# Impact of immune-related adverse events on response to neoadjuvant chemoimmunotherapy in triple-negative breast cancer: a single-institution retrospective study

## TL;DR

This study finds that immune-related side effects may indicate better treatment response in a diverse group of patients with a specific type of breast cancer.

## Contribution

The study identifies immune-related adverse events as a potential response marker in neoadjuvant chemoimmunotherapy for triple-negative breast cancer.

## Key findings

- Patients with immune-related adverse events had higher rates of pathologic complete response.
- Higher tumor-infiltrating lymphocytes were associated with better treatment outcomes.
- Hispanic patients had higher pCR rates, while Black race and older age were linked to lower pCR rates.

## Abstract

Immune-related adverse events (irAEs) have emerged as a potential surrogate marker for immunotherapy response across tumor types. We evaluated the association between irAEs and pathologic complete response (pCR) in a racially diverse cohort of patients with triple-negative breast cancer (TNBC) treated with neoadjuvant chemoimmunotherapy.

We conducted a retrospective analysis of 46 patients with early-stage TNBC treated with neoadjuvant chemoimmunotherapy between January 2021 and March 2023 at a single NCI-designated Comprehensive Cancer Center. irAEs, tumor-infiltrating lymphocytes (TILs), and clinicopathologic characteristics were abstracted from the medical record. Associations with pCR were analyzed using Fisher’s exact and Wilcoxon rank-sum tests.

Among 46 patients, the median age was 60.5 years. Most identified as Black (n = 27, 58.7%) or Hispanic (n = 14, 30.4%). irAEs occurred in 13 patients (28.2%), most commonly hypothyroidism, rash, and arthritis. The pCR rate was 55.8% (24/43 evaluable patients). Patients who developed irAEs were more likely to achieve pCR (84.6% vs. 45.2%, p = 0.039). Higher TILs (median 29%) were associated with pCR both as a continuous variable (p = 0.004) and categorically (p = 0.002), but not with irAE development (p = 0.341). pCR was more common among Hispanic patients (p = 0.005), and inversely associated with Black race (p = 0.003) and older age (p = 0.028).

IrAEs may serve as a surrogate for treatment response to neoadjuvant chemoimmunotherapy in early TNBC. Additionally, racial and age-based differences in treatment response suggest underlying immunologic or biologic variation. These findings highlight the importance of diverse cohort representation in immunotherapy studies and warrant validation in prospective trials.