Long-term outcome of posterior fossa medulloblastoma in patients surviving more than 20 years following primary treatment in childhood

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   Having dealt with treatment of pediatric brain tumor in Oslo since the middle of the last century, our hospital’s team of pediatric neurosurgeons and oncologists has inherited and further deepened the experience gathered over the last seven decades. Also, because the Norwegian population is quite small, and although Norway is an open and dynamic society, we have benefited from the opportunity of life-long follow-up of our patients. Thus, we have been able to collect consecutive patient series with different pediatric brain tumor entities, with practically no patients being lost to follow-up, even many decades following completed treatment. 

  During the last few years, we have reflected this experience in several retrospective studies, mostly focusing on long-term outcome data after treatment of different types of brain tumors in childhood [8,2,1,6,7,4,3]. During the preparation of these studies and particularly during the review process and requested revisions, we have noticed general recognition of our message, namely that the outcome data are important and interesting but also somehow disappointing. A significant part of this disappointment is due to the fact that some patients – and probably more than we would like to see – suffer equally or even more from late consequences of aggressive oncological treatment, even though the tumor disease itself is well controlled [5]. It has been our impression that some colleagues are surprised by these negative findings from long-term survivors, and also - unfortunately enough - that highlighting such a message is not always popular in the oncological community. 

   By documenting the observed survival figures, not only the estimated ones, the results become very reliable, but it takes time to obtain such sort of data. Based on the figures from the present series of patients, we must assume and fear that by the time we will be able to show complete 50-year observed survival data (i.e., in 2037), there will no longer be many patients left who still are alive and well-functioning. 

   In the present study and as correctly pointed by one of the reviewers, we report results that are consequences of a treatment strategy that was actually abandoned more than 30 years ago, i.e., radiotherapy against brain given to children under 3-4 years of age. We may hope that the development of modern and more protective treatment strategies will enable us to cause less damage to children’s brains. To achieve this goal, however, we also need to increase our insight on late effects of treatment of brain tumors. The reality today is – as also our present study indicates so strongly – that the morbidity and mortality associated with brain tumors and their treatment is quite serious and progressive over time.  

1. Lundar T. et al. Neurosurgical treatment of brain tumors in the first 6 months of life: long-term follow-up of a single consecutive institutional series of 30 patients. Childs Nerv Syst 31:2283-2290 (2015)

2. Lundar T. et al. Neurosurgical treatment of pediatric low-grade midbrain tumors: a single consecutive institutional series of 15 patients. J Neurosurg Pediatrics 14:598-603 (2014)

3. Lundar T., Due-Tønnessen B.J., Frič R., Brandal P. & Due-Tønnessen P. Adult outcome after treatment of pediatric posterior fossa ependymoma: long-term follow-up of a single consecutive institutional series of 22 patients with more than 5 years of survival. J Neurosurg Pediatrics:1-5. doi:10.3171/2020.1.Peds19700 (2020)

4. Lundar T. et al. Adult outcome after neurosurgical treatment of brain tumours in the first year of life: long-term follow-up of a single consecutive institutional series of 34 patients. Acta Neurochir 161:1793-1798 (2019)

5. Lundar T., Due-Tønnessen B.J., Frič R. & Due-Tønnessen P. Postoperative radiotherapy for pediatric brain tumor: a lesson learned from treatment of a 5-year-old girl for posterior fossa astrocytoma (WHO1) in 1967. Acta Neurochir160:2065-2066 (2018)

6. Lundar T. et al. Neurosurgical treatment of gangliogliomas in children and adolescents: long-term follow-up of a single-institution series of 32 patients. Acta Neurochir 160:1207-1214 (2018)

7. Lundar T. et al. Neurosurgical treatment of pediatric pleomorphic xanthoastrocytomas: long-term follow-up of a single-institution, consecutive series of 12 patients. J Neurosurg Pediatrics:1-5. doi:10.3171/2018.11.Peds18449 (2019)

8. Stensvold E. et al. Outcome for children treated for medulloblastoma and supratentorial primitive neuroectodermal tumor (CNS-PNET) - a retrospective analysis spanning 40 years of treatment. Acta Oncol 56:698-705 (2017)

Radek Frič

Senior Consultant Neurosurgeon, Oslo University Hospital

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