Chinese new year.
The Study: Results with post-mastectomy hypofractionation were initially presented in 2017, but it's taken this long to see enough breast cancer events for final reporting. As a reminder, this Chinese phase 3 trial randomized women who have received mastectomy for pT3-4 or pN2 breast cancer of any subtype to  conventionally-fractionated radiation of 50 Gy in 25 fractions to the chest wall, supraclavicular nodes, and level III axillary or  the condensed 43.5 Gy in 15 fractions to the same regions. As expected with this population, all received some form of standard chemo. The primary endpoint of locoregional recurrence rate at 5 years was 8% in each arm, with confidence intervals now meeting non-inferiority thresholds. Also important to note is that all late toxicities were pretty much identical without even one grade 3 pneumonitis. How is this possible? Easy. Noone received breast reconstruction. Not having to deal with rounded chests or internal mammary coverage allowed for virtually universal 2D-planning using electrons for the chest wall. This all translated to otherwise unachievable heart means (0.3-0.8 Gy on average) and volumes of ipsilateral lung receiving at least 20 Gy (<20% on average).
Bottom Line: Adjuvant radiation in only 15 treatments is a safe option for women undergoing mastectomy without reconstruction for locally-advanced breast cancer. | Wang, Lancet Oncol 2019