11C-Choline PET-CT in planning curative radiotherapy in prostate cancer

Abstract

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Objectives: Radiotherapy of the prostate or its bed is used in patients with primary or recurrent prostate cancer (PC). It was the aim of this study to assess the influence of 11C-Choline PET-CT on the therapeutic strategy in PC.

Methods: 35 patients (23 primary PC, 12 suspected local recurrent PC, mean age 69 years, mean PSA 7.8 ng/ml) were studied with 11C-Choline PET-CT, using a positioning technique suitable for radiotherapy planning. An experienced radiotherapy physician decided, whether PET-CT findings affected the therapeutic strategy (palliative instead of curative, choice of RTX technique, or other).

Results: Choline uptake in the prostate was present in 22/23 primary PC. PC patients with suspected recurrence showed variable accumulation in the prostate bed. Results of 11C-Choline PET-CT suggested a change in the therapeutic concept in 2/23 patients (9%) with primary PC (2 suspected lymph node metastases, one being false positive). In 2/12 (17%) patients with suspected local recurrence the results of 11C-Choline PET-CT suggested a change in concept (suspected locoregional lymph nodes (2), suspected bone metastasis (1)). Besides the three cases, 11C-Choline PET did not change initial indication of curative local radiotherapy or CT based target volumes.

Conclusions: 11C-Choline PET had little impact on the therapeutic strategy in patients referred for radiotherapy of PC. A high proportion of patients on antihormonal therapy (n=10) and of patients with low PSA levels may explain the relatively low incidence of positive findings outside the prostate (bed). Yet no PET-CT based local dose-escalation was intended in the present group. 11C-Choline PET-CT may have the potential of defining individualized and PET-guided dose-distributions using IMRT.