Five’s a dime.

Top Line: Many of us have been treating breast cancers with 5-fraction adjuvant radiation for weeks.

The Study: And now we have a published manuscript to back it up. In uniquely British style, the UK phase 3 FAST-Forward trial randomized nearly 4100 women to one of three adjuvant whole breast radiation arms: one being the standard of 40 Gy in 15 daily treatments and the other two being strikingly similar yet a tad different. Arm 2 received 27 Gy in 5 daily treatments and arm 3 received 26 Gy in 5 daily treatments. A quarter of patients in all arms received a tumor bed boost, usually of 10 Gy in 5 daily treatments. The primary endpoint was non-inferiority in local recurrences with the 5-fraction regimens as compared to the standard 15-fraction regimen, pre-specified as an absolute difference <+1.6% or a hazard ratio (HR) <1.81. Realized local recurrence rates at 5 years for arms 1-3 were 2.1%, 1.8% (HR 0·86), and 1.4% (HR 0·67), respectively. In other words, 5-fraction whole breast regimens definitely resulted in non-inferior tumor control. The obvious next question is cosmesis, which was graded by physicians, patients, and blinded reviewers of photographs. When compared to arm 1 (10%), the rate of at least moderate cosmetic changes per physician were significantly higher in arm 2 (15%) but not in arm 3 (12%). Similarly, patients and blinded reviewers graded worse cosmesis in arm 2, but not arm 3, when compared to arm 1.

TBL: Adjuvant whole breast radiation to 26 (but not 27!) Gy delivered in 5 daily fractions achieves non-inferior local tumor control without notable differences in late cosmetic outcomes. | Brunt, Lancet 2020