Modern prostate cancer imaging: application of the right scan at the right time

A new “opinion” article in the Journal of Clinical Oncology this week has addressed the complex issue of how best to think about (a) how we are regulating use of and (b) how we are applying new forms of imaging technique in the management of prostate cancer — and particularly in the management of high-risk, localized disease and early recurrence after first-line therapy.

The article by Vapiwala et al. initially notes that the use of MRI scanning in the monitoring of men on active surveillance seems to be getting swell worked out (but see below).  It then goes on to carefully capture a spectrum of other issues that are impacting current use (or non-use) of techniques like:

  • Traditional bone scintigraphic scans — using [99Tc]methylene diphosphonate (also commonly referred to as Tc-99m or 99Tc MDP)
  • Traditional CT scans
  • Multiparametric, prostate-specific  and pelvic MRI scans —
  • Whole-body MRI scans
  • [11C]choline PET/CT scans
  • [11C]acetate PET/CT scans
  • [18F]fluciclovine PET/CT scans (the Axumin PET/CT scans)
  • 18F-DCFPyl PET/CT scans
  • 68Ga-PSMA PET/CT scans
  • 177Lu-PSMA PET/CT scans

We are not going to get into the details here because the entire article is accessible on line for interested readers to look at for themselves. Suffice it to sat that critical issues currently impacting the use of these differing types of scan include:

  • The differing regulatory requirements for approval of these imaging techniques in different countries
  • The fact that although many of these techniques may facilitate identification of lesions that either suggest or confirm the presence of cancer outside the prostate, the identification of these lesions can actually lead to poor decisions about the treatment of individual patients
  • The differing costs associated with the differing types of imaging technique (which can vary considerably from country to country and center to center, for all sorts of reasons)

One item that is not addressed in the article — and which (arguably) deserved to be mentioned — is the issue of risk associated with use of gadolinium-based contrast agents (GBCAs) in many types of multiparametric MRI scan (see here). This is a controversial issue in which the relative benefits of using such contrast agents in order to facilitate high quality multiparametric MR images needs to be balanced against the risks for long-term gadolinium deposition, most particularly in the brain. We would note that, for some patients concerned about this risk, it may be possible to have biparametric as opposed to multiparametric MRI scans. Such biparametric MRI scans do not necessitate the use of GBCAs, and there is at least some data to suggest that biparametric MR images may be as good (or at least nearly as good) as the multiparametric MR images.

4 Responses

  1. Thank you for reviewing this article.

    Unfortunately, in the US, PSMA PET/CT scans are only available on a research basis to patients with already diagnosed prostate cancer, as they are not FDA approved. Hopefully, this will change soon and they will get FDA approval.

    It is worth pointing out that the past year has seen a plethora of studies comparing post-op whole-mount pathology and pre-op mp MRI in prostate cancer patients. They have all confirmed the limited utility of mpMRI in prostate cancer because of low sensitivity and