Clinical outcomes after 1 versus 2-3 lines of neoadjuvant therapy in stage III inflammatory breast cancer

PURPOSE

Many stage III inflammatory breast cancer (IBC) patients experience a sufficient response to first-line (1L) neoadjuvant chemotherapy (NAC) to allow surgery, while some require additional NAC. We evaluated the pathologic complete response (pCR), breast cancer-free survival (BCFS) and overall survival (OS) among patients requiring 1 vs. 2-3 lines (L) of NAC prior to surgery.

METHODS

Stage III IBC patients from 2 institutions who received 1L or 2-3L of NAC prior to surgery were identified. Hormone receptor and HER2 status, grade, and pCR were evaluated. BCFS and OS were evaluated by the Kaplan-Meier method. Multivariable Cox models were utilized to estimate the hazard ratio (HR).

RESULTS

808 eligible patients (1997-2020) were identified (median age 51 years, median follow-up 69 months). 733 (91%) had 1L and 75 (9%) had 2-3L of NAC. Grade III, triple-negative and HER2-positive disease were more prevalent in 2-3L patients. 178 (24%) 1L and 14 (19%) 2-3L patients had pCR. 376 1L patients and 41 2-3L patients had recurrences. The 5-year BCFS was worse for the 2-3L group (33 vs. 46%, HR = 1.37; 95% CI 0.99-1.91). However, in 192 patients with a pCR, BCFS was similar (76 vs. 83% in 1L vs. 2-3L, respectively). There were 308 deaths (276 among 1L and 32 among 2-3L patients). The 5-year OS in 1L vs. 2-3L was 60 vs. 53% (HR = 1.32, 95% CI 0.91-1.93).

CONCLUSIONS

Among stage III IBC patients, pCR rates were similar, irrespective of the NAC lines number, and BCFS and OS were comparable with pCR after 1L and 2-3L.

Clinical outcomes of de novo metastatic HER2-positive inflammatory breast cancer

Inflammatory breast cancer (IBC) is a rare, aggressive form of breast cancer that presents as de novo metastatic disease in 20-30% of cases, with one-third of cases demonstrating HER2-positivity. There has been limited investigation into locoregional therapy utilization following HER2-directed systemic therapy for these patients, and their locoregional progression or recurrence (LRPR) and survival outcomes. Patients with de novo HER2-positive metastatic IBC (mIBC) were identified from an IRB-approved IBC registry at Dana-Farber Cancer Institute. Clinical, pathology, and treatment data were abstracted. Rates of LRPR, progression-free survival (PFS), overall survival (OS), and pathologic complete response (pCR) were determined. Seventy-eight patients diagnosed between 1998 and 2019 were identified. First-line systemic therapy comprised chemotherapy for most patients (97.4%) and HER2-directed therapy for all patients (trastuzumab [47.4%]; trastuzumab+pertuzumab [51.3%]; or trastuzumab emtansine [1.3%]). At a median follow-up of 2.7 years, the median PFS was 1.0 year, and the median OS was 4.6 years. The 1- and 2-year cumulative incidence of LRPR was 20.7% and 29.0%, respectively. Mastectomy was performed after systemic therapy in 41/78 patients (52.6%); 10 had a pCR (24.4%) and all were alive at last follow-up (1.3-8.9 years after surgery). Among 56 patients who were alive and LRPR-free at one year, 10 developed LRPR (surgery group = 1; no-surgery group = 9). In conclusion, patients with de novo HER2-positive mIBC who undergo surgery have favorable outcomes. More than half of patients received systemic and local therapy with good locoregional control and prolonged survival, suggesting a potential role for local therapy.

Interrupting Endocrine Therapy to Attempt Pregnancy after Breast Cancer

BACKGROUND

Prospective data on the risk of recurrence among women with hormone receptor-positive early breast cancer who temporarily discontinue endocrine therapy to attempt pregnancy are lacking.

METHODS

We conducted a single-group trial in which we evaluated the temporary interruption of adjuvant endocrine therapy to attempt pregnancy in young women with previous breast cancer. Eligible women were 42 years of age or younger; had had stage I, II, or III disease; had received adjuvant endocrine therapy for 18 to 30 months; and desired pregnancy. The primary end point was the number of breast cancer events (defined as local, regional, or distant recurrence of invasive breast cancer or new contralateral invasive breast cancer) during follow-up. The primary analysis was planned to be performed after 1600 patient-years of follow-up. The prespecified safety threshold was the occurrence of 46 breast cancer events during this period. Breast cancer outcomes in this treatment-interruption group were compared with those in an external control cohort consisting of women who would have met the entry criteria for the current trial.

