Abstract P2-16-23: Weekly vs. every-3-week (q3wk) carboplatin (Cb) with paclitaxel (P) in neoadjuvant chemotherapy (NACT) for triple-negative breast cancer (TNBC): A retrospective analysis background

Abstract

Abstract Background: Randomized studies have demonstrated that adding Cb to P as part of NACT for stage II-III TNBC significantly increases pathologic complete response (pCR) rates, but its optimal dose and schedule are uncertain. Since hematologic toxicities associated with higher dose (AUC 5-6) q3wk Cb with P necessitate treatment delays or omissions in some patients (pts), some oncologists favor administering lower dose (AUC 1.5-2) weekly Cb with P instead. While many believe that this approach is better tolerated, there is limited published data on its efficacy in TNBC. Oncologists at University of Vermont and Women and Infants Hospital of Rhode Island decided to analyze results achieved with weekly Cb/P in this setting, particularly pCR rate, and to compare them to those achieved with q3wk Cb/P. Methods: Databases at our institutions were reviewed to identify pts who received P and Cb as initial NACT for TNBC over the past 10 years for whom pathologic results and post-op follow-up were available. pCR was defined as ypT0/isN0, as reported by the institutional pathologists. We also assessed delivery of P and Cb. Disease-free survival was censored as of the patient’s last follow-up visit. Results: Of 76 pts identified (median age 49), 47 received weekly Cb/P and 29 q3wk Cb/P. All but 4 (all in the weekly Cb cohort) subsequently received doxorubicin and cyclophosphamide (AC). In the q3wk Cb cohort, 15 pts also received bevacizumab and 3 each may have received veliparib or atezolizumab on blinded clinical trials. pCR rates are tabulated below: Patient groupNpCR (95% CI)vs. q3week CbAll7654% (42-65%)Stage IIA-IIIA6058%Stage IIIB-IIIC1638%BRCA1/2 mutated989%q3week Cb/P2955% (36-74%)Weekly Cb/P4753% (38-68%)p>0.99 Most pts - 89% of weekly Cb and 90% of q3wk Cb - received ≥11 doses of weekly P; 83% of weekly Cb pts received ≥11 doses of Cb and 90% of q3wk Cb pts received all 4 planned doses of Cb. At median follow-up of 19 months (range <1-118), 93% of pts who achieved pCR and 74% of non-pCRs are free from recurrence; median f/u is much longer (54 vs. 14 months) for the q3wk Cb pts. Conclusions In this retrospective analysis, treatment with weekly Cb/P (typically followed by AC) resulted in a pCR rate similar to that seen with q3wk Cb/P, both in our own pts and as reported from CALGB 40603 (54%) and BrighTNess (58%). Given the ongoing debate on the role of Cb in NACT for TNBC, we believe that the weekly Cb/P regimen should be explored further, as it may be easier to administer without sacrificing efficacy. Citation Format: Kitty E Victoria, Pouyan N Changizzadeh, Bernard Cole, Pulluri Bhargavi, Jessica L Lyon, Marie E Wood, William M Sikov. Weekly vs. every-3-week (q3wk) carboplatin (Cb) with paclitaxel (P) in neoadjuvant chemotherapy (NACT) for triple-negative breast cancer (TNBC): A retrospective analysis background [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 P2-16-23.