Safety of inactivated vaccines in patients with genitourinary (GU) malignancies receiving immune checkpoint inhibitors (ICI).

Abstract

e17108 Background: ICI therapy has become the standard of care for many advanced GU cancers, but immune-related adverse events (IRAE) may result in treatment delays or discontinuation. Concurrent vaccine use has been posited to increase the IRAE risk, but safety data is mixed. There are no published data regarding safety of concurrent inactivated vaccines other than influenza, including and especially in the GU cancer population. Methods: We performed a single-institution, retrospective, matched-cohort (1:2, cohort A:B, vaccinated to control) study of all GU cancer patients treated with an inactivated vaccine 30 days prior to or 60 days following ICI therapy from 2015-2019. Baseline clinical characteristics were abstracted from the electronic health record (EHR). Clinically significant IRAEs were defined as any event developing during or 30 days following ICI therapy requiring therapy with ≥ Prednisone 20 mg daily (or equivalent) or other immunosuppression. Delays were defined as ICI therapy given > 14 days past expected date for cycle 2 or beyond. Bivariate analysis with chi-squared statistics were used to describe incidence. Results: Sixty patients were included: 20 in cohort A (vaccinated) and 40 in cohort B (control). Thirty-seven (61.7%) patients had renal cell carcinoma, 17 (31.7%) had urothelial carcinoma, and 4 (6.7%) had prostate cancer. There was no difference in incidence of clinically significant IRAEs between cohorts A and B (15% vs 32.5%, p = 0.148), nor were differences observed in rates of treatment delays (10% vs 12.5%, p = 0.776) or discontinuation (10% vs 12.5%, p = 0.776) due to IRAEs. Most common vaccines were inactivated influenza (n = 18, 90%) and pneumococcal vaccine (n = 3, 15%). Among the 16 patients experiencing clinically-significant IRAEs, the most common were colitis (n = 3), dermatitis (n = 3), and pneumonitis (n = 3). All patients requiring immunosuppressive therapy received systemic corticosteroids. Conclusions: This retrospective cohort study demonstrates that GU cancer patients receiving inactivated vaccines during ICI therapy does not increase IRAE incidence, treatment delays, or discontinuation, suggesting that inactivated vaccines may be safely administered during ICI therapy in this population. Though influenza vaccines were still the most common, this is the first study to include other inactivated vaccines. Limitations include sample size, EHR accuracy and use of surrogate markers for determination of IRAE incidence. Next steps will include a multi-institutional retrospective study.