RESULTS

Among 516 women, the median age was 37 years, the median time from breast cancer diagnosis to enrollment was 29 months, and 93.4% had stage I or II disease. Among 497 women who were followed for pregnancy status, 368 (74.0%) had at least one pregnancy and 317 (63.8%) had at least one live birth. In total, 365 babies were born. At 1638 patient-years of follow-up (median follow-up, 41 months), 44 patients had a breast cancer event, a result that did not exceed the safety threshold. The 3-year incidence of breast cancer events was 8.9% (95% confidence interval [CI], 6.3 to 11.6) in the treatment-interruption group and 9.2% (95% CI, 7.6 to 10.8) in the control cohort.

CONCLUSIONS

Among select women with previous hormone receptor-positive early breast cancer, temporary interruption of endocrine therapy to attempt pregnancy did not confer a greater short-term risk of breast cancer events, including distant recurrence, than that in the external control cohort. Further follow-up is critical to inform longer-term safety. (Funded by ETOP IBCSG Partners Foundation and others; POSITIVE ClinicalTrials.gov number, NCT02308085.).

Abstract GS4-09: Pregnancy Outcome and Safety of Interrupting Therapy for women with endocrine responsIVE breast cancer: Primary Results from the POSITIVE Trial (IBCSG 48-14/BIG 8-13)

Background: Pregnancy after breast cancer (BC) is of substantial importance for many young women at diagnosis and during follow-up. BC treatment including standard endocrine therapy (ET) (5-10 years) may reduce ovarian reserve and the chances of subsequent successful pregnancy, given conception is contraindicated during ET. A temporary interruption of ET to attempt and carry a pregnancy in this population has never been prospectively studied.

Methods: POSITIVE is a single-arm, prospective, investigator-initiated, international trial evaluating the safety and pregnancy outcomes of interrupting ET for young women with early-stage hormone-receptor-positive (HR+) BC who desire pregnancy. The primary objective is to assess the risk of BC relapse associated with ET interruption for ~2 years to achieve pregnancy. Women ≤42 years with stage I-III HR+ BC who received adjuvant ET (SERM alone, GnRH analogue plus SERM or AI) for 18 to 30 months and wished to interrupt ET to attempt pregnancy were eligible. The primary endpoint is breast cancer free interval (BCFI) defined as the time from enrollment to the first BC event (local, regional, distant recurrence or a new invasive contralateral BC). Planned sample size was 500 patients. Three interim analyses of BCFI were reviewed by the Data Safety Monitoring Committee (DSMC) to assure a 95% chance of stopping the trial early if the annual BCFI event rate exceeded 4%; with primary analysis triggered after 1600 patient years of follow-up (pyfu) and no more than 46 BCFI events defined as the safety threshold. The DSMC recommended continuing the study following each interim analysis. We now report the primary results.

Results: From 12/2014 to 12/2019, 518 women were enrolled. At enrollment, the median age of participants was 37 years (27-43 years); 75.0% were nulliparous, 93.4% had stage I/II disease, 66.3% node-negative. Median time from BC diagnosis to enrollment was 29 months (IQR: 25-32). Tamoxifen alone was the most prescribed ET (41.7%), followed by tamoxifen+ovarian function suppression (35.7%). 62.0% of participants had received neo/adjuvant chemotherapy. At a median follow-up of 41 months (1638 pyfu), 44 participants had experienced a BCFI event, not exceeding the pre-specified safety threshold of 46 events. The 3-year BCFI failure percent was 8.9% (95% CI: 6.3 to 11.6%), similar to the 9.2% (95% CI: 7.6 to 10.8%) calculated in the comparative external control cohort from the SOFT/TEXT trials (Sun et al, Breast 2020). Of 497 women followed for pregnancy status, 368 (74.0%) had at least one pregnancy, 317 (63.8%) had at least one live birth, with a total of 365 babies born. Based on competing risk analysis, 76.3% of patients resumed ET (half within 26 months), 8.3% had BCFI event/death before ET resumption, and 15.4% had not resumed ET yet.

Conclusions: The POSITIVE trial demonstrates that for young women with early HR+ BC desiring pregnancy, temporary interruption of ET to attempt pregnancy does not confer a greater short-term risk of recurrence than that observed in a modern historical control group that did not interrupt ET. Most participants have had a live birth. Further follow-up is planned to confirm long-term safety. These results should be considered in counselling BC patients desiring future pregnancy.

