Shorter Course of Radiation Equivalent to Standard 5-Week Course for Invasive Breast Cancer

A 10-year follow-up of the 2-part UK Standardisation of Breast Radiotherapy Trial (START) supports the 5-year findings, which demonstrated that a shorter course of adjuvant radiation therapy is equivalent to a 5-week course of radiation for women with invasive breast cancer. Both 5-year and 10-year follow-up confirm that patients can be safely and effectively treated with a total lower dose of radiation with fewer fractions than the historical standard of 50 Gy delivered over 5 weeks.

“These results support the current NICE [National Institute for Health and Clinical Excellence] guidelines for 40 Gy in 15 fractions as the UK standard of care for all patients with invasive breast cancer,” stated J. R. Yarnold, MD, lead author, on behalf of the START investigators. Yarnold is affiliated with the Institute of Cancer Research in London.

START A enrolled 2236 women with complete surgical excision of invasive breast cancer stages I through III with 1 involved lymph node and no known metastasis. Patients were randomized to 50 Gy delivered in 25 fractions over 5 weeks (control group) or 39 Gy delivered in 13 fractions over 5 weeks, or 41.6 Gy in 13 fractions delivered over 5 weeks.

START B enrolled 2215 patients with the same criteria from 35 centers in the UK. Patients were randomized to receive the same control-arm treatment versus 40 Gy in 15 fractions over 3 weeks.

In START A, the control arm was not superior to the other 2 arms for adverse events, and 39 Gy was associated with fewer side effects, he continued. No significant differences were observed between 50 Gy and 41.6 Gy in tumor control; local recurrence rates were comparable.

START B showed a clear reduction in adverse events with 40 Gy delivered in 15 fractions versus 50 Gy in 25 fractions. The risk of adverse events was reduced by 23% using the shorter schedule, with an absolute 8% reduction in adverse events.

According to physician assessment, rates of adverse events were lower in the 40-Gy arm, including breast shrinkage, induration, and edema. No difference in recurrence was observed between the 2 arms.
Subgroup analysis of both START A and B showed no difference in outcomes by age, primary surgery type, presence or absence of axillary nodes, tumor grade, use of boost radiation, and adjuvant therapy. Yarnold said, “I see no reason why 40 Gy delivered in 15 fractions should not be adopted as the standard as adjuvant therapy for all women with invasive breast cancer in other countries.”

In the United States and Canada, the shorter course is generally reserved for node-negative patients, and is being used at some centers. However, 25% of the women in Yarnold’s study were node-positive. Data from randomized controlled trials would be needed to confirm use of the shorter course in node-positive patients in the United States.