Background: Management of cancer-related pain with opioids is hypothesized to decrease efficacy of immune checkpoint inhibitors (ICIs) through immunosuppressive effects of opioids, such as down-regulation of major histocompatibility complex class II. There is limited evidence on how opioids affect outcomes in patients receiving ICIs. Methods: We identified 212 patients at the University of Illinois Hospital and Health Sciences System who received an ICI between January 1, 2015 and July 31, 2021. Overall survival (OS) and progression-free survival (PFS) were compared in patients who were not treated with opioids, patients treated with low-dose opioids (defined as less than 60 morphine milliequivalents per day), and patients treated with high-dose opioids (defined as at least 60 morphine milliequivalents per day). Results: Out of 212 patients who received an ICI, 98 (46.2%) received no opioids, 69 (32.6%) received low-dose opioids, and 45 (21.2%) received high-dose opioids. Among all patients, 105 (49.5%) died during the study duration. The overall median survival time was 23 (95% CI = 16, 38) months for the entire sample. Patients who received opioids at any dose had a median OS of 17 months compared to 37 months in those who received no opioids (HR = 1.53, p = 0.0385). When patients receiving opioids were further divided by dose, survival time was highest in those receiving no opioids, next highest in those receiving low-dose opioids, and lowest in those receiving high-dose opioids (37 months vs 18 months vs 10 months, p = 0.0515). Among all 212 patients, progression of disease occurred in 84 (39.6%) patients. The overall median time-to-progression was 24 months. There was no significant difference in median PFS between those treated with opioids (36 months) versus not (23 months, p = 0.156). Conclusions: We observed an association between opioid therapy, especially at higher doses, and decreased median OS in patients receiving ICIs. On the other hand, there was no statistical association between opioid therapy and median PFS. These data highlight a potential drug interaction in oncology care, and further analysis looking at duration of opioid use and ECOG PS is planned.

^*:Not enough progression was observed in the group to estimate upper confidence limit.