Treatment of Recurrent Childhood Medulloblastoma and Other CNS Embryonal Tumors

Recurrence of all forms of central nervous system (CNS) embryonal tumors is not uncommon and usually occurs within 36 months of treatment. However, recurrent tumors may also develop many years after initial treatment.[1-3] In such late relapses, especially those occurring 5 or more years after diagnosis, differentiation from secondary tumors such as high-grade gliomas can be difficult. Histological confirmation is recommended and usually required. In a 2021 report, a paired molecular cohort was assembled, consisting of 127 patients with tissue specimens available from both their primary medulloblastomas and subsequent tumors associated with relapse. Comparative molecular analyses were performed using the patient-matched tumor specimens. DNA methylation-based classification identified nine relapse cases (7%) as histologies other than medulloblastoma.[4] Disease may recur at the primary site or may be disseminated at the time of relapse. Sites of noncontiguous relapse may include the spinal leptomeninges, intracranial sites, and cerebrospinal fluid, in isolation or in any combination, and may be associated with primary tumor relapse.[1,2,5] Extraneural disease relapse is rare and is seen primarily in patients who were treated with radiation therapy alone.[6][Level of evidence C1]

Studies have found that even in patients with nondisseminated disease at diagnosis, and independent of the dose of radiation therapy or the type of chemotherapy, approximately one-third of patients will experience a relapse at the primary tumor site alone, one-third at the primary tumor site plus distant sites, and one-third at distant sites without relapse at the primary site.[1,2,5]