SABCS: 10-Year Follow-Up Analysis Confirms Long-Term Safety, Efficacy of Hypofractionated Breast Cancer Radiotherapy
Hypofractionated radiotherapy delivers lower total therapeutic radiation doses in fewer but larger dose fractions.
“Long-term follow-up confirms that breast cancer and the surrounding dose-limiting healthy tissues respond similarly to radiotherapy fraction size and thus that appropriately-dosed hypofractionated radiotherapy is safe and effective in treatment of patients with early breast cancer,” reported John Yarnold, MBBS, professor of clinical oncology at The Institute of Cancer Research in London, England, and his coauthors. “41.6 Gy in 13 fractions and 40 Gy in 15 fractions each appear comparable to 50 Gy in 25 fractions in terms of local-regional tumor control and late normal tissue effects.”
The researchers analyzed 10-year follow-up data from participants in the START (Standardization of Breast Radiotherapy) clinical trial, who received radiotherapy following completely excised early-stage breast cancer. Participants had been randomized to receive either 50 Gy in 25 fractions over 5 weeks, or one of three hypofractionated regimens: 41.6 Gy or 39 Gy in 13 fractions over 5 weeks (“START A”), or 40 Gy in 15 fractions over 3 weeks (“START B”).“In START A, the 10-year rate of loco-regional relapse was 7.4% (95% CI, 5.5-10.0) after 50 Gy, 6.3% (95% CI, 4.7-8.5) after 41.6 Gy, and 8.8% (95% CI, 6.7-11.4) after 39Gy,” Dr. Yarnold reported. “In START B, the 10-year rate of locoregional relapse was 5.5% (95% CI, 4.2-7.2) after 50 Gy and 4.3% (95% CI, 3.2-5.9) after 40 Gy.”
At 10-year median follow-up, late normal-tissue effects were seen in 43.9% of 39 Gy-arm patients and 49.5% of 41.6 Gy-arm patients from START A, and 37.9% of patients in the 40 Gy START B arm, he noted. (START A and START B 50 Gy-arm late effects were seen in 50.4% and 45.3% of patients, respectively.)
Dr. Yarnold's team is now testing a 1-week fractionated whole-breast radiotherapy regimen in the UK FAST-Forward clinical trial, he noted.
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