Impact of 18FDG-PET CT in the management of invasive bladder cancer.

Abstract

444 Background: Guidelines do not recommend FDG-Positron Emission Tomography (PET) Computed Tomography (CT) for the staging of Muscle Invasive Bladder Cancer (MIBC), but rather CT scan for lymph node (LN) and metastatic staging, despite its low accuracy. We performed a retrospective analysis of patients (pts) with MIBC who had a FDG-PET CT for staging, indicated by multidisciplinary team, in two centers, and analyzed its utility in this setting. Methods: All pts who had a FDG-PET CT performed at the time of diagnosis of MIBC from 01/2005 to 12/2017 in Bordeaux (Bergonie Institute and University Hospital) were retrospectively reviewed. Nodal and metastatic staging on CT and FDG-PET CT were done independently according to the 8th TNM classification. The aims of the study were to evaluate the accuracy of the FDG-PET CT for LN staging and to determine the rate of treatment modification (neoadjuvant chemotherapy for curative intent, no surgery for metastatic disease), according to FDG-PET CT results. Results: Among the 130 pts included, with a median age of 65 years, 74% were considered free from nodal metastasis (N0) by CT whereas only 44% were N0 from FDG-PET CT. Based on CT results, 88% of pts were free from distant metastasis (M0) but only 75% were classified M0, on FDG-PET CT. Accuracy of LN staging for CT and FDG-PET CT at initial diagnosis were analyzed for 85 pts (including 70 pts treated with neoadjuvant chemotherapy) and compared to pathological examination of resected LN. Sensitivity of FDG-PET CT was better than CT (respectively 80.8% versus 26.9%) but the specificity was low (respectively 54.2% versus 83.1%). Youden index was better for FDG-PET CT (0.35; 0.1 for CT), being more accurate for determining LN staging of MIBC. FDG-PET CT findings allowed a treatment decision modification in 34/130 pts (26.1%): therapeutic intensification in 12 pts (9.2%), including surgery not previously indicated, modified radiotherapy; or de-escalation in 22 pts (16.9%), mostly avoiding surgery. Conclusions: FDG-PET CT is more sensitive to detect LN involvement at initial diagnosis of MIBC than standard CT scan. Moreover, in the present study, treatment decisions were modified, according to FDG-PET CT results, in a quarter of pts according to LN and distant metastatic staging.