SABCS: Shorter Adjuvant Radiation Course Found Safe and Effective After Lumpectomy

Michael Smith
SAN ANTONIO, Dec. 14 -- A three-week course of whole-breast irradiation after breast-conserving surgery is as effective and safe as the standard five-week program, a researcher said here.
After 10 years, so-called accelerated hypofractionated whole-breast irradiation demonstrated excellent local control of breast cancer, according to Tim Whelan, B.M., B.Ch., of McMaster University in Hamilton, Ontario.
At the same time, results from a randomized controlled trial showed that the shorter program was not associated with excess long-term morbidity, Dr. Whelan said at the San Antonio Breast Cancer Symposium.
The 10-year results of the study -- confirming earlier reports with five years of follow-up -- should prompt "broader use of this promising modality," Dr. Whelan said.
Despite the known benefits of breast irradiation after breast-conserving surgery, he added, up to 30% of women don't get the treatment because of cost or inconvenience.
The shorter regimen can help to overcome those obstacles, he said, but has not been widely adopted in the U.S. because of lingering concerns of long-term morbidity that were not dispelled by the five-year results of the study.
Standard whole-breast irradiation involves 50 Gy of radiation given as 25 2-Gy fractions daily over five weeks. The shorter regimen gives 40 to 42.5 Gy in 15 or 16 2.7-Gy fractions over three weeks.
The researchers randomized 1,234 women with invasive breast cancer treated by lumpectomy with pathologically clear resection margins and negative axillary nodes to one of the two arms from April 1993 through September 1996. Median follow-up has reached 12 years, he said.
At five years of follow-up, the two regimens were virtually identical, he said, with a 3% local recurrence and similar cosmetic outcomes in each arm.
At 10 years, he said, local recurrence was higher -- at 6.7% for the standard regimen and 6.2% for the shorter regimen -- but still not significantly different between the arms.
Probability of survival was also not different, at 84.6% for the shorter regimen and 84.4% for the standard course, he said.
Cosmetic outcome was defined as a combination of skin and soft tissue toxicity, breast appearance, and noncancer deaths. For each aspect, Dr. Whelan said, "no difference was evident between the two arms."
The study was originally designed to demonstrate noninferiority, Dr. Whelan said, with a 5% difference in efficacy set as the cutoff for equivalence.
In fact, the shorter regimen was slightly better than the standard regimen in efficacy and the 95% confidence interval was within the 5% pre-set difference.
"There has been some gradual acceptance of the shorter schedule," commented Phillip Devlin, M.D., of Brigham and Women's Hospital in Boston, who was not involved in the study.
"In our clinic, we use this schema as a fallback when there are circumstances -- including transportation circumstances -- that make [the longer regimen] inconvenient."
"It's also more economic," he said. "If it's 13 days shorter, it has to cost less."
Dr. Whelan did not report support for the study. He said he had no potential conflicts.
Primary source: Breast Cancer Research and TreatmentSource reference:Whelan T, et al "Long-term results of a randomized trial of accelerated hypofractionated whole-breast irradiation following breast-conserving surgery in women with node negative breast cancer" Breast Cancer Res Treat 2007; 106 (Supp1): Abstract 21.