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Contrary to current national treatment guidelines, researchers have found that radiation therapy is best in preventing the need for a later mastectomy in early-stage breast cancer patients. 

The national treatment guidelines in place recommend that older women with early stage, estrogen-positive disease be treated with lumpectomy followed by estrogen blocker therapy alone -- and forgo radiation therapy post-surgery.

The findings are published in the journal Cancer.

Researchers from The University of Texas MD Anderson Cancer Center 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, says 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.

Benjamin Smith, assistant professor in the Department of Radiation Therapy at MD Anderson and the study's corresponding author, said he thinks that the national guidelines may gloss over the certain nuances needed for making critical decisions with patients.

"Our study may shed additional light on some of those nuances and provides data that physicians can use when talking to their patients about whether to go forward with radiation," Smith said. "Personally, having this data point, together with the previous findings, gives me the confidence to not routinely recommend radiation in women age 75 and over with non-high grade tumors."

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. 

"The motivation for this new research was to do a similarly designed study with longer term follow up," Smith said. "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."