Secondary validation of an ovarian cancer-specific comorbidity index in a US population

Objectives The Ovarian Cancer Comorbidity Index (OCCI) is an age-specific index developed and previously found to be more predictive of overall and cancer-specific survival than the Charlson Comorbidity Index (CCI). The objective was to perform secondary validation of the OCCI in a US population. Methods A cohort of ovarian cancer patients undergoing primary or interval cytoreductive surgery from January 2005 to January 2012 was identified in SEER-Medicare. OCCI scores were calculated with the regression coefficients determined from the original developmental cohort for five comorbidities. Cox regression analyses were used to calculate associations between the OCCI risk groups and 5-year overall survival and 5-year cancer-specific survival in comparison to the CCI. Results A total of 5052 patients were included. Median age was 74 (range 66-82) years. 47% (n=2375) had stage III and 24% (n=1197) had stage IV disease at diagnosis. 67% had a serous histology subtype (n=3403). All patients were categorized as moderate (48.4%) or high risk (51.6%). The prevalence of the five predictive comorbidities were: coronary artery disease 3.7%, hypertension 67.5%, chronic obstructive pulmonary disease 16.7%, diabetes 21.8%, and dementia 1.2%. Controlling for histology, grade, and age-stratification, worse overall survival was associated with both a higher OCCI (hazard ratio (HR) 1.57; 95% confidence interval (CI) 1.46 to 1.69) and CCI (HR 1.96; 95% CI 1.66 to 2.32). Cancer-specific survival was associated with the OCCI (HR 1.33; 95% CI 1.22 to 1.44) but was not associated with the CCI (HR 1.15; 95% CI 0.93 to 1.43). Conclusions This internationally developed comorbidity score for ovarian cancer patients is predictive for both overall and cancer-specific survival in a US population. CCI was not predictive for cancer-specific survival. This score may have research applications when utilizing large administrative datasets.