Spatial Analysis of Advanced-Stage Ovarian Cancer Mortality in California

abstract

def: spatial

OBJECTIVE:

To determine the impact of geographic location on advanced-stage ovarian cancer mortality in relation to adherence to National Comprehensive Cancer Network (NCCN) treatment guidelines and hospital case volume.

STUDY DESIGN:

Retrospective observational cohort study of patients diagnosed with stage IIIC/IV epithelial ovarian cancer (1/1/96-12/31/06) identified from the California Cancer Registry. Generalized additive models were created to assess the effect of spatial distributions of geographic location, demographic characteristics, disease-related variables, adherence to NCCN guidelines, and hospital case volume, with simultaneous smoothing of geographic location and adjustment for confounding variables.

RESULTS:

A total of 11,765 patients were identified. Twelve of the 378 hospitals (3.2%) were high-volume hospitals (≥20 cases/year, HVH) and cared for 2,112 patients (17.9%). For all patients, the median distance to a HVH was 22.7km/14.1mi and 80% were located within 79.6km/49.5mi of a HVH. Overall, 45.4% of patients were treated according to NCCN guidelines. The global test for location revealed that geographic position within the state was significantly correlated with ovarian cancer mortality after adjusting for other variables (p<0.001). Distance to receive care ≥32km/20mi was protective against mortality (HR=0.86, 95%CI=0.79-0.93), while distance from a HVH ≥80km/50mi was associated with an increased risk of death (HR=1.13, 95%CI=1.03-1.23). The effects of geographic predictors were attenuated when non-adherence to NCCN guidelines (HR=1.25, 95%CI=1.18-1.32) and care at a HVH (HR=0.87, 95%CI=0.81-0.93) were introduced into the model.

CONCLUSIONS:

Geographic location is a significant predictor of advanced-stage ovarian cancer mortality and the effect is primarily related to the likelihood of receiving NCCN guideline adherent care and treatment at a HVH.