Five-fraction Radiotherapy for Breast Cancer: FAST-Forward to Implementation

Area of Science:

• Oncology
• Radiotherapy
• Clinical Trials

Background:

• The FAST-Forward trial investigated accelerated partial breast irradiation (APBI) schedules.
• Conventional APBI involves 40 Gy in 15 fractions over 3 weeks.
• Shorter, intensified schedules are being explored to improve patient convenience and resource utilization.

Purpose of the Study:

• To compare the efficacy and safety of a 26 Gy schedule delivered in 5 fractions over 1 week versus the standard 40 Gy in 15 fractions over 3 weeks for breast radiotherapy.
• To assess the rates of ipsilateral breast tumour relapse (IBTR) and normal tissue effects (NTE).

Main Methods:

• Phase 3 randomized controlled trial (FAST-Forward) involving approximately 4000 patients.
• Comparison of two radiotherapy schedules: 26 Gy in 5 fractions (1 week) vs. 40 Gy in 15 fractions (3 weeks).
• Evaluation of 5-year IBTR and clinician-assessed NTE.

Main Results:

• Non-inferiority in 5-year IBTR was demonstrated for both 26 Gy (1.4%) and 27 Gy (1.7%) schedules compared to 40 Gy (2.1%).
• Subgroup analyses showed no significant differential effect on IBTR or NTE based on patient or tumour characteristics.
• Low rates of moderate/marked NTE were observed, predominantly moderate, with no significant difference between schedules.

Conclusions:

• The 26 Gy in 5 fractions schedule is recommended for clinical implementation due to its non-inferiority to the 40 Gy schedule and similar safety profile.
• This accelerated regimen offers a more convenient treatment option for breast cancer patients.
• Further research may explore radiobiological implications of time-related effects in radiotherapy schedules.