title: Tumor shrinkage assessed by volumetric MRI in long-term follow-up after fractionated stereotactic radiotherapy of nonfunctioning pituitary adenoma.
abstract: OBJECTIVE
  To evaluate tumor control and side effects associated with fractionated stereotactic radiotherapy (FSRT) in the management of residual or recurrent nonfunctioning pituitary adenomas (NFPAs).
  
  
  METHODS
  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 three-dimensional 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 with 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, sex, or number of previous surgeries.
  
  
  CONCLUSIONS
  By using 3D MRI in all patients undergoing FSRT of an 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.
authors.affiliation: Klinik und Poliklinik für Strahlentherapie und Radiologische Onkologie, Klinikum rechts der Isar, Technische Universität München, Munich, Germany. Christine.Kopp@lrz.tu-muenchen.de
authors.forename: Christine
authors.initials: C
authors.lastname: Kopp
authors.forename: Marilena
authors.initials: M
authors.lastname: Theodorou
authors.forename: Nektarios
authors.initials: N
authors.lastname: Poullos
authors.forename: Vesna
authors.initials: V
authors.lastname: Jacob
authors.forename: Sabrina T
authors.initials: ST
authors.lastname: Astner
authors.forename: Michael
authors.initials: M
authors.lastname: Molls
authors.forename: Anca-Ligia
authors.initials: AL
authors.lastname: Grosu
mesh_terms: D000236:Adenoma / Q000473:pathology* / Q000601:surgery; D000293:Adolescent; D000328:Adult; D000368:Aged; D003287:Contrast Media; D005260:Female; D005500:Follow-Up Studies; D005682:Gadolinium; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010911:Pituitary Neoplasms / Q000473:pathology* / Q000601:surgery; D016634:Radiosurgery / Q000009:adverse effects / Q000379:methods*; D011879:Radiotherapy Dosage; D013997:Time Factors; D047368:Tumor Burden / Q000528:radiation effects; D055815:Young Adult
chemical_list: D003287:Contrast Media; D005682:Gadolinium