The use of 40 Gy in 15 fractions over 3 weeks is as effective and causes less damage to nearby tissue than a higher total dose of radiotherapy for breast cancer, according to the results of a 10-year follow-up study.
The 5-year results of the UK Standardisation of Breast Radiotherapy (START) trials suggested that lower total doses of radiotherapy delivered in fewer, larger doses (fractions) were at least as safe and effective as the historical standard regimen (50 Gy in 25 fractions) for women after primary surgery for early breast cancer. In a prespecified analysis, researchers evaluated the 10-year results of the START trials, which included trials A and B.
In START-A, patients were randomly assigned to a regimen of either 50 Gy in 25 fractions over 5 weeks or 41.6 Gy or 39 Gy in 13 fractions over 5 weeks (n=2236). In START-B, patients were randomized to either 50 Gy in 25 fractions over 5 weeks or 40 Gy in 15 fractions over 3 weeks (n=2215).
In the 3 START-A groups, the tumor control rate was similar. Cancer relapse rates were low—139 total locoregional relapses in 9.3 years—with 7.4% relapsing in the 50-Gy group, 6.3% in the 41.6-Gy group, and 8.8% in the 39-Gy group. Compared with women in the 50-Gy group, women in the 39-Gy group had significantly fewer incidences of breast induration, edema, and telangiectasia. However, the normal tissue effects did not differ between the 41.6-Gy and the 50-Gy groups.
In the START-B groups, 95 locoregional relapses occurred after 9.9 years. As with the START-A group, the relapse rates in the start B groups were similar, with 4.3% relapsing in the 40-Gy group and 5.5% in the 50-Gy group. However, women in the 40-Gy group were less likely than those in the 50-Gy group to experience breast shrinkage, telangiectasia, and edema.
Other findings were that an unexpected 5-year survival benefit found in the initial trial for the 3-week 40-Gy 15-dose schedule persisted at the 10-year follow-up. In addition, the outcomes were irrespective of age, tumor grade, stage, chemotherapy use, or use of tumor bed boost.
“These 10-year results reassure us that 3 weeks of radiotherapy is as good as the 5 weeks still used in many countries, with less damage to nearby healthy tissue, as well as being more convenient for women (shorter waiting lists and fewer hospital visits) and cheaper for health services,” said study leader Professor John Yarnold, of The Institute of Cancer Research, London, and The Royal Marsden NHS Foundation Trust, Sutton, UK.
- Hypofractionated radiotherapy was associated with fewer normal tissue effects than traditional radiotherapy.
- The 10-years relapse rates between women receiving traditional radiotherapy versus hypofractionated radiotherapy were similar.
- An unexpected 5-year survival benefit found in the initial trial for the 3-week 40-Gy 15-dose schedule persisted at the 10-year follow-up.
- Outcomes were irrespective of age, tumor grade, stage, chemotherapy use, or use of tumor bed boost.