Hypofractionated radiotherapy safe, effective for early breast cancer

Hypofractionated radiotherapy administered in appropriate doses proved safe and effective for patients with early breast cancer, according to results of two randomized, multicenter studies.

The United Kingdom Standardization of Breast Radiotherapy (START) studies A and B enrolled women with early-stage breast cancer who had undergone primary surgery between 1999 and 2002. The median age at baseline was 57 years.

Local-regional tumor relapse and late normal tissue effects served as primary endpoints.

The START-A study included 2,236 patients. Researchers compared results from a control group — who received the standard regimen of 50 Gy in 25 fractions over 5 weeks — with two other arms, 13 fractions totaling 41.6 Gy or 13 fractions totaling 39 Gy.

Median follow-up was 9.3 years.

Overall, 139 patients (6.2%) experienced local-regional relapse. Compared with the control group, researchers reported HRs of .91 (95% CI, 0.59-1.38) for those assigned to the 41.6 Gy regimen and 1.18 (95% CI, 0.79-1.76) for those assigned to the 39 Gy arm.

Researchers observed no statistically significant differences between the control group and the 41.6 Gy arm with respect to late tissue effects. However, patients in the 39 Gy arm experienced significantly less moderate or marked breast induration (P=.034), telangiectasia (P=.003) and breast edema (P=.001).

Researchers reported 392 deaths. They included 273 from breast cancer (92 in the 50 Gy arm; 86 in the 41.6 Gy arm; and 95 in the 39 Gy arm).

In START-B, researchers randomly assigned 2,215 women to the standard 50 Gy in 25 fractions over 5 weeks, or 40 Gy in 15 fractions over 3 weeks.

Median follow-up was 9.9 years. Overall, 95 patients (4.3%) experienced local-regional relapse (HR=.77; 95% CI, 0.51-1.16).

The 40 Gy regimen was associated with less moderate or marked breast shrinkage (P=.015), telangiectasia (P=.032) and breast edema (P=.001) compared with the control arm.

Researchers reported 351 deaths. They included 236 from breast cancer (130 in the 50 Gy arm and 106 in the 40 Gy arm).

“Although the absolute numbers of events have increased over time, the relative differences between the hypofractionated and control schedules at 10 years remain similar to those at 5 years, confirming that appropriately dosed hypofractionated radiotherapy for women with early breast cancer is safe and effective,” the researchers wrote. “The results support the continued use of 40 Gy in 15 fractions, which has already been adopted by most UK centers as the standard of care for women requiring adjuvant radiotherapy for invasive early breast cancer.”

 

Disclosure: The researchers report no relevant financial disclosures.