Accelerated partial breast irradiation acceptable for small subset of breast cancers

ASTRO task force said the technique is “suitable” for some older women with early stage disease.

A task force with the American Society for Radiation Oncology has issued a consensus statement addressing the use of accelerated partial breast irradiation. In it the association recommends that the procedure be restricted to women aged 60 or older with early stage, invasive disease.

Task force members identified four published randomized clinical trials and 38 prospective single-arm studies out of 3,381 articles pertaining to accelerated partial breast irradiation. They relied on published data whenever possible in drafting the consensus statement, but acknowledged that there is little evidence showing that accelerated partial breast irradiation is equivalent to whole breast irradiation. They felt it was important to address the issue because of increasing interest in and use of the procedure.

“To date, there is very limited data from randomized clinical trials to demonstrate that accelerated partial breast irradiation has equivalent safety and efficacy to whole breast irradiation,” said Maj. Benjamin D. Smith, MD, chief of radiation oncology with Wilford Medical Center at Lackland Air Force Base, Texas, and one of the authors of the statement. “As a result, we recommended a relatively conservative group for whom we feel accelerated partial breast irradiation may be acceptable.”

Patients assigned to accelerated partial breast irradiation following lumpectomy receive high doses of radiation, but finish their course of treatment in a week’s time. Additionally, patients may experience less toxicity because less tissue is exposed to radiation. The fear is that such targeted radiation could miss tumor tissue, leading to late failures.

Smith said there is also concern that such intensive radiation could lead to scarring and poor cosmetic outcomes, and that the invasive techniques used with some types of accelerated partial breast irradiation could increase the risk for infection or abscess.

Appropriate patient groups

The statement segregates patients into suitable, cautionary and unsuitable groups. Patients must meet a long list of selection criteria to be considered suitable for accelerated partial breast irradiation including negative node status, positive ER–status and negative margins of at least 2 mm. The authors wrote that their goal was to identify a subset of patients with a very low risk of clinically occult disease remote from the lumpectomy cavity.

“The primary recommendation from this consensus statement is to define who should not be treated with partial breast irradiation, and which patients fall into a cautionary group for whom great caution and concern should be exercised when using partial breast irradiation,” Smith said. “The primary purpose of this guideline is to instruct clinicians as to the limits of the current data, and identify which patients should not be receiving accelerated partial breast irradiation. We did define a narrow subgroup for whom, based on the prospective phase-2 trials, it seems that partial breast irradiation is relatively safe and effective. But we do recommend that all patients treated with partial breast irradiation are counseled that whole breast irradiation is an alternative treatment with a proven track record demonstrating its safety and effectiveness.”

Smith said accelerated partial breast irradiation is an alternative to whole breast irradiation, not a replacement. He added that with more experience, physicians may be able to define a particular group of patients for whom partial breast irradiation does provide equivalent cancer control and cosmetic outcome.

In an accompanying editorial, Leonard R. Prosnitz, MD, and colleagues said they’re anxiously awaiting the results of RTOG 0413/NSABP B-39, a randomized phase-3 trial comparing accelerated partial breast irradiation with whole breast irradiation. In lieu of those results, due in about 10 years, they praised the task force for crafting well thought out guidelines on the use of accelerated partial breast irradiation outside of a clinical trial. However, they said that conventional whole breast irradiation is the gold standard and added that patients should be advised as such. – by Jason Harris