Abstract PO5-01-02: A retrospective review of pathological complete response and toxicity rates to a modified version of TCHP (Paclitaxel, Trastuzumab, Pertuzumab, Carboplatin) for HER2 positive breast cancer stage II and III

Abstract Background In 2018 the TRAIN-2 clinical trial demonstrated that in stage II–III HER2-positive breast cancer, the use of a neoadjuvant non-anthracycline chemotherapy regimen of 9 cycles of TCHP [paclitaxel and carboplatin (AUC 6 mg/mL/min) with trastuzumab and pertuzumab resulted in lower toxicity and comparable pathological complete responses to an anthracycline based regimen. A pathological complete response was recorded in 141 (67%) of 212 patients in the anthracycline group and in 140 (68%) of 206 in the non-anthracycline group. Our primary aim was to identify rates of pathological complete response and rates of toxicity with a less intensive regimen of 6 cycles of TCHP where carboplatin was dose adjusted to AUC5. Methods In this single center cohort study, we reviewed patients with stage II-III Her2-positive breast cancer who received a modified chemotherapy regimen of 6 cycles of neoadjuvant paclitaxel (80 mg/m2 days 1 and 8) and reduced dose of carboplatin (AUC= 5 mg/mL/min) with trastuzumab (6 mg/kg; loading dose 8 mg/kg) and pertuzumab (420 mg intravenously; loading dose 840 mg) every 3 weeks from 2021- June 2023. Clinicopathologic data, the number and length of treatment delays, treatment related toxicities of all grades, and pCR rate were extracted from the electronic medical record. Results 32 patients were included in the analysis. The median age of the cohort was 51 years (30-65). No patient had a BRCA mutation. 20 (62.5%) had T1-2 disease and 12 (37.5%) had T3-4 disease. 14(43.75%) patients had N0 disease and 20 (62.5%) had N1-3 disease. ECOG Performance status was 0, 1 and 2 in 26 patients (81.25%), 4 (12.5%) patients and 2(6.25%) patients respectively. At the time of analysis, 2 patients (6.25%) were continuing active treatment, while 30 (93.75%) had completed planned neoadjuvant therapy and underwent surgery. Of patients who completed planned neoadjuvant therapy, 6 patients (18.75%) had 1 or more hospitalisations due to toxicity. 10 patients (31.25%) required dose reductions and 3(9.38%) had early treatment discontinuation. Rates of adverse events will be presented. pCR rate was 60 % (N=18/30). 19 (63%) of 30 patients underwent mastectomy and 11 (36.7%) underwent breast-conserving surgery. Updated analysis will be included at time of presentation. Conclusion In this single-center retrospective study of patients receiving a modified version of TCHP we found a 60% pCR rate. The rate of dose reductions and treatment discontinuations appears favorable with use of this modified regimen. This was in a heterogeneous population of patients treated in routine clinical practice where there was a high rate of patients with locally advanced disease. Limitations of our study include immaturity of data and small sample size; however, these data warrant further exploration through longer-term follow-up and multi-center validation. Citation Format: Carolyn Moloney, Maggie Louise O'Connor, Caroline O'Leary, Aislinn Reilly, Simon Barry, David O'Reilly, Philip Bredin, Hadia Paryani, David Solaligue, Bryan Hennessy, Megan Greally, Patrick G. Morris. A retrospective review of pathological complete response and toxicity rates to a modified version of TCHP (Paclitaxel, Trastuzumab, Pertuzumab, Carboplatin) for HER2 positive breast cancer stage II and III [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-01-02.