Ovarian cancer in California: Guideline adherence, survival, and the impact of geographic location, 1996-2014.

Background: Evidence suggests that geographic location may independently contribute to ovarian cancer survival. We aimed to investigate how the association between residential location and ovarian cancer-specific survival in California varies by race/ethnicity and socioeconomic status.

Methods: Additive Cox proportional hazard models were used to predict hazard ratios (HRs) and 95% confidence intervals (CI) for the association between geographic location throughout California and survival among 29,844 women diagnosed with epithelial ovarian cancer between 1996 and 2014. We conducted permutation tests to determine a global P-value for significance of location. Adjusted analyses considered distance traveled for care, distance to closest high-quality-of-care hospital, and receipt of National Comprehensive Cancer Network guideline care. Models were also stratified by stage, race/ethnicity, and socioeconomic status.

Results: Location was significant in unadjusted models (P = 0.009 among all stages) but not in adjusted models (P = 0.20). HRs ranged from 0.81 (95% CI: 0.70, 0.93) in Southern Central Valley to 1.41 (95% CI: 1.15, 1.73) in Northern California but were attenuated after adjustment (maximum HR = 1.17, 95% CI: 1.08, 1.27). Better survival was generally observed for patients traveling longer distances for care. Associations between survival and proximity to closest high-quality-of-care hospitals were null except for women of lowest socioeconomic status living furthest away (HR = 1.22, 95% CI: 1.03, 1.43).

Conclusions: Overall, geographic variations observed in ovarian cancer-specific survival were due to important predictors such as receiving guideline-adherent care. Improving access to expert care and ensuring receipt of guideline-adherent treatment should be priorities in optimizing ovarian cancer survival.