Quantifying surgical extent as a prognostic factor in advanced ovarian cancer: initial validation of the Karolinska surgical extent and complexity score

BACKGROUND: Complete macroscopic cytoreductive surgery provides the best survival outcomes in advanced ovarian cancer (aOC), yet the extent and complexity of surgery also influence prognosis. In the absence of a standardised contemporary instrument to quantify surgical extent, this study aimed to perform the initial validation of a new scoring system for aOC surgery. METHODS: This observational, registry-based study included all women with aOC who underwent surgery in the Stockholm Region, Sweden, between 2009 and 2018. Patient and treatment data were obtained from the Swedish Quality Registry of Gynaecologic Cancer and vital status was cross-linked with the Swedish Population Registry. Surgical extent was quantified using the Karolinska Surgical Extent and Complexity Score (K-SECS), which assigns weighted complexity scores to cytoreductive procedures. The association between K-SECS and overall survival was evaluated using proportional hazards regression adjusted for relevant covariates. RESULTS: A total of 772 patients were included. Three prognostic K-SECS categories were identified: Intermediate (0-9), High (10-18) and Very High (≥19). A Very High K-SECS increased the hazard of death by 89% (HR 1.89; 95% CI 1.24-2.88; p = 0.002), while a High K-SECS increased the hazard by 46% (HR 1.46; 95% CI 1.20-1.79; p < 0.001). Adjusted absolute survival differences were 10.3% (95% CI 3.3-17.3) for Intermediate vs High and 18.5% (95% CI 6.3-30.8) for Intermediate vs Very High. CONCLUSION: Surgical extent and complexity independently predict survival in aOC. This study provides the initial validation of K-SECS as a contemporary instrument for adjusting surgical extent when reporting oncological outcomes.