Citation Format: Ann Partridge, Olivia Pagani, Samuel M. Niman, Monica Ruggeri, Fedro Alessandro A. Peccatori, Hatem A. Azim, Marco Colleoni, Cristina Saura, Chikako Shimizu, Anna Saetersdal, Judith Kroep, Audrey Mailliez, Ellen Warner, Virginia F. Borges, Frédéric Amant, Andrea Gombos, Akemi Kataoka, Christine Rousset-Jablonski, Simona Borstnar, Junko Takei, Jeong Eon Lee, Janice Walshe, Manuel Ruiz Borrego, Halle Moore, Christobel Saunders, Vesna Bjelic-Radisic, Snezana Susnjar, Fatima Cardoso, Karen L. Smith, Teresa Ferreiro Vilarino, Karin Ribi, Kathryn Ruddy, Sarra El-Abed, Martine Piccart, Larissa A. Korde, Aron Goldhirsch, Richard D. Gelber. Pregnancy Outcome and Safety of Interrupting Therapy for women with endocrine responsIVE breast cancer: Primary Results from the POSITIVE Trial (IBCSG 48-14/BIG 8-13) [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 GS4-09.

Incidence, characteristics, and management of central nervous system metastases in patients with inflammatory breast cancer

BACKGROUND

Patients with inflammatory breast cancer (IBC) have a high risk of central nervous system metastasis (mCNS). The purpose of this study was to quantify the incidence of and identify risk factors for mCNS in patients with IBC.

METHODS

The authors retrospectively reviewed patients diagnosed with IBC between 1997 and 2019. mCNS-free survival time was defined as the date from the diagnosis of IBC to the date of diagnosis of mCNS or the date of death, whichever occurred first. A competing risks hazard model was used to evaluate risk factors for mCNS.

RESULTS

A total of 531 patients were identified; 372 patients with stage III and 159 patients with de novo stage IV disease. During the study, there were a total of 124 patients who had mCNS. The 1-, 2-, and 5-year incidence of mCNS was 5%, 9%, and 18% in stage III patients (median follow-up: 5.6 years) and 17%, 30%, and 42% in stage IV patients (1.8 years). Multivariate analysis identified triple-negative tumor subtype as a significant risk factor for mCNS for stage III patients. For patients diagnosed with metastatic disease, visceral metastasis as first metastatic site, triple-negative subtype, and younger age at diagnosis of metastases were risk factors for mCNS.

CONCLUSIONS

Patients with IBC, particularly those with triple-negative IBC, visceral metastasis, and those at a younger age at diagnosis of metastatic disease, are at significant risk of developing mCNS. Further investigation into prevention of mCNS and whether early detection of mCNS is associated with improved IBC patient outcomes is warranted.

HER2-low inflammatory breast cancer: Clinicopathologic features and prognostic implications

BACKGROUND

HER2)-low expression is a predictive biomarker for novel anti-HER2 antibody-drug conjugates. However, little is known about its clinical significance in inflammatory breast cancer (IBC).

METHODS

Patients diagnosed with HER2-negative IBC between December 1999 and December 2020 were identified from the Dana-Farber Cancer Institute IBC registry. Patients were divided into HER2-low (IHC 1+ or 2+/ISH-) and HER2-zero (IHC 0), comparing clinicopathologic features and disease outcomes between the two subgroups.

RESULTS

The study included 276 patients. Among patients with stage III (n = 209) and stage IV (n = 67) IBC, 54% and 39% had HER2-low tumours, respectively. Oestrogen receptor (ER)-expressing tumours were more common in patients with HER2-low versus HER2-zero stage III IBC (65% versus 38%, p < 0.01). Among stage III patients undergoing surgery (n = 182), pathologic complete response (pCR) rates were higher for HER2-zero versus HER2-low IBC (11% versus 6%, OR: 1.8, 95%CI:0.6-5.3), but minimal differences persisted when separately analysing pCR by ER status. Similar invasive disease-free survival (iDFS) outcomes were observed among ER-positive HER2-zero versus HER2-low IBC (48-month iDFS: 63% versus 63%, HR: 1.10, 95%CI:0.57-2.13) and ER-negative HER2-zero versus HER2-low IBC (48-month iDFS: 28% versus 25%, HR: 1.19, 95%CI:0.69-2.04). Differences in overall survival (OS) were small, both among ER-positive HER2-zero versus HER2-low IBC (48-month OS: 80% versus 81%, HR: 0.82, 95%CI:0.39-1.73) and ER-negative HER2-zero versus HER2-low IBC (48-month OS: 34% versus 47%, HR: 1.34, 95%CI: 0.74-2.41).

