The Role of Radiology in Metastatic Prostate Cancer

Rajan T. Gupta, MD:Imaging is used for the diagnosis of metastatic prostate cancer in many different ways. We can be looking for solid organ metastatic disease as well as bone metastatic disease. Depending on the situation with the PSA, we may be looking at different areas. So, the different modalities that are available inside of the armamentarium of the radiologist, as well as the oncologist, is CT, PET/CT, MRI, and then also some multiparametric MRI of the prostate.

The decision tree about when to do imaging in patients with metastatic prostate cancer is dependent on local patterns as well as some of the national guidelines. I think the key things we have to be looking at are, what kind of treatment the patient had, what their PSA trajectory is, and what is their level of suspicion that they have metastatic disease—whether that be clinical symptoms, etc.

So, some people are advocating seeing CT or PET/CT at intervals every 6 to 12 months. I think that it really has to be personalized depending on the patients’ PSA situations and also looking at some of the national guidelines. One of the things about prostate cancer is, every patient is very unique, and so some of the experiences that we’ve had have shown me that some people manifest their disease in very, very different ways. I think choosing the right imaging modality is as critical as how often we do the imaging. And so, trying to identify where the most suspected site of recurrence is going to be—is that going to be a wildly metastatic disease or an oligometastatic disease pattern—is extremely important. I think choosing the imaging modality is really, really critical in assessing it. And with some of the new advents in technology out there with regard to new types of PET technology, I think it’s a very exciting time to be able to offer these types of modalities to our patients.

So, the patient who we talk about in this case here is really interesting in the fact that they had what was suspected to be low-grade disease and then they were on active surveillance for a long time. Once a decision was made to actually pursue more active treatment, part of that was informed by a biopsy change that had shown that they actually had more aggressive disease, and I think that that’s a potential place where we could implement something like multi-parametric MRI to assist.

The ability of multi-parametric MRI is really to inform decision making by talking about the degree and grade of the tumor, as well as the possibility of extra prostatic extension. So, I think that that’s one place where we could have implemented imaging. I think the guidelines are stating to us that in patients with PSAs below a certain level, CTs really aren’t that helpful in assessing for metastatic disease and then specifically assessing for local progression of disease. I think before the metastatic disease, multi-parametric MRI could be a very helpful technique for assessing the grade of this person’s tumor.

After the development of metastatic disease, I think the critical aspects about determining the intervals for imaging should be the PSA and also a symptomatology from a clinical standpoint. So, if this patient has developed bony metastatic disease, as we’ve seen on both the CT as well as on the PET scan, we want to ensure that should the patient’s symptoms worsen at all, we image them to make sure that they don’t have any complications of these metastatic diseases in their bones. In addition, we want to make sure that we have enough cross-sectional imaging as well to ensure about the presence or absence of lymph node metastatic disease and also solid organ metastatic disease as well.

I think multidisciplinary care is at the very heart of prostate cancer care and really all oncology care right now. I feel very fortunate to be part of a group that talks about cases at length when we have patients come in, and really, the patient comes to one room and all of us rotate around that patient. That discussion can be extremely helpful: the radiologist providing some guidance as to what imaging tests are available, the oncologist providing some guidance as to what they might be looking for, and the radiation oncologist and the urologist being informed and being aware of what the possible options are with regards to treatment. So, I think it’s a really helpful thing and it’s hopefully where prostate cancer care is going all over the world.

The most critical thing in regards to multidisciplinary collaboration is communication and having regular meetings where we get a chance to talk about these patients, how they’re doing, and also how each of our groups can assist the other. I think that is the most important part of coordinating care. I think having tumor boards as well as multidisciplinary case conferences where these more straightforward cases, but also the more difficult cases, are discussed is extremely helpful and will really help our patients.

Transcript edited for clarity.

November 2014

• A 55-year old gentleman presented with nocturia and PSA level of 4.5 ng/mL
• PMH: Insignificant
• DRE revealed an abnormal area of hardness
• Biopsy showed adenocarcinoma of the prostate gland with a Gleason score 6 [3+3], clinical tumor stage T1c                                                                                                                                                                  
• The patient remained on active surveillance

November 2015

• When he returned after 1 year:
  • PSA, 10 ng/mL
  • Repeat biopsy showed Gleason 7 [4+3] with 8 of 12 cores positive
  • CT scan was negative for metastases
  • He remained asymptomatic
• He was started on a 3-month depot injection of goserelin

February 2016

• PSA, 34 ng/mL
• CT scan was negative for metastases
• He was started on abiraterone and prednisone
  • PSA declined to 15 ng/mL and remained stable
  • After 4 months, he developed cardiac arrhythmia attributed to prednisone; he was switched to enzalutamide
  • PSA remained stable

August 2016

• 3 months following therapy switch, the patient complained of severe fatigue
  • CT scan showed enlarged lumbar spine and pelvic bone metastases
  • ¹⁸F-FDG PET showed increased FDG uptake in several areas of the lumbar spine and pelvis
  • PSA, 45 ng/mL
  • ALP, 225 U/I
• Radium-223 therapy was initiated and enzalutamide was continued
• After 4 cycles of radium-223:
  • Fatigue decreased significantly
  • PSA, 25 ng/mL
  • ALP, WNL
  • CT showed no new bone metastases