Opting for radiation therapy after undergoing breast conserving surgery may help older women with early stage breast cancer avoid the need for mastectomy later on in their treatment process, researchers said.
The findings from The University of Texas MD Anderson Cancer Center are contrary to current national treatment guidelines, which recommend that older women with early stage, estrogen-positive disease should be treated with lumpectomy followed by estrogen blocker therapy alone-and forgo radiation therapy post-surgery.
The potential benefit of radiation in this patient population has been the focus of much research over the past decade, said Benjamin Smith, M.D., assistant professor in the Department of Radiation Therapy at MD Anderson and the study's corresponding author.
In 2004, a major study found that women who received tamoxifen alone, compared to tamoxifen and six weeks of radiation, had a slightly higher incidence of breast cancer recurrence.
Yet, there was no difference in mastectomy rates or survival among the two cohorts, said Smith.
Based on these findings, the NCCN adjusted its treatment guidelines, and radiation therapy following lumpectomy was no longer recommended. Smith then followed up this guideline-changing research with a population-based study, confirming the earlier findings with respect to breast cancer recurrence.
"The motivation for this new research was to do a similarly designed study with longer term follow up. We wanted to do a 10-year update, focusing specifically on the mastectomy question. The fundamental reason it was determined that women didn't need radiation was because the additional therapy did not change mastectomy rates," said Smith.
For the population-based study, Smith and his colleagues derived a cohort of Medicare patients from the National Cancer Institute's Surveillance, Epidemiology and End Results (SEER) registry who would have been eligible for the 2004 study. The researchers identified 7,403 patients ages 70-79 treated with a lumpectomy for early-stage estrogen-positive breast cancer. All were diagnosed between 1992 and 2002, with follow up through 2007. Of the 7,403 women, 88 percent received radiation after their lumpectomy.
Within 10 years of their treatment, 6.3 percent of the women who did not receive radiation therapy had a mastectomy, likely because of a breast cancer recurrence, said Smith, compared to 3.2 percent who had the additional treatment.
In patients with high-grade tumors, regardless of other factors such as age and/or tumor characteristics, radiation seemed to be highly beneficial.
The researchers also found a subset of women for whom radiation did not benefit, and thus could be omitted from care regimen: those 75- 79 years of age who had their lymph nodes assessed and did not have high-grade tumors.
The findings appeared in the journal Cancer.