Impact of antibiotics on survival outcomes and risk of gastritis/colitis in advanced-stage melanoma patients receiving immune checkpoint inhibitor therapy.

[AIM] To determine the impact of antibiotic spectrum of activity and exposure timing on survival outcomes and development of gastritis/colitis.

[METHODS] We conducted a single-center, retrospective cohort study of 214 patients with advanced, metastatic, or unresectable melanoma treated with immune checkpoint inhibitors. Antibiotic exposure was classified by spectrum of activity (with and without anaerobic coverage) and antibiotic timing. Primary outcomes were the effect of antibiotic administration 30-days prior to starting ICI therapy and during ICI therapy on overall survival (OS) and progression-free survival (PFS).

[RESULTS] Antibiotic exposure during ICI was associated with improved OS (HR: 0.57, 95% CI (0.35-0.92),  = 0.023). Use of antibiotics without anaerobic coverage was associated with improved PFS (HR: 0.53, 95% CI (0.32-0.87),  = 0.013), and OS (HR: 0.47, 95% CI (0.24-0.92),  = 0.026). There was a trend toward increased risk of gastritis/colitis with antibiotics without anaerobic coverage during ICI therapy, although this did not reach statistical significance (OR 2.08, 95% CI (0.43-5.46),  = 0.069).

[CONCLUSION] Antibiotic timing and spectrum of activity may be predictive of survival outcomes and risk of developing gastritis/colitis in ICI-treated patients with advanced-stage melanoma. Unlike previous studies, we found improved survival in patients receiving antibiotics during treatment and in those receiving antibiotics without anaerobic coverage.