Late Effects of Craniospinal Irradiation Using Electron Spinal Fields for Pediatric Patients With Cancer

Purpose: For children, craniospinal irradiation (CSI) with photons is associated with significant toxic effects. The use of electrons for spinal fields is hypothesized to spare anterior structures but the long-term effects remain uncertain. We studied late effects of CSI using electrons for spinal radiation therapy (RT). Methods and Materials: Records of 84 consecutive patients treated with CSI using electrons for the spine at a single institution between 1983 and 2014 were reviewed. Median age at RT was 5 (range, 1-14) years. The most common histologies were medulloblastoma/primitive neuroectodermal tumor (59%) and ependymoma (8%). The median prescribed dose to the entire spine was 30 Gy (range, 6-45). A subset of 48 (57%) patients aged 2 to 14 at RT with clinical follow-up for ≥5 years was analyzed for late effects. Height z scores adjusted for age before and after CSI were assessed using stature-for-age charts and compared with a t test. Results: At median follow-up of 19 years (range, 0-38 years), the median survival was 22 years (95% confidence interval, 12-28 years) after RT, with 47 patients (56%) alive at last follow-up. On subset analysis for late effects, 19 (40%) patients developed hypothyroidism and 5 (10%) developed secondary malignancies. Other complications reported were esophageal stricture and periaortic hemorrhage in 1 and restrictive pulmonary disease in 1 patient. Median height z score before treatment was –0.4 (36th percentile; interquartile range, –1.0 to 0.0) and at last follow-up was –2.2 (first percentile; interquartile range, –3.1 to –1.6; P <.001). Of 44 patients with spinal curvature assessments, 15 (34%) had scoliosis with median Cobb angle 15° (range, 10°-35°) and 1 (2%) required surgery. Conclusions: Frequent musculoskeletal toxic effects and predominantly decreased height were seen with long-term follow-up. Scoliosis and hypothyroidism were each seen in at least one-third of long-term survivors. However, clinically evident esophageal, pulmonary, and cardiac toxic effects were infrequent.