Kate Johnson

June 02, 2015

CHICAGO — Routine shaving around the cavity after a partial mastectomy results in significantly reduced rates of positive margins and re-excisions, according to the results of a new study.

The findings were presented May 30 at the American Society of Clinical Oncology (ASCO) 2015 Annual Meeting and were published simultaneously in the New England Journal of Medicine.

In addition, patients who undergo shaving do not experience worse cosmetic results compared with patients who do not do so, reported lead investigator Anees B. Chagpar, MD, an associate professor of surgery from the Yale Cancer Center, in New Haven, Connecticut.

"Before we embarked upon the trial, I was not an advocate of doing routine cavity shave margins, but I think given the data we have, where a very simple technique can reduce positive margins and reduce re-excisions by 50% without any detriment in cosmetic outcome or increase in complication rates, certainly has changed my own personal practice and the practice of many surgeons at Yale," said Dr Chagpar during an ASCO 2015 discussion session featuring her results.

The prospective study included 235 breast cancer patients (disease stage, 0 to III; median patient age, 61 years) who were undergoing partial mastectomy with or without excision of selective margins.

"Surgeons were instructed to perform standard partial mastectomy according to their usual practice, including resection of margins where the tumor was believed to be close to the edge of the specimen on the basis of standard intraoperative imaging or their own gross evaluation (or both)," she wrote.

Patients were randomly assigned intraoperatively, once the partial mastectomy was completed, either to receive additional circumferential shaving of the cavity margins (n = 119) or to undergo no further excision (n = 116).

For patients in the shave group, the amount of extra tissue removed could not be standardized because of each individual's tumor size and body shape, but surgeons were instructed to resect "such that cavity shave margins encompassing the entire cavity were removed. Superior, inferior, medial, and lateral shave margins were mandated, along with anterior and posterior margins if the resection had not extended to the dermis and pectoralis fascia, respectively."

The primary outcome of the study was the rate of positive margins on final pathologic testing. Margin positivity was defined as "tumor touching the edge of the specimen that was removed in patients with invasive cancer and tumor that was within 1 mm of the edge of the specimen removed in those with ductal carcinoma in situ."

Re-excision rates were defined as the proportion of patients who were returned to the operating room for further surgery for margin clearance.

Secondary outcomes included the volume of tissue excised and patient-reported cosmetic outcome.

After a median follow-up of 22 months, the study revealed a significantly lower rate of positive margins among patients in the shave group compared with those in the no-shave group (19% vs 34%; P = .01).

The re-excision rate was also significantly lower among patients in the shave vs no-shave group (10% vs 21%; P = .02).

Although the volume of tissue excised was significantly larger in the shave group than in the no-shave group (median, 115.1 cm3 vs 74.2 cm3; P < .001), patients in both groups had similar perceptions of the cosmetic outcome of their surgery (P = .69).

"We found that the perception of cosmetic outcome was equivalent in the two groups...despite the fact that the shave group had more tissue excised," her group reported.

"Although some have argued that routine cavity shaving may not be needed if surgeons excise margins where the tumor is deemed to be close to the edge of the specimen on the basis of intraoperative imaging or gross evaluation, we found that selective intraoperative resection of margins was insufficient to reduce the rates of positive margins," they added.

In fact, in this trial, after standard partial mastectomy and before randomization, 30% of patients were found to have positive margins on pathology, a rate that is consistent with other published reports.

Among 76 patients in the shave group, further cancer was found in the cavity shave margins of 9 (12%).

This finding "calls into question the accuracy of margin status in predicting residual disease. These patients had multifocal disease that was detected only after cavity shaving," the authors write.

"Although one could argue that finding additional occult disease may not affect outcome, excising additional disease in more than 10% of patients may have a significant long-term effect on the rate of local recurrence."

Although avoiding re-excision is important for many reasons, one less-recognized reason is the avoidance of elective bilateral mastectomy, noted Tari A. King, MD, the discussant for the article from Memorial Sloane Kettering Cancer Center, in New York City.

"By now, we are all well aware of the trend toward increasing use of bilateral mastectomy," she said, noting that according to the California Cancer Registry, one third of women being treated for unilateral breast cancer choose bilateral mastectomy ( JAMA. 2014;312:902-14).

Research performed at her institution showed that failed attempts at re-excision are significantly associated with the decision to pursue a contralateral elective mastectomy even though "this is rarely needed, and the chance of getting cancer in the healthy breast is usually very low," she said.

"Failing breast conservation is something that we as surgeons can potentially modify by paying attention to our surgical technique and avoiding re-excision with wider margins."

The study was funded by the Yale Cancer Center. Dr Chagpar has disclosed no relevant financial relationships.

American Society of Clinical Oncology (ASCO) 2015 Annual Meeting. Abstract 1012. Presented May 30, 2015.

N Engl J Med. Published online May 30, 2015. Abstract

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