Abstract
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Objectives Leiomyosarcoma (LMS) is the most common subtype of uterine sarcomas, rare and aggressive tumours, considering carcinosarcoma as subset of endometrial carcinoma. The aim of the study was to assess the performances of F-18 FDG PET/CT in four clinical settings: initial staging, restaging, monitoring of response to therapy and post-therapy surveillance of uterine LMS. A secondary end-point was the search for prognostic value in initial staging or monitoring of response to therapy.
Methods A bicentric retrospective study was performed including 21 patients with uterine LMS for whom a total of 52 PET/CT scans were available in initial staging (n=11), restaging (n=11), monitoring of response to therapy (n=17) and post-therapy surveillance (n=13). Clinical (minimum six months after PET/CT scan) and/or imaging follow-up and histopathology were used as the reference standard.
Results In initial staging, the sensitivity, specificity, accuracy, positive predictive value and negative predictive value of PET/CT were 80%, 100%, 90.9%, 100% and 85.7%, respectively. In restaging and monitoring of response to therapy, all these indices were 100% whereas they were lower in post-therapy surveillance: 75%, 100%, 84.6%, 100% and 71.4%, respectively. False negative lesions were an infracentimetric lung nodule in initial staging and a peritoneal nodule increased in size between two PET/CT scans in post-therapy surveillance. PET negative lesions were all identified on the CT part of the PET/CT. FDG-avid metastases were frequently located in the lung (n=9), bone (n=6), iliac and retroperitoneal lymph nodes (n=6) and muscles (n=5). In initial staging, PET/CT showed visceral metastases (bone and lung) in one patient and lymph node metastases in another. PET/CT detected metastatic lesions in two patients before contrast enhanced CT scan: one peritoneal nodule in suspicion of recurrence and one bone lesion in systematic surveillance. No correlation was found between PET/CT results in initial staging and overall survival (p=0.91) or progression free survival (p=0.70), nor with PET/CT in monitoring of response to therapy and overall survival (p=0.07).
Conclusions F-18 FDG PET/CT has high diagnostic yield in initial staging and restaging of uterine LMS, but seems less sensitive in post-therapy surveillance. Evaluation of the CT part improves the sensitivity of PET scan. No prognostic value was found, but confirmation of the results in a larger study is needed.