2861 - Combustible Cannabis Use and Treatment Outcomes in Patients with Head and Neck Cancer Treated with Radiation Therapy

Purpose/Objective(s): With increasing use of all forms of cannabis following state-level legalization, there are mixed results for the impact of cannabis on treatment tolerance and outcomes for head and neck squamous cell carcinoma (HN-SCC). We explored the interaction of combustible cannabis (C-Can) (smoked marijuana), with radiation therapy (RT) induced toxicity, including narcotic use, and survival outcomes for patients with HN-SCC.

Materials/Methods: We used our institutional database of RT-managed patients with HN-SCC to identify C-Can users and never-users treated between 2015 and 2021. Only patients formally assessed by a head and neck clinical psychologist with a pre-treatment semi-structured psychosocial interview with a detailed substance use history, were included. We reviewed these notes to verify the regular use of C-Can at least once a week within a year of starting RT. We excluded patients with irregular/social use or distant use, and patients using non-smoking formulations. We compared demographics, clinicopathological details, RT-induced toxicities, and narcotic use outcomes for the study groups. The study groups were well-balanced. We assessed the impact of C-Can use on recurrence free (RFS), locoregional recurrence free (LRFS) distant metastases free (DMFS), and overall (OS) survival using multivariable Cox-regression analyses (MVA).

Results: We identified 135 patients (62 C-Can users, 46% and 73 never users, 54%): median age 62 years (range: 38-85), male 73 %, White 76.3% and Black 21.5%. Tobacco ever-smokers were 73.4% with a median pack-years of 30.5 (range: 1-155) and 76.3% reported alcohol use. Oropharynx was the most common subsite (54.8%; 78% HPV+), followed by larynx (30%). The majority received definitive RT (71%), and 29% had adjuvant RT, with concomitant systemic therapy administered in 71.9%. C-Can use was significantly associated with male gender, younger age, low baseline comorbidities, and with tobacco use (p<0.05 for all). Narcotic pain medications were used more frequently by C-Can users, with significantly higher mean morphine milligram equivalent/day (MME) (97.8 vs 60.2; p=0.013). Weight loss (>5% of baseline) (24.2% vs 38.3%) and feeding tube insertion (41.7% vs 49.2%) were less frequent with C-Can users vs non-users, however these were non-significant (p>0.05). RT delays and other RT-induced toxicities (grade = 3 dermatitis, mucositis, xerostomia and dysphagia) were not significantly different across study groups. C-Can use predicted worse OS (HR 2.9 [CI: 1.8-7.2]; p=0.02) and DMFS (HR 4.2 [CI: 1.1-16.2]; p=0.036) and was marginal for RFS (HR 2.7 [CI: 0.99-7.1]; p=0.052) and non-significant for LRFS (p=0.24), after adjusting for other factors in MVA.

Conclusion: C-Can use was associated with being male, younger, otherwise healthy, and ever-tobacco user. C-Can use did not offer benefits to weight loss, or pain management during RT for HN-SCC. However, C-Can use was associated with higher doses of narcotics, as well as predicting worse OS and DMFS.