Influence of (11)C-choline PET/CT on the treatment planning for salvage radiation therapy in patients with biochemical recurrence of prostate cancer.

BACKGROUND AND PURPOSE: The present study evaluates the incidence of (11)C-choline PET/CT positive findings in patients with recurrent prostate cancer referred for salvage radiotherapy (SRT) and the influence on the definition of the planning target volume (PTV).

MATERIAL AND METHODS: Thirty-seven patients treated with radical prostatectomy and referred to SRT to the prostatic fossa because of biochemical relapse, were analysed retrospectively. All patients underwent (11)C-choline PET/CT before radiotherapy. The influence of PET/CT on the extent of the PTV was analysed. The median total follow up after SRT was 51.2 months.

RESULTS: 11/37 (30%) patients had a positive finding in the (11)C-choline PET/CT, 5 (13%) outside of the prostatic fossa (iliac lymph nodes), implicating an extension of the PTV. Patients with positive (11)C-choline PET/CT had a significant higher PSA value than patients with no pathologic uptake (p=0.03). Overall, at the end of follow up 56% of the patients had a PSA ≤ 0.2ng/ml and 44% had a biochemical relapse of prostate cancer.

CONCLUSIONS: (11)C-choline PET/CT detects abnormalities outside of the prostatic fossa in 13% of patients referred for SRT because of biochemical relapse after radical prostatectomy, affecting the extent of the PTV. Prospective studies need to be implemented to evaluate the benefit of SRT with a PTV based on (11)C-choline PET/CT.