SABCS: 10-year study shows targeted radiation can be as effective as whole-breast doses against cancer

operating room
After a decade-long study, 3.3% of patients who had a lower dose of irradiation saw their cancer return, compared to 2.6% of those who received whole breast irradiation. The difference was not statistically significant. (Pixabay)

A decade-long study found patients with early breast cancer may be spared radiation procedures that span the whole breast, and that shorter and less invasive courses of treatment aimed at portions of the breast may be just as effective.

After surgery to remove the tumor, patients who received accelerated partial breast irradiation saw similar rates of recurrence to those who received whole breast irradiation, according to the data presented at the San Antonio Breast Cancer Symposium.

The randomized phase 3 study followed 520 women over age 40 for 10 years. Half received a targeted daily dose of 30 gray units of radiation, spread out among five treatments per day, aimed at the bed of tissue that previously surrounded the tumor.

The second group received about twice as much radiation per day, across the entire breast: 50 gray across 25 daily treatments, plus a booster of 10 gray through five more procedures.

The women—who had either stage 1 or 2 breast cancer and received endocrine treatments along with surgery and radiation—showed little difference in tumor recurrence or overall survival rates at both the five- and 10-year marks of the study.

After a decade, 3.3% of patients who had the lower dose saw their cancer return, compared to 2.6% of those who received whole breast irradiation. At five years, the recurrence rates were 2.4% and 1.2%, respectively. Neither difference was statistically significant.

Survival rates at 10 years were also similar—at 92.7% and 93.3%—while breast cancer-specific survival rates were nearly tied at 97.6% and 97.5%, and distant metastasis-free survival was the exact same at 96.9%.

“In well-selected cases, there is no difference in patients’ outcomes whether they are treated with [accelerated partial] or [whole breast irradiation],” said the study’s lead author, Icro Meattini, of the University of Florence in Italy—adding that the shorter, targeted therapy may also lead to improved quality of life, with less toxicity and fewer cosmetic changes, as well as being less expensive overall.

A 10-year clinical trial of over 4,200 patients presented at the annual San Antonio symposium last year also found that it was unable to reject the idea that lower-dose radiation therapy was less effective compared to whole-breast treatments, with little difference between its two study arms.

“Partial breast irradiation is one of the primary examples of effective de-escalation of treatment in breast oncology,” said Meattini. “For many patients, partial breast irradiation may be an optimal choice that is cost-effective, safe and efficacious.”