Rolling in the steep.
Top Line: There’s been a lot of rethinking stereotactic radiation (SBRT) techniques for early-stage non-small cell lung cancer (NSCLC) since the 2018 publication of a retrospective study demonstrating a huge increase in distant metastases when the mean dose to a 3 cm shell surrounding the target volume was less than 21 Gy.
The Study: Importantly, this hasn’t yet been replicated by another institution’s experience. UPMC has stepped up to evaluate if a similar concept holds true among their patients. Among 304 patients with 325 NSCLC lesions (larger than the previously referenced study that included 217 patients) receiving SBRT for NSCLC, there indeed was no correlation between distant mets and the mean dose to the 3 cm shell surrounding the target. In fact, among those receiving 4-5 fraction SBRT (n=136), there was a significant correlation between distant mets and a mean EQD2 dose to the 3 cm shell around the target of less than 21 Gy. But no need for wild speculation as to why this could be. We all know conformity (i.e. steep dose gradients) increases with diminishing target volumes, and here both increased gross tumor and final target sizes were significantly directly correlated with increased risk of distant mets, as expected.
TBL: The ideal target volume and planning techniques for SBRT for early-stage NSCLC remain TBD. | Lalonde, Radiother Oncol 2022