[Association between HER2 overexpression and recurrence rate in patients with non-muscle-invasive bladder cancer following anthracycline-based intravesical instillation therapy].

Objective: To assess the clinicopathological characteristics of non-muscle-invasive bladder cancers (NMIBC) with high expression of human epidermal growth factor receptor 2 (HER2) and to examine the prognostic values of HER2 expression in NMIBC patients with intravesical anthracycline instillation. Methods: A total of 221 NMIBC samples diagnosed between January 1, 2017 and April 15, 2024 were collected. Their clinical, diagnostic and treatment features were analyzed. The expression of HER2 protein and the Ki-67 proliferation index were assessed using immunohistochemistry (IHC). For the patients with HER2 high-expression (IHC 3+), the clinical pathological features (age, gender, tumor grade, Ki-67 expression level, tumor size, and tumor number) were compared with those without (i.e., HER2 IHC 0/1+/2+). The impact of HER2 expression on the recurrence-free survival (RFS) of patients with intravesical anthracycline (epirubicin or pirarubicin) instillation after transurethral resection of bladder tumor (TURBT) was evaluated. Results: Among the 221 NMIBC patients, 30 (13.6%) were HER2 IHC 3+, 142 (64.3%) HER 2+, 46 (20.8%) HER2 1+, and 3 (1.4%) HER2 IHC 0. The proportion of high-grade tumors in patients with HER2 high-expression was higher than that in patients without (83.3% versus 44.5%, P<0.001). Additionally, a high Ki-67 index (≥20%) was more commonly noted in HER2 high-expression tumors (P=0.003). In the patients treated with intravesical anthracycline instillation, HER2 high-expression was associated with a shorter RFS (P<0.001). Conclusion: HER2 high-expression seems to be not only associated with worse clinicopathological features of NMIBC but also a poor RFS in NMIBC patients treated with anthracycline instillation after TURBT.