ASPO Abstracts
The association between marijuana smoking and breast cancer risk
Category: Lifestyles Behavior, Energy Balance & Chemoprevention
Conference Year: 2022
Abstract Body:
Purpose: Marijuana is a commonly used substance in the United States. Smoking marijuana may plausibly contribute to cancer risk in part due to shared properties with tobacco smoke. Laboratory evidence suggests it may also inhibit proliferation of estrogen receptor (ER) positive breast cancer cell lines by inhibiting DNA synthesis and promoting apoptosis. The association between marijuana use and breast cancer risk has not been well studied. Our objective was to examine the association between smoking marijuana and incident breast cancer in a nationwide prospective cohort.Methods: We used data from the Sister Study (2003-2009), a cohort study of 50,884 women aged 35-74 at enrollment, who had a sister previously diagnosed with breast cancer. At enrollment, participants self-reported whether they have ever used marijuana and the duration of use. We used Cox proportional hazards models to estimate hazard ratios (HRs) and 95% CIs for the association between history of marijuana use and incident breast cancer among 48,001 eligible women. We adjusted for race/ethnicity, and socioeconomic, reproductive, and behavioral factors. We examined effect measure modification by race/ethnicity and menopausal status. We also used case-only analyses to assess etiologic heterogeneity for ER negative versus positive breast cancer.Results: Through follow-up (mean=10.8 years), 3,711 women were diagnosed with breast cancer. 23, 150 (48%) reported ever smoking marijuana. After adjustment, a history of ever smoking marijuana was not associated with breast cancer risk (HR=0.95, 95% CI: 0.87-1.03). No differences by race/ethnicity or menopausal status were observed. Women who reported ever smoking marijuana and later developed breast cancer were at reduced odds for the ER-negative type (aOR=0.87; CI: 0.71-1.06).Conclusion: In this cohort of women, a history of smoking marijuana was not associated with breast cancer risk. A history of ever smoking marijuana may be associated with a reduced likelihood of developing ER-negative BC.
Keywords: Marijuana use, breast cancer risk