Update on Accelerated Whole Breast Irradiation

Adjuvant whole breast irradiation (WBI) is commonly delivered following breast conserving surgery (BCS) and has been associated with a reduction in local recurrence compared with BCS alone. Traditionally, WBI was delivered in 25 to 30 fractions; however, accelerated WBI regimens have emerged. At this time, data supports that moderately hypofractionated WBI (15-16 fractions) is standard of care for most patients while data for ultra-hypofractionated WBI (5 fractions) are promising. Since the advent of breast conservation, adjuvant radiation therapy (RT) has been standard of care following breast conser ving surger y (BCS). Radiation therapy following BCS has traditionally been whole breast irradiation (WBI); studies comparing breast conservation to mastectomy utilized standard fractionation WBI, which delivers treatment daily over 5 to 7 weeks (1.8-2 Gy/fraction) and was the standard for decades. More recently, multiple randomized trials have compared standard fractionation WBI to moderately hypofractionated WBI (2.66 Gy/fraction, 15-16 fractions), which allows for completion of treatment in 3 to 4 weeks. Results have demonstrated no difference in local control between these two approaches with comparable toxicity and cosmetic outcomes with long-term follow-up. As such, moderately hypofractionated WBI represents the standard of care approach for most patients with early-stage breast cancer following BCS at this time. In the past few years, ultra-hypofractionated WBI (5.2-5.7 Gy/fraction, 5 fractions) has emerged with promising outcomes; 5-year outcomes from the FAST-Forward randomized trial demonstrated noninferi-ority between ultra-hypofractionated WBI and moderately hypofractionated WBI. Moving forward, long-term outcomes from ultra-hypofractionated WBI studies are expected, as well as the potential for incorporating moderately hypofraction-ated regimens into patients requiring regional nodal irradiation following BCS. Finally, the advent of ultra-short regimens may allow clinicians to re-evaluate treatment de-intensification in early-stage breast cancer to consider radiation therapy alone following BCS in lieu of endocrine therapy.