DIPG/DIPT Discussion

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Friday, May 17, 2013

Feasibility, safety, and indications for surgical biopsy of intrinsic brainstem tumors in children

The USCF pediatric neurosurgical department this week had a publication come out electronically ahead of print regarding biopsy issues for intrinsic brainstem lesions.  These doctors note that the situation with pediatric brainstem tumors is "virtually unlike any other location in the brain" because for these other areas the first step is obtaining a tissue diagnosis to devise an appropriate treatment course.   The reason for the lack of biopsy has been the perception of excessive risk of pediatric brainstem biopsy.   The article also notes that the current approach of investigating a wide array of chemotherapeutic options in multitudinous trials without biologic tumor analysis has not lead to any increased survival in the last two decade.  The authors evaluated the feasibility and safety of pediatric brainstem biopsy at their institution.

Nine children ( 4 male and 5 female witht he average age of 5.7 years) underwent brainstem biopsy between 2000 and 2011 under approval from the Committee for Human Research.   Children were exlcuded from the study if the tumor originated from the cerebellum or cerebral hemispheres, were exophytic or well defined lesions. All included children had typical DIPG imaging features.  The included children presented with cranial nerve palsies (7/9), ataxia (5/9) and headache (3/9).  Rarer symptoms included head tilt, nausea,  weakness on one side and respiratory distress.

The authors did discuss target selection.   All children had stereotactic biospies via a transcerebellar approach. The course was chosen to minimize passing through the brainstem avoiding the lateral edge of the 4th ventical, pontine tegmentum and ventral corticospinal tracts.   In some cases diffusion tensor imaging was used to locate the corticospinal tracts.    Unless there was an obviously enhancing, aggressive area the site selection was just deep to the middle cerebellar penduncle.  One to four specimens were taken.

All cases were gliomas.  Five of the children had high grade gliomas and four were low grade. None of the children suffered intraoperative complications.  One of hte children developed seizures and hypercephalus postoperative which was treated with a shunt.      Seven of the patients underwent radiation and chemotherapy and two underwent chemotherapy only.   All children did experience the natural progresssion of DIPG with decline in neurologic and functional status.  At the time of the publication writing 4 children had died- 2 high grade at 12 months and 2 low grade at 6 and 11 months.

The authors point out the the tremendous lack of progress with DIPG statitics has lead to "therapeutic nihilism".   However, they point out ther are many targeted biologic agents that might have potential on the horizon.   The problem is for phase II trials there will "certainly require tissue in order to determine molecular pheontype prior to treatment assignement".

It seems that this publication is looking specificially forward to those biologic agent trials so that DIPG children will not be excluded just on the basis of not having a tissue analysis.  Although biopsy did not aid the children in this study, it did outline that biopsy can be preformed safely in children with DIPG and gives some tips on the approach of such biospies.

With biospy and convection enhanced delivery I would hope that more pediatric neurosurgeons will become increasingly interested in options for children with DIPG.

Feasibility, safety and indications for surgical biopsy of intrinsic brainstem tumors in children