Tumor Shrinkage Assessed by Volumetric MRI in the Long Term Follow-Up after Fractionated Stereotactic Radiotherapy of Non-functioning Pituitary Adenoma

摘要

Purpose: To evaluate tumor control and side effects associated with fractionated stereotactic radiotherapy (FSRT) in the management of residual or recurrent non-functioning pituitary adenomas (NFPAs). Methods and Materials: We assessed exact tumor volume shrinkage in 16 patients with NFPA after FSRT. All patients had previously undergone surgery. Gross tumor volume (GTV) was outlined on contrast-enhanced Magnetic Resonance Imaging (MRI) before and median 63 months (range 28 - 100 months) after FSRT. MRI was performed as an axial 3D gradient echo T1-weighted sequence at 1.6 mm slice thickness without gap (3D MRI). Results: Mean tumor size of all 16 pituitary adenomas before treatment was 7.4 ml (3.3 - 18.9 ml). We found shrinkage of the treated pituitary adenoma in all patients. Within a median follow-up of 63 months (28 - 100 months) an absolute mean volume reduction of 3.8 ml (0.9 - 12.4 ml) was seen. The mean relative size reduction compared to the volume before radiotherapy was 51% (22 - 95%). Shrinkage measured by 3D MRI was greater at longer time intervals after radiotherapy. A strong negative correlation between the initial tumor volume and the absolute volume reduction after FSRT was found. There was no correlation between tumor size reduction and patient age, gender or number of previous surgeries. Conclusions: By using 3D MRI in all patients undergoing FSRT of a NFPA, tumor shrinkage is detected. Our data demonstrate that volumetric assessment based on 3D MRI adds additional information to routinely used radiological response measurements. After FSRT a mean relative size reduction of 51% can be expected within 5 years.