Unexpected heterogeneity in CNS-PNET patients treated as a single entity

Eugene I. Hwang, M.D., a neuro-oncologist in the Center for Cancer and Blood Disorders, and other researchers at Children’s National Health System, Seattle Children’s Hospital and Research Institute, the Fred Hutchinson Cancer Research Center and the Hopp-Children’s Cancer Center at the NCT Heidelberg recently published the results of a clinical trial focusing on children with histologically diagnosed supratentorial primitive neuroectodermal tumors (CNS-PNET) and pineblastomas (PBLs).

The clinical trial, published online October 17, 2018 in the Journal of Clinical Oncology, included children and adolescents aged 3-22 with these brain cancers who were randomly assigned to receive carboplatin during radiation and/or isotretinoin after the standard intensive therapy (high-dose craniospinal radiation and months of inpatient chemotherapy).  Importantly, because each patient was treated prospectively according to the clinical trial design, the conclusions related to tumor biology were felt to be less affected by varied treatment plans.

“This trial really highlighted the importance of new molecular testing methods in accurately diagnosing some of the brain cancers included in the trial. We found that some patients diagnosed with standard tools underwent much more treatment than necessary or intended.” says Dr. Hwang. “Kids who aren’t receiving the right form of cancer treatment may not get better despite months and months of intensive treatment.”

During this clinical trial, 85 participants with institutionally-diagnosed CNS-PNETs/PBLs were enrolled. Out of the 60 patients with sufficient tissue, 31 were non-pineal in location, 22 of which represented tumors that did not fit in the diagnoses intended for trial inclusion.

The researchers discovered that patient outcomes across each molecularly-diagnosed tumor type were strikingly different. Patients with molecularly-confirmed supratentorial embryonal tumors/PBLs exhibited a five-year event free survival (EFS) and an overall survival rate of 62 percent and 78.5 percent, respectively. However, patients with molecularly-classified high-grade gliomas (HGGs) had a five-year EFS of 5.6 percent and OS of 12 percent, showing no benefit even with the chemotherapy and craniospinal radiation.

Researchers determined that for patients with CNS-PNETs/PBLs, prognosis is considerably better than previously assumed when molecularly-confirmed HGG are removed. Dr. Hwang and co-authors concluded that molecular diagnosis can greatly aid standard pathological diagnostic tools, preventing unnecessary intensive therapy for some patients while enabling more rational treatment for others.

“The findings from our clinical trial have highlighted the immense challenges of histology-based diagnosis for some types of pediatric brain tumors, and the enormous importance this has for children with brain cancer,” Dr. Hwang says. “We hope that ultimately our study will pave the way for molecular profiling to become a standard component of initial diagnosis.”