The risk of peri-hippocampal recurrence is low in pediatric patients with medulloblastoma, according to a retrospective study published in Cancer.
Based on this finding, researchers suggest that hippocampal-sparing radiation should be evaluated prospectively in this patient population.
The retrospective study included 179 pediatric patients with medulloblastoma who underwent proton radiotherapy between 2002 and 2016.
The researchers examined recurrence in 3 hippocampal zones corresponding to 0-5 mm (HZ‐1), 6-10 mm (HZ‐2), and more than10 mm (HZ‐3) distance of the recurrence from the contoured hippocampi.
A total of 38 patients had local or distant recurrence at a median of 1.6 years. Twenty-five of these patients had detailed MRI of their recurrence.
There were no recurrences within the hippocampus, but 2 patients had recurrence within HZ-1. One of these patients was high-risk, and 1 was standard-risk. The crude incidence of peri-hippocampal failure was 8%.
“[T]his is the largest patterns of failure study to date to demonstrate a lack of isolated hippocampal failures in pediatric patients with medulloblastoma,” the researchers wrote.
The team also tested the feasibility of hippocampal avoidance (HA) in 3 standard-risk patients using either a volumetric-modulated arc therapy (VMAT) or intensity-modulated proton therapy (IMPT) hippocampal-sparing plan.
Both the HA-VMAT and the HA-IMPT plans were associated with a reduced mean dose to the right and left hippocampus, compared with a non-hippocampal-sparing IMPT plan (P <.05).
According to the researchers, this reduction is consistent with prior research. However, the researchers were surprised to find that HA‐VMAT was as effective as HA‐IMPT in reducing the mean hippocampal dose.
“Although proton therapy was much more effective at reducing dose to the pituitary and temporal lobes, this technology is not available in the majority of radiation centers in the United States,” the researchers wrote. “Therefore, HA‐VMAT may be an alternate strategy for hippocampal sparing in centers where proton technology is not currently available.”
Baliga S, Adams JA, Bajaj BVM, et al. Patterns of failure in pediatric medulloblastoma and implications for hippocampal sparing. Cancer. Published online December 11, 2022. doi:10.1002/cancr.34574