In this study, the authors assess PET/CT, an increasingly utilized imaging modality, as a comparator to traditional CT imaging in patients who have completed NAC and are scheduled to undergo radical cystectomy (RC). FDG-PET-CT scans were performed at 3 time points: prior to start of chemotherapy, after 2 cycles and after completion of the regimen. Patients who were down-staged from muscle-invasive to non-muscle invasive cancer (NMIBC) or had complete response (pT0) were considered to have a chemo-sensitive tumor. As an objective measure, they used percentage reduction in SUVmax from PET-CT scans.
This was a pilot study. 37 patients who had muscle invasive bladder cancer and underwent NAC followed by RC were included in the final analysis. Clinical data about the patients is below:
FDG-PET-CT had 78.5% sensitivity (95.6% specificity) in identifying complete pathologic responders (pT0) with a -100% change in SUVmax. On the other hand, 3 patients with complete resolution of the primary tumor on PET-CT had a residual pT1 tumor on pathology (false positive).
PET-CT had 83% sensitivity (94% specificity) for the detection of chemo-sensitive tumors (pT0 or downstaging to NMIBC). Only one patient had complete resolution of cancer on imaging but had a small focus of pT2 on final pathology (false positive).
Two patients had 71.7% and 68% reduction in SUVmax and had pT1 and pTis on final pathology respectively, but did not meet the study criteria to be considered as a chemo-sensitive tumor.
While it would appear that FDG-PET-CT can help determine the response of the primary tumor to neoadjuvant chemotherapy in patients with muscle-invasive bladder cancer, they did not compare these current imaging standards such as CT and MRI – and unfortunately, it is is not, therefore, clear if it is cost-effective. If they provide the same degree of information, then is it worth it?
Presented by: Ayman Soubra, University of Minnesota, Minneapolis, Minnesota
Co-Authors: Mehmet Gencturk, Jerry Froehlich, Priya Balaji, Shilpa Gupta, Gautam Jha, Badrinath Konety
Written by: Thenappan Chandrasekar, MD, Clinical Fellow, University of Toronto, @tchandra_uromd at the 2018 AUA Annual Meeting - May 18 - 21, 2018 – San Francisco, CA USA