Radiation therapy for DCIS: Controversial or standard of care?

SAN FRANCISCO—There may be a small subset of women with DCIS who may not benefit from radiation therapy, but researchers maintain that this particular group has not yet been defined, and until they are clearly defined, radiation therapy remains the standard of care for those patients with DCIS who opt for breast-conserving surgery.

Beryl McCormick, MD, acting chair, Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, discussed the issue at a current controversies session of the ASCO Breast Cancer Symposium.

"All studies, including the most recent study from Sweden focusing on women screened with mammography, conclude that radiation [after breast-conserving surgery for DCIS] reduces the risk of recurrence in the treated breast by at least 50%," Dr. McCormick said. The Swedish study appeared last year (Emdin SO et al: Acta Oncologica 45:536-543, 2006).

Why does this controversy persist despite numerous clinical trials and retrospective studies pointing to the benefit of radiation? Dr. McCormick said the answer lies in the nuances surrounding DCIS itself. Researchers now recognize that DCIS is a disease encompassing a broad array of clinical entities with diverse characteristics that may or may not impact a patient's risk for local recurrence (see article on page 3).

Additionally, Dr. McCormick said, patients with local recurrences are generally treated successfully, with very low breast cancer mortality rates in this group—approximately 1%, according to a study in the American Journal of Surgery (192:416-419, 2006). In other words, she said, adding radiation therapy after wide local excision has been shown to have a positive impact on local recurrence but not on patient survival.

Things we need to know

"What would we like to know?" Dr. McCormick asked. "First, we would really like to know who is getting invasive recurrences. Second, we would like to know which patients really are at lowest risk of having local failures after breast conservation. Assuming that half of those local failures are invasive cancer, what risk is so low as to rationalize no benefit from radiation?"

At the moment, Dr. McCormick concludes that we just don't know the answers to these critical questions. "It's going to remain a controversy, for now, since we cannot define a subset of women who do not benefit from radiation therapy, and, at present, we cannot predict which DCIS patients will have an invasive recurrence —the ones we really want to prevent," she said.

So, until clinicians do define the subset of women with DCIS who may not benefit from radiation therapy following breast-conserving surgery, Dr. McCormick said, "we continue with the evidence we do possess, which keeps radiation as the standard of care."