CONCLUSIONS

Marginal differences in clinicopathologic features and outcomes were observed in HER2-low versus HER2-zero IBC when controlling for ER status, not supporting the definition of HER2-low as a distinct subtype of IBC.

Historical early treatment effects of adjuvant endocrine therapy for breast cancer in high-risk subgroups: Reanalysis of BIG 1-98, SOFT and TEXT

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Background: Clinical trials testing adjuvant endocrine therapy (ET) have not historically limited enrollment to patients with clinically high-risk breast cancer (BC), nor estimated treatment (trt) effects prior to 5 yrs. In light of recent trial results for adjuvant CDK4/6 inhibitors, we estimated early relative and absolute trt effects of aromatase inhibitor (AI) vs tamoxifen (T), with ovarian suppression (OFS) if premenopausal, in high risk subgroups. Methods: From pts enrolled in adjuvant phase 3 randomized clinical trials BIG 1-98 (postmenopausal, 5yr AI v T), TEXT (5yr AI+OFS v T+OFS) and SOFT (5yr AI+OFS v T+OFS v T), we identified subgroups with HR+/HER2- BC and high risk features (≥4 pLN; or 1-3 pLN with grade 3, pT≥5 cm and/or Ki-67≥20% [retrospectively centrally assessed]). TEXT randomized at start of adjuvant trt; BIG 1-98 and SOFT after chemotherapy. Disease-free survival (DFS) was defined from randomization to invasive recurrence at local, regional, distant or contralateral breast, second non-breast malignancy or death. We estimated trt effects as differences in 2, 3 and 5yr DFS Kaplan-Meier estimates (KM diffs at t yrs) and hazard ratios over time intervals of 0-2, 0-3 and 0-5 yrs (HRs over 0 to t yrs) to approximate the maturity of trial results with increasing follow-up. Results: The high-risk HR+/HER2- subgroups were 695/4922, 707/2660 and 526/3047 pts in BIG 1-98, TEXT and SOFT with 202, 122, 142 DFS events observed by 5 yrs since randomization. 60%, 46% and 44% of pts had ≥4 pLNs; 42%, 90% and 92% had chemotherapy. The table summarizes results. Conclusions: In re-analysis of clinical high risk HR+/HER2- subgroups of 3 trials each ̃700 pts, 5 yrs AI vs T had similar magnitude of early trt effects after 2-3 yrs follow-up of all pts vs trt effects observed after 27 mos median follow-up in monarchE trial (HR=0.70; KM diffs 2.7% at 2 yrs, 5.4% at 3 yrs; n=5637). Relative and absolute trt effects sometimes diminished when estimated over 5 yrs rather than over 2 yrs, but meaningful absolute differences remained at 5 yrs in contrast to Penelope-B trial results. Design and interpretation of high risk HR+/HER2- early BC trials may depend on timing of randomization and selection of backbone adjuvant trts; follow-up >5 yrs must remain standard. [Table: see text]

Who are the women who enrolled in the POSITIVE trial: A global study to support young hormone receptor positive breast cancer survivors desiring pregnancy

Background

Premenopausal women with early hormone-receptor positive (HR+) breast cancer receive 5–10 years of adjuvant endocrine therapy (ET) during which pregnancy is contraindicated and fertility may wane. The POSITIVE study investigates the impact of temporary ET interruption to allow pregnancy.

Methods

POSITIVE enrolled women with stage I-III HR + early breast cancer, ≤42 years, who had received 18–30 months of adjuvant ET and wished to interrupt ET for pregnancy. Treatment interruption for up to 2 years was permitted to allow pregnancy, delivery and breastfeeding, followed by ET resumption to complete the planned duration.

Findings

From 12/2014 to 12/2019, 518 women were enrolled at 116 institutions/20 countries/4 continents. At enrolment, the median age was 37 years and 74.9 % were nulliparous. Fertility preservation was used by 51.5 % of women. 93.2 % of patients had stage I/II disease, 66.0 % were node-negative, 54.7 % had breast conserving surgery, 61.9 % had received neo/adjuvant chemotherapy. Tamoxifen alone was the most prescribed ET (41.8 %), followed by tamoxifen + ovarian function suppression (OFS) (35.4 %). A greater proportion of North American women were <35 years at enrolment (42.7 %), had mastectomy (59.0 %) and received tamoxifen alone (59.8 %). More Asian women were nulliparous (81.0 %), had node-negative disease (76.2%) and received tamoxifen + OFS (56.0 %). More European women had received chemotherapy (69.3 %).

