Traditionally, whole breast external beam radiation for breast cancer involves 25 treatment sessions over the course of 5 weeks. During each session, 2 Gy doses of radiation are given, totaling 50 Gy by the end of the 5 weeks of treatment. An outstanding question in the field of radiation oncology has been whether slightly larger daily doses given over a shorter treatment time is a safe and effective strategy for treating early-stage breast cancer.
To answer this question, researchers in the United Kingdom initiated the START B trial. This trial compared the traditional 50 Gy delivered in 25 sessions over 5 weeks scheme to 40 Gy delivered in 15 sessions over 3 weeks. After a median follow-up of almost 10 years, the results show no difference in the rate of local-regional breast cancer recurrence between the groups. Furthermore, there were fewer side effects on normal tissues in the 40 Gy group. The results of this trial have changed the standard of care in the United Kingdom to 40 Gy given in 15 doses over 3 weeks. Clinicians at the 2012 San Antonio Breast Cancer Symposium, where the results of the START trial were presented, commented that the standard of care in the United States may be resistant to change, mainly due to the way that radiation therapy is billed to health insurance in the United States.