As reported in the Journal of Clinical Oncology by Brunt et al, 10-year follow-up in the FAST trial of women with early breast cancer showed greater risk for photographic- and physician-assessed normal tissue effects with an adjuvant radiotherapy regimen of 30 Gy in 5 once-weekly fractions—but not 28.5 Gy in 5 once-weekly fractions—compared with a standard regimen of 50 Gy/25 fractions.
Study Details
In the multicenter study, 915 women age 50 or older with low-risk invasive breast carcinoma were randomly assigned to receive whole-breast radiotherapy with 50 Gy/25 fractions, 30 Gy/5 weekly fractions (6 Gy/fraction), or 28.5 Gy/5 weekly fractions (5.7 Gy/fraction). The primary endpoint was change in photographic breast appearance at 2 and 5 years. Secondary outcome measures included physician assessment of normal tissue effects (shrinkage, induration, telangiectasia, and edema). Patients underwent annual follow-up.
“At 10 years, there was no significant difference in normal tissue effect rates after 28.5 Gy/5 fractions compared with 50 Gy/25 fractions, but normal tissue effects were higher after 30 Gy/5 fractions."— Brunt et al
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Key Findings
On the basis of photographic breast appearance at 5 years, compared with 50 Gy/25 fractions, odds ratios for mild to marked changes were 1.64 (P = .019) for 30 Gy/5 fractions and 1.10 (P = .686) for 28.5 Gy/5 fractions. It was estimated that a 5-fraction schedule of 28 Gy was radiobiologically equivalent to 50 Gy/25 fractions in terms of normal tissue effects.
On physician assessment at 5 years, compared with 50 Gy/25 fractions, risk ratios for moderate/marked vs no/mild normal tissue effects were 2.12 (P < .001) for 30 Gy/5 fractions and 1.22 (P = .248) for 28.5 Gy/5 fractions.
On physician assessment at 10 years, compared with 50 Gy/25 fractions, risk ratios for moderate/marked vs no/mild normal tissue effects were 2.40 (P < .001) for 30 Gy/5 fractions and 1.32 (P = .349) for 28.5 Gy/5 fractions.
On longitudinal analysis including all follow-up assessments, compared with 50 Gy/25 fractions, odds ratios for any moderate/marked physician-assessed normal tissue effects were 2.12 (P < .001) for 30 Gy/5 fractions and 1.22 (P = .248) for 28.5 Gy/5 fractions.
After median follow-up of 9.9 years, there were 11 ipsilateral breast cancer events, including 3 in the 50-Gy group, 4 in the 30-Gy group, and 4 in the 28.5-Gy group. A total of 96 deaths were reported, including 30 in the 50-Gy group, 33 in the 30-Gy group, and 33 in the 28.5-Gy group; 25 women died due to breast cancer, including 7, 8, and 10 patients, respectively.
The investigators concluded, “At 10 years, there was no significant difference in normal tissue effect rates after 28.5 Gy/5 fractions compared with 50 Gy/25 fractions, but normal tissue effects were higher after 30 Gy/5 fractions. Results confirm the published 3-year findings that a once-weekly 5-fraction schedule of whole-breast radiotherapy can be identified that appears to be radiobiologically comparable for normal tissue effects to a conventionally fractionated regimen.”
Adrian Murray Brunt, FRCR, of the Clinical Trials and Statistics Unit, The Institute of Cancer Research, London, is the corresponding author for the Journal of Clinical Oncology article.
Disclosure: The study was funded by Cancer Research UK and the National Health Service. For full disclosures of the study authors, visit ascopubs.org.
