Targeted Breast Cancer Radiotherapy Reduces Side Effects

Partial-breast radiotherapy (RT) restricted to the vicinity of the original tumor results in fewer late normal-tissue adverse effects, claims a new study.

Researchers at the University of Cambridge (United Kingdom), The Institute of Cancer Research (ICR; London, United Kingdom), and other institutions conducted a multicenter, randomized, phase 3 trial in 30 RT centers across the UK involving 2,016 women aged 50 or older who underwent breast-conserving surgery for unifocal invasive ductal adenocarcinoma, with a tumor size of three cm or less, none to three positive axillary nodes, and minimum microscopic margins of non-cancerous tissue of two mm or more.

The patients were randomized to a reduced-dose RT group (673 patients), a partial-breast RT group (669 patients), and a whole-breast RT control group (674 patients). Field-in-field (FIF) intensity-modulated RT was delivered using standard tangential beams that were simply reduced in length for the partial-breast group. The primary endpoint was ipsilateral local relapse at five years for each experimental group. The results showed that 5-year absolute differences in local relapse (compared with the control group) were −0·73% for the reduced-dose and −0·38% for the partial-breast groups.

According to the researchers, the results indicate that non-inferiority can be claimed for both reduced-dose and partial-breast RT. Photographic evaluation and patient and clinical assessments recorded similar adverse effects following reduced-dose or partial-breast RT, including two patient domains--change in breast appearance and breast harder or firmer--that achieved significantly lower adverse effects as compared with whole-breast RT. The study was published on August 1, 2017, in The Lancet.

“We started this trial because there was evidence that if someone’s cancer returns, it tends to do so close to the site of the original tumor, suggesting that some women receive unnecessary radiation to the whole breast,” said lead author Charlotte Coles, MD, reader in breast radiation oncology at Cambridge University. “Now we have evidence to support the use of less, but equally effective, radiotherapy for selected patients.”

“We’re delighted that the results of this trial have the potential to lead to a real change in the way selected breast cancer patients are treated,” said senior author Professor Judith Bliss, PhD, of the ICR. “The technique used here can be carried out on standard radiotherapy machines, so we anticipate that these results will lead to further uptake of this treatment at centers across the country and worldwide.”

Related Links:
University of Cambridge
Institute of Cancer Research