The significance of radiotherapy treatment duration in intracranial ependymoma

Abstract

Purpose: To determine if radiation therapy treatment duration has an impact on the outcome of intracranial ependymoma. Methods and Materials: From 1965 to 1997, 34 patients with intracranial ependymoma were seen and treated with postoperative radiotherapy (RT). There were 26 male and 8 female patients with a median age of 14 years (range, 18 months to 60 years). Tumor location was infratentorial in 23 (67.6%) and supratentorial in 11 (32.4%). Pathology was low-grade in 25 (73.5%) and high-grade in 9 (26.5%). Two (5.9%) patients had M+ disease at initial diagnosis. Gross total resection was achieved in 12 (35.3%), subtotal resection in 19 (55.9%), and biopsy alone in 3 (8.8%). Median RT dose to the primary site was 5400 cGy (range, 4500 cGy to 6600 cGy). The entire neuraxis was treated in 14 (41.2%), whole brain in 9 (26.5%), and the primary site alone in 11 (32.4%). Median radiotherapy treatment duration was 43 days (range, 26 to 122 days). Patients treated with craniospinal RT were more likely to have treatment duration of ≥50 days. Median follow-up was 108 months (range, 24 to 252 months). Results: The 5-, 10-, and 15-year overall survival rates were 71.5%, 63.3%, and 55.4%. Local control rates at 5, 10, and 15 years were 61.8%, 57.7%, and 57.7%. For patients with RT treatment duration <50 days, the 5-, 10-, and 15-year overall survivals were 85.5%, 78.9%, and 65.7% whereas for those with treatment duration ≥50 days, the corresponding rates were 45.5%, 36.4%, and 36.4% ( p = 0.01, log-rank test). Local control rate at 5, 10, and 15 years was 70.6% for patients with RT treatment duration <50 days and 45.5%, 36.4%, and 36.4% for patients with RT treatment duration ≥50 days ( p = 0.05, log-rank test). Age, gender, tumor location, tumor grade, degree of surgical resection, RT volume, and RT dose (4500–5399 cGy vs. 5400–6600 cGy) were not found to have a statistically significant impact on overall survival, disease-free survival, or local control. The most common site of failure was local, found in 13 (38.2%) patients. Three patients also had spinal failure in addition to a primary site failure. There were no isolated nonprimary site brain or spine failures. Conclusions: Radiation therapy treatment duration is an important prognostic factor for survival and local control with patients having treatment duration <50 days having a better outcome than those with treatment duration ≥50 days. Because the overwhelming site of failure was local, we recommend local field irradiation in patients with M0 disease.