Associations Between Hospital and Surgeon Procedure Volumes and Patient Outcomes After Ovarian Cancer Resection

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Abstract
Background: Strong associations between provider (i.e., hospital or surgeon) procedure volumes and patient outcomes have been demonstrated for many types of cancer operation. We performed a population-based cohort study to examine these associations for ovarian cancer resections. Methods: We used the Surveillance, Epidemiology, and End Results (SEER)–Medicare linked database to identify 2952 patients aged 65 years or older who had surgery for a primary ovarian cancer diagnosed from 1992 through 1999. Hospital- and surgeon-specific procedure volumes were ascertained based on the number of claims submitted during the 8-year study period. Primary outcome measures were mortality at 60 days and 2 years after surgery, and overall survival. Length of hospital stay was also examined. Patient age at diagnosis, race, marital status, comorbid illness, cancer stage, and median income and population density in the area of residence were used to adjust for differences in case mix. All P values are two-sided. Results: Neither hospital- nor surgeon-specific procedure volume was statistically significantly associated with 60-day mortality following primary ovarian cancer resection. However, differences by hospital volume were seen with 2-year mortality; patients treated at the low-, intermediate-, and high-volume hospitals had 2-year mortality rates of 45.2% (95% confidence interval [CI] = 42.1% to 48.4%), 41.1% (95% CI = 38.1% to 44.3%), and 40.4% (95% CI = 37.4% to 43.4%), respectively. The inverse association between hospital procedure volume and 2-year mortality was statistically significant both before ( P = .011) and after ( P = .006) case-mix adjustment but not after adjustment for surgeon volume. Two-year mortality for patients treated by low-, intermediate-, and high-volume surgeons was 43.2% (95% CI = 40.7% to 45.8%), 42.9% (95% CI = 39.5% to 46.4%), and 39.5% (95% CI = 36.0% to 43.2%), respectively; there was no association between 2-year mortality and surgeon procedure volume, with or without case-mix adjustment. After case-mix adjustment, neither hospital volume ( P = .031) nor surgeon volume ( P = .062) was strongly associated with overall survival. Conclusion: Hospital- and surgeon-specific procedure volumes are not strong predictors of survival outcomes following surgery for ovarian cancer among women aged 65 years or older.