AUA 2018: FDG-Positron Emission Tomography for Assessing the Response to Neo-Adjuvant Chemotherapy in Bladder Cancer Patients

San Francisco, CA ( Neoadjuvant chemotherapy (NAC) is a standard of care for muscle-invasive bladder cancer (MIBC), though the overall survival benefit is modest. Though it is not without its adverse effects, it is still recommended for all eligible patients prior to radical cystectomy. Yet, many medical oncologists will consider imaging during NAC or at the end of NAC to assess chemotherapy response and re-stage patients. Unfortunately, there is no consensus on the utilization or modality of this repeat imaging – and the interpretation of the anatomic information provided by CT scan or MRI is challenging post NAC because any hemorrhagic inflammation and necrosis can mimic a residual tumor. 

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:

UroToday AUA2018 FDG PET CT

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
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