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 > or =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 > or = 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 > or =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 > or =50 days. Because the overwhelming site of failure was local, we recommend local field irradiation in patients with M0 disease.