The NCDB is a collaborative project of the American College of Surgeons and the American Cancer Society. The NCDB prospectively collects cancer data, including patient and hospital characteristics, from more than 1,500 Commission on Cancer facilities representing approximately 70% of all cancer cases in the United States.(24 (link)) As Physician National Provider Identification (NPI) reporting became mandatory in 2009, we included the diagnosis years 2010–2013 in our analysis of all patients older than 18 years of age who underwent radical cystectomy, resulting in 20,713 patients in 1,003 facilities.
After excluding 6 facilities where surgeon NPIs were attributed to the facility, there were 20,569 patients in 998 facilities. An additional 1,223 patients were excluded from 71 hospitals where no NPIs were reported, resulting in 19,346 patients in 927 facilities, with 2,927 distinct surgeon NPI numbers. Among these patients, 1,210 resections (6.3%) were missing Surgeon NPIs. Average annual surgical and hospital volume was calculated for all patients, and the methods of Raghunathan and colleagues (25 ) were used to impute average annual surgical volume for the 1,210 physicians with missing NPIs.
Table 1 displays surgical volume by hospital volume, where it can be seen that very few high volume surgeons practice in low volume hospitals, and vice-versa. For this reason, it was not possible to use similar surgeon groupings within each hospital, since the number of patients in some groups would be quite small and the statistical models would not be identifiable. Combinations of surgeon and hospital volume groups were based on having a sufficient number of cases in each group that would allow for reliable estimation. Hospitals performing fewer than 10 cases per year were defined as low volume, those performing 10–29 were moderate volume, and 30+ were considered high volume. Within low volume hospitals, SV were defined as <2 (low), 2–4 (moderate), and >=5 (high); within moderate volume hospitals, low, moderate, and high SV were defined as <5, 5–9, >=10, respectively; and within high volume hospitals, SV were defined as <10 (low), 10–19(moderate), and 20–29 (high).
A non-imputed file, including hospitals where at least 70% of Surgeon NPIs were reported, was used to compare hospital and surgeon volume results with the imputed volume results. This file included 18,176 patients in 864 hospitals, with 548 patients missing surgeon NPIs.