Long-Term Outcomes Following Conventionally Fractionated Stereotactic Boost for High-Grade Gliomas in Close Proximity to Critical Organs at Risk.

Purpose/Objective: High-gradeglioma is the most common primary malignant tumor of the CNS, with death often resulting from uncontrollable intracranial disease. Radiation dose may be limited by the tolerance of critical structures, such as the brainstemand optic apparatus. In this report, long-term outcomes in patients treated with conventionallyfractionated stereotactic boost for tumors in close proximity to critical structures are presented. Materials/Methods: Patients eligible for inclusion in this single institution retrospective review had a pathologically confirmed high-gradeglioma status postsurgical resection. Inclusion criteria required tumor location within one centimeter of a critical structure, including the optic chiasm, optic nerve, and brainstem. Radiation therapy consisted of external beam radiation followed by a conventionallyfractionated stereotactic boost. Oncologic outcomes and toxicity were assessed. Results: Thirty patients eligible for study inclusion underwent resection of a high-gradeglioma. The median initial adjuvant EBRT dose was 50 Gy with a median conventionallyfractionated stereotactic boost of 10 Gy. All stereotactic treatments were given in 2 Gy daily fractions. Median follow-up time for the entire cohort was 38 months with a median overall survival of 45 months and five-year overall survival of 32.5%. The median freedom from local progression was 45 months, and the five-year freedom from local progression was 29.7%. Two cases of radiation retinopathywere identified following treatment. No patient experienced toxicity attributable to the optic chiasm, optic nerve, or brainstemand no grade 3+ radionecrosis was observed. Conclusions: Oncologic and toxicity outcomes in high-gradeglioma patients with tumors in unfavorable locations treated with conventionallyfractionated stereotactic boost are comparable to those reported in the literature. This treatment strategy is appropriate for those patients with resected high-gradeglioma in close proximity to critical structures.