Ravi Madan, MD, discusses clinical findings utilizing PET imaging and Tc99 scans in patients with metastatic castration-resistant prostate cancer who are being treated with enzalutamide
At the 2021 European Society for Medical Oncology Annual Congress, CancerNetwork® spoke with Ravi A. Madan, MD, clinical director of the genitourinary malignancies branch at the Center for Cancer Research, National Cancer Institute, about key findings from a clinical trial (NCT01867333) utilizing PET imaging and paired technetium (Tc99) scans in patients with metastatic castration-resistant prostate cancer who are undergoing treatment with enzalutamide (Xtandi).
The key highlights of this research in the context of 1 big finding [that wasn’t] surprising [was that] we did a pretty good job of helping patients understand that staying on [drug] until radiographic progression was an important way of optimizing and really getting all the benefit you can out of enzalutamide. In a separate analysis that we previously presented, which isn't probably too surprising to people who use the drug, is that on average, [patients on] enzalutamide patients had a first [prostate-specific antigen] rise at 6 months but radiographic progression didn't occur until 23 months. That gave us an opportunity in the interim to evaluate what was going on [in] the sodium fluoride PET scans.
What we saw in this population that was treated with enzalutamide and immunotherapy...was that even though patients had stable disease on the Tc99 scans and were still deriving clinical benefit in terms of stable symptoms, a lot was going on [with] the Tc99 scans. But not all of that represented progression of disease, which, if they only got 1 or 2 scans, at certain intervals, it could have been misinterpreted. What we saw was, among these 18 patients [was] nearly 400 new lesions appear on the sodium fluoride scans, nearly 28% of [which] actually resolved over time. [Therefore], they weren't representing clinically relevant progressive disease, in my opinion. Of the 18 patients, 14 had lesions that appeared and disappeared despite stable technetium scans. One of the important takeaways is that even though you're seeing what could be considered new lesions or findings on a platform like sodium fluoride, it may not represent treatment failure.
Madan RA, Gandhy SU, Bilusic M, et al. Analysis of serial PET imaging and paired Tc99 scans in metastatic castration resistant prostate cancer (mCRPC) treated with enzalutamide. Presented at the 2021 European Society for Medical Oncology Annual Congress; September 16-21, 2021; virtual. Abstract 605P.