Objective: HIV infection affects the immune system and may influence the safety and efficacy of immune checkpoint inhibitors (ICIs). This study aimed to evaluate HIV seroprevalence among cancer patients receiving ICIs and contextualize the findings using national prevalence estimates.
Materials and Methods: We retrospectively analyzed 590 patients treated with ICIs between January 2015 and July 2025. Viral serology, including anti-HIV, hepatitis B virus (HBV), and hepatitis C virus (HCV) markers, was evaluated. HIV positivity was defined based on confirmatory testing. Statistical analyses were performed using SPSS, version 27.
Results: The median age was 65 years (IQR, 55–73 years), and 65.9% of the patients were male. The most common diagnoses were melanoma (37.4%), genitourinary tumors (26.4%), and lung cancer (21.5%). Viral serology results were available for 354 patients (60%). Only one patient had confirmed HIV positivity, corresponding to a prevalence of 0.28% (exact 95% CI, 0.007%–1.56%). This patient had metastatic melanoma and tested negative for HBV and HCV. The observed point estimate was numerically similar to the reported national adult HIV prevalence estimates in Türkiye (0.1%–0.2%). Patients tested for HIV were younger and more likely to have comorbidities, and the distribution of tumor types differed between tested and untested patients. In the multivariable analysis, younger age, the presence of comorbidities, and tumor type were independently associated with HIV testing.
Conclusion: HIV prevalence among cancer patients treated with ICIs was low. Given the incomplete testing coverage and the clinical implications of undiagnosed HIV infection, routine pretreatment HIV screening should be incorporated into standard viral serology panels.