Practice Updates in Prostate Cancer Imaging - Episode 18
Dr Steven Finkelstein explains a clinical example of a 65-year-old patient with a history of robotic radical prostatectomy for Gleason 9 adenocarcinoma.
Neal Shore, MD, FACS: Let’s go to the next case. Steve, this is yours if you like to describe it. Then we’ll go to the imaging.
Steven Finkelstein, MD, DABR, FACRO: This is a 65-year-old gentleman with history of robotic radical prostatectomy in 2015 for Gleason 9 adenocarcinoma with extracapsular extension, involvement of seminal vesicle, and a positive margin. Obviously these are all worrisome things that would make a radiation oncologist think about the use of postprostatectomy radiation. His PSA [prostate-specific antigen] rose to 0.37 ng/mL. He got on androgen deprivation therapy and, ultimately, postprostatectomy radiation therapy by external beam. But his PSA started to rise. It went to 8 ng/mL. What would be the next step for you guys?
Neal Shore, MD, FACS: Let’s go to Larry. PSA is 8 ng/mL. Is there a role for getting a CT scan and a technician bone scan? Or do you go right to the PET [positron emission tomography] PSMA [prostate-specific membrane antigen]?
Lawrence Saperstein, MD: I’d go to the PSMA PET/CT at this point. Bone scan, which we’ve talked about, is notoriously insensitive. I’d love to hear what people think about this.
Michael Gorin, MD: This case and the prior case highlight 1 of the challenges that PSMA imaging has inserted into our field. In the past, these patients would have received conventional imaging. Assuming that was negative, we would have delayed initiation of hormonal therapy until they had sites of metastatic disease on that conventional imaging. On initiating that therapy, there was a benefit; however, if it were initiated prior to seeing metastatic disease, there was no benefit. Now, we’re taking patients who probably have negative findings on conventional imaging. We’re doing PSMA PET. We’re finding these sites of disease. Are these the few patients who would have benefit from androgen deprivation therapy [ADT] had we started it prior to conventional imaging findings? Or are we needlessly treating these patients because we’ve convinced ourselves that their disease state is different from what it had been in the past? I struggle with that. Should these patients be followed with conventional imaging at this point, and then we initiate systemic therapy? Because that’s all we have clinical data for.
Neal Shore, MD, FACS: It’s an excellent point. You’re right. You look at a study like the EMBARK trial, which is looking at patients very similar to this and has completely accrued. It’s pCR [pathologic complete response] with traditional ADT in the form of agonist vs agonist in androgen receptor inhibitor enzalutamide vs monotherapy enzalutamide. Everything has been done based on conventional imaging. But lo and behold, we now have the PSMA PET, which is bringing in new data but not the same level 1 evidence that we have with conventional imaging. Does it lead to some lead-time bias in starting T [testosterone] suppression or any other systemic therapy that we don’t have the evidence for? Nonetheless, it’s a fascinating time. Steven, you ordered a PET PSMA. What were your findings?
Steven Finkelstein, MD, DABR, FACRO: As you can see, there’s disease in the postprostatectomy bed. The disease is in this cut on the right seminal vesicle. But there’s also disease in other sites, potentially 2 or more bone sites of disease. What would you do here?
It’s very interesting. When we look at this case, we see disease that looks as if it’s in the right seminal vesicle. For many, we’d think that was surgically resected back at the initial postprostatectomy procedure. But speaking for myself—Mike, I’ll let you chime in—we’ve seen many patients with Axumin FACBC [fluciclovine 18F] imaging who now use next-generation imaging with PSMA imaging. We’re finding disease in areas that look like the seminal vesicles. Mike, do you want to comment about that?
Michael Gorin, MD: It’s not uncommon for someone who has recurred after radiation therapy to see disease in the seminal vesicle. Even in the early experience of robotic prostatectomy, there are times when parts of seminal vesicles or the entire seminal vesicles are left in situ, perhaps for nerve-sparing considerations and whatnot. Depending on the patient’s extent of disease, there’s a unique opportunity to re-treat the bed in an area that hasn’t been treated by the local therapies that have been delivered.
Steven Finkelstein, MD, DABR, FACRO: Yes, that’s a very important point. The other point I wanted to make highlights Mike and Larry’s data. When this patient was started on ADT because their PSA rose to 0.37 ng/mL, the mindset was that it’s only 0.37 ng/mL. But with respect to the data so eloquently presented by Mike, there is no threshold for waiting for to get that PSA was rising. You could have gotten that next-generation imaging in 2022, and maybe you would have seen that there’s a seminal vesicle…. Today gives us the opportunity to pull the trigger earlier, with earlier next-generation imaging, to help our patients find the true sites of disease.
Lawrence Saperstein, MD: Those are great points. From an imaging perspective, which may be helpful to the audience, we saw a benign bone lesion. These are unequivocally tumor lesions. What’s interesting is that on the bone windows, there’s no corresponding CT abnormality. That doesn’t change my impression of the scan. What may happen in the practical application is if the study is hedged, the patient may undergo an MRI or additional imaging, which probably isn’t necessary to call these metastases.
Transcript edited for clarity.