Reporting 'Denominator' data is essential for benchmarking and quality standards in ovarian cancer

Combined surgery and platinum-based chemotherapy is the internationally agreed standard therapy for advanced ovarian cancer (AOC). However international cancer registry datasets demonstrate a significant proportion of patients do not receive both or either therapies. Our objective was to evaluate the effect of total patient cohort data ('Denominator') on median overall survival (OS) and determine how frequently this was reported in literature.

We retrospectively reviewed OS outcomes for 593 patients diagnosed with AOC for 77 months at a regional cancer centre. Patients were stratified into five progressively overlapping categories based on treatment received - Primary debulking surgery (PDS), PDS or Interval debulking (IDS), all surgery and those considered for IDS, patients receiving any treatment and total patient cohort. A systematic search of literature was performed.

Median OS progressively decreased from 54.5 months in patients receiving PDS, 38.7 months in the PDS+IDS group, 35.4 months in the PDS/IDS+patients considered for IDS, 33.3 months in patients receiving any treatment and 30.2 months in the total patient cohort. OS in the surgically treated group was statistically significantly different from the OS in the total patient cohort (Denominator)(p=0.000353). Denominator descriptors were identified in 11% of studies.

Denominator data is critical to understanding selection and OS in AOC. Published outcomes of selected cohorts should routinely incorporate outcomes for all women managed within the reporting Centre. This is essential for benchmarking and quality assurance in gynaecological cancer and should be an integral part of any publication on outcomes from AOC.