Big planning techniques.
The Study: The 3 year outcomes were just published, but there’s also a great article from 3 years ago describing acute toxicities plus more radiation details. First important point is this trial was done in the heart of Texas—and you know what they say about Texas. Over 40% of patients had a BMI >30 and over 30% had chest wall separation >25 cm. Furthermore, over 80% of patients didn't meet the 2011 ASTRO criteria for hypofractionation. Second, they aimed to include DCIS (~25%) and women who received chemo (~30%). Third, they were pretty soft on using an absolute max dose to exclude patients. This is important because the old constraint of a dose max ≤107% can be tough to achieve across a vast area. They instead shot for <1 cc getting ≥108%. In the end, roughly 50% of patients had a dose max >107%, of whom only one crossed over to receive conventional fractionation. Finally, over half of patients had a majority of their monitor units delivered by 18 MV tangential beams. In fact, 25% of treatments were delivered with at least 75% of beams being 18 MV. The one remaining question is what to make of the group who received chemo. Though numbers were small, their cosmesis “trended” slightly worse with hypofractionation.
Bottom Line: The planning details of breast hypofractionation performed on trial are probably more lenient than you think. | Shaitelman, J Clin Oncol 2018 & Shaitelman, JAMA Oncol 2015