title: Analysis of intraprostatic therapeutic effects in prostate cancer patients using [(11)C]-choline pet/ct after external-beam radiation therapy.
abstract: OBJECTIVE
  The objective of the present study was to analyze, with relatively high sensitivity and specificity, uptake properties of [(11)C]-choline in prostate cancer patients by means of positron-emission tomography (pet)/computed tomography (ct) imaging using objectively defined pet parameters to test for statistically significant changes before, during, and after external-beam radiation therapy (ebrt) and to identify the time points at which the changes occur.
  
  
  METHODS
  The study enrolled 11 patients with intermediate-risk prostate cancer treated with ebrt, who were followed for up to 12 months after ebrt. The [(11)C]-choline pet scans were performed before treatment (baseline); at weeks 4 and 8 of ebrt; and at 1, 2, 3, 6, and 12 months after ebrt.
  
  
  RESULTS
  Analysis of [(11)C]-choline uptake in prostate tissue before treatment resulted in a maximum standardized uptake value (suvmax) of 4.0 ± 0.4 (n = 11) at 40 minutes after injection. During week 8 of ebrt, the suvmax declined to 2.9 ± 0.1 (n = 10, p < 0.05). At 2 and 12 months after ebrt, suvmax values were 2.3 ± 0.3 (n = 10, p < 0.01) and 2.2 ± 0.2 (n = 11, p < 0.001) respectively, indicating that, after ebrt, maximum radiotracer uptake in the prostate was significantly reduced. Similar effects were observed when analyzing the tumour:muscle ratio (tmr). The tmr declined from 7.4 ± 0.6 (n = 11) before ebrt to 6.1 ± 0.4 (n = 11, nonsignificant) during week 8 of ebrt, to 5.6 ± 0.03 (n = 11, p < 0.05) at 2 months after ebrt, and to 4.4 ± 0.4 (n = 11, p < 0.001) at 12 months after ebrt.
  
  
  CONCLUSIONS
  Our study demonstrated that intraprostatic [(11)C]-choline uptake in the 11 analyzed prostate cancer patients significantly declined during and after ebrt. The pet parameters SUVmax and tmr also declined significantly. These effects can be detected during radiation therapy and up to 1 year after therapy. The prognostic value of these early and statistically significant changes in intraprostatic [(11)C]-choline pet avidity during and after ebrt are not yet established. Future studies are indicated to correlate changes in [(11)C]-choline uptake parameters with long-term biochemical recurrence to further evaluate [(11)C]-choline pet changes as a possible, but currently unproven, biomarker of response.
authors.affiliation: Division of Radiation Oncology, Department of Oncology, University of Alberta, Cross Cancer Institute, Edmonton, AB.
authors.forename: J
authors.initials: J
authors.lastname: Amanie
authors.forename: H S
authors.initials: HS
authors.lastname: Jans
authors.forename: M
authors.initials: M
authors.lastname: Wuest
authors.forename: N
authors.initials: N
authors.lastname: Pervez
authors.forename: A
authors.initials: A
authors.lastname: Murtha
authors.forename: N
authors.initials: N
authors.lastname: Usmani
authors.forename: D
authors.initials: D
authors.lastname: Yee
authors.forename: R
authors.initials: R
authors.lastname: Pearcey
authors.forename: B
authors.initials: B
authors.lastname: Danielson
authors.forename: S
authors.initials: S
authors.lastname: Patel
authors.forename: R
authors.initials: R
authors.lastname: Macewan
authors.forename: C
authors.initials: C
authors.lastname: Field
authors.forename: D
authors.initials: D
authors.lastname: Robinson
authors.forename: J
authors.initials: J
authors.lastname: Wilson
authors.forename: D
authors.initials: D
authors.lastname: Lewis
authors.forename: M
authors.initials: M
authors.lastname: Parliament
authors.forename: A J B
authors.initials: AJ
authors.lastname: McEwan
keywords: External-beam radiation therapy; [11C]-choline; ebrt; pet; positron-emission tomography
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