Combination of DWI/DCE-MRI and [18F]FECH PET/CT in Patients with Biochemical Relapse of Prostate Cancer: Impact on Treatment Decision Making, EANM’14, Annual Congress of the European Association of Nuclear Medicine

Background/Aim: In prostate cancer (PCa) patients with biochemical recurrence, distinguishing between local and distant failure is crucial to choose the most suitable treatment. In this study we assessed if the combination of f‐MRI and [18F]FECH PET/CT could serve to optimize treatment decision making in patients with recurrent PCa after curative first‐line treatment. Patients and Methods: 30 patients (mean age 72±7 yr) with biochemical relapse of PCa presenting about 6 yr after radical prostatectomy (mean total PSA 3.3 ng/mL) underwent consecutive DWI/DCE‐MRI (including T1‐weighted fat suppressed T2‐weighted, DWI, and contrast enhanced fat suppressed T1‐weighted images) (GE Signa Exite HD 12.0, GE, Milwaukee, WI) and [18F]FECH PET/CT dynamic PET imaging of the pelvic region + whole‐body images (Discovery 690; GE, Milwaukee, WI), for a total of 60 studies. Each exam was classified as: indeterminate, negative or positive. Positive scans were further classified as positive for local relapse (candidate for standard salvage EBRT), oligo‐metastatic (≤5 total lesions, candidate for EBRT) and pluri‐metastatic disease (>5 total lesions, candidate for hormonal therapy, ADT). Results: The combination of DWI/DCE‐MRI and [18F]FECH PET/CT detected disease recurrence in 27/30 patients: local relapse in 7, oligometastatic in 18 and plurimetastatic in 2. MRI was clearly superior in detecting local recurrence, by revealing local relapse in 9 patients versus 3 patients detected by [18F]FECH PET/CT. On the other hand, [18F]FECH PET/CT detected more tumor lesions in case of metastatic disease, thus allowing accurate definition of treatment planning. Indeed, in 15/26 patients PET/CT visualized lesions undetected by MR; such lesions were subsequently treated with EBRT/HD IGRT in 13/26 cases; in the remaining 2 patients disease was eventually classified as plurimetastatic and treated with ADT. Patients’ follow‐up is ongoing. Conclusion: By combining DWI/DCE‐MRI and [18F]FECH PET/CT we were able to impact on the subsequent patients' management by increasing the number of patients treated with EBRT/HD IGRT instead of ADT and by a more accurate definition of the number of lesions included in the radiation planning. Because of the high detection rate reached by combining DWI/DCE‐MRI and [18F]FECH PET/CT, it seems feasible to select therapeutic strategies based on the pattern of disease recurrence, thus introducing new treatment options for patients who would have been treated with ADT (an expensive treatment with potentially serious long‐term side‐effects), which can be reserved in case of subsequent disease progression.