# Neoadjuvant Pembrolizumab Associated with Chemotherapy in Early Triple-Negative Breast Cancer Patients: Real-World Data from a French Single-Center Experience

## TL;DR

This study examines the real-world use of pembrolizumab with chemotherapy for early triple-negative breast cancer, finding a 61% response rate and manageable side effects.

## Contribution

The study provides real-world data on pembrolizumab plus chemotherapy for early triple-negative breast cancer in a French setting.

## Key findings

- Grade 3–4 immune-related adverse events occurred in 20% of patients, with no treatment-related deaths.
- The pathological complete response rate was 61.1%, with no link to pembrolizumab cycle count.
- Patients with grade 3–4 irAEs showed a trend toward higher pCR (80% vs. 56.7%).

## Abstract

This retrospective study assessed the real-world feasibility, safety, and efficacy of neoadjuvant pembrolizumab plus chemotherapy for early triple-negative breast cancer (TNBC) at Montpellier Cancer Institute (2022–2024). Ninety-two patients were included (median age 50). Grade 3–4 immune-related adverse events (irAEs) occurred in 20% of patients, most commonly hepatitis, colitis, skin toxicity, myocarditis, and rare hematologic or endocrine events; no treatment-related deaths were reported. Discontinuation of immunotherapy because of irAEs was reported in 29.3% of patients. The pathological complete response (pCR) rate was 61.1%, with no association between pCR and the number of pembrolizumab cycles. Patients experiencing grade 3–4 irAEs showed a trend toward higher pCR (80% vs. 56.7%). Baseline antinuclear antibodies were not linked to increased toxicity. Overall, real-world toxicity and efficacy were consistent with KEYNOTE-522 findings.

Introduction: The addition of immunotherapy to neoadjuvant treatment for early triple-negative breast cancer (TNBC) has been adopted in clinical practice in France since March 2022, with little real-world data published on the topic. The aim of this study was to evaluate real-world data on treatment feasibility, efficacy, and related toxicities, with a specific focus on immune-related adverse events (irAEs). Methods: We conducted a retrospective analysis of patients who completed at least the neoadjuvant sequence of pembrolizumab combined with chemotherapy for early-stage TNBC at Montpellier Cancer Institute from April 2022 to July 2024. Adverse events were graded according to the Common Terminology Criteria for Adverse Events (CTCAE) v5.0. The pathological complete response (pCR) was defined as the absence of residual invasive disease in the breast and axillary lymph nodes (ypT0/Tis ypN0). Results: We reviewed data from 92 patient records. The median age at diagnosis was 50 years (range: 27–76). The history of autoimmune disease was noted in 3.2% of patients. Grade 3–4 irAEs were observed in 20% of patients and included hepatitis (8.6%), colitis (3.3%), skin toxicity (2.1%), myocarditis (2%), arthralgia (1%), autoimmune hemolytic anemia (1%), hypothyroidism (1%), and adrenal insufficiency (1%). No treatment-related deaths were reported. Immunotherapy was discontinued due to irAEs in 29.3% of patients in the study population. The pCR rate was 61,1%, with no significant association between the number of neoadjuvant pembrolizumab cycles and the pCR rate (p = 0.7). Patients experiencing grade 3–4 irAEs had a pCR rate of 80%, compared to 56.7% in those without such toxicities (p = 0.079). Initial positivity of antinuclear antibodies (ANA) was not associated with an increased incidence of irAEs. Conclusions: The immune-related adverse events and efficacy data observed in our cohort were broadly comparable to those reported in the KEYNOTE-522 trial, with no treatment-related deaths. Patients with grade 3–4 irAEs tended to have higher pCR rates.