Re-irradiation of ntracranial tumors with active beam scanning protons

Recently, there has been a growing interest in the use of active beam scanning proton therapy for re-irradiation of CNS tumors. Although this treatment option for recurrent intracranial tumors is considered effective, however, it is rarely used because of severe radiation-induced neurologic complications. We present 3 case reports of using active beam scanning proton therapy for re-irradiation of intracranial tumors. In the first case, the patient with high-grade glioma was treated with proton beam therapy 1.5 years after the previous conventional external beam radiation therapy. Tumor regression lasting 18 months was achieved. In the second case, the patient received repeated proton beam therapy for recurrent esthesioneuroblastoma. After 1.5 years of follow-up, no evidence of recurrence and late toxicity was observed. The third case was unique, since the patient with recurrent hemangiopericitoma of the orbit received 4 courses of radiotherapy to the same area. A significant regression with no evidence of radiation-induced damage was also seen 12 months after the completion of radiation treatment. Conclusion. Recent advances in proton therapy allow for re-irradiation of CNS tumors in effective total doses, while reducing exposure to surrounding normal tissues. The use of PET-CT for contouring the target allows the localization and volume of the metabolically active tumor tissue to be precisely determined.