Association Between Primary Care Use Prior to Cancer Diagnosis and Subsequent Cancer Mortality in the Veterans Affairs Health System

IMPORTANCE: Primary care physicians (PCPs) are significant contributors of early cancer detection, yet few studies have investigated whether consistent primary care translates to improved downstream outcomes. OBJECTIVE: To evaluate the association of prediagnostic primary care use with metastatic disease at diagnosis and cancer-specific mortality (CSM). DESIGN, SETTING, AND PARTICIPANTS: This cohort study used databases with primary care and referral linkage from multiple Veterans’ Affairs centers from 2004 to 2017 and had a 68-month median follow-up. Analysis was completed between July 2021 and September 2022. Participants included veterans older than 39 years who had been diagnosed with 1 of 12 cancers. Inclusion criteria included known clinical staging, survival follow-up, cause of death, and receiving care at the Veterans Affairs health system (VA). EXPOSURES: Prediagnostic PCP use, measured in the 5 years prior to diagnosis. PCP visits were binned into none (0 visits), some (1-4 visits), and annual (5 visits). MAIN OUTCOMES AND MEASURES: Metastatic disease at diagnosis, cancer-specific mortality (CSM) for entire cohort and stratified by tumor subtype. RESULTS: Among 245 425 patients representing 12 tumor subtypes, mean age was 65.8 (9.3) years, and the cohort skewed male (97.6%), and White (76.1%), with higher levels of comorbidity (58.6% with Charlson Comorbidity Index scores ≥2). Compared with no prior visit, some PCP use was associated with 26% decreased odds of metastatic disease at diagnosis (odds ratio [OR], 0.74; 95% CI, 0.71-0.76; P < .001) and 12% reduced risk of CSM (subdistribution hazard ratio [SHR], 0.88; 95% CI, 0.86-0.89; P < .001). Annual PCP use was associated with 39% decreased odds of metastatic disease (OR, 0.61; 95% CI, 0.59-0.63; P < .001) and 21% reduced risk of CSM (SHR, 0.79; 95% CI, 0.77-0.81; P < .001). Among tumor subtypes, prostate cancer had the largest effect size for prior PCP use on metastatic disease at diagnosis (OR for annual use, 0.32; 95% CI, 0.30-0.35; P < .001) and CSM (SHR for annual use, 0.51; 95% CI, 0.48-0.55; P < .001). CONCLUSIONS AND RELEVANCE: In this cohort study, increased primary care use before cancer diagnosis was associated with significant decreases in metastatic disease at diagnosis and cancer-related death, with potentially the greatest difference from annual use. PCPs play a vital role in cancer prevention, and additional resources should be allocated to assist these physicians.