Effects of radiation treatment planning and patient fixation on the results of postoperative radiotherapy of childhood medulloblastoma.

Abstract

To assess the prognostic factors and the benefit of introducing head fixation and CT-assisted radiation treatment planning following postoperative radiotherapy in 83 children with medulloblastoma. In 24 children treated between 1986 and 1994, no head fixation was applied and boost irradiation was not based on individual radiation treatment planning. Since 1995, boost irradiation has been assisted by CT-based individual radiation treatment planning and ORFIT head fixation in 59 patients. The influence of various factors including age, sex, tumor location, extent, type of surgery, risk group, radiation dose to posterior fossa and spinal axis, and the effect of head fixation and CT-assisted radiation treatment planning on 5-year relapse-free and 5-year overall survival was investigated. Overall and relapse-free survival rates for all 83 patients were 73.5% and 60.7%. Univariate analysis identified metastatic disease (p = 0.034) and the application of head fixation and individual radiation treatment planning (p = 0.013) as significant prognostic factors for overall survival. Relapse-free survival rates were influenced by metastatic disease (p = 0.028) and the application of head fixation and individual radiation treatment planning (p = 0.009). On multivariate analysis, metastatic disease (p = 0.04) and the application of head fixation and individual radiation treatment planning (p = 0.045) were significant factors for overall and relapse-free survival (p = 0.036 and p = 0.041) as well. Metastatic disease appears to be correlated with a worse prognosis in this analysis. Individual radiation treatment planning and head fixation have a positive impact on survival. For postoperative radiotherapy of the posterior fossa, the application of head fixation and individual CT-based radiation treatment planning is considered indispensable in each case.