Ten-Year Data Confirm Shorter Radiotherapy Best for Breast Cancer

Nick Mulcahy

September 19, 2013

Three weeks of adjuvant radiotherapy for early breast cancer is as effective and safe as 5 weeks, which is the current standard in much of the world, according to 10-year follow-up data from the landmark UK Standardization of Breast Radiotherapy (START) trials.

The results are an endorsement of hypofractionated radiotherapy — fewer, higher doses over a shorter treatment time — in this setting.

"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 lead study author John Yarnold, MD, from the Institute of Cancer Research in London, United Kingdom, in a press statement

The findings were published online today in the Lancet Oncology.

The results were first presented at the San Antonio Breast Cancer Symposium last year, as reported at that time by Medscape Medical News.

At that time, a German breast cancer expert who was not involved in the study doubted that the START data would affect practice in that country.

"Our standard is still 50 Gy, with 1.8 Gy per session over 5 to 6 weeks, said Sibylle Loibl, MD, from the University of Frankfurt in Germany. "I doubt very much that these data will make a difference," she said.

Adjuvant radiotherapy for women with early breast cancer has repeatedly been shown to improve local cancer control and overall survival benefits in clinical trials, Dr. Yarnold and colleagues note.

However, most of these older studies have used a 5-week treatment regimen consisting of 50 Gy delivered in 25 fractions of 2 Gy.

The investigators explain the thinking behind this common strategy. "This standard regimen is based on a historical assumption that breast cancer is less sensitive to changes in the dose per fraction than dose-limiting healthy normal tissues."

Thus, the small fractions spare the healthy tissue (relatively), but still get the job done with the cancer. That was the conventional wisdom, they note.

But subsequent studies challenged that wisdom, and suggested that both breast tumors and the surrounding healthy tissue are equally sensitive to fraction size. So why not increase the fraction and shorten treatment time, investigators asked. This led to the design of the START-A and START-B trials.

Trial Results

The investigators recruited 4451 women from 35 radiotherapy centers across the United Kingdom from 1999 to 2002 to participate in the 2 trials.

In START-A, the international standard regimen (50 Gy delivered in 25 small doses of 2 Gy over 5 weeks) was compared with a pair of 13-fraction regimens (41.6 Gy delivered in 3.2 Gy doses and 39 Gy delivered in 3.0 Gy doses over 5 weeks).

Among the 2236 women enrolled in START-A, 139 local-regional relapses occurred during the median follow-up of 9.3 years.

The 10-year rates of local-regional relapse did not differ significantly between the standard 50 Gy regimen (7.4%), the 41.6 Gy regimen (6.3%), and the 39 Gy regimen (8.8%).

The damage to normal tissue was much the same with the 3 regimens. However, moderate or marked breast induration, telangiectasia, and breast edema were significantly less common normal-tissue effects with the 39 Gy regimen than with the 50 Gy regimen.

In START-B, the standard regimen was compared with a hypofractionated regimen (40 Gy delivered in 15 doses of 2.67 Gy over 3 weeks).

Among the 2215 women enrolled in START-B, 95 local-regional relapses occurred during the median follow-up of 9.9 years.

In START-B, the 10-year rates of local-regional relapse did not differ significantly between the 50 Gy and 40 Gy regimens (5.5% vs 4.3%). However, there was significantly less harm to healthy tissue with the shorter 40 Gy 15-dose schedule.

The study was supported by Cancer Research UK, the Medical Research Council, and the National Cancer Research Institute. Dr. Yarnold and Dr. Loibl have disclosed no relevant financial relationships.

Lancet Oncol. Published online September 19, 2013. Abstract

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