(ChemotherapyAdvisor) – Substantial surgeon and institutional variation in re-excision rates following partial mastectomy in women with invasive breast cancer exist that could not be explained by a patient’s clinical characteristics, results of an observational study in the February 1 issue of JAMA concluded.

The study examined data from 2,206 women with 2,220 invasive breast cancers who underwent partial mastectomy at four institutions—the University of Vermont, Kaiser Permanente Colorado, Group Health, and Marshfield Clinic—between 2003 and 2008, according to Laurence E. McCahill, MD, of the Richard J. Lacks Cancer Center, Grand Rapids, MI, and colleagues. Average age of the patients was 62 years, and 92.8% of participants with reported race/ethnicity were non-Hispanic white.

A total of 509 patients (22.9%) had re-excision; 89.2% (n=454) had 1, 9.4% (n=48) had 2, and 1.4% (n=7) had 3 re-excissions. A total mastectomy was performed in 8.5% (n=190). Following initial surgery, re-excision rates were 85.9% for initial positive margins, 47.9% for <1.0 mm margins, 20.2% for 1.0–1.9 mm margins, and 6.3% for 2.0–2.9mm margins.

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Re-excision rates for patients with negative margins were found to vary widely among surgeons, ranging from 0% to 70% (P=0.003), which “were not associated with surgeon procedure volume after adjusting for case mix (P=0.92),” the investigators wrote. Institutional rates ranged from 1.7% to 20.9% (P<0.001).

“There is no consensus among surgeons and radiation oncologists as to what constitutes an optimal negative margin width, because the question has not been addressed in prospective randomized trials,” Monica Morrow, MD, and Steven J. Katz, MD, MPH, wrote in an accompanying editorial. “The observational design used in the McCahill et al study is valuable for illuminating the nature of potential quality gaps, but cannot be used to inform the validity of candidate quality measures.”

“Variability in Reexcision Following Breast Conservation Surgery,” The Journal of the American Medical Association