Ensuring coverage

SABR-5 offered further support of the safety of ablative radiation for oligomets across sites, though liver and adrenal proved the trickiest. Here is a dosimetric evaluation of the potential benefit of using the SMART approach (stereotactic MR-guided adaptive radiation therapy) versus the more standard CT-guided VMAT approach for 20 patients receiving five-fraction ablative radiation (to a median of 50 Gy) for adrenal mets—with each case planned using both techniques. Interestingly, the baseline CT-guided VMAT plan employing breath hold for motion management resulted in superior target coverage and conformality as well as better bowel and kidney dosimetry compared to the base SMART plan. However, since the SMART approach involves adaptive replanning when indicated at each fraction, and the CT-guided plan was simply projected at each fraction, CT-guided VMAT was 3x more likely to result in the prescription dose covering <95% of the target.