After breast-conserving surgery, how much radiation therapy is enough?

Clinical trials have long since proved that breast-conserving surgery combined with radiation therapy is an effective alternative to mastectomy. But uncertainty persists about the required doses of radiation, and whether some breast cancer patients can forego “boost” doses to the tumor bed after whole-breast radiotherapy.

OHSU’s Charlotte Dai Kubicky, M.D., Ph.D., an associate professor in the Department of Radiation Medicine, brings some clarity to the issue in an editorial in JAMA Oncology co-authored with Laurie Cuttino, M.D., of Virginia Commonwealth University. Kubicky is a radiation oncologist with the Knight Cancer Institute breast cancer clinic.

The editorial focused on the latest findings from the European Organization for Research and Treatment of Cancer trial in which 5,500 patients treated with breast conservation surgery and whole breast radiation were randomly assigned to receive boost radiation or no boost. After 20 years, the risk of tumor recurrence in the same breast was significantly reduced with the addition of a boost, most clearly in patients younger than 50, those with high-grade tumors, and those with estrogen receptor-negative tumors. A boost was not significantly helpful for older patients with low-grade, estrogen receptor-positive tumors.

Kubicky and Cuttino note that in the years since the EORTC study was designed in the 1980s, advances in imaging, surgical technique, pathology and systemic treatments have significantly reduced the number of local recurrences expected after breast-conserving surgery.

Although the absolute benefit of a boost is likely much smaller now, they say, certain women clearly remain at high risk of cancer returning after breast-conserving surgery and should receive a boost after whole-breast radiotherapy: younger patients, patients with high-grade tumors, and those with estrogen receptor-negative tumors. Older patients with low-grade, estrogen receptor-positive tumors with clear surgical margins do not benefit from the addition of a boost.

“In the future, the use of molecular subtyping, radiosensitivity signatures, and other advances will likely provide more insight into which patients require radiotherapy after breast-conserving surgery, and who will benefit from higher doses to the tumor bed.”

You can read the full commentary at the JAMA Network.