Suryavanshi M, Jaipuria J, Panigrahi MK, et al. - Given that leptomeningeal (LM) involvement is seen in more than 9% cases of EGFR mutant NSCLC, researchers assessed the diagnostic ability of cfDNA EGFR testing in CSF utilizing DdPCR vs MRI and CSF cytology, as well as exploring known EGFR mutations in the CSF sample. Using paired plasma samples, these mutations were also examined. Furthermore, experts compared which constituent of CSF (pellet/supernatant) showed better yield. They noted that 100% specificity and positive predictive value were seen with all modalities. However, a poor negative predictive value was seen with MRI and CSF cytology. cfDNA was shown to have the highest sensitivity (92.3%), negative predictive value (75%), accuracy (94.1%), as well as net comparative benefit. Overall, experts suggested a potential role of EGFR detection in CSF for diagnosing LM involvement. After first and second-generation TKIs, T790 M resistance mutations were not common in CSF. It was inferred that use of both supernatant and pellet samples are valid for the extraction of cell-free DNA in CSF.