Impact of H1 Antihistamines on Bacillus Calmette-Guérin-treated Non-muscle-invasive Bladder Cancer

Concomitant H1 antihistamine (H1-AH) administration is associated with better survival outcomes for patients with metastatic urothelial carcinoma receiving immunotherapy. However, the role of H1-AHs among patients with non-muscle-invasive bladder cancer (NMIBC) treated with adjuvant intravesical bacillus Calmette-Guérin (BCG) immunotherapy has not been explored. Our aim was to investigate the impact of H1-AH use on survival outcomes for patients with BCG-treated NMIBC.

We conducted a territory-wide retrospective observational study. Patients with NMIBC who received intravesical immunotherapy with a single BCG strain in Hong Kong from 2001 to 2020 were identified. H1-AH prescription data were recorded. Overall survival (OS), cancer-specific survival (CSS), recurrence-free survival (RFS), and progression-free survival (PFS) outcomes were compared between H1-AH and control groups using the Kaplan-Meier method and multivariable Cox regression.

Our analysis included 2028 patients with NMIBC who received intravesical BCG immunotherapy. Of these, 1539 patients (76%) had a H1-AH prescription at baseline and 489 (24%) never received any H1-AH prescription during the study period. Median follow-up was 11.0 yr. Kaplan-Meier analysis revealed that the H1-AH group had better CSS (p = 0.017) and PFS (p = 0.001). Subgroup analysis by H1-AH timing (before or during BCG therapy) showed that concomitant H1-AH treatment during intravesical BCG immunotherapy was associated with better CSS (p = 0.002) and PFS (p = 0.005). Multivariable Cox regression results demonstrated that concomitant H1-AH treatment was associated with better OS (hazard ratio [HR] 0.69, 95% confidence interval [CI] 0.58-0.82), CSS (HR 0.44, 95% CI 0.30-0.65), RFS (HR 0.81, 95% CI 0.67-0.98), and PFS (HR 0.64, 95% CI 0.45-0.91).

Concomitant H1-AH treatment was associated with better OS, CSS, RFS, and PFS for patients with NMIBC receiving adjuvant intravesical BCG.

The treatment for non-muscle-invasive bladder cancer (NMIBC) typically includes a solution of BCG (bacillus Calmette-Guérin) instilled into the bladder. We found better survival outcomes (overall survival, cancer-specific survival, recurrence-free survival, and progression-free survival) for patients who took a H1 antihistamine during their BCG treatment for intermediate-risk or high-risk NMIBC. More research is needed to confirm our results.