6533b833fe1ef96bd129c282

RESEARCH PRODUCT

Pattern of occult nodal relapse diagnosed with 18F-fluoro-choline PET/CT in prostate cancer patients with biochemical failure after prostate-only radiotherapy

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Abstract Introduction The purpose of this study was to describe the pattern of nodal relapse with 18 F-fluoro-choline (FCH) Positron Emission Tomography/Computerized Tomography (PET/CT) in prostate cancer patients after radiotherapy. Materials and methods Eighty-three patients had a FCH PET/CT at time of biochemical failure. Of 65 patients with positive findings, 33 had positive nodes. This analysis included 31 patients who had undergone prior prostate-only radiotherapy with or without a prior radical prostatectomy. Each FCH positive node was assigned to a lymph node station with respect to the CTV defined by the RTOG guidelines (CTV RTOG ). 3D mapping was performed after each node was manually placed in a reference planning CT scan after automatic co-registration of the two scans based on bone anatomy. Eighteen patients (58%) underwent focal salvage FCH PET-guided stereotactic radiotherapy with no hormones. Results Fourteen patients (45.2%) had a relapse outside the CTV RTOG . Of the 17 patients with a positive node inside the CTV RTOG , 15 had a single node (88.2%) while seven patients out of the 13 evaluable patients (53.9%) who had a relapse outside the CTV RTOG had ⩾2 positive nodes on FCH PET/CT (OR=8.75, [95% CI: 1.38–54.80], p =0.020). Relapses that occurred outside the CTV RTOG involved the proximal common iliac (19.3%) and lower periaortic nodes (19.3%) up to L2–L3. Conclusion 3D mapping of nodal relapses evaluated with FCH PET/CT suggests that with IMRT the upper field limit of pelvic radiotherapy could be extended to L2–L3 safely to cover 95% of nodal stations at risk of an occult relapse.