The role of MRI in patients with astrocytoma WHO II treated with fractionated stereotactic radiotherapy.

Aim of this study was to evaluate the role of pre-therapeutic and follow-up MRI in the clinical treatment and outcome in patients with astrocytoma WHO grade II after fractionated stereotactic radiation therapy (FSRT). One hundred thirty-nine patients with histologically proven astrocytoma WHO grade II were treated with FSRT and retrospectively evaluated. All patients had follow-up MRI studies (Gd-DTPA-enhanced T1- and T2-weighted MR images). Progression-free survival (PFS) and overall survival (OS) rates were calculated using the Kaplan-Meier method. Multivariate analysis was performed on five potential MRI related prognosticators. Median follow-up was 3.8 years. Positive contrast enhancement (CM+) prior to FSRT proved to be a significant prognosticator for PFS and OS (p<0.01). Pre-therapeutic oedema on T2-weighted images and multifocality of contrast medium (CM) enhancement did not prove to be significant prognosticators. Also, diameter and volume of CM enhancement showed no significance on clinical outcome. Negative contrast enhancing (CM-) patients developing a de novo CM enhancement during follow-up showed a significantly worse clinical outcome compared with generally CM- patients (p<0.05). Pre-therapeutic CM enhancement and the development of CM-enhancing areas during follow-up are negative prognosticators for PFS and OS. They must be interpreted as signs of secondary malignity.