Long-Term Results of UK START Trials Support Hypofractionated Adjuvant Radiotherapy in Invasive Early Breast Cancer
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 were at least as safe and effective as the historical standard regimen of 50 Gy in 25 fractions as adjuvant therapy for early breast cancer. In an article published in The Lancet Oncology, Joanne S. Haviland, MSc, and colleagues in the START Trialists’ Group reported a prespecified 10-year follow up of the two trials. The results support continued use of the 40 Gy in 15 fraction regimen widely used in the United Kingdom.
Study Details
The randomized START trials evaluated 13- and 15-fraction radiotherapy regimens in women with completely excised invasive breast cancer (pT1–3a, pN0–1, M0). The START-A trial (N = 2,236) compared regimens of 50 Gy in 25 fractions over 5 weeks vs 41.6 Gy or 39 Gy in 13 fractions over 5 weeks. The START-B trial (N = 2,215) compared 50 Gy in 25 fractions over 5 weeks vs 40 Gy in 15 fractions over 3 weeks. The primary endpoints were local-regional relapse and late normal tissue effects. Follow-up data are still being collected.
START-A Outcomes
After median follow-up of 9.3 years in START-A, 10-year rates of local-regional relapse did not differ between the 41.6-Gy group and the 50-Gy group (6.3% vs 7.4%, hazard ratio [HR] = 0.91, P=.65) or between the 39-Gy group (8.8%) and the 50-Gy group (HR = 1.18, P = .41). Moderate or marked breast induration (22% vs 27%, P = .034), telangiectasia (3% vs 7%, P = .003), and breast edema (7% vs 13.5%, P = .001) were significantly less common in the 39-Gy group than in the 50-Gy group. Normal tissue effects did not differ significantly between the 41.6-Gy and 50-Gy groups. No significant differences in 10-year all-cause mortality were observed (20.3% in 39-Gy group, 18.4% in 41.6-Gy group, and 19.8% in 50-Gy group).
START-B Outcomes
After median follow-up of 9.9 years in START-B, there was no significant difference in 10-year local-regional relapse in the 40-Gy vs 50-Gy group (4.3% vs 5.5%, HR = 077, P = .21). Breast shrinkage (26% vs 31%, P = .015), telangiectasia (4% vs 6%, P = .032), and breast edema (5% vs 9%, P = .001) were significantly less common in the 40-Gy group. Ten-year all-cause mortality was reduced in the 40-Gy group (15.9% vs 19.2%, P = .042).
The investigators concluded: “Long-term follow-up confirms that appropriately dosed hypofractionated radiotherapy is safe and effective for patients with early breast cancer. The results support the continued use of 40 Gy in 15 fractions, which has already been adopted by most UK centres as the standard of care for women requiring adjuvant radiotherapy for invasive early breast cancer.”
Judith M. Bliss, MSc, of The Institute of Cancer Research in Sutton, and John R. Yarnold, FRCR, of The Institute of Cancer Research and Royal Marsden NHS Foundation Trust in Sutton, contributed equally to The Lancet Oncology article, for which Dr. Yarnold is corresponding author.
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