Substance use disorders following cancer diagnosis in adolescents and young adults: A Canadian population-based study.

e23102 Background: Substance use disorders (SUDs) can adversely affect cancer treatment and survivorship outcomes, including the risk of secondary malignancies among adolescents and young adults (AYAs) with cancer. However, data on the burden of SUDs and associated risk factors in this population remain limited. This study examined the five-year cumulative incidence of SUDs following cancer diagnosis and factors associated with its development among AYAs with cancer. Methods: This retrospective, population-based cohort study used the Manitoba Cancer Registry to identify AYAs aged 15–39 years diagnosed with invasive cancer between 1989 and 2019. Incident SUDs were identified using validated administrative definitions based on one or more hospitalizations or physician visits with diagnoses of alcohol- or drug-related psychoses, dependence, or non-dependent substance abuse (ICD-9 codes 291–305; ICD-10 codes F10–F19, F55, Z50.2, Z50.3). Competing risks regression was used to assess the five-year cumulative incidence of SUDs and the association of age, sex, comorbidities, income, residence, tumor type (sex-specific vs non–sex-specific), calendar year, and receipt of chemotherapy, surgery, or radiation with SUDs. Sex-specific cancers included breast, ovarian, uterine, and cervical cancers in females, and prostate and testicular cancers in males. Results: Among 3,818 AYAs with cancer (mean age at diagnosis, 30.7 years), 2,125 (56%) were female, and 3124 (81%) had solid tumors. The unadjusted 5-year cumulative incidence of SUDs post cancer diagnosis was 4.1% 95% Confidence Interval (CI), 3.5–4.8. In competing-risk regression analyses, those in the highest income quintile had the lowest risk of developing SUDs compared to those in the lowest income quintile sub-Hazard ratio (sHR), 0.40; 95% CI 0.25–0.66) (Table 1). Receipt of chemotherapy (sHR, 1.53; 95% CI 1.07–2.28) and radiation therapy (sHR, 1.60; 95% CI 1.10–2.34) were independently associated with increased SUDs risk, whereas the presence of one or more comorbidities at diagnosis (sHR, 0.62; 95% CI 0.41–0.93) and more recent calendar year of diagnosis (sHR per year, 0.97; 95% CI 0.95–0.99) were associated with reduced risk. Conclusions: SUDs among AYAs with cancer post cancer diagnosis are higher among those in lower income quintiles and those receiving chemotherapy or radiation therapy. These findings support the integration of early, targeted substance use screening and equity-informed interventions into routine AYA oncology care for patients undergoing intensive treatment and those from socioeconomically disadvantaged backgrounds. Five-year adjusted cumulative incidence of substance use disorders by income quintile. Income Quintile 5-Year Adjusted Cumulative Incidence (%) Q1 (lowest income) 6.3 Q2 3.4 Q3 3.6 Q4 2.0 Q5 (highest income) 2.7