This study by the Sloan Kettering group, New York, reported the results of a randomized phase II trial comparing Photon involved-field radiotherapy (IFRT) and proton craniospinal irradiation (pCSI) for leptomeningeal metastasis (LM). 42 and 21 patients non-small-cell lung cancer and breast cancers with LM were randomly assigned to pCSI and IFRT. At the interim analysis, a significant benefit in CNS PFS was observed with pCSI (median 7.5 months) compared with IFRT (2.3 months) (P < .001), and OS benefit with pCSI (9.9 months) versus IFRT (6.0 months) (P = .029). There was no difference in the rate of grade 3 and 4 TAEs (P = .19). The authors concluded that pCSI improved CNS PFS and OS for this subset of LM patients.