Race and the neoadjuvant-to-adjuvant pembrolizumab transition for early-stage triple-negative breast cancer in the KEYNOTE-522 era: A TriNetX US Collaborative Network analysis.

Abstract

238 Background: Pembrolizumab plus chemotherapy is standard neoadjuvant therapy for high-risk early-stage triple-negative breast cancer (TNBC) per KEYNOTE-522. Prior real-world studies have documented Black-White disparities in initial KEYNOTE-522 receipt and regimen tolerability, but the discrete neoadjuvant-to-adjuvant care transition has not been examined by race. We assessed whether Black and White patients differ in initiation of adjuvant pembrolizumab following neoadjuvant chemoimmunotherapy and curative-intent surgery. Methods: Retrospective cohort using the TriNetX US Collaborative Network. Eligible patients were adult women with a breast cancer diagnosis (ICD-10 C50) who received pembrolizumab within 42 days before a curative-intent breast surgery (CPT 19301-19307) performed 7/1/2021-12/31/2025; ≥1 neoadjuvant chemotherapy agent (carboplatin, paclitaxel, doxorubicin, or cyclophosphamide) within 180 days pre-surgery; and ≥1 in-network encounter 30-90 days post-surgery. Patients with distant metastatic codes (C77-C79) were excluded. TNBC was identified by treatment pattern, as pembrolizumab is FDA-approved only for TNBC in this setting. The primary outcome was receipt of ≥1 pembrolizumab dose 1-84 days after the index surgery, comparing Black vs White patients. We applied 1:1 propensity-score matching on age at index and Hispanic ethnicity, and estimated risk difference (RD), odds ratio (OR), and Cox hazard ratio (HR). Results: Of 1,016 patients, 249 (24.5%) were Black, 619 (60.9%) White, and 148 (14.6%) other/unknown. After 1:1 propensity matching (248 Black:248 White), baseline characteristics were balanced (Table). Adjuvant pembrolizumab receipt and time-to-initiation did not differ. Approximately 16% in both arms failed to transition within 84 days. Conclusions: Among patients with early-stage TNBC who received KEYNOTE-522–pattern neoadjuvant therapy and underwent curative-intent surgery, adjuvant pembrolizumab receipt and time to initiation did not differ significantly between Black and White patients. This contrasts with documented disparities in initial regimen access, suggesting racial inequity in this pathway is concentrated upstream at treatment initiation rather than in the neoadjuvant-to-adjuvant transition. The ~16% of patients in both arms who failed to transition represent a substantial, equitable population for future quality-improvement targeting. Black (n=248) White (n=248) Comparison (95% CI) Age at index, mean (SD), years 55.5 (12.2) 55.4 (12.2) balanced (PSM) Hispanic ethnicity, n (%) 10 (4.0) 10 (4.0) balanced (PSM) Adjuvant pembrolizumab 1-84d, n (%) 206 (83.1) 209 (84.3) RD -1.2% (-7.7, +5.3), p=0.72 Odds ratio - reference OR 0.92 (0.57, 1.47) Median time to pembrolizumab, days 27 26 HR 0.93 (0.77, 1.13), log-rank p=0.44