Surgeon and breast unit volume-outcome relationships in breast cancer surgery and treatment.

Objectives: To determine whether surgeon case volume and Unit case volume affected specific recognized key performance indicators (KPIs) of breast cancer surgical management. Background: An increasing body of evidence suggests that a higher standard of cancer care, demonstrated by improved outcomes, is provided in high-volume units or by high-volume surgeons. The volume-outcome relationship pertaining to screen-detected breast cancers has yet to be thoroughly established and remains a pertinent issue in view of the debate surrounding breast cancer screening. Methods: The study population comprised all women with a new screen diagnosed breast cancer between 2004-2005 and 2009-2010. Surgeons' mean annual patient volumes were calculated and grouped as very low (< 5), low (5-15), medium (16-49), or high volume (> 50). The effect of breast screening unit volume was also evaluated. Statistical analyses were performed using Minitab V16.0 software (State College, PA) and R V2.13.0. Results: There were 81,416 patients aged 61 (+/-6.8) years treated by 682 surgeons across 82 units. There were 209 very low-, 126 low-, 295 medium-, and 51 high-volume surgeons. The proportion of patients managed by very low-, low-, medium-, and high-volume surgeons was 1.2%, 6.9%, 65.5%, and 25.7%, respectively. Patients managed by high-volume surgeons were more likely to have breast-conserving surgery (BCS) than those managed by low-volume surgeons (P < 0.001). There was a higher proportion of sentinel lymph node biopsies (SLNB) performed by high-volume surgeons in invasive cancers (P= 0.005). High-volume units performed more BCS and SLNB than low-volume units (P < 0.001 and P < 0.001, respectively). Conclusions: Even in a setting with established quality control measures (KPIs) surgeon and unit volume have potent influences on initial patient management and treatment.