Primitive Neuroectodermal Tumors (PNET)
Dear OncoLink "Ask the Experts,"
My 8-year-old daughter had a Primitive Neuroectodermal Tumor (PNET) removed from her spinal cord at T4 &T5 just this past December. Information on this type of cancer and at this type of local is extremely difficult to find. What can you tell me about the cancer, her prognosis and her future?
Hui-Kuo G. Shu, MD, PhD, an Assistant Professor in the Department of Radiation Oncology at the University of Pennsylvania, responds:
A Primitive Neuroectodermal Tumor (PNET) of the spinal cord is an extremely rare diagnosis. The total number of cases reported in the literature numbers less than 20, with fewer than half of these in the pediatric patient population. Therefore, the possibilities that this infra/supratentorial PNET originating from the brain with drop metastasis to the spinal cord versus an alternative pathologic entity needs to be ruled out. If the spine is found to be the only site of disease after careful workup and the pathology is confirmed to be a PNET by an experienced pathologist, then I would be comfortable with a diagnosis of spinal cord PNET.
The most common site of PNETs in the CNS is the posterior fossa (cerebellar region) where it is known as a medulloblastoma. These are "small, round blue cell" embryonal tumors and have a tendency for spread in the fluid surrounding the central nervous system. While classically, radiation therapy was used as adjuvant therapy following surgical resection, these tumors are sensitive to chemotherapy as well. If a patient is diagnosed at the age of 3 or older, the current standard is to treat these patients with a combination radiation to the spine and brain and chemotherapy after surgical resection.
Since there are so few cases of spinal cord PNET reported, it is difficult to know what the "real prognosis" is. Most of the pediatric cases reported in the literature had relatively early recurrences (within 2 years). However, these cases were generally from an era when chemotherapy was not routinely used. The most recent case that I was able to find in the literature of a spinal cord PNET was in a 4 year old patient reported in a Japanese medical journal. This patient had gross total resection of a thoracic PNET followed by radiation therapy/chemotherapy and has been free of recurrence for 6 years. While this represents only a single case, it does illustrate that long-term control can be achieved with modern, aggressive combined-modality therapy.