Variability found for rate of additional surgery after partial mastectomy
MedWire News: The number of women needing additional surgery after partial mastectomy varies substantially by surgeon and institution, say researchers.
Their study, published in JAMA, shows nearly one in four women who undergo partial mastectomy for breast cancer require additional tissue removal, and the substantial institutional and surgeon variation that exists in the rate of further surgery cannot be explained by patients' clinical factors.
Laurence McCahill (Michigan State University, Grand Rapids, USA) and colleagues investigated data collected from medical records at four medical institutions and three large health plan providers.
"Breast-conserving therapy, or partial mastectomy, is one of the most commonly performed cancer operations in the United States," they explain. "Currently, there are no readily identifiable quality measures that allow for meaningful comparisons of breast cancer surgical outcomes among treating surgeons and hospitals."
A total of 2206 patients, with 2220 newly identified breast cancers, whose first surgical procedure was partial mastectomy were included in the study. Overall, 22.9% (n=509) of these patients underwent re-excision.
A significant majority (89.2%) had only one re-excision; 48 (9.4%) patients required two, and seven (1.4%) women required three procedures.
Re-excision rates were 85.9% among patients with positive margins at the initial mastectomy, 47.9% for those with margins less than 1.0 mm surrounding the cancerous tissue, 20.2% for margins between 1.0 and 1.9 mm, and 6.3% for margins between 2.0 and 2.9 mm.
The researchers found that re-excision rates varied widely between surgeons, ranging from 0.0% to 70.0%, and among institutions, ranging from 1.7% to 20.9%.
The median odds ratio for re-excision between two randomly selected surgeons was 1.6, which the researchers say suggests that for patients under similar clinical conditions the need for re-excision depends on the surgeon treating them.
"Possible explanations might include differences in surgical training, surgeon confidence in their operative technique in localizing tumors, utilization of intraoperative assessment of margins, and surgeon's and pathologist's coordination of specimen orientation and margin interpretation," write McCahill and team.
"Surgical experience may play a role, but we did not observe differences in re-excision rates between high- and low-volume surgeons."
The institutional variation seen is likely to be due, at least in part, to the surgeons' practice patterns at these institutions, the researchers suggest.
"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," write Monica Morrow (Memorial Sloan-Kettering Cancer Center, New York, USA) and Steven Katz (University of Michigan, Ann Arbor, USA) 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."
By Chloe McIvor