Top Line: Not all leptomeningeal disease (LMD) is created equal.
The Study: One strategy for stratifying risk in the setting of minimal symptoms is radiographic appearance, where nodularity often fares much better than the “sugar-coating” we typically picture with LMD. A spin-off of a prospective trial of proton craniospinal irradiation (CSI) for LMD, this analysis evaluates the prognostic impact of circulating tumor cells detected in the cerebrospinal fluid (CTC-CSF) among 58 consecutive patients receiving proton CSI for LMD at MSKCC. Let’s back up for a minute. CSF cytology performs poorly at ruling out LMD with a sensitivity of roughly 50%. Enter CTC-CSF as an add-on test after a lumbar puncture to enhance diagnostic accuracy. Using a post-hoc detected binary cut-off, pre-treatment CTC-CSF <53 cells/3mL was associated with double to median CNS progression free survival (12 v 6 months). Another standout indicator, particularly among the group with a pre-treatment CTC-CSF ≥53, was a post-treatment decrease in CTC-CSF of 37 or more. On multivariate analysis, CTC-CSF was significantly prognostic of both CNS-PFS and overall survival. On the other hand, levels of CTC in blood had no association with survival outcomes nor with CTC-CSF. Furthermore, radiographic findings on MRI such as presence of discrete parenchymal brain mets or hydrocephalus were less reliable at predicting treatment outcomes than CTC-CSF.
TBL: It may be hard to wrap your head around proton CSI for patients with LMD, but preliminary data points to low-burden CTC-CSF as a pre-treatment indicator for who best can achieve prolonged survival outcomes. | Wijetunga, Neurooncol Adv 2021