(213) Safety and Tolerability of Adjuvant Combination Treatments following Keynote-522 for Early-Stage/Locally Advanced Breast Cancer with Residual Disease

Poster Abstract: Patients with residual early-stage breast cancer after receiving neoadjuvant chemotherapy, per the Keynote-522 regimen, have poor prognoses. Previous trials (Create-X and OlympiA) have shown promising outcomes and acceptable safety profiles with the use of adjuvant capecitabine or olaparib in those with residual disease. No data exists for the efficacy and toxicity of these agents when used in combination with pembrolizumab or with radiation. The primary objective was to assess the tolerability and safety of the combinations of pembrolizumab plus capecitabine and pembrolizumab plus olaparib, both regimens with or without radiation, in patients with residual disease. The secondary objectives included pathologic complete response rate and median time to recurrence. A retrospective, single-centered chart review was performed on eligible patients treated at Yale New Haven Health System (YNHHS) from 03/01/2020 to 12/15/2023. Eligible patients aged ≥18 years with triple negative or hormone-receptor low positive early-stage breast cancer were included if they were treated with the Keynote-522 regimen (neoadjuvant pembrolizumab, carboplatin, and paclitaxel followed by pembrolizumab, doxorubicin, and cyclophosphamide). After definitive surgery, patients were assessed for residual disease status and whether they received adjuvant pembrolizumab with or without radiation and with or without capecitabine or olaparib. Patients were excluded if they were < 18 years of age, had distant metastatic breast cancer or any other cancer types, and were human epidermal growth factor receptor 2 (HER2) positive. Along with patient demographics and disease characteristics, the past and current treatment history and time to recurrence was collected for all patients. Toxicities, dose adjustments, doses held, and discontinuations were reported for patients on the combination regimens. Results will be presented at HOPA’s annual conference pending final statistical analyses. Conclusions will be presented at HOPA’s annual conference pending final statistical analyses.

References (must also be included in final poster): 1. Schmid P et al. Pembrolizumab for Early Triple-Negative Breast Cancer. N Engl J Med. 2020; 382:810-821. DOI: 10.1056/NEJ/Moa1910549.
2. Masuda N et al. Adjuvant Capecitabine for Breast Cancer after Preoperative Chemotherapy. N Eng J Med. 2017; 376:2147-2159.
3. Tutt A et al. Adjuvant Olaparib for Patients with BRCA1- or BRCA2-Mutated Breast Cancer. N Eng J Med. 2021; 384:2394-2405.