Recurrence rates after accelerated partial breast RT on par with whole-breast RT

BOSTON-Accelerated partial breast irradiation using balloon brachytherapy drastically shortens treatment duration without affecting mortality and ipsilateral recurrence rates, according to three- and four-year follow-up data presented at ASTRO 2008.

The most recent analysis of the American Society of Breast Surgeons MammoSite (Hologic) Registry suggests that outcomes for women who receive APBI, which involves one week of radiation therapy, do not differ significantly from a historical cohort of women who received up to seven weeks of standard wholebreast irradiation. The analysis included three-year follow-up for 1,441 patients with primary early-stage breast cancer and a median of 44 months of follow-up for the fi rst 400 registered patients.

APBI using the MammoSite radiation therapy system begins with the surgical insertion of a small balloon into the target area shortly following the lumpectomy procedure. Radioactive seeds are then delivered to the balloon, via a catheter, every day for five days.

The drastically abbreviated treatment course could mean more than just added convenience for women who otherwise might forego radiation following a lumpectomy procedure or opt for more aggressive surgery, according to lead author Peter Beitsch, MD, a surgical oncologist at Medical City Dallas Hospital.

“Texas is a big state. There are women who live 100 or 200 miles from the nearest radiation center,” Dr. Beitsch explained. “Prior to accelerated partial breast irradiation, they had to have a mastectomy because they couldn’t travel that far, every day, for six or seven weeks. These women can now have a lumpectomy, and we can actually save their breast.”

Although clinicians have been concerned that partial irradiation might be more likely to miss tiny areas of pathology outside the tumor bed, Dr. Beitsch and colleagues found that APBI was associated with no greater incidence of ipsilateral breast tumor recurrence (IBRT) than whole-breast irradiation. The actuarial rate of IBTR was 2.15% at three years and 2.65% at four years.

The investigators were unable to conclusively identify any factors as significant contributors to IBTR rate following APBI, having looked at margin status, nodal status, tumor location, histologic grade, extensive intraductal carcinoma, age, tumor size, bra size, placement method, tamoxifen use, or chemotherapy use. Non-tamoxifen use and extensive intraductal component, however, were associated with nonsignifi cant trends toward increased IBTR (abstract 5).

Commentary

In the first 400 patients, overall four-year actuarial survival was 93.9%, with cancer-specific survival of 100%. However, Patient selection for balloon brachytherapy needs refinement longer follow-up is needed, said Anthony Zietman, MD, professor of radiation oncology at Harvard Medical School in Boston.

“Everyone’s very intrigued by balloon brachytherapy,” Dr. Zietman said. “We have three to four years of follow-up. We need a bit more. And we need to figure out who is best served by balloon brachytherapy.”

The registry initially was set up to track patients for seven years, but Dr. Beitsch said the researchers are hoping to extend that to a decade.