Abstract PD18-06: Image-guided optimization of neoadjuvant chemotherapy duration in stage II and III HER2-positive breast cancer: radiologic and pathologic complete response (pCR) rates in the multicenter phase 2 TRAIN-3 study (BOOG 2018-01)

Background pCR rates in stage II – III HER2-positive breast cancer have greatly improved since the addition of HER2 targeted agents to neoadjuvant chemotherapy and are associated with excellent long-term survival. While longer treatment regimens increase pCR rate, early complete responses are also common. We evaluated an image-guided approach to tailor chemotherapy duration based on the identification of early complete responders.

Methods 45 hospitals across the Netherlands participated in the phase 2 TRAIN-3 trial. Patients received neoadjuvant systemic treatment consisting of paclitaxel, trastuzumab, carboplatin and pertuzumab (PTC-Ptz). Response to treatment was monitored every three cycles and patients were referred for surgery in case of a radiologic complete response (rCR) or after a maximum of 9 cycles. RCR was defined as the absence of pathological enhancement on MRI breast plus negative vacuum assisted core biopsies in case of hormone-receptor positive (HR+) tumors. In addition, negative fine needle aspiration or lymph node biopsy was required in patients with nodal involvement at baseline. The primary endpoint was 3-year event-free survival (EFS). Here, we report locally assessed rCR and pCR rates after 3, 6 and 9 cycles, the negative predictive value of rCR assessment and the incidence of adverse events (AEs). Analyses are stratified by HR-status.

Results We included 467 patients between April 2019 and May 2021. Median age was 51 years, 69% had stage II disease and 232 had HR+ tumors. 33.6% of HR- patients and 15.5% of HR+ patients achieved pCR after 3 cycles of PTC-Ptz (see table). The NPV was higher in HR- patients and independent of the number of cycles. AE evaluation is currently ongoing.

Conclusion Three cycles of PTC-Ptz induce an early pCR in one in three HR- and one in six HR+ tumors in patients with stage II-III HER2+ breast cancer. Dynamic contrast enhanced MRI-based response evaluation identifies these patients with ±87% certainty in HR- disease and ±58% in HR+ disease. Continuation of PTC-Ptz after 6 cycles further improves pCR rates and can be considered to reduce the need for adjuvant T-DM1. Efficacy and safety of this image-guided approach to tailor treatment duration need to be confirmed with follow-up in EFS and OS analyses.

Table 1: Cumulative rCR & pCR according to HR-status *Including patients who underwent surgery for other reasons than rCR

Citation Format: Anna van der Voort, Mette S. van Ramshorst, Rob Kessels, Ingrid A. Mandjes, Inge Kemper, Mariëtte J. Agterof, Wim A. van der Steeg, Joan B. Heijns, Marlies L. van Bekkum, Ester J. Siemerink, Philomeen M. Kuijer, Astrid Scholten, Jelle Wesseling, Marie-Jeanne T.F.D. Vrancken Peeters, Ritse M. Mann, Gabe S. Sonke. Image-guided optimization of neoadjuvant chemotherapy duration in stage II and III HER2-positive breast cancer: radiologic and pathologic complete response (pCR) rates in the multicenter phase 2 TRAIN-3 study (BOOG 2018-01) [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 PD18-06.

Oncoplastic breast conserving surgery: is there a need for standardization? Results of a nationwide survey

Introduction The NABON Breast Cancer Audit showed that more than 70% of the Dutch women undergoing surgery for breast cancer (BC) maintained their breast contour by breast conserving surgery (BCS) or by immediate reconstruction after ablative surgery. The proportion of oncoplastic surgery applied in patients undergoing breast conserving treatment (BCT) remains unknown. The aim of our study was to assess the need for standardization of oncoplastic breast conserving surgery (OPBCS) in an attempt to enable measurement of the quality of OPBCS. Methods To gain a better understanding of current practice in OPBCS we sent a questionnaire to all breast surgeons in the Netherlands who are member of the breast surgery working group (n=134). Results A total of 60 breast surgeons, representing different hospitals in the Netherlands, responded. 61.7% of the breast surgeons performed BCS in 60%-100% of their patients. 68.3% responded that BCS was performed using OPS techniques in up to 40% of their patients. OPBCS was defined as level I volume displacement by 45.2% of the breast surgeons and as BCS performed by a breast surgeon and plastic surgeon together by 32.3% of the breast surgeons. 94.5% indicated that there is a need for standardization of the definition of OPBCS in the Netherlands. Conclusion This study demonstrates that OPBCS is a major part of daily clinical practice of Dutch breast surgeons treating BC patients. Despite of this, there is no clear definition of OPS in BCT in the Netherlands. Only after standardization, a classification code and quality indicator can be initiated for OPBCS. Ultimately, this will facilitate improvement in quality of BC care.

Abstract GS5-06: Towards omitting breast surgery in patients with a pathologic complete response after neoadjuvant systemic treatment: interim analysis of the MICRA trial (Minimally Invasive Complete Response Assessment)

Background and Objectives: Improvements in neoadjuvant systemic therapy (NST) for breast cancer patients have led to increasing rates of pathologic complete response (pCR). In patients with an excellent response, imaging alone is not reliable enough to differentiate between patients with residual disease, who should be surgically treated or patients with pCR where surgery could be considered overtreatment. Several trials currently investigate the accuracy of minimal invasive biopsies to assess presence of pCR of the breast. We initiated the MICRA trial (Minimal Invasive Complete Response Assessment NTR6120) combining MRI and minimal invasive biopsies of the breast.

