Relationship Between Number of Breast Cancer Operations Performed and 5-Year Survival After Treatment for Early-Stage Breast Cancer
Mary Ann Gilligan, MD, MPH,
Joan Neuner, MD, MPH,
Xu Zhang, MS,
Rodney Sparapani, MS,
Purushottam W. Laud, PhD and
Ann B. Nattinger, MD, MPH
Mary Ann Gilligan, Joan Neuner, and Ann B. Nattinger are with the Department of Medicine and Health Policy Institute, Medical College of Wisconsin, Milwaukee. At the time of the study, Xu Zhang was with the Division of Biostatistics, Medical College of Wisconsin, Milwaukee. Rodney Sparapani and Purushottam W. Laud are with the Division of Biostatistics, Medical College of Wisconsin, Milwaukee.
FIGURE 1——Unadjusted all-cause mortality survival curve, by annual hospital volumea of Medicare breast cancer cases: United States, 1994–1996.
aLow volume = 0–19 operations performed per year; medium volume = 20–39 operations performed per year; and high volume = 40 or more operations performed per year.
FIGURE 2——Adjusted all-cause mortality survival curve, by annual hospital volumea of Medicare breast cancer cases: United States, 1994–1996.
Note. Shown are survival curves constructed for 2 patient profiles differing only in their lymph node status (positive [bottom 3 lines] or negative [top 3 lines]). Covariates that were held constant for the 2 profiles included age (70 years), race (White), area or residence (urban), comorbidity index value (0), tumor size (less than 20 mm), estrogen receptor/progesterone receptor positive, tumor grade (1 or 2), per capita income (less than $15 008), and propensity group (midlevel). aLow volume =0–19 operations performed per year; medium volume = 20–39 operations performed per year; and high volume = 40 or more operations performed per year.
