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Top Line: If we’re really concerned about the development of leptomeningeal disease (LMD) after resection of large brain mets, maybe we shouldn’t be resecting them.
The Study: Did we just say that? Well, we did just talk about predictors of LMD following surgery and post-op radiosurgery, and one thing they all had in common was surgery. Here’s a look back at 125 patients treated for brain mets >3 cm at the University of Alabama at Birmingham. Two-thirds were treated, again, with resection followed by radiosurgery (SRS) to a median of 16 Gy. The remaining third, though, received hypofractionated SRS alone, typically 6 Gy x 5 = 30 Gy. The primary endpoint of post-treatment rates of LMD was a whopping 45% after surgery + SRS versus 19% after SRS alone. Side bar: the authors do recognize this is a very high rate of LMD across the board (for instance, it was 11% in the aforementioned series) and attribute it to a particularly stringent definition of LMD, namely any leptomeningeal enhancement from brain to cauda that was at least 5 mm from the index lesion spanning the gamut from nodular to sugar-coated (see figure 1). Who knows, it might also have to do with the fact they standardly target the post-op cavity with zero margin. While the surgery cohort on the whole had worse disease characteristics, multivariate analysis concluded receipt of surgery and total number of brain mets were the major predictors of developing LMD. Importantly, local control was approximately 70% in each cohort.
TBL: Notwithstanding the uncontrollable biases here, skipping surgery when symptoms allow and going straight to hypofractionated SRS for brain mets >3 cm may minimize LMD without sacrificing local control. | Marcrom, Adv Radiat Oncol 2019