The American Society for Radiation Oncology (ASTRO) and the Society of Surgical Oncology (SSO) have published a consensus guideline on margins for breast-conserving surgery with whole-breast irradiation in stages I and II invasive breast cancer.

Led by Meena S. Moran, MD, of the Yale School of Medicine in New Haven, Conn., and Monica Morrow, MD, of the Memorial Sloan-Kettering Cancer Center in New York City, the consensus guideline stemmed from a collaboration amongst radiation oncology and surgical oncology experts.

Based on the results of a meta-analysis of margin width and ipsilateral breast tumor recurrence (IBTR) from a comprehensive review of 33 research studies and MEDLINE and evidence-based medicine, the guideline not only determines the ideal margin width that minimizes the risk of IBTR, but also details an evidence-based surgical treatment path that could eliminate unnecessary surgery for patients.

Included in the guideline are eight clinical practice recommendations:

• Positive margins—ink on invasive cancer or ductal carcinoma in situ—are associated with at least a two-fold increase in IBTR. This increased risk is not annulled by systemic therapy or favorable biology.
• Negative margins—no ink on tumor—optimizes IBTR, and wider margins do not significantly reduce this risk.
• IBTR rates are lowered with the use of systemic therapy. If a patient does not receive adjuvant systemic therapy, no evidence suggests that margins wider than no ink on tumor are needed.
• Margins wider than no ink on tumor are not indicated based on biologic subtype.
• Whole-breast irradiation delivery technique, fractionation, and boost dose choices should not be dependent on margin width.
• Wider negative margins than no ink on tumor are not indicated for invasive lobular cancer. Classic lobular carcinoma in situ (LCIS) at the margin does not indicate re-excision. The significance of pleomorphic LCIS at the margin is uncertain.
• Young age (here defined as 40 years old) is associated with an increased risk of local relapse on the chest wall after mastectomy and is more frequently associated with adverse biologic and pathologic features. There is no evidence that increased margin width nullifies the increased risk of IBTR in young patients.
• An extensive intraductal component (EIC) identifies patients who may have a large residual DCIS burden after lumpectomy. There is no evidence of an association between increased risk of IBTR and EIC when margins are negative.

“A significant portion of breast cancer surgeries in the United States are performed by surgical oncologists, and the definition of an adequate margin has been a major controversy. Therefore, it was only natural that we decided to create a definitive guideline that helps to minimize unnecessary surgery while maintaining the excellent outcomes seen with lumpectomy and radiation therapy,” said Morrow in the ASTRO press release. “We are proud to provide this pivotal document to the oncology community, which will improve the lives and treatment of patients touched by this disease.”