Interpretation

The characteristics of participants in the POSITIVE study provide insights to which patients and doctors considered it acceptable to interrupt ET to pursue pregnancy. Similarities and variations from a regional, sociodemographic, disease and treatment standpoint suggest specific sociocultural attitudes across the world.

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Fertility and pregnancy are priority concerns for young breast cancer survivors.

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POSITIVE explores a transient interruption of endocrine therapy to allow conception.

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Patients' characteristics highlight features considered suitable to study enrolment.

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Overall, patients enrolled had a relatively high median age and low-risk disease.

•

Variations emerged across continents suggesting specific sociocultural attitudes.

Circulating tumor cell number and endocrine therapy index in ER positive metastatic breast cancer patients

Circulating tumor cells (CTC) are prognostic in metastatic breast cancer (MBC). The CTC-endocrine therapy index (CTC-ETI), consisting of CTC-ER (estrogen receptor), BCL2, human epidermal growth factor receptor (HER2), and Ki67 expression, might predict resistance to endocrine therapy (ET) in patients with ER-positive MBC. One hundred twenty-one patients with ER-positive/HER2-negative MBC initiating a new ET after ≥1 lines of ET were enrolled in a prospective, multi-institutional clinical trial. CTC-ETI and clinical/imaging follow-up were performed at baseline and serial time points. Progression-free survival (PFS) and rapid progression (RP; determined at the 3-month time point) were primary endpoints. Associations with clinical outcomes used logrank and Fisher’s exact tests. At baseline, 36% (38/107) of patients had ≥5 CTC/7.5 ml whole blood (WB). Patients with ≥5 vs. <5 CTC/7.5 ml WB had significantly worse PFS (median 3.3 vs. 5.9 months, P = 0.03). Elevated CTC at 1 month was associated with even worse PFS (1.9 vs. 5.0 months from the 1-month sample, P < 0.001). Low, intermediate, and high CTC-ETI were observed in 71 (66%), 8 (8%), and 28 (26%) patients, with median PFS of 6.9, 8.5, and 2.8 months, respectively (P = 0.008). Patients with high vs. low CTC and CTC-ETI more frequently experienced RP (CTC: 66% vs. 41%; P = 0.03; CTC-ETI: 79% vs. 40%; P = 0.002). In conclusion, CTC enumeration and the CTC-ETI assay are prognostic at baseline and follow-up in patients with ER-positive/HER2-negative MBC starting new ET. CTC at first follow-up might identify a group of patients with ER-positive MBC that could forego ET, but CTC-ETI did not contribute further.

Abstract PD13-06: Incidence and management of central nervous system metastases in patients with inflammatory breast cancer

