title: Comparative evaluation of 201Tl SPECT and CT in the follow-up of irradiated brain tumors.
abstract: BACKGROUND
  Radiation-induced changes in post-irradiated brain tumors may produce morphological alterations similar to those of tumor recurrence on computed tomography (CT). However, 201Tl single-photon-emission computed tomography (SPECT), with its ability to image metabolic changes, may differentiate post-irradiated gliotic changes from metabolically active congregations of viable tumor cells. This study was carried out to compare these two imaging modalities for the follow-up evaluation of post-irradiated brain tumors.
  
  
  METHODS
  Thirty-five patients with previously irradiated primary brain tumors were evaluated for this study. 201Tl SPECT and CT were carried out during follow-up, which ranged from 3 to 125 months (median, 18 months). These findings were compared with the clinical outcome, as observed during the subsequent follow-up.
  
  
  RESULTS
  Sensitivity, specificity, and the overall accuracy of 201Tl SPECT were 82.7%, 83.3%, and 82.8%, compared to 58.6%, 66.6%, and 58.3%, respectively, for CT. Post-scan progression-free survival (PFS) was significantly different for those patients having positive and those having negative evidence of tumor recurrence based on the imaging studies during follow-up. However, PFS was better correlated with 201Tl SPECT results than with the CT results. With 201Tl SPECT, median PFS was 4 months for those with positive reports, versus 33 months for those with negative reports (P = 0.003), compared to a corresponding median PFS of 3 months versus 14 months (P = 0.025), respectively, with CT. On multivariate analysis, age and 201Tl SPECT were the only significant variables for predicting post-scan PFS.
  
  
  CONCLUSIONS
  201Tl SPECT, with its ability to be taken up by viable tumor tissues, is superior to CT for the follow-up evaluation of post-irradiated brain tumors.
authors.affiliation: Department of Radiotherapy, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Rae Barelli Road, Lucknow-226014, India. nrdatta@sgpgi.ac.in
authors.forename: Niloy Ranjan
authors.initials: NR
authors.lastname: Datta
authors.forename: Rajesh
authors.initials: R
authors.lastname: Pasricha
authors.forename: Sanjay
authors.initials: S
authors.lastname: Gambhir
authors.forename: Shambhu Nath
authors.initials: SN
authors.lastname: Prasad
authors.forename: Rajendra Vishnu
authors.initials: RV
authors.lastname: Phadke
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging / Q000473:pathology; D001932:Brain Neoplasms / Q000175:diagnosis* / Q000401:mortality / Q000532:radiotherapy*; D002648:Child; D018572:Disease-Free Survival; D005260:Female; D005500:Follow-Up Studies; D005910:Glioma / Q000175:diagnosis* / Q000401:mortality / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis / Q000209:etiology / Q000401:mortality; D011237:Predictive Value of Tests; D011859:Radiography; D019275:Radiopharmaceuticals; D011878:Radiotherapy / Q000009:adverse effects*; D012680:Sensitivity and Specificity; D013794:Thallium Radioisotopes; D013997:Time Factors; D015899:Tomography, Emission-Computed, Single-Photon; D041622:Tomography, Optical; D016896:Treatment Outcome
chemical_list: D019275:Radiopharmaceuticals; D013794:Thallium Radioisotopes