The relationship between surgical volume and clinical outcomes is complex and varies considerably across surgical specialties. While the role of hospital volume is well-established, the specific contribution of surgeon-level volume and the interaction between these two factors are less clear.

This study investigates the association between surgeon volume and clinical outcomes for surgeons performing breast-conserving surgery for malignant breast cancer, laparoscopic cholecystectomy and surgery for malignant colon cancer.

Data from the Lazio Region’s health information systems (2020–2023) were analysed. Primary outcomes included 120-day reinterventions after breast-conserving surgery for breast cancer, 30-day complications after laparoscopic cholecystectomy and 30-day mortality after colon cancer surgery. The association between surgeon volume and outcomes was examined for all surgeons performing at least five procedures annually in Lazio hospitals. A stratified analysis was conducted to assess the impact of hospital volume on the surgeon-volume-outcome relationship, comparing outcomes between surgeons in low-volume and high-volume hospitals. Fractional polynomial and segmented regression models were employed to identify non-linear relationships and potential breakpoints in the surgeon volume-outcome association.

Higher-volume surgeons demonstrated significantly improved outcomes across all three procedures, including lower reintervention rates, fewer complications and reduced mortality. This positive association was further amplified for surgeons practising in high-volume hospitals. Graphical analysis, which involved stratifying the volume-outcome relationship for individual surgeons by hospital volume (high vs low), strongly suggested a synergistic effect between surgeon and hospital volume, clearly illustrating how the benefits of higher surgeon volume were further amplified in high-volume settings.

These findings underscore the critical role of both surgeon-level and hospital-level factors in determining surgical outcomes. Optimising patient care requires a comprehensive approach that considers both individual surgeon performance and the overall quality of the healthcare system. Future research should focus on elucidating the underlying mechanisms driving these associations to inform the development of strategies for improving surgical care delivery.