Needle-track metastasis in diffuse intrinsic pontine glioma: Need for a standardized surgical strategy?

Diffuse intrinsic pontine glioma (DIPG) remains uniformly lethal. Stereotactic biopsy confirms the diagnosis and enables molecular profiling. Metastasis along the biopsy track (BTM) has been reported only anecdotally; its prevalence, clinical relevance, and implications for treatment remain unclear.

A multicenter retrospective study in patients with confirmed DIPG and BTM was conducted based on central neuroradiologic review. Radiotherapy schedules were re-assessed to evaluate the feasibility of upfront biopsy track irradiation.

Ten children met inclusion criteria (median age 6.8 years). Biopsy route was supratentorial in six and infratentorial in four children, and side-cutting needles were used predominantly. H3F3A mutations were most frequent (n = 8); TP53 alterations were common in tumors with extended molecular profiling available. Median PFS was 8.1 months. Five patients each developed BTM prior to (median 2.7 months) or concurrently with progression of primary tumor. There was no difference in overall survival (median OS 12.0 months) compared with the reference cohort. Estimated BTM prevalence among biopsied DIPG from additional registry data was between 6.9% and 13.0%. Primary biopsy track irradiation proved to be feasible, and comparing the surgical access routes, the infratentorial biopsy track hardly increased radiation exposure of the whole brain.

Needle track metastasis is a rare progression pattern in stereotactic biopsied DIPG. Upfront irradiation of the biopsy track may represent a strategy to mitigate the potential risk of BTM. From a dosimetric perspective, an infratentorial approach may therefore be considered, as it was associated with only marginally increased radiation exposure.