Performing a cavity shave margin in patients undergoing a partial mastectomy can reduce the need for re-excision and the rate of positive margins after surgery, according to the results of the SHAVE trial (abstract 1012) presented at the 2015 American Society of Clinical Oncology (ASCO) Annual Meeting held May 29 to June 2 in Chicago.
Patients randomized to cavity shave margins had a margin rate of 18.3% compared with 33.6% of patients randomized to standard partial mastectomy (P = .006). Though not all margins could be excised due to their positioning, cavity shave margins resulted in a reduction of the re-excision rate (20.8% in the standard partial mastectomy group compared with 9.5% in the cavity shave margin group; P = .014).
“The most important thing this study demonstrates is that with a relatively simple technique of just taking a little bit more tissue all the way around the cavity at the first operation, we can spare half the women a return trip to the operating room,” said lead study author Anees B. Chagpar, MD, associate professor of surgery and director of the Breast Center at Smilow Cancer Hospital at Yale-New Haven. “No one likes to go back to the operating room—not the patients, not the surgeons, and not the healthcare system.”
Chagpar and colleagues randomized 251 patients with stage 0 to 3 breast cancer who were to undergo partial mastectomy 1:1 to either cavity shave margins or standard partial mastectomy. Patients had a median age of 61 years. A total of 23% of patients had invasive cancer, 19% had ductal carcinoma in situ (DCIS), and 53% had a combination of both. The median size of the invasive tumors was 1 cm, and 0.9 cm in patients with DCIS.
The margin status prior to intraoperative randomization was similar between the two groups (34.9% for cavity shave margins vs 33.6% for standard partial mastectomy; P = .894).
Cosmetic outcomes were considered “excellent” in 37% of both intervention groups.
Notably, in the 12% of women who initially had negative margins but who underwent the cavity shave as part of this trial, the pathologists subsequently found additional cancer within the shave margin tissue. “This would have gone unnoticed if it were not for the shave margins,” said Chagpar. This raises the question of how accurately margins predict residual disease and whether finding this disease is crucial despite the use of systemic and radiation therapy.
The SHAVE trial is following patients for 5 years for both local recurrence and cosmesis, which should at least partially address these questions.
The study also showed that only thorough cavity margin shaving, not selective margin shaving, resulted in negative margins during the final post-surgery pathology analysis. This shows that surgeons cannot truly predict when the tumor is close to the edge of the surgical margins, said Chagpar.
Prior to this study, there were no large randomized studies that evaluated whether taking out more tissue around the partial mastectomy cavity could reduce the need for more surgeries. “There was controversy about what effect taking more tissue would have on cosmesis,” Chagpar told Cancer Network. “Now we have the data that demonstrate taking more tissue can cut in half the likelihood that a patient would need to go back to the operating room for a second surgery—and that this procedure is not associated with a worse cosmetic outcome or higher complication rate.”
Chagpar says the results have changed her practice. “I never used to take routine cavity shave margins. But it is hard to argue against the strength of Level 1 evidence,” she told Cancer Network. “It’s an easy technique, a few extra minutes in the operating room, but if it can save patients the harrowing experience and angst of a return trip to the operating room, it’s well worth it.”