An article published Online First and in an upcoming Lancet reveals that radiotherapy reduces breast cancer recurrence by 50% during the following 10-years after breast conserving surgery and reduces the risk of breast cancer mortality by one sixth over the next 15 years after surgery.

In the largest study on this topic to-date, researchers from the Early Breast Cancer Trialists’ Collaborative Group (EBCTCG) analyzed data of 10,801 women with breast cancer, following each woman for an average period of 10 years. The worldwide study is a collaboration of all female participants who participated in 17 radiotherapy trials following their breast conserving surgery. The research was funded by Cancer Research UK, the British Heart Foundation, and the UK Medical Research Council.

Findings reveal a clear reduction in cancer recurrence within the first year after radiotherapy, which continues throughout the first decade.

Compared with 19% of women who received radiotherapy treatment, 35% of the women who did not have radiotherapy had a recurrence within 10 years after their breast cancer diagnosis. Although the effect of radiotherapy on breast cancer mortality rates take longer to establish than those of the recurrence rate, researchers found that 15 years following diagnosis, only 21% of women with radiotherapy died of breast cancer compared with 25% of those who did not.

The authors highlight that radiotherapy showed no significant adverse effect on the 15-year mortality risk from all collective causes other than breast cancer, meaning that the reduced 15-year mortality risk from all causes was comparable with the risk in breast cancer mortality for women who received radiotherapy.

“The overall findings from these trials show that radiotherapy after breast-conserving surgery not only substantially reduces the risk of recurrence but also moderately reduces the risk of death from breast cancer. These results suggest that killing microscopic tumor foci in the conserved breast with radiotherapy reduces the potential for both local recurrence and distant metastasis,” comment the authors, concluding that, “Screening, surgery, pathology, radiotherapy, and systemic therapy have all changed substantially since most of these women were randomly assigned, so the absolute recurrence reduction with radiotherapy in future patients might differ greatly from that recorded in these trials…Nevertheless, the finding that radiotherapy roughly halved the recurrence rate after breast-conserving surgery in a wide range of patients with very different absolute risks suggests that it might also roughly halve the recurrence rate in future patients given breast-conserving surgery.”

Dr Thomas A Buchholz, Head of the Division of Radiation Oncology at the University of Texas MD Anderson Cancer Center in Houston, Texas, USA, writes in a linked comment:

“The data from many thousands of clinical trial patients reviewed by the EBCTCG investigators continue to provide us with crucially important insights. The data reinforce the important role that radiotherapy has in management of breast cancer, and the fact that the benefits of radiation are complementary to the advances in both surgery and systemic treatment is particularly rewarding. The incremental benefits of each component of treatment contribute to the ongoing success in reduction of breast cancer mortality rates.”

Written by Petra Rattue