Top Line: The phase 3 SJMB03 trial initiated in 2003 assessed limiting a posterior fossa tumor bed boost to a 1 cm margin in pediatric patients with medulloblastoma, but since that time we’ve learned this disease actually comprises four distinct molecular entities.
The Study: This secondary analysis makes for a great modern look at failure patterns with what has landed as the current standard treatment regimen. To recap, 155 patients received craniospinal irradiation (CSI) to 23.4 Gy (for average risk) or 36-39.6 Gy (for high risk) followed by a conformal tumor bed boost to a cumulative dose of 55.8 Gy. At a median follow-up of over a decade, local failure capped out at 5% across the board. Distant failure, however, is where things stratify quickly with our current understanding of molecular subtypes. Rates of distant failure at 5 years were 7% versus 28% for average versus high risk disease, respectively, and 0% for WNT, 15% for SHH (32% HR v 10% AR), 33% for Group 3, and 10% for Group 4 disease.
TBL: The next iteration of trials in medulloblastoma will further reform deintensification (think: WNT) and intensification (think: group 4 and HR SHH) strategies to optimize the therapeutic ratio of our treatments. | Lucas, Neuro Oncol 2021