Relapse patterns in pediatric embryonal central nervous system tumors.

Embryonal tumors of the central nervous system (CNS) share histological features and were therefore initially grouped as primitive neuroectodermal tumors (PNET) and treated similarly. We sought to determine the relapse patterns of specific embryonal CNS tumors. We conducted a historical cohort study of children diagnosed with CNS embryonal tumors from January 2000 to December 2011 in two pediatric neuro-oncology centers. Patients of 21 years of age or younger at time of presentation with a diagnosis of medulloblastoma, supratentorial PNET, pineoblastoma or atypical teratoid/rhabdoid tumor (ATRT) and at least one surveillance MRI were included. A total of 133 patients met inclusion criteria and 49 (37 %) patients relapsed during the observation period. The majority (79 %) of sPNET relapses were local, whereas all (100 %) PB relapses were associated with diffuse leptomeningeal disease. Relapse patterns for MB were more diverse with local recurrence in 27 %, distant recurrence in 35 % and diffuse leptomeningeal disease in 38 %. The frequency of relapses involving the spine differed (p < 0.001) between tumor types (MB 28/55 [51 %], sPNET 3/33 [9 %], ATRT 3/7 [43 %] and PB 12/12 [100 %]). No sPNET patients had isolated spinal relapse (0/14). Embryonal tumors were found to have divergent patterns of recurrence. While medulloblastoma has variable relapse presentations, sPNET relapses locally and pineoblastoma recurs with diffuse leptomeningeal disease involving the spine. These results point toward possibly new upfront treatment stratification among embryonal tumors in accordance with relapse pattern.