Eyes on Evidence: Benefit of adjuvant radiotherapy in breast cancer

Overview: Breast cancer is the most common cancer affecting women in Englandand Wales, with about 40,500 new cases diagnosed and 10,900 deaths recorded in Englandand Waleseach year. In men breast cancer is rare, with about 260 cases diagnosed and 68 deaths in Englandand Waleseach year.

Current treatment: Treatment for breast cancer usually involves surgery to remove part, or all, of the breast. Depending on the type and stage of breast cancer, this may be followed by radiotherapy, endocrine therapy, biological therapy or chemotherapy.

The NICE Pathway: breast cancer, brings together all related NICE guidance and associated products on the condition in a set of interactive topic-based diagrams. For all patients with early breast cancer NICE advises starting adjuvant chemotherapy or radiotherapy as soon as clinically possible and within 31 days of surgery.
New evidence: A meta-analysis by The Early Breast Cancer Trialists’ Collaborative Group (EBCTCG) of individual patient data for 10,801 women in 17 randomised trials examined the effect of radiotherapy after breast-conserving surgery on 10 year recurrence and 15 year breast cancer death (Darby 2011).

The findings show a reduction in cancer recurrence within the first year after radiotherapy which lasts throughout the first decade. By 10 years after breast cancer diagnosis, 35% of the women who did not have radiotherapy had a recurrence, compared with only 19% of the women who had radiotherapy. The effect of radiotherapy on breast cancer mortality was evident 15 years after breast cancer diagnosis, by which time 25% of the women who did not have radiotherapy had died from breast cancer compared with 21% of the women who had radiotherapy. These results suggest that killing microscopic tumour foci in the conserved breast with radiotherapy reduces the potential for both local recurrence and distant metastatis.

The researchers note that there was no substantial adverse effect of radiotherapy on the 15-year risk of death from the aggregate of all causes other than breast cancer so that, among the women who did have radiotherapy, the 15-year risk of death from any cause was reduced by almost as much as the reduction in breast cancer mortality. They add 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.

However, because 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.

Commentary: “This report updates an earlier 2005 systematic overview of radiotherapy effects in women undergoing adjuvant radiotherapy for early breast cancer. It represents the most authoritative statement available on treatment outcomes, based as it is on level I evidence. The updated evidence confirms that the beneficial effects persist for at least 15 years, and that there is no evidence of adverse effects on survival even after this long interval. The subgroup analyses suggest that identifiable populations of women have more to gain than others, particularly younger age groups and those of any age with higher grade tumours. Older age groups with small, oestrogen receptor rich, low grade tumours appear to have low risks of local relapse after complete microscopic resection and adjuvant endocrine therapy, even without radiotherapy, raising the opportunity for prospective cohort studies evaluating selective avoidance of radiotherapy in future”. –

John Yarnold, Professor of Clinical Oncology,InstituteofCancerResearch andRoyal MarsdenHospital, Sutton.

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