Purpose: Supratentorial primitive neuroectodermal tumor (PNET) accounts for 2-3% of all pediatric brain tumors. We retrospectively reviewed all supratentorial PNET cases treated with radiotherapy (RT) at our institutions.
Methods and materials: A total of 25 patients (17 males and 8 females, median age 9 years) were treated with RT between 1980 and 2001. The primary site location was the pineal region in 7 (28%), temporal lobe in 5 (20%), thalamus in 5 (20%), frontal lobe in 4 (16%), parietal lobe in 2 (8%), and suprasellar region in 2 (8%). Five patients (20%) had neuraxis dissemination (M+ disease) at initial diagnosis. The RT treatment volumes were craniospinal (CS) in 17 (68%), whole brain (WB) followed by a boost in 2 (8%), and primary site (PS) alone in 6 (24%). The median dose to the primary site was 54 Gy (range, 31-55.8 Gy). The median dose to patients receiving WB and spinal fields was 36 Gy (range, 23.4-39.6 Gy). Sixteen patients (64%) received chemotherapy; the most common type was the "8 in 1" chemotherapy regimen in 9 children. The median follow-up of surviving patients was 70 months (range, 34-251 months).
Results: The 5-year and 10-year progression-free survival rate was 36% and 27%, respectively, and the median time to progression was 22 months. The 5-year and 10-year progression-free survival rate was 47.1% and 47.1% for those receiving CSRT and 12.5% and 0% for those receiving WBRT or PSRT, respectively. The 5-year and 10-year progression-free survival rate for those with M0 disease was 40.0% and 30.0%, respectively; for those with M+ disease, the corresponding figures were 20.0% and 0%. On multivariate analysis, only M status (p = 0.01) and RT volume (p = 0.02) were statistically significant according to the Cox proportional hazards model. The primary site control rate at 5 and 10 years was 62%. Failure at nontreated neuraxis sites was a common cause of progression in patients receiving WBRT or PSRT, as seen in 6 (75%) of 8 cases. Of the 17 patients undergoing CSRT, 8 had no recurrence. Eight of the nine CSRT relapses had a leptomeningeal component. Four (80%) of 5 M+ children and 4 (33%) of 12 M0 children who underwent CSRT developed recurrence in the neuraxis (p = 0.1, Fisher's exact test).
Conclusion: The craniospinal axis is the standard volume that needs to be treated in supratentorial PNET. Leptomeningeal dissemination was the main obstacle for cure even in patients receiving CSRT, regardless of M status.