Partial-breast and reduced-dose radiotherapy was found to be noninferior in preventing local relapse compared with whole-breast radiotherapy in patients with early stage breast cancer whose risk of relapse is lower than average, according to a study published in The Lancet.

Large reductions in the rate of relapse are seen in patients with breast cancer who undergo radiation therapy after breast conservation surgery. Current standards for radiation therapy call for whole-breast radiotherapy which increases the risk of toxicity, although evidence shows that most instances of relapse occur in the vicinity of the original tumor.

In the IMPORT LOW phase 3 study, researchers analyzed the 5-year outcomes of 674 women who received 40 Gy whole-breast radiotherapy, 673 women who received reduced-dose (experimental schedules of 36 Gy whole breast and 40 Gy partial breast) radiotherapy, and 669 women who received 40 Gy partial-breast radiotherapy. Patients were scheduled for annual follow-ups for 10 years, and the median follow-up was 72.2 months.

Local relapse occurred in 9 (1%) patients in the whole-breast group, 3 (<1%) patients in the reduced-dose group, and 9 (1%) patients in the partial-breast group.

Five-year estimated cumulative incidence of local relapse in the whole-breast group was 1.1% (95% CI, 0.5-2.3), 0.2% (95% CI, 0.02-1.2) in the reduced-dose group, and 0.5% (95% CI, 0.2-1.4) in the partial-breast group. 

Five-year estimated absolute differences in local relapse compared with the whole-breast group were –0.73% (95% CI, –0.99-0.22) for the reduced dose group and –0.38% (95% CI, –0.84-0.90) in the partial-breast group. 

The authors conclude that partial-breast radiotherapy is noninferior in the rate of local relapse compared with whole-breast radiotherapy, and “seems to be safe and effective and could be implemented easily within most radiotherapy centers worldwide.”

Reference

Coles CE, Griffin CL, Kirby AM, et al. Partial-breast radiotherapy after breast conservation surgery for patients with early breast cancer (UK IMPORT LOW trial): 5-year results from a multicentre, randomised, controlled, phase 3, non-inferiority trial [published online August 2, 2017]. Lancet. doi: 10.1016/S0140-6736(17)31145-5