Background: Patients (pts) with inflammatory breast cancer (IBC) have a high risk of central nervous system (CNS) metastasis (mets) with their associated impact on longevity and quality of life. Given evolving CNS-directed treatments, including focal radiation (RT), we compared the proportion of pts diagnosed with asymptomatic CNS mets before and after 2012 as data from Phase III trials in the preceding years (yr) increasingly supported the use of stereotactic radiosurgery (SRS). Specific attention was paid to pts treated with tri-modality therapy (TMT), defined as preoperative systemic therapy, surgery, and RT to determine whether screening for asymptomatic CNS mets would be beneficial. Methods: We retrospectively reviewed the records of pts diagnosed with IBC 1997-2019 and enrolled in an IRB-approved registry at a dedicated IBC center. CNS met-free survival time was defined as the time from IBC diagnosis to date of CNS mets. Alive CNS met-free pts were censored at their latest survival date and death was treated as a competing risk. Cumulative CNS mets incidence was computed. Analyses were stratified based on stage at diagnosis (III vs. de novo IV) and receipt of TMT. For pts completing TMT, the completion date was the starting point for cumulative incidence calculations. Overall survival (OS) was estimated as the time from CNS mets diagnosis to death, with censoring for pts who were still alive. Results: A total of 531 pts were identified; 372 (70%) with stage III; 159 (30%) with de novo Stage IV disease. The median follow-up for pts presenting with stage III and stage IV disease at diagnosis was 5.6 yr and 1.8 yr, respectively. 124 pts had CNS mets; 5 of them at diagnosis. CNS was the first site of mets or progression in 50 pts (9.4%). The cumulative incidence of CNS mets stratified by stage at diagnosis and receipt of TMT is seen in Table 1. Among the 50 de novo Stage IV pts who completed TMT, 4 developed CNS mets prior to surgery. The median overall survival (mOS) after CNS mets was 0.6 yr (IQR: 0.2 - 1.4). Results stratified by tumor subtype were: HER2+ disease (n=51) 1.4 yr (IQR: 0.6 - 3.7); hormone receptor+/HER2- (n=27) 0.6 yr (IQR: 0.2 - 1.2); triple negative (n=40) 0.2 yr (IQR: 0.1 - 0.5). Most pts with CNS mets (87/124, 70%) had neurologic symptoms prompting imaging. There was no difference in the proportion of asymptomatic pts diagnosed with CNS mets prior to or after 2012. Management of CNS mets was as follows: 47 pts (38%) received whole brain RT (WBRT) alone, 22 (18%) SRS alone, 15 WBRT + SRS (12%), 6 resection + WBRT (5%), and 5 resection + SRS (4%). The remaining pts received several of these modalities with or without intrathecal chemotherapy (13, 11%) or CNS treatment was not documented (16, 13%). A total of 258/531 pts have died (49%). Of these pts, 103 (40%) had CNS mets. 67/103 (65%) died due to CNS mets. Conclusions: Among pts with IBC completing TMT, the incidence of CNS mets is as high as 20% both in de novo Stage IV pts at 1 yr and in Stage III pts within 5 yrs, supporting routine surveillance brain MRI among pt with Stage IV disease. The majority of pts continue to receive WBRT with its resultant toxicities. Efforts should be made to identify CNS mets early to facilitate more focal therapy. Future research on systemic therapy with CNS penetrance for IBC patients should be pursued. These data support an ongoing prospective study of screening brain MRI in pts with Stage III IBC to quantify the incidence of CNS mets, utilization of WBRT and impact on neurologic quality of life (NCT04030507).

Cumulative Incidence of CNS MetsNo.1 year (95% CI)2 year (95% CI)3 year (95% CI)Stage III (All)3725% (3-7)9% (6-12)18% (14-23)Stage IV (All)15417% (12-24)30% (22-37)42% (32-51)Stage III (TMT)3045% (3-8)11% (8-16)19% (14-24)Stage IV (TMT)4621% (10-34)28% (16-43)35% (20-50)

Citation Format: Laura Warren, Samuel M Niman, Marie Claire Remolano, Jean Landry, Faina Nakhlis, Jennifer R Bellon, Meredith M Regan, Beth A Overmoyer. Incidence and management of central nervous system metastases in patients with inflammatory breast cancer [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 PD13-06.

Abstract PS10-34: Clinical outcomes in de novo metastatic HER2-positive inflammatory breast cancer

