Prognostic impact of radiation therapy and molecular classification of infant atypical teratoid/rhabdoid tumors

Atypical teratoid/rhabdoid tumor (AT/RT) is a rare and lethal childhood cancer. Although radiation therapy in children less than three years of age is generally deferred because of its neural toxicity, recent studies have shown that multimodal therapies, including radiation therapy, are effective in pediatric patients with AT/RT less than three years of age. We treated four infant AT/RT patients and investigated the impact of radiation therapy and genetic classification on the prognosis. The mean age at the time of the operation was 9.3 months and all patients were female. All patients underwent surgical resection. Of the four patients, two received combined irradiation and chemotherapy. Specifically, one patient received conformai craniospinal radiation therapy and the other received craniospinal irradiation with proton beams. Immunohistochemical analyses of tumor specimens revealed that the two patients were positive for ASCL1, a regulator of Notch signaling. Patients who received radiation therapy and exhibited ASCL1-positive tumors had a better prognosis. We conclude that radiation therapy may prolong survival in AT/RT patients who are less than 3 years of age. However, further study is required to evaluate long-term functional outcomes.