ROBOT-ASSISTED STEREOTACTIC BIOPSY IN DIPG

Recent advancements in molecular characterization of diffuse intrinsic pontine gliomas (DIPG) have favored the reintroduction of stereotactic biopsy to obtain tumor samples. Acceptable morbidity has been documented in experienced Centers performing biopsies in clinical trials. Transcerebellar transpeduncular approach has been proposed as a safer and easier way to perform pontine biopsies with favorable risk profile (5-10% of new neurological deficit). From January 2015 to January 2016 six biopsies were performed using the Rosa robotic arm system using a transfrontal precoronary approach. Whenever feasible target was chosen in high diffusion restriction areas or contrast enhancing areas on MRI imaging and fused with CT scan images to maximize precision. Four to six samples were obtained from each procedure allowing histological characterization and H3K27 mutation identification in all cases. We were able to save freshly frozen samples for biological characterization to guide target therapy in all cases. We observed transient worsening of diplopia in two patients, returning to baseline within 1 month. No bleeding was documented at early CT scan and reaching of planned target was observed in all cases. We confirm an acceptable risk profile of DIPG biopsy in experienced hands. Transfrontal approach has the theoretical advantage to be parallel to white matter long tracts of the pons, however a longer needle track is required. Further advantages are supine position during the procedure and possibility to use robotic systems with submillimetric precision and high stability of biopsy needle. These procedures should better be performed at selected Centers offering clinical trials for DIPG