Top Line: What are the long term outcomes of ultrahypofractionated whole breast radiation?
The Study: FAST-Forward was the landmark phase 3 trial that compared hypofractionated and ultrahypofractionated radiation for breast cancer. The trial randomized 4087 patients with pT1–3 pN0–1 invasive breast cancer to receive, 40 Gy in 15 fractions, 27 Gy in 5 fractions, or 26 Gy in 5 fractions to the breast or chest wall. While post-mastectomy patients were allowed, they only made up about 6% of the study population. The 5-year analysis already established non-inferiority for local control. Now with a median follow up just over 10 years, there remained no significant difference in ipsilateral breast recurrence among arms (3.6% v 2.9% v 2.1%). No differences emerged in any subgroups including young age or high grade disease. Late adverse effects was the real story where 10-year clinician-reported moderate or marked breast effects were nearly identical for 26 Gy and 40 Gy (14.4% vs 13.1%), while 27 Gy ran higher at 19.3%. A total of 11 secondary angiosarcomas developed, but they were evenly spread among arms. This report also included 5 year outcomes from a substudy of 466 patients who received treatment to the axilla (but not the internal mammary nodes). It was underpowered for efficacy, but at 5 years, the cumulative rate of locoregional recurrence was similar between hypofractionation and ultrahypofractionation (4.1% v 4.2%).
TBL: A decade of follow up establishes 26 Gy in 5 fractions as a standard option alongside 40 Gy in 15 fractions for adjuvant breast RT with comparable efficacy and late adverse effects. Though the data was more limited, the substudy also suggests including the axilla may also be reasonably safe and effective. | Brunt, Lancet Oncol 2026
The Study: FAST-Forward was the landmark phase 3 trial that compared hypofractionated and ultrahypofractionated radiation for breast cancer. The trial randomized 4087 patients with pT1–3 pN0–1 invasive breast cancer to receive, 40 Gy in 15 fractions, 27 Gy in 5 fractions, or 26 Gy in 5 fractions to the breast or chest wall. While post-mastectomy patients were allowed, they only made up about 6% of the study population. The 5-year analysis already established non-inferiority for local control. Now with a median follow up just over 10 years, there remained no significant difference in ipsilateral breast recurrence among arms (3.6% v 2.9% v 2.1%). No differences emerged in any subgroups including young age or high grade disease. Late adverse effects was the real story where 10-year clinician-reported moderate or marked breast effects were nearly identical for 26 Gy and 40 Gy (14.4% vs 13.1%), while 27 Gy ran higher at 19.3%. A total of 11 secondary angiosarcomas developed, but they were evenly spread among arms. This report also included 5 year outcomes from a substudy of 466 patients who received treatment to the axilla (but not the internal mammary nodes). It was underpowered for efficacy, but at 5 years, the cumulative rate of locoregional recurrence was similar between hypofractionation and ultrahypofractionation (4.1% v 4.2%).
TBL: A decade of follow up establishes 26 Gy in 5 fractions as a standard option alongside 40 Gy in 15 fractions for adjuvant breast RT with comparable efficacy and late adverse effects. Though the data was more limited, the substudy also suggests including the axilla may also be reasonably safe and effective. | Brunt, Lancet Oncol 2026