219 Background: Digestive Neuroendocrine Neoplasms (DNENs) express in up to 80% of cases somatostatin receptors (SSTRs), which can be detected by Functional Imaging Tests (FITs). FITs are needed at DNENs first diagnosis to define therapy but their role in follow-up (FU) is unclear. Moreover, with the introduction of targeted therapies, RECIST criteria are showing difficulties to assess tumor response to these drugs. The aim of this study was to evaluate, in metastatic DNENs FU, the diagnostic yield of FITs associated to Computed Tomography scan (CT) in terms of detecting new distant metastases (primary outcome) and of clinical usefulness (secondary outcome). Methods: Retrospective analysis of stage IV DNENs expressing SSTRs and with at least 24 month-FU. From 1995 to 2008 FIT performed was Octreoscan (OCT), subsequently it was 68Ga-DOTA- PET/CT (GaPET). CT was repeated every 6-12 months, FIT yearly. FU time was divided into 12 month-“units”, in which each patient had faced at least 1 CT and 1 FIT. Units were analyzed separately and then compared to each other. The gold standard adopted was the result of the imaging tests, the surgical and pathological findings collected for each patient during FU. Clinical usefulness was defined as “appropriate changes” in management (indication to further imaging tests, surgery, biopsy, change in therapy) due to CT and/or FITs. Results: Interim analysis of 381 units (median 3 per patient, range 2-7) obtained from 121 patients included so far (67.8% metastatic since diagnosis). New lesions were detected by CT alone in 82.3% of cases; adding OCT, the diagnostic yield was 9.6%, while adding GaPET 21.7% (P<0.05). CT was responsible in 83.5% of cases of useful changes in patients management; adding OCT, the diagnostic yield was 9.7% (P<0.05), while with GaPET 27.9% (P<0.05). Conclusions: In metastatic DNENs FU, the addition of FITs to CT significantly improves the detection rate of new lesions; this advantage influences clinical practice increasing the clinical usefulness, especially when GaPET is adopted.
Sources of error with cardiovascular PET/CT and PET/MRI and questions to be answered to achieve clinical usefulness
