Cancer Screening, Diagnosis, and Survival in California Prisons

Importance: Cancer is the leading cause of death in prison. Limited literature suggests cancer screening rates in prison are low, but population-level screening data in prisons are scarce. Objective: To determine screening rates for 5 cancer types, identify individual and incarceration characteristics associated with receipt of screening, and characterize outcomes for screen-detectable cancers in California prisons. Design, Setting, and Participants: This cohort study included individuals incarcerated in California state prisons who were eligible for breast, cervical, colorectal, liver, or lung cancer screening between January 1, 2014, and June 30, 2023. Incarceration data were linked to state cancer registry data from 2014 to 2021 to identify screen-detectable cancers diagnosed in the study population. Analyses were conducted between August 2024 and July 2025. Exposures: Receipt of screening within 3 months before a cancer diagnosis. Main Outcomes and Measures: Receipt of cancer screening; screening rates; and cancer diagnosis, stage, and survival were calculated. Multivariable models evaluated characteristics associated with screening receipt and associations between screening receipt and stage at diagnosis and survival, with adjustment for demographic and incarceration characteristics. Results: The study included 106 352 incarcerated individuals (median [IQR] age at first eligibility, 50 [47-55] years; 86 559 males [81.4%]). By June 30, 2023 (data cutoff), 89.4%, 81.2%, 80.0%, 70.1%, and 76.0% of individuals were up-to-date with screening for breast, colorectal, cervical, lung, and liver cancer screening, respectively. Characteristics associated with higher likelihood of ever receiving screening included mental health service use, prison security level 3 or 4, recent change in primary care practitioner, and incarceration within the past year before screening eligibility. Of 812 patients with screening data, 92 (11.3%) were diagnosed with screen-detectable cancer before they met eligibility for screening, including 56 with liver cancer. A total of 392 screening-eligible patients (48.3%) were diagnosed with screen-detectable cancer while in prison during the study period. Approximately 71% of patients received screening within 3 months before diagnosis, which was associated with lower odds of stage IV disease at diagnosis (odds ratio, 0.44; 95% CI, 0.23-0.85) and better survival (hazard ratio, 0.63; 95% CI, 0.44-0.88); rates of stage IV cancer were lower for individuals with recent screening than those without recent screening (10.0% vs 21.0%). Conclusions and Relevance: In this cohort study of incarcerated individuals in California prisons, screening rates were high and associated with early-stage cancer diagnoses, suggesting that effective cancer screening is achievable in prison settings. Future work should examine whether increased screening ameliorates incarceration-related cancer disparities.