18F-Choline PET/CT and multiparametric MRI for the detection of early local recurrence of prostate cancer initially treated by radiotherapy: comparison with systematic 3D-transperineal mapping biopsy
Résumé
Purpose
To compare the diagnostic performance of 18F-Fluorocholine PET/CT (FCH-PET/CT), multiparametric prostate MRI (mpMRI) and a combination of both techniques for the detection of local recurrence of prostate cancer initially treated by radiotherapy.
Methods
This was a retrospective single-institution study of 32 patients with suspected prostate cancer recurrence, who underwent both FCH-PET/CT and 3T mpMRI within 3 months of one another for the detection of recurrence. All included patients had to be cleared for metastatic recurrence. The reference procedure was systematic 3D-transperineal prostate biopsy for the final assessment of local recurrence. Both imaging modalities were analyzed by two experienced readers blinded to clinical data. The analysis was made per-patient and per-segment using a 4-segment model.
Results
The median PSA at the time of imaging was 2.92ng/mL. The mean PSA doubling time was 14 months. Of the 32 patients, 31 had a positive 3D-transperineal mapping biopsy for a local relapse. On a patient-based analysis, the detection rate was 71% (22/31) for mpMRI and 74% (23/31) for FCH-PET/CT. On a segment-based analysis, the sensitivity and specificity were 32% and 87% for mpMRI, 34% and 87% for FCH-PET/CT, and 43% and 83% for the combined analysis of both techniques. Accuracy was 64, 65 and 66% respectively. The inter-observer agreement was kappa=0.92 for FCH-PET/CT and kappa=0.74 for mpMRI.
Conclusions
Both mpMRI and FCH-PET/CT show limited sensitivity but good specificity for the detection of local cancer recurrence after radiotherapy, when compared with 3D-transperineal mapping biopsy. Prostate biopsy still appears mandatory to diagnose local relapse and select patients who could benefit from local salvage therapy.