This study reviewed ninety-five patients (54 XRT and 41 PRT) treated with craniospinal irradiation (CSI) who had baseline and yearly follow-up for thyroid studies. With a median time post radiation of 3.8 years in PRT and 9.6 years in XRT, 33/95 (34.7%) patients developed hypothyroidism. Hypothyroidism developed in 25/54 (46.3%) who received XRT vs. 8/41 (19%) in the PRT group (HR =1.85, p = .14).

The study concluded that the use of PRT in patients with medulloblastoma was associated with numerically lower but not significantly lower risk of hypothyroidism. Further studies including larger numbers and longer follow up must be performed to assess whether lower radiation doses achieved with PRT show statistically significant differences.