Methods: Breast cancer patients treated with NST resulting in a radiologic complete (rCR) or partial response (rPR, > 30 % decrease and < 2 cm residual diameter) on MRI are eligible. Post-NST, eight ultrasound-guided 14G core biopsies of the pre-NST marked tumor area are obtained. Pathology results of biopsies and surgical specimens are compared. The primary endpoint is the false-negative rate (FNR) of the biopsy procedure i.e. the proportion of patients with non-pCR in the surgical specimen but with pCR in the biopsies. Here we report results of the interim analysis.

Results: 219 patients were enrolled in the trial. Biopsies were successfully obtained and analyzed in 167 patients. Main age was 49 yrs (range 24-74). Tumor subtype was 26% hormone receptor positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-), 14% HR-/HER2+, 36% triple negative and 24% HR+HER2+. 135 patients had a rCR and 32 patients a rPR on MRI. There were 89 patients (53%) with pCR in the surgical specimen, all correctly identified by post-NST biopsies (false-positive rate 0%). Post-NST biopsies however missed residual disease in 29/78 patients (FNR 37%). FNR was higher in patients with rCR (FNR 45%; 26/55 patients with residual disease missed on biopsies) than in patients with rPR (FNR 13 %; 3/23 patients with residual disease missed with biopsies). The conditional power estimating the probability of the FNR being ≤ 8% at final analysis was < 1%.

MICRA patients total n=167Specimen negSpecimen posBiopsy neg8929118FNR= 29/7837%Biopsy pos049498978167

Conclusions: Ultrasound-guided core biopsies of the breast in patients with excellent response on MRI after NST are not accurate enough to safely select patients with pCR for omission of surgery.

Citation Format: Marie-Jeanne T.F.D. Vrancken Peeters, A van Loevezijn, M EM van der Noordaa, F H van Duijnhoven, C E Loo, E van Werkhoven, K K van de Vijver, T Wiersma, H AO Winter-Warnars, G S Sonke, C. Blanken, B. Zonnevels. Towards omitting breast surgery in patients with a pathologic complete response after neoadjuvant systemic treatment: interim analysis of the MICRA trial (Minimally Invasive Complete Response Assessment) [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr GS5-06.

Abstract P2-14-07: Association between initiation of adjuvant chemotherapy beyond 30 days following surgery and overall survival among patients with triple-negative breast cancer

Background: The optimal time between surgery and initiation of adjuvant chemotherapy is unknown, though delayed time to chemotherapy (TTC) is associated with decreased outcomes of breast cancer patients. Recently, studies have suggested that the association might be subtype-dependent and that TTC within 30 days should be warranted particularly in high-risk triple-negative breast cancer (TNBC) patients. Objective: To determine the extent to which TTC beyond 30 days is associated with reduced overall survival (OS) in TNBC patients. Methods: Using the population-based nationwide Netherlands Cancer Registry we identified TNBC patients diagnosed between 2006 and 2014 who received adjuvant chemotherapy. We distinguished between patients who underwent breast-conserving surgery (BCS) versus mastectomy given the difference in preoperative characteristics and outcomes. Median (95% confidence interval) follow-up was 82.9 (80.5-86.5) and 81.4 (79.5-83.9) months, respectively. Main outcomes and measures: The association between TTC beyond 30 days and OS was estimated with hazard ratios (HR) using propensity-score matched Cox proportional hazard analyses separately for patients who underwent BCS and mastectomy. Results: In total, 3016 patients were included, of whom 1079 (35.8%) underwent BCS and 1937 (64.2%) underwent a mastectomy. In matched patients who underwent BCS, 10-year OS was significantly better for patients with TTC within 30 days compared to patients with TTC beyond 30 days (84.4% vs. 76.9%, P=0.001). Patients with TTC beyond 30 days were more likely than those with TTC within 30 days to die within 10 years after surgery (HR 1.69 (95% CI 1.22-2.34), P=0.002). In matched patients who underwent mastectomy, there was no difference in 10-year OS between those with TTC within or beyond 30 days (74.5% vs. 74.7%, P=0.716), nor an increased risk of death for those with TTC beyond 30 days (HR 1.04 (95%-CI 0.84-1.28), P=0.716). In both populations, the associations were independent of adjuvant radiotherapy. Conclusions: The current results suggest that initiation of chemotherapy beyond 30 days is associated with decreased OS in TNBC patients who underwent BCS; no association was observed for patients who underwent a mastectomy. Therefore, timelier initiation of chemotherapy in TNBC patients undergoing BCS seems warranted.

Citation Format: Erik Heeg, Perla J. Marang-van de Mheen, Marissa C. Van Maaren, Kay Schreuder, Rob A.E.M. Tollenaar, Sabine Siesling, Monique E.M.M. Bos, Marie-Jeanne T.F.D. Vrancken Peeters. Association between initiation of adjuvant chemotherapy beyond 30 days following surgery and overall survival among patients with triple-negative breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-14-07.