Background: Advances in HER2-directed therapy have significantly improved survival in HER2+ metastatic breast cancer. Approximately 30% of de novo metastatic inflammatory breast cancer (mIBC) is HER2+, though there has been limited IBC representation in clinical trials evaluating the role of HER2-directed agents as first-line metastatic therapy. Elevated rates of locoregional progression or recurrence (LRPR) with systemic therapy alone also raise the question of whether trimodality therapy (TMT) may improve outcomes in IBC patients (pts) with limited metastatic disease, particularly in the setting of increasingly effective anti-HER2 therapy. Methods: Pts diagnosed with de novo HER2+ mIBC were identified from an IRB-approved IBC registry at Dana-Farber Cancer Institute. Clinical, pathology and treatment data were manually abstracted by chart review. Progression-free survival (PFS) was defined as time from IBC diagnosis to LRPR, distant progression/relapse or death (in the absence of event, censored at date of last follow-up). Overall survival (OS) was defined as time from IBC diagnosis to death from any cause or censored at date last known alive. For pts who underwent surgery of the primary tumor, pathologic complete response (pCR) was defined as no residual invasive carcinoma in the breast and axilla and survival was estimated from date of surgery. Median PFS and OS were estimated by Kaplan-Meier method; cumulative incidence of CNS metastasis and LRPR were estimated with death as competing risk. Results: 78 pts diagnosed between 1998-2019 with de novo HER2+ mIBC (41 hormone receptor (HR)-positive; 37 HR-negative) were identified. Median age at diagnosis was 53 years (yr; range: 24-91). Sites of metastatic disease at presentation included bone only (n=12), lymph node/contralateral chest wall only (n=17), bone and lymph node (n=5), visceral (n=40) and CNS with extracranial disease (n=4). As initial HER2-directed therapy, 37 pts received trastuzumab (H), 40 H plus pertuzumab and 1 T-DM1. At a median follow-up of 2.7 yr in the overall cohort, median PFS was 1.0 yr (IQR: 0.5-2.8 yr; 60 events) and median OS was 4.6 yr (IQR: 2.9-8.7 yr; 39 deaths). 34 pts had CNS metastasis with a cumulative incidence of 20% and 28% at 1 and 2 yr, respectively. LRPR developed in 26 pts, of which 16 occurred within 12 months (mo) of diagnosis. Cumulative incidence of LRPR at 1 and 2 yr was 21% and 29%, respectively. In 41 pts (53%), mastectomy was performed after receipt of systemic therapy. Median time from IBC diagnosis to surgery was 7.5 mo (IQR: 6.0-9.9 mo). Radiation was administered in 33 pts, 3 pre- and 30 post-mastectomy. Median OS from surgery was 5.2 yr (IQR: 3.1-8.4 yr). 9/41 pts (22%) achieved pCR; all pCR pts were alive at 1.3-8.9 yr since surgery. To investigate the value of therapy for locoregional control, a landmark analysis was performed in the subset of pts alive and LRPR free at 12 mo from diagnosis (n=56). 27 had surgery within 12 mo from diagnosis and 29 did not. LRPR occurred in 10/56; 9 were among pts who did not undergo surgery. Cumulative LRPR incidence at 1 and 2 yr since the 12 mo landmark was 21% and 29%, respectively, in pts who did not undergo surgery, and 0% at both time points in pts who had surgery (1 LRPR at 8 yr). Conclusion: Long-term outcomes in de novo HER2+ mIBC are overall similar to those reported in metastatic HER2+ non-IBC. More than half of pts underwent systemic and local therapy with good locoregional control and prolonged survival, suggesting a potential role for aggressive local therapy in this mIBC subset with favorable prognosis and effective systemic therapy. The high incidence of early CNS involvement in de novo HER2+ mIBC prompted us to explore this group in detail (Warren SABCS 2020 abstract). Larger studies are needed to better understand the effectiveness of TMT in HER2+ mIBC, highlighting the importance of collaborative research efforts in this rare subset.

Citation Format: Ana C. Garrido-Castro, Samuel M. Niman, Marie Claire Remolano, Jennifer M. Rosenbluth, Caroline Block, Laura E. Warren, Jennifer Bellon, Beth T. Harrison, Faina Nakhlis, Meredith Regan, Beth Overmoyer. Clinical outcomes in de novo metastatic HER2-positive inflammatory breast cancer [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 PS10-34.

Abstract PS12-17: Baseline characteristics of women enrolled in the POSITIVE trial (pregnancy outcome and safety of interrupting therapy for women with endocrine responsIVE breast cancer)

Background: Pregnancy is a major concern for young breast cancer (BC) survivors. Conception after BC in women with hormone receptor positive (HR+) disease is affected by the standard 5-10 years of adjuvant endocrine therapy (ET) during which pregnancy is contraindicated and fertility may be waning. The POSITIVE Trial (IBCSG 48-14/BIG 8-13/Alliance A221405/NCT02308085) investigates the impact of temporary ET interruption to allow pregnancy.

Methods: POSITIVE enrolled premenopausal women with stage I-III HR+ early BC, ≤42 years of age, who had received adjuvant ET (SERM alone, ovarian function suppression (OFS) plus SERM or AI) for 18 to 30 months, and wished to interrupt ET to attempt pregnancy. An interruption of ET for up to 2 years was foreseen to allow pregnancy (after a 3-month ET washout period), delivery, and breastfeeding if desired/feasible. Resumption of ET to complete 5-10 years of treatment was planned as soon as pregnancy/breastfeeding was completed or after it was ensured conception was not possible. We report baseline characteristics of participants enrolled in POSITIVE by region of enrollment.

Results: From 12/2014 to 12/2019, 518 participants were enrolled at 116 centers in 20 countries across 4 continents. The table shows the baseline characteristics of the enrolled women.

Several differences were seen across regions: A higher proportion of participants &lt;35 yrs (43%) enrolled in North America than in Europe (33%) or Asia (26%). Eighty-one percent of Asian women had no children at enrollment compared to 75% and 68% of European and North American women, respectively. Consistently, a greater percent of women in Asia (56%) had used fertility preservation measures, compared to Europe (53%) and North America (43%). Stage distribution was also different across continents: a greater percent of Asian participants had stage I, grade 1 and node-negative disease (51%, 29% and 76 %, respectively) compared to European (46%, 14% and 67%) and North American (43%, 16% and 55%) women. Only 19% of Asian women had either 1-3 positive nodes and grade 3 tumors, the proportion increased to 28% and 35% in Europe and to 41% and 38% in North America, respectively. North American women were more likely to have had mastectomy (60% vs. Asian (44%) and European (41%)); European women were more likely to have had chemotherapy (69% vs. North American (56%) and Asian (42%)). ET administration prior to enrollment differed substantially by region: Most North American women had SERM (T) alone (58%), and when OFS was added to oral ET, it was combined with AI in 19% and with T in 8% of participants, respectively. In Asia most women received T + OFS (55%), followed by T alone (36%), and AI + OFS (6%). In Europe, T + OFS was the most frequent treatment (40%), followed by T alone (37%) and AI + OFS (17%). Median duration of ET before enrollment was similar across regions (22-24 months).

Conclusion: Regional variation of baseline characteristics of women enrolled in the POSITIVE trial may provide important insights into different medical and sociocultural attributes and attitudes of the study participants and investigators from those regions.

Affiliation: POSITIVE Investigators, International Breast Cancer Study Group, Alliance for Clinical Trials in Oncology, Breast International Group, North American Breast Cancer Group

CharacteristicRegion: Europe / North America / Asia-Pacific61% / 23% / 16%Median age at enrollment, yrs (IQR)37 (33-39)Caucasian race77%No children prior to enrollment74%Prior fertility preservation measures taken51%Stage I / II46% / 45%0 / 1 positive nodes65% / 21%Grade 2 / 348% / 33%HER2-negative74%Mastectomy46%Chemotherapy61%ET: SERM alone / SERM+OFS / AI+OFS41% / 35% / 16%Median duration of prior ET, mos (IQR)23 (20-27)

Citation Format: Ann H Partridge, Samuel M Niman, Monica Ruggeri, Fedro A Peccatori, Hatem A Azim, Jr, Marco Colleoni, Cristina Saura, Chikako Shimizu, Anna Barbro Sætersdal, Judith Kroep, Ellen Warner, Virginia F Borges, Andrea Gombos, Akemi Kataoka, Christine Rousset-Jablonski, Simona Borstnar, Hideko Yamauchi, Jeong Eon Lee, Janice M Walshe, Manuel Ruíz Borrego, Halle CF Moore, Christobel Saunders, Fatima Cardoso, Snezana Susnjar, Vesna Bjelic-Radisic, Karen L Smith, Martine Piccart, Larissa A Korde, Aron Goldhirsch, Richard D Gelber, Olivia Pagani. Baseline characteristics of women enrolled in the POSITIVE trial (pregnancy outcome and safety of interrupting therapy for women with endocrine responsIVE breast cancer) [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 PS12-17.

Estimation of historical control rate for a single arm de-escalation study - Application to the POSITIVE trial

BACKGROUND

Although randomized controlled clinical trials are optimal to evaluate the effect of an experimental therapy, single-arm trials are required whenever randomization is unethical or not feasible, such as de-escalation studies. We propose using prospectively identified historical controls to place results of single-arm, de-escalation trials into context.

METHODS

POSITIVE is a prospective, single-arm study in young women with hormone-receptor-positive early breast cancer to determine if temporarily interrupting adjuvant endocrine therapy in order to become pregnant increases the risk of a breast cancer event. After 272 women enrolled in POSITIVE, we identified a cohort of 1499 SOFT/TEXT patients potentially eligible to enroll in POSITIVE who did not interrupt endocrine therapy. Method I used the SOFT/TEXT cohort to calculate annualized hazard rates by a piecewise exponential model. Method II used the SOFT/TEXT cohort to group-match SOFT/TEXT patients to POSITIVE patients; sample sets of SOFT/TEXT patients were randomly drawn 5000 times to obtain sets having patient, disease, and treatment characteristics more balanced with POSITIVE participants.

RESULTS

Compared with SOFT/TEXT, POSITIVE participants were younger, less likely to be overweight/obese, had fewer positive nodes, and fewer received aromatase inhibitor or chemotherapy. The estimated 3-year breast cancer free interval event rates were 9.5% (95% CI: 7.9%,11.1%) for Method I and 9.4% (95% CI: 7.8%,10.9%) for Method II, compared with 5.8% initially assumed when POSITIVE was designed.

CONCLUSION

External control datasets should be identified before launching single-arm, de-escalation trials and methods applied during their conduct to provide context for interim monitoring and interpretation of the final analysis.