When is it safe to skip breast radiotherapy?

Forgoing radiation therapy after breast-conserving surgery may not negatively affect survival outcomes for some women with breast cancer, according to new study data presented at the 2020 San Antonio Breast Cancer Symposium.

Ten-year survival outcomes were similar for older women with hormone receptor-positive (HR+) breast cancer, regardless of whether they received radiation therapy after breast-conserving surgery. The findings suggest older women with early-stage, nonaggressive breast cancers may not need radiation therapy.

"Based on these results, we believe that omission of radiation therapy after breast-conserving surgery should be an option for older patients with localized, HR-positive breast cancer who are receiving adjuvant hormone therapy and meet certain clinico-pathological criteria," stated Dr. Ian Kunkler, a professor of clinical oncology at the Western General Hospital, University of Edinburgh, in a press release.

The data come from a 10-year update to the PRIME II study, which looked at long-term outcomes for 1,326 women ages 65 years or older with nonmetastatic, HR+ breast cancer. All patients were treated with breast-conserving surgery and adjuvant hormone therapy, and half were randomly assigned to also receive radiation therapy.

At 10-year follow-up, the two groups had similar rates of distant metastasis, recurrence in the opposite breast, and overall survival rates. However, the rate of local recurrence was significantly greater in patients who did not receive radiation therapy.

In addition, the majority of patients who died during the study period died of conditions other than breast cancer. Of the 167 patients who died, 7% died from breast cancer compared with 32% who died from another type of cancer. Another 14% of patients died from cardiovascular disease and 54% died from unknown causes.

The findings were consistent with previously reported five-year outcomes in the PRIME II cohort. At that time point, women who received radiation were less likely to have local recurrence, but no more likely to have distant metastases or new breast cancers. The five-year survival rates were also similar for women who did and did not receive radiation therapy.

Although women over the age of 65 typically have less aggressive breast cancers, many continue to opt for whole-breast radiation therapy after surgery. The research shows that forgoing radiation therapy may boost the quality of life of these women without hindering survival rates.

"Over half the patients diagnosed with breast cancer in developed countries are over the age of 65 years," stated Kunkler. "We found that omitting postoperative radiation therapy did not compromise survival or increase the risk of distant metastasis."