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START: Lower radiation dose shows promise at 10-year follow-up
SAN ANTONIO — Lower hypofractionated radiotherapy doses were gentle on healthy tissue without losing efficacy in controlling locoregional early breast cancer, according to long-term results of the United Kingdom Standardization of Breast Radiotherapy Trials, or START.
John Yarnold, MBBS, professor of clinical oncology at The Institute of Cancer Research in London and honorary consultant at The Royal Marsden NHS Foundation Trust, reviewed the two START trials in a press conference at the 2012 CTRC-AACR San Antonio Breast Cancer Symposium.
The trials involved women with completely excised invasive breast cancer.
Trial A included 2,236 patients overall. They were assigned standard therapy of 50 Gy in 25 fractions for 5 weeks (n=749), test regimens of 39 Gy in 13 fractions for 5 weeks (n=750) or 41.6 Gy in 13 fractions for 5 weeks (n=737). Trial B included 2,215 patients who received 50 Gy in 25 fractions for 5 weeks (n=1,105) or 40 Gy in 15 fractions for 3 weeks (n=1,110).
The primary endpoint was local-regional relapse, and secondary endpoints included normal tissue effects, DFS and OS.
Results of Trial A indicated that adverse events continued to accumulate during a 10-year period, according to Yarnold.
“Secondly, you can easily discriminate the difference between the test dose fractions of 39 and 41.6, which are clearly statistically significant,” he said. “Thirdly, the test dose that most clearly resembles the control group of 50 Gy is the 41.6-Gy regimen. The question is then: Which dose most closely resembles the standard group in terms of local tumor control?”
Yarnold said the 41.6-Gy dose was similar to the 50-Gy dose in terms of locoregional relapse rates. “It shows that the breast cancer and the normal tissue are responding the same way to this lower total dose,” he said. “Which shows that this regimen, at least in principle, would be both safe and effective.”
Yarnold suggested that Trial B is more pragmatic and more useful to clinicians.
“The test group is showing fewer adverse events,” he said. “This was a noninferiority trial, and we see no evidence that the test schedule is inferior to the control group.”
Yarnold concluded that there is no advantage in continuing with the 50-Gy, 5-week schedule. “Forty gray in 15 fractions is now the standard of care for all patients in the United Kingdom,” he said.
The trials were conducted between 1999 and 2002. Recruitment was from 35 centers in the United Kingdom. Median follow-up was 9.3 years for Trial A and 9.9 years for Trial B.
For more information:
Haviland JS. #S4-1. Presented at: the 2012 CTRC-AACR San Antonio Breast Cancer Symposium; Dec. 4-8, 2012; San Antonio.
Disclosure: Yarnold reports no relevant financial disclosures.