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Top Line: Stereotactic magnetic resonance (MR)-guided adaptive radiation therapy (SMART) is helping rad oncs dose-escalate to ne’er before seen radiation doses in tricky locations.
The Study: Here’s a single institution series of 44 patients treated at Wash U with a SMART approach to deliver 10 Gy x 5 = 50 Gy to non-metastatic inoperable pancreatic adenocarcinoma. Systemic therapy was held one week prior to, during, and one week after radiation. The name of the game here was dose constraints. All GI structures including esophagus, stomach, duodenum, and small and large bowel were limited to < 0.75cc receiving ≥ 36 Gy. The goal was ≥ 95% of the planning target volume to receive ≥ 95% or prescription, but—and this is key—this objective was forfeited in favor of the aforementioned constraints. All patients received MR simulation with daily deformable MR image guidance with a new plan generated if any constraint was violated or if there was significant potential to improve target coverage. In the end, a whopping 93% of all treatments required reoptimization. So was it all worth it? At a median follow-up of 16 months—limited by survival, which was also 16 months—there were only three grade 2 and two grade 3 late toxicities, all GI as expected. Equally impressive were the local control rates of 84% at one year and 59% at two years. Freedom from any progression or death was 52% at one year and only 14% at two years, serving as a stark reminder that further advances in systemic therapy remain paramount.
TBL: MR-guided adaptive radiation appears to be a safe and effective, if also workflow-intensive, way of achieving excellent local control of advanced pancreatic cancer. | Hassanzadeh, Adv Radiat Oncol 2020