Results from a 10-year study confirm that giving radiotherapy to women with early breast cancer in a lower overall dose through fewer, higher doses is at least as effective and safe as the current standard of a higher overall dose.
The finding comes from the UK Standardisation of Breast Radiotherapy (START) trials, results of which were recently published in The Lancet Oncology.
During the study, 4,451 women from 35 radiotherapy centers in the UK were recruited between 1999 and 2002 for two different subsets of the trial.
Each group compared different doses with the international standard, which is a total dose of 50 Gy - the unit of absorbed radiation - delivered in 25 small doses of 2 Gy over 5 weeks.
The two subsets were:
- START A (5 weeks): compared the international standard with 41.6 Gy of 3.2 Gy and 39 Gy of 3.0 Gy given in 13 treatments over 5 weeks.
- START B (3 weeks): compared the international standard with 40 Gy delivered in 15 doses of 2.67 Gy over 3 weeks.
After 10 years, the tumor control rates of the women in START A were similar to both START B and the international standard. Very few women in START B experienced a relapse of their cancer, and they showed similar damage to surrounding healthy breast tissue.
Similarly, in START B, the number of women whose cancer returned was comparable after 10 years. However, the women in this group showed "significantly less harm" to the healthy breast tissue.
John Yarnold, study leader and professor from The Institute of Cancer Research, London, says:
"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."
The researchers note that these outcomes were similar "irrespective of age, tumor grade, stage, chemotherapy use, or use of tumor bed boost."
Prof. Yarnold continues by saying "the upshot is that - contrary to conventional thinking - cancer cells are just as sensitive to the size of daily radiotherapy dose as the normal tissues responsible for late onset side effects."
This means that continuing to use the standard lower doses "spares the cancer as much as the healthy tissue," effectively offering no benefit to the patients.
Prof. Yarnold concludes:
"Our results support the continued use of 40 Gy in 15 fractions, which has already been adopted as the standard of care by most UK centers."