Cannabis use among patients receiving immune checkpoint inhibitors.

416 Background: Although cannabis has promise as a supportive care agent for patients with cancer undergoing traditional therapies, there is little evidence for its harms and benefits for patients undergoing immune checkpoint inhibitor (ICI) therapy. Furthermore, there is mixed evidence suggesting that cannabis may impede the effectiveness of ICIs. In this context of limited evidence, we aimed to characterize the current extent of cannabis use, reasons for use, and experiences among patients undergoing ICIs. Methods: At a large cancer center, we conducted a cross-sectional survey in 2024 among English-speaking adults currently receiving ICI therapy (with or without other therapies) for any stage or histology of melanoma or kidney cancer, two of the cancers most commonly treated with ICIs. Patients completed a survey online or on the phone. The survey measured cannabis use since the start of immunotherapy, including reasons for use (or non-use), timing of use, experiences with cannabis, mode of cannabis ingestion, and frequency of cannabis use since start of ICI treatment. The survey elicited sociodemographics and health behaviors (education, marital status, tobacco, alcohol, physical activity). Clinical data came from medical records. Results: 160 patients (N = 108 kidney, N = 52 melanoma, 40% response rate) completed the survey. Respondents had a median age of 65 years, 90% were White, and 70% were male. 21% (N = 34) reported using cannabis during ICI therapy; younger patients and those who had a history of tobacco use were more likely to use cannabis during treatment. Of those who used cannabis during treatment, 65% did so at least a few times a month. Among patients who used cannabis in the past month, 15% did so at least daily (median 10 days per month). Cannabis users most commonly ingested cannabis in food (70%) and smoked it (41%). Most cannabis users aimed to address a symptom (65%), most commonly for mood impairment (N = 15), difficulty sleeping (N = 11), aching muscles and joints (N = 10), or lack of appetite (N = 5). Only 18% of respondents talked with their doctors about cannabis use during ICI. Of the 126 patients who did not use cannabis during ICI treatment, only 9% reported avoiding cannabis due to concerns that their immunotherapy would not work as well. Conclusions: In a large cancer center, nearly a quarter of kidney cancer and melanoma patients receiving ICIs use cannabis, primarily to mitigate symptoms. Doctors do not appear to be discussing cannabis or dissuading its use among these patients. Prevalence of cannabis use among ICI-treated patients in our study is similar to prevalence of cannabis use reported in other studies among patients receiving any cancer treatment. With almost half of cancer patients eligible for ICI therapy, and with cannabis commonly used by patients undergoing ICIs, additional research to understand the harms and benefits of cannabis is warranted.