The study, published in the August 13 issue of The Lancet Oncology, assessed a large cohort of these rare tumours and for the first time, identified molecular markers to differentiate them. Researchers found three molecular subgroups of CNS PNETs that are promising diagnostic and prognostic molecular markers that may allow for more specific treatment of the disease.
Embryonal tumours are the largest group of malignant paediatric brain tumours and include medulloblastoma, atypical rhabdoid teratoid tumour and CNS PNETs. Despite histological resemblance to medulloblastoma, patients with CNS PNETs fare poorly even with intensified therapy designed for patients with metastatic medulloblastoma.
“CNS PNETs may appear very similar to many other tumours but don’t behave the same, so this group can be very difficult to diagnose and design specific treatment for,” says Dr. Annie Huang, Principal Investigator of the study and Staff Oncologist and Scientist at SickKids.
To develop more specific diagnostic and treatment approaches to this group of tumours, they had to be studied at a molecular level. This group of tumour only makes up about three to five per cent of all paediatric brain tumours, and since they are so rare, no one had previously studied a large number at a molecular level, explains Huang.
“This is a very uncommon disease. People weren’t studying it because there weren’t enough samples to do so,” says Huang. “We only see one case a year at SickKids, maybe two on a bad year, which is why we had to go internationally to get enough samples.”
Huang adds that this study provides data so clinicians can approach the disease with more insight, and that it will hopefully provide a global framework for even more refined studies of these rare diseases in the future. “We hope that the data from the current study can be used ultimately to more accurately diagnose this group of diseases and may allow for the development of more specific treatment approaches for this group of tumours.”
The study, taking 10 years to complete, undertook a multicentre, international collaboration with the aim of providing a concerted molecular analysis of a substantial number of primary CNS PNETs. Researchers obtained 142 samples from 20 institutions in nine countries. To assess clinical significance of potential CNS PNET molecular subgroups, they examined whether subgroups differed in patient characteristics and outcome and identified two markers – one strongly correlated with poorer overall outcome, and a second with chance of metastatic disease. By using these markers, doctors may be able to begin to evaluate whether high dose brain and spine radiation, which is the standard therapy for these tumours, is necessary for all patients.
The study was supported by the Canadian Institute of Health Research, Brainchild/SickKids Foundation and the Samantha Dickson Brain Tumour Trust.
The Hospital for Sick Children (SickKids).