Until 2020, the standard radiotherapy course for early-stage breast cancer after lumpectomy was fifteen sessions over three weeks. The FAST Forward trial — a large, randomised clinical trial run across NHS centres in the UK — changed that. It demonstrated that five sessions over one week delivers equivalent cancer control and, in some measures, fewer late side effects. The NHS updated its national guidance accordingly, and one-week radiotherapy is now the standard for most women with early-stage breast cancer.
What the trial found
FAST Forward, published in The Lancet in 2020, compared three radiotherapy schedules: the previous fifteen-session standard, a five-session course at 26 Gy, and a five-session course at 27 Gy. At five-year follow-up, rates of local tumour recurrence were equivalent across all three arms. The 26 Gy five-fraction schedule showed a slightly improved normal-tissue side-effect profile compared to the fifteen-session course. The trial randomised 4,096 women across 97 UK centres, making it one of the largest radiotherapy trials ever conducted.
What this means for patients in practice
- Most women with early-stage breast cancer after lumpectomy now receive five radiotherapy sessions rather than fifteen
- Treatment is completed in one week rather than three — significantly reducing disruption to work and family life
- Fewer hospital visits is also associated with reduced fatigue from travel and reduced out-of-pocket costs for patients
- The change applies specifically to whole-breast radiotherapy after breast-conserving surgery for early-stage disease
- Women with more complex treatment needs (post-mastectomy, nodal irradiation) may still have longer courses
Side effects: what to expect from the five-fraction course
Radiotherapy to the breast can cause fatigue, skin redness and soreness in the treated area during and immediately after treatment. These side effects are generally manageable and resolve within a few weeks. Long-term side effects — including breast firmness, skin changes and rare heart or lung effects — are monitored over time. The FAST Forward results suggest the five-fraction schedule may reduce some late tissue effects compared to the previous standard.
The global gap in radiotherapy access
For women in high-income countries, the shift to one-week radiotherapy is a meaningful improvement in quality of care. For the estimated 70% of women in low-income countries who cannot access radiotherapy at all, it highlights a different crisis. Radiotherapy infrastructure — linear accelerators, trained staff, treatment planning systems — requires significant capital investment. Where it does not exist, women who could be cured with surgery and radiotherapy are instead managed with mastectomy alone, or not treated at all. Closing that gap is one of the defining global health challenges in oncology.