Tobacco-cannabis co-use among cancer patients and survivors: findings from 2 US cancer centers.

Background: Cannabis use is prevalent among cancer patients and survivors and may provide some therapeutic benefits for this population. However, benefits may be attenuated when cannabis is co-used with tobacco, which is associated with more severe tobacco and cannabis use and adverse outcomes in noncancer populations. We compared cannabis use, primary mode of use, and therapeutic and/or nontherapeutic use among 3 groups of patients and survivors based on cigarette smoking status.

Methods: Survey data was collected from patients and survivors with cancer (n = 1732) at 2 US National Cancer Institute-designated cancer centers in states with varying cannabis regulatory policy. Prevalence of cannabis use (prior to diagnosis, after diagnosis, before treatment, after treatment), primary mode of use, and therapeutic and/or nontherapeutic use were assessed by cigarette smoking status (current, former, never) within and across centers using weighted bivariate analyses and multivariable logistic regression, controlling for demographic and clinical variables.

Results: Current cigarette use was associated with greater rates of cannabis use prior to diagnosis, after diagnosis, during treatment, and after treatment within each center (all P < .001) and in pooled analyses across centers (all P < .001). Primary mode of use, knowledge of cannabis products, and therapeutic and/or nontherapeutic use also statistically differed by tobacco status and study site.

Conclusions: Results illustrate the importance of conducting assessments for both tobacco and cannabis use among cancer patients during and after cancer treatment, regardless of the cannabis regulatory environment. Given previous data indicating harms from co-use and continued tobacco use during cancer treatment, this issue introduces new priorities for cancer care delivery and research.