After adjustment for case-mix variables and hospital volume, perioperative complications (15.2% compared with 11.7%) (OR 0.57; 95 CI 0.38–0.85) and medical complications (31.4% compared with 22.0%) (OR 0.57; 95% CI 0.37–0.88) were less common in patients treated by high-volume surgeons (Table 4). Likewise, ICU utilization (8.9% compared with 3.5%) (OR 0.47; 95% CI 0.28–0.80) was lower in patients treated by high-volume surgeons. Surgeon volume had no independent effect on the rates of operative injury (OR 0.82; 95% CI 0.32–2.08), transfusion (OR 2.33; 95% CI 0.93–5.36), length of stay (OR 0.60; 95% CI 0.25–1.41), or readmission (OR 1.05; 95% CI 0.51–2.14).
After adjustment for case-mix variables and surgeon volume, hospital volume had no effect on operative injuries (OR 0.87; 95% CI 0.45–1.65), perioperative complications (OR 1.44; 95% CI 0.99–2.11), medical complications (OR 1.54; 95% CI 0.96–2.46), transfusion (OR 1.37; 95% CI 0.73–2.58), length of stay (OR 1.15; 95% CI 0.51–2.61), or readmission (OR 1.51; 95% CI 0.55–4.13). Patients treated at high-volume hospitals were less likely to require ICU care (9.3% compared with 4.3%) (OR 0.44; 95% CI 025–0.77). The unadjusted mortality was 1.1% in patients treated by low-volume surgeons compared with 0.4% for those operated on by high-volume providers. The odds ratio for death was 0.38 (95% CI 0.15–0.93) after adjusting for case-mix variables. The small number of deaths precluded adjustment for case-mix variables and hospital volume.
Among women with endometrial cancer, we noted improved perioperative outcomes in those patients treated by high-volume surgeons. Perioperative surgical complications, medical complications, and ICU requirements were all lower in patients who were treated by high-volume surgeons. In contrast, hospital volume had little independent effect on outcomes.
The association between volume and outcome has been demonstrated for a number of cancer-directed surgeries; those patients operated on by high-volume surgeons and at high-volume hospitals have improved outcomes.6–9,17 The majority of these reports have focused on high-risk oncologic procedures that are associated with substantial morbidity.7,8 Volume appears to have less of an effect on outcomes for lower-risk procedures and on operations that are performed more commonly.19–21 Studies examining the effect of volume on morbidity in women undergoing hysterectomy have reported mixed results.17,21–25 An analysis of patients who underwent hysterectomy for benign disease in New York noted that morbidity and mortality were decreased when the procedure was performed by high-volume surgeons.22 In one of the only studies specifically examining the volume-outcome paradigm for uterine cancer, Díaz-Montes and colleagues noted a 48% reduction in in-hospital mortality in patients operated on by high-volume surgeons. There was no apparent effect of hospital volume on outcome.23 In our cohort, perioperative surgical complications as well as postoperative medical complications were reduced by 43% in patients treated by high-volume surgeons.
We noted that whereas surgeon volume influenced outcome, hospital volume had little independent effect on perioperative morbidity. In an analysis of Medicare patients, much of the variation in operative mortality was the result of surgeon and not hospital volume; survival was improved even in high-volume hospitals if the procedures were performed by high-volume surgeons.8 Although a number of factors undoubtedly underlie the effect of volume on outcome, for procedures like hysterectomy, surgeon characteristics appear to play a dominant role. Although surgeon characteristics may influence complication rates, previous work has shown that variations in hospital volume and quality are important factors predicting outcome in those patients who do experience a complication.12,26,27
In addition to volume, a number of physician characteristics including training and subspecialization likely influence outcomes.10,11,17,28 Previous studies of women with endometrial cancer have shown that patients treated by gynecologic oncologists are more likely to undergo comprehensive surgical staging and less likely to require adjuvant radiation.29,30 In a large sample of women with ovarian cancer, whereas neither surgeon nor hospital volume influenced mortality, those patients treated by gynecologic oncologists had improved outcomes.11 Given the lack of tumor characteristics in our data set, a priori we chose to include only patients treated by gynecologic oncologists to minimize case selection bias. Our results are notable in that even among subspecialists there appears to be a volume-outcome effect.
We recognize several important limitations. Given that the primary purpose of administrative data are for billing, we likely were unable to capture all perioperative complications. To minimize this bias we limited our analysis to major complications that have been examined in previous studies.31 The Perspective database lacks data on tumor characteristics. For women with endometrial cancer, tumor characteristics influence not only operative planning but also perioperative outcomes. Parameters such as stage and histology likely influenced our findings and would be important variables for risk adjustment if they were available. Whereas we were able to examine short-term morbidity and mortality, the Perspective database does not allow for longitudinal follow-up. Further work is ongoing to determine how surgeon and hospital volume influence the patterns of adjuvant care and long-term outcomes for women with endometrial cancer. Our study focused exclusively on women who underwent abdominal hysterectomy. As the use of minimally invasive surgery is rapidly increasing, further worked specifically evaluating the influence of volume on outcomes for minimally invasive hysterectomy is ongoing. Finally, whereas we noted significant volume-based differences in outcomes, our findings are clinically modest, especially when compared with other oncologic surgeries.
Our findings raise the question of how surgical volume should influence the care of women with endometrial cancer. Public reporting initiatives such as the Leapfrog group have recommended care by high-volume providers for a number of procedures and diseases. Emerging data suggest that for many high-risk surgeries there has been a gradual concentration of procedures to high-volume surgeons. In a study of patients treated across the United States, there was a 54% increase in the number of gastrectomies performed by high-volume surgeons from 1999 to 2005, a 31% increase in pancreatectomies, and a 23% increase in thyroidectomies performed by high-volume providers during the same timeframe.32 Although concentration of care to tertiary referral centers may be appealing, regionalization of care has proven difficult for patients and physicians alike, particularly for common procedures such as hysterectomy.33,34 Other strategies have focused on improving the care of low-volume providers with initiatives such as minimum volume requirements for credentialing, public reporting of quality metrics, and pay-for-performance programs.35–37
In conclusion, we noted that surgical volume is associated with outcomes for women with endometrial cancer who undergo abdominal hysterectomy. Perioperative morbidity and ICU usage are lower in women treated by high-volume surgeons. Hospital volume has little effect on outcome. Further work is needed to determine the long-term influence of surgical volume on outcome and to develop interventions to reduce volume-related disparities.
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