Background: The use of cannabis by cancer patients has become increasingly common. With expanding access to medical cannabis, unsanctioned cannabis use is likely to increase. Despite this, the extent to which patients seeking specialized palliative or supportive care for cancer-related symptoms are actively using cannabis has not been well established. Objective: We sought to determine the extent to which patients seeking specialized symptom management were using cannabis and to compare the severity of cancer-related symptoms between users and nonusers. Methods: We conducted a retrospective review of objectively measured tetrahydrocannabinol (THC) and subjectively reported cannabis use, its demographic and clinical correlates, and patient-reported symptoms in 816 cancer patients in active treatment referred to a supportive/palliative care outpatient clinic for specialized symptom management between January 2014 and May 2017. Results: Nearly one-fifth (19.12%) tested positive for THC on urine drug testing. Users were younger, more likely to be men, single, and to have a history of cigarette smoking. Users also were likely to be more recently diagnosed and to have received radiotherapy. Certain moderate-to-severe symptoms, such as lack of appetite, shortness of breath, tiredness, difficulty sleeping, anxiety, and depression, were associated with use after accounting for sociodemographic and clinical differences between cannabis users and nonusers. Conclusions: Findings suggest patients seeking specialized symptom management are self-treating with cannabis, despite the lack of high-quality evidence for its use in palliative care. Unsanctioned use is likely to increase in cancer patients. Accurate information is urgently needed to help manage patient expectations for its use and increase understanding of risks and benefits.
Keywords: cancer; cannabis; oncology; symptom management.