Breast cancer margins, radiotherapy, axillary dissection evolve




SAN FRANCISCO – Recent research and guidelines have changed how surgeons should be thinking about some aspects of treating breast cancer, a panel of experts said in a press briefing at the annual clinical congress of the American College of Surgeons.

New guidelines on surgical margins, data supporting radiation rather than complete lymphadenectomy for patients with positive sentinel nodes, and other studies supporting targeted radiation therapy instead of whole-breast irradiation after lumpectomy should be on a surgeons’s radar, the speakers said.

The first U.S. guidelines on surgical margins for lumpectomy in women with breast cancer who are planning to undergo whole-breast radiation therapy adopted a standard of “no ink on tumor,” meaning no cancer at the edge of the tissue that was removed, Dr. Richard J. Gray said. The 2014 joint guidelines from the Society of Surgical Oncology and the American Society of Radiation Oncology based the recommendations on a meta-analysis of studies that found no advantage to wider excision margins for preventing in-breast recurrence (Ann. Surg. Oncol. 2014;21:717-730).

Dr. Richard J. Gray

Dr. Richard J. Gray

Previously, many surgeons sought to take 1, 2, or 3 mm of normal tissue around the cancer removed to reduce the risk of recurrence, he said.

“This guideline will become the standard throughout the United States. The evidence on which this is based is reasonable, but it will be important for individual institutions and national databases to track the rates of local recurrence over time as these guidelines are implemented,” said Dr. Gray of the Mayo Clinic, Scottsdale, Ariz. He confessed to being “a recovering addict” to margins of 2 mm or greater.

The guidelines apply only to patients with invasive cancer undergoing breast-conserving treatment, he noted. There are no guidelines yet specifically for surgical margins in women undergoing mastectomy for breast cancer, nor for women with ductal carcinoma in situ (DCIS).

While there is no evidence that a margin width wider than “no ink on tumor” is better for women undergoing mastectomy, Dr. Gray cautioned against extrapolating the guidelines to women having mastectomies “because they will generally not undergo adjuvant radiation therapy,” he said.

For women with DCIS, the available evidence suggests that a minimum 2-mm margin of excision is reasonable for those undergoing lumpectomy or at least negative margins (no ink on tumor) for those undergoing mastectomy, Dr. Gray said. Wider margins may help select patients with DCIS who undergo lumpectomy to avoid adjuvant radiation therapy, he added.

A separate recent study should change the way surgeons approach decisions about axillary surgery in patients with breast cancer, Dr. Roshni Rao said. She reported on a study that randomized women who had cancer in sentinel lymph nodes after mastectomy to further treatment by removing the rest of the lymph nodes under the arm, as is common practice, or to radiation of the lymph nodes area.

Dr. Rashni Rao

Dr. Rashni Rao

Rates of cancer recurrence did not differ between groups but the radiation approach significantly reduced the risk of lymphedema and other morbidity, said Dr. Rao of the University of Texas Southwestern Medical Center, Dallas.

“Going forward, we’re going to be performing less and less axillary lymph node dissections,” she said.

Also on the topic of radiation therapy, two recent studies of targeted breast irradiation rather than whole-breast radiotherapy suggest that the targeted approach may be beneficial, Dr. Courtney A. Vito said. Whole-breast radiation after lumpectomy reduces the risk of local recurrence by 50%, previous studies have shown, but it comes with potential side effects including burns, lymphedema, and damage to underlying structures like the heart and lungs. Patients who don’t live near specialized radiation centers may not be able to access the daily month-long treatments.

A randomized Italian trial of 1,305 patients found similar rates of overall survival or breast cancer–specific survival in patients treated with whole-breast radiation therapy or with intraoperative radiation therapy, in which a single, more intense dose of radiation is directed just at the site of lumpectomy during surgery. Survival rates were similar between groups but the rate of local recurrence after 5 years was 10 times higher in the intraoperative radiation group (4.4%), compared with the whole-breast radiation group (0.4%) (Lancet Oncol. 2013;14:1269-77).

Dr. Courtney A. Vito

Dr. Courtney A. Vito

Subset analyses showed, however, that most of the recurrences were in women who would not be considered ideal candidates for intraoperative radiotherapy in the United States because they had tumors larger than 2 cm, four or more positive lymph nodes, estrogen receptor–negative tumors, or other aggressive tumor biology, said Dr. Vito of the City of Hope National Medical Center, Duarte, Calif. Recurrence rates were more favorable in patients with lower-risk tumors.

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