of immune infiltrate or molecular targets.

Intra- and Interlaboratory Reproducibility of the Sensitivity to Endocrine Therapy Assay for Stage II/III Breast Cancer

BACKGROUND

The sensitivity to endocrine therapy assay (SET2,3) predicts treatment outcomes in Stage II-III breast cancer. SET2,3 measures transcription related to estrogen and progesterone receptors (SETER/PR index) and the molecular subtype (RNA4: ESR1, PGR, ERBB2, AURKA) from formalin-fixed paraffin-embedded (FFPE) tissue sections.

METHODS

We designed a nested study across 3 pathology laboratories, each testing 60 breast cancers twice in controlled batches. Laboratories macrodissected and directly homogenized the unstained FFPE tumor sections, then performed the QuantiGene Plex bead-based hybridization assay. SET2,3 was calculated centrally using predefined statistical R-scripts and applying pre-defined cutpoints. Concordance correlation coefficient (CCC) was calculated from continuous measurements and Kappa statistic from categorical results. A mixed-effects model estimated contributions to bias (fixed effects) and variance (random effects) from the replicated design.

RESULTS

Intralaboratory (CCC 0.96-0.99) and interlaboratory (CCC 0.98-0.99) SET2,3 results were concordant, with rates of agreement for high/low categorization within (Kappa 0.83-0.93) and between laboratories (Kappa 0.87-0.88). The relative contributions to overall variance of SET2,3 measurements were 96.90% from biological differences between cancers, 0.67% from interlaboratory variability, and 2.44% from residual causes including intralaboratory replicates. Similar results were obtained with SETER/PR, the baseline prognostic index calculated using pathological or clinical tumor and nodal staging information, and the 4 individual genes (ESR1, PGR, ERBB2, and AURKA).

CONCLUSION

Intra- and interpathology laboratory measurements of SET2,3 and its components were highly reproducible when tested from FFPE tumor sections.

Durvalumab with olaparib and paclitaxel for high-risk HER2-negative stage II/III breast cancer: Results from the adaptively randomized I-SPY2 trial

The combination of PD-L1 inhibitor durvalumab and PARP inhibitor olaparib added to standard paclitaxel neoadjuvant chemotherapy (durvalumab/olaparib/paclitaxel [DOP]) was investigated in the phase II I-SPY2 trial of stage II/III HER2-negative breast cancer. Seventy-three participants were randomized to DOP and 299 to standard of care (paclitaxel) control. DOP increased pathologic complete response (pCR) rates in all HER2-negative (20%-37%), hormone receptor (HR)-positive/HER2-negative (14%-28%), and triple-negative breast cancer (TNBC) (27%-47%). In HR-positive/HER2-negative cancers, MammaPrint ultra-high (MP2) cases benefited selectively from DOP (pCR 64% versus 22%), no benefit was seen in MP1 cancers (pCR 9% versus 10%). Overall, 12.3% of patients in the DOP arm experienced immune-related grade 3 adverse events versus 1.3% in control. Gene expression signatures associated with immune response were positively associated with pCR in both arms, while a mast cell signature was associated with non-pCR. DOP has superior efficacy over standard neoadjuvant chemotherapy in HER2-negative breast cancer, particularly in a highly sensitive subset of high-risk HR-positive/HER2-negative patients.

Association of Immunophenotype With Pathologic Complete Response to Neoadjuvant Chemotherapy for Triple-Negative Breast Cancer: A Secondary Analysis of the BrighTNess Phase 3 Randomized Clinical Trial

Importance

Adding carboplatin to standard neoadjuvant chemotherapy (NAC) in triple-negative breast cancer (TNBC) likely benefits a subset of patients; however, determinants of benefit are poorly understood.

Objective

To define the association of molecular subtype, tumor proliferation, and immunophenotype with benefit of carboplatin added to NAC for patients with stages II to III TNBC.

Design, Setting, and Participants

This was a prespecified secondary analysis of a phase 3, double-blind, randomized clinical trial (BrighTNess) that enrolled 634 women across 145 centers in 15 countries. Women with clinical stages II to III TNBC who had undergone pretreatment biopsy were eligible to participate. Whole transcriptome RNA sequencing was performed on the biopsy specimens. The prespecified end point was association of pathologic complete response (pCR) with gene expression-based molecular subtype, with secondary end points investigating established signatures (proliferation, immune) and exploratory analyses of immunophenotype. Data were collected from April 2014 to March 2016. The study analyses were performed from January 2018 to March 2019.

Interventions

Neoadjuvant chemotherapy with paclitaxel followed by doxorubicin and cyclophosphamide, or this same regimen with carboplatin or carboplatin plus veliparib.

Main Outcomes and Measures

Association of gene expression-based molecular subtype (PAM50 and TNBC subtypes) with pCR.

Results

Of the 634 women (median age, 51 [range, 22-78] years) enrolled in BrighTNess, 482 (76%) patients had evaluable RNA sequencing data, with similar baseline characteristics relative to the overall intention-to-treat population. Pathologic complete response was significantly more frequent in PAM50 basal-like vs nonbasal-like cancers overall (202 of 386 [52.3%] vs 34 of 96 [35.4%]; P = .003). Carboplatin benefit was not significantly different in basal-like vs nonbasal-like subgroups (P = .80 for interaction). In multivariable analysis, proliferation (hazard ratio, 0.36; 95% CI, 0.21-0.61; P < .001) and immune (hazard ratio, 0.62; 95% CI, 0.49-0.79; P < .001) signatures were independently associated with pCR. Tumors above the median for proliferation and immune signatures had the highest pCR rate (84 of 125; 67%), while those below the median for both signatures had the lowest pCR rate (42 of 125; 34%). Exploratory gene expression immune analyses suggested that tumors with higher inferred CD8+ T-cell infiltration may receive greater benefit with addition of carboplatin.

Conclusions and Relevance

In this secondary analysis of a randomized clinical trial, triple-negative breast cancer subtyping revealed high pCR rates in basal-like and immunomodulatory subsets. Analysis of biological processes related to basal-like and immunomodulatory phenotypes identified tumor cell proliferation and immune scores as independent factors associated with achieving pCR; the benefit of carboplatin on pCR was seen across all molecular subtypes. Further validation of immunophenotype with existing biomarkers may help to escalate or de-escalate therapy for patients with TNBC.

Trial Registration

ClinicalTrials.gov Identifier: NCT02032277.

Technical Validity of a Customized Assay of Sensitivity to Endocrine Therapy Using Sections from Fixed Breast Cancer Tissue

BACKGROUND

We translated a multigene expression index to predict sensitivity to endocrine therapy for Stage II-III breast cancer (SET2,3) to hybridization-based expression assays of formalin-fixed paraffin-embedded (FFPE) tissue sections. Here we report the technical validity with FFPE samples, including preanalytical and analytical performance.

METHODS

We calibrated SET2,3 from microarrays (Affymetrix U133A) of frozen samples to hybridization-based assays of FFPE tissue, using bead-based QuantiGene Plex (QGP) and slide-based NanoString (NS). The following preanalytical and analytical conditions were tested in controlled studies: replicates within and between frozen and fixed samples, age of paraffin blocks, homogenization of fixed sections versus extracted RNA, core biopsy versus surgically resected tumor, technical replicates, precision over 20 weeks, limiting dilution, linear range, and analytical sensitivity. Lin's concordance correlation coefficient (CCC) was used to measure concordance between measurements.

RESULTS

SET2,3 index was calibrated to use with QGP (CCC 0.94) and NS (CCC 0.93) technical platforms, and was validated in two cohorts of older fixed samples using QGP (CCC 0.72, 0.85) and NS (CCC 0.78, 0.78). QGP assay was concordant using direct homogenization of fixed sections versus purified RNA (CCC 0.97) and between core and surgical sample types (CCC 0.90), with 100% accuracy in technical replicates, 1-9% coefficient of variation over 20 weekly tests, linear range 3.0-11.5 (log2 counts), and analytical sensitivity ≥2.0 (log2 counts).

CONCLUSIONS

Measurement of the novel SET2,3 assay was technically valid from fixed tumor sections of biopsy or resection samples using simple, inexpensive, hybridization methods, without the need for RNA purification.

Predicted sensitivity to endocrine therapy for stage II-III hormone receptor-positive and HER2-negative (HR+/HER2-) breast cancer before chemo-endocrine therapy

BACKGROUND

We proposed that a test for sensitivity to the adjuvant endocrine therapy component of treatment for patients with stage II-III breast cancer (SET2,3) should measure transcription related to estrogen and progesterone receptors (SET_ER/PR index) adjusted for a baseline prognostic index (BPI) combining clinical tumor and nodal stage with molecular subtype by RNA4 (ESR1, PGR, ERBB2, and AURKA).

PATIENTS AND METHODS

Patients with clinically high-risk, hormone receptor-positive (HR+), human epidermal growth factor receptor 2 (HER2)-negative (HR+/HER2-) breast cancer received neoadjuvant taxane-anthracycline chemotherapy, surgery with measurement of residual cancer burden (RCB), and then adjuvant endocrine therapy. SET2,3 was measured from pre-treatment tumor biopsies, evaluated first in an MD Anderson Cancer Center (MDACC) cohort (n = 307, 11 years' follow-up, U133A microarrays), cut point was determined, and then independent, blinded evaluation was carried out in the I-SPY2 trial (n = 268, high-risk MammaPrint result, 3.8 years' follow-up, Agilent-44K microarrays, NCI Clinical Trials ID: NCT01042379). Primary outcome measure was distant relapse-free survival. Multivariate Cox regression models tested prognostic independence of SET2,3 relative to RCB and other molecular prognostic signatures, and whether other prognostic signatures could substitute for SET_ER/PR or RNA4 components of SET2,3.

RESULTS

SET2,3 added independent prognostic information to RCB in the MDACC cohort: SET2,3 [hazard ratio (HR) 0.23, P = 0.004] and RCB (HR 1.77, P < 0.001); and the I-SPY2 trial: SET2,3 (HR 0.27, P = 0.031) and RCB (HR 1.68, P = 0.008). SET2,3 provided similar prognostic information irrespective of whether RCB-II or RCB-III after chemotherapy, and in both luminal subtypes. Conversely, RCB was most strongly prognostic in cancers with low SET2,3 status (MDACC P < 0.001, I-SPY2 P < 0.001). Other molecular signatures were not independently prognostic; they could effectively substitute for RNA4 subtype within the BPI component of SET2,3, but they could not effectively substitute for SET_ER/PR index.

CONCLUSIONS

SET2,3 added independent prognostic information to chemotherapy response (RCB) and baseline prognostic score or subtype. Approximately 40% of patients with clinically high-risk HR+/HER2- disease had high SET2,3 and could be considered for clinical trials of neoadjuvant endocrine-based treatment.

Abstract PS4-10: Serial MRI and pathology combined to select candidates for therapy de-escalation in the I-SPY 2 TRIAL

Background: The I-SPY 2 TRIAL, open to patients with locally advanced, molecular high-risk breast cancer, aims to bring each patient to pathologic complete response (pCR) with a minimum of toxicity. Here we test the hypothesis that imaging (MR volume predictors) combined with core biopsy may be used to accurately select candidates who show early response and provide an option of treatment de-escalation at mid-therapy (12 weeks). Methods: Of 100 I-SPY 2 patients with pathologist-assessed core biopsies at the inter-regimen time point (~12 weeks through treatment) and pCR data, 87 also had serial MR images and were considered in this study. Eleven I-SPY 2 TRIAL pathologists independently provided a digital assessment of the presence or absence of residual invasive cancer from H&E stained, and any requested ancillary IHC, images from imaging-guided core biopsies. Pathology predicts pCR if there is a consensus of no invasive residual disease. We generated predictions for all (55) unique pairs over the 11 pathologists, where pCR is predicted if both pathologists find no invasive cells. MRI pCR prediction models were previously developed on an independent dataset of ~990 I-SPY 2 patients, and applied to this cohort. Volume-based prediction models were previously optimized within each subtype and predicted probability thresholds were selected over a range of positive predictive value (PPV). In this study, MR predicts pCR (positive test) if the predicted probability is above a threshold that yields a given PPV value. For each pathologist pair, we combined pathology-based and MR-based predictors into a predictive-RCB (pre-RCB); and pre-RCB predicts a patient as pCR (RCB0) if both MR and pathology predicts pCR. Predictive performance is assessed by calculating the mean and range of PPV and sensitivity.Results: 39% (34/87) of the patients in this study achieved pCR. Over all pairs of pathologists, on average 80% of pathology-only predicted pCRs were true pCRs (mean PPV = 80% [range: 69-92%]), and 74% of patients who achieved pCR were predicted pCR by pathology alone (mean sensitivity = 74% [65-82%]). We assessed combinations with MR probability thresholds at PPV levels 50%-70%; and observed the best balance of PPV and sensitivity for the pre-RCB when MR thresholds were set at 50% PPV level. At this threshold setting, the pre-RCB achieved a PPV = 92% [83-100%], meaning on average 92% of predicted pCRs were true pCRs, and this improvement in positive predictive performance over pathology alone is achieved with a lower but still-reasonable 53% sensitivity [33-62%].

Conclusion: Pre-RCB, which predicts a patient as pCR if both MR and inter-regimen pathology predicts pCR, provides clinically actionable accuracy for treatment de-escalation for early responders (PPV&gt;90%). Adding a final MR review at the time of early surgery may further improve performance. Resulting from data presented in this abstract, the pre-RCB algorithm, including the final MR review, has been operationalized and will be used prospectively to identify patients who are highly likely to have already achieved pCR by the inter-regimen timepoint.

Citation Format: Sara J Venters, Wen Li, Denise M Wolf, Jodi M Carter, Molly E Klein, Kamaljeet Singh, Kimmie Rabe, I Tolgay Ocal, David Newitt, Christina Yau, Natsuko Onishi, Jessica Gibbs, Sunati Sahoo, Shuko Harada, Laila Khazai, Malini Harigopal, Alexander D Borowsky, Gregor Krings, Ronald Balassanian, Yunn-Yi Chen, Kimberley Cole, Sonal Shad, Barbara LeStage, Amy Delson, Sandra Finestone, Lamorna Brown-Swigart, I-SPY 2 Imaging Working Group, I-SPY 2 TRIAL Consortium, Laura Esserman, Laura van ‘t Veer, W Fraser Symmans, Nola M Hylton. Serial MRI and pathology combined to select candidates for therapy de-escalation in the I-SPY 2 TRIAL [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS4-10.

Abstract PD12-06: Treatment-related amenorrhea with T-DM1 plus pertuzumab (KP) is lower than with docetaxel/carboplatin/trastuzumab/pertuzumab (TCHP) in the phase III neoadjuvant KRISTINE trial

Background: Cytotoxic chemotherapy (CT) in combination with trastuzumab and pertuzumab (HP) is standard of care for patients (pts) diagnosed with HER2-positive early breast cancer (EBC). While highly effective, the toxicity associated with CT is challenging. In KRISTINE/TRIO-021, neoadjuvant T-DM1 was combined with pertuzumab (KP) and compared to standard TCHP. Pts. received six cycles of neoadjuvant treatment followed by adjuvant therapy (KP or HP). Pts. in the KP arm were allowed to receive standard adjuvant CT. Pathologic complete response (pCR) rate was significantly lower with KP versus TCHP and more pts. had disease progression prior to surgery with KP, resulting in a meaningfully lower event-free survival rate vs. the control (85.3% vs 94.2%). However, 3-year invasive disease-free survival was numerically similar in both arms. Neoadjuvant KP demonstrated less toxicity than standard CT, although treatment discontinuation was higher post-surgery. Association of KP and TCHP with treatment-related amenorrhea (TRA) in premenopausal EBC pts. has not been ascertained. Methods: All pts. with premenopausal status at study entry (those not meeting the menopause definition based on National Comprehensive Cancer Network Guidelines v3, 2012) and with menstrual period documented within 3 months of randomization, were independently evaluated for presence or absence of TRA by two reviewers. TRA, a prespecified exploratory endpoint of KRISTINE, was defined as cessation of menstruation for &gt;12 months in the absence of treatment with ovarian suppression or other interventions that can induce amenorrhea. Pts. were followed from the time of study entry through the 3-year follow up period after surgery. For cases with inconsistent determination between the two reviewers, a third reviewer adjudicated. TRA rates were calculated per arm, hormone-receptor (HR) status, adjuvant CT and age group. Proportions were compared by estimating the odds ratio (OR) and the 95% confidence interval. Results: Of 444 pts. enrolled, 205 were excluded based on being post-menopausal per NCCN guidelines. Of 239 pts. remaining, 56 were excluded due to insufficient data. The median age of pts. included was 40 years (range: 22-53) for TCHP and 42.5 (range: 23-52) for KP. TRA was observed in 55% (50/91) of pts. treated with TCHP compared to 30% (28/92) treated with KP (OR=2.79; 95% CI 1.52-5.12). In pts. with HR-positive EBC, TRA occurred in 62% with TCHP vs 35% for KP (OR=2.998; 95% CI 1.44-6.25). In those with HR-negative EBC, TRA was observed in 42% with TCHP vs. 21% with KP (OR=2.77; 95% CI 0.88-8.72). In the KP arm, TRA was observed in 38% (8/21) of pts. treated with standard adjuvant CT vs. 28% (20/71) of those that did not (OR 1.57; 95% CI 0.57-4.36). For women age ≤ 40, the rate of TRA was 38% with TCHP vs. 17% with KP (OR=3.00; 95% CI 1.05-8.60). For those &gt; 40 years, TRA was observed in 74% treated with TCHP vs. 39% of those with KP (OR=4.50; 95% CI 1.88-10.73). Conclusion: The rate of TRA with standard TCHP is nearly double that observed with KP, suggesting that targeted CT with an antibody-drug conjugate regimen is associated with less gonadal toxicity. Rates of TRA are higher in women over the age of 40 for each treatment arm however KP is associated with lower rate of TRA in each age group. Association of TRA with efficacy outcomes (pCR, iDFS) will be presented.

Citation Format: Sara A Hurvitz, Rodrigo Fresco, Karen Afenjar, Daniil Stroyakovskiy, Chiun-Sheng Huang, Hans Wildiers, Kyung Hae Jung, Jean-François Boileau, Mario Campone, Miguel Martín, Vicente Valero, Joseph A. Sparano, W. Fraser Symmans, Peter A. Fasching, Alastair M. Thompson, Nadia Harbeck, Vanesa López-Valverde, Chunyan Song, Thomas Boulet, Eleonora Restuccia, Dennis J. Slamon. Treatment-related amenorrhea with T-DM1 plus pertuzumab (KP) is lower than with docetaxel/carboplatin/trastuzumab/pertuzumab (TCHP) in the phase III neoadjuvant KRISTINE trial [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD12-06.

Abstract PS4-09: Pathologic features of the inter-regimen biopsy predict response to neoadjuvant therapy in the I-SPY 2 TRIAL

Background: I-SPY 2 is a neoadjuvant platform trial open to patients with locally advanced, molecular high-risk breast cancer. In a concerted pursuit of mid-therapy response biomarkers, we evaluated inter-regimen biopsies, to identify patients who may be candidates for treatment de-escalation. In a pilot study, we observed that absence of carcinoma in an inter-regimen biopsy may predict pathologic complete response (pCR). In this expanded study of 100 participants, we sought to confirm that finding and assess pathologic features of the inter-regimen biopsy as predictors of tumor response to neoadjuvant therapy.

Methods: Digital H&E images of 100 inter-regimen (12 week) image-guided breast biopsies +/- ancillary immunohistochemistry (p63 and/or cytokeratin) were reviewed by 9 I-SPY affiliated pathologists to record 1) tumor bed and 2) presence/absence of residual invasive carcinoma (IC) (with tumor cellularity scored as 0-100%). The data set included 393 cores (mean 3.9 (2-4) cores/biopsy). Fisher’s exact t-test was used for association of presence/absence of IC with pCR, and tumoral hormone receptor (HR) and HER2 status. Association between biopsy tumor cellularity and residual cancer burden (RCB) indices used Pearson’s correlation.

Results: In the biopsy set, 84 (84%) had ≥80% inter-observer diagnostic agreement on both 1) presence of tumor bed and 2) presence/absence of IC (53 IC+ /31 IC-). IC+/IC- biopsies had equal numbers of evaluable tissue cores. The primary tumors were 63% HR+/37% HR-. The presence of IC in the biopsy correlated with tumoral HR/HER2 status (p=0.0014: 74%: HR+HER2-; 62%: TN; 60%: HR+HER2+; 10%: HR-HER2+). Of 31 patients with IC- biopsies, 25 (80%) went on to pCR, whereas only 7/53 (13%) of patients with IC+ biopsies had pCR, conferring an odds ratio for pCR of 26, Fisher p=7.5E-10. Overall, IC- biopsies had a positive predictive value (PPV) for pCR of 81%, with a PPV for HR- tumors of 94% vs. 67% for HR+ tumors (Table 1). In the 6 IC- biopsies from patients with non-pCR (“false-negatives”), most were HR+ (5/6, Table 1), and tumor bed size in the resection specimen was smaller than for IC+ biopsies with non-pCR: 276 mm2 (0.4-1000 mm2) vs. 1166 mm2 (1-11960 mm2). In contrast, the 46/53 IC+ biopsies in patients with non-pCR had a PPV for predicting non-pCR of 86%, (PPV for HR+ tumors: 94% vs. PPV for HR- tumors: 66%. Tumor cellularity in the biopsy (mean 37%, [2.5-93%]) did not correlate with RCB index (p=0.57) or RCB breast-only index (p = 0.17) at resection.

Conclusion: In this 100 biopsy set from the I-SPY2 trial, the absence of residual carcinoma in inter-regimen biopsies was highly predictive of pCR, particularly for HR- tumors. The “false-negative” biopsies (IC-/non-pCR) were predominantly HR+ tumors with small residual tumor beds at resection. Conversely, the presence of carcinoma in inter-regimen biopsies was highly predictive of non-pCR, particularly for HR+ tumors. These data demonstrate the utility, and the limitations, of the inter-regimen biopsy as one tool to identify patients who may benefit from therapeutic de-escalation.

Table 1: PPV for pCR/non-PCR by Inter-regimen Biopsy StatusInter-regimen biopsy with or without Invasive carcinoma (IC+/-)pCRnon-pCRPPV (Sensitivity) for pCR(IC- Biopsies)PPV (Sensitivity) for non-pCR(IC+ biopsies)IC- biopsiesAll25681% (78%)-HR+10567% (83%)-HR-15194% (75%)-IC+ biopsiesAll746-86% (88%)HR+236-94% (88%)HR-510-66% (91%)

Citation Format: Jodi M Carter, Molly E Klein, Sara J Venters, Kimmie Rabe, I Tolgay Ocal, Kamaljeet Singh, Denise M Wolf, Sunati Sahoo, Shuko Harada, Laila Khazai, Malini Harigopal, Alexander D Borowsky, Gregor Krings, Ronald Balassanian, Yunn-Yi Chen, Kimberley Cole, Sonal Shad, Amy Delson, Lamorna Brown-Swigart, I-SPY 2 TRIAL Consortium, Laura Esserman, Laura van ‘t Veer, W Fraser Symmans. Pathologic features of the inter-regimen biopsy predict response to neoadjuvant therapy in the I-SPY 2 TRIAL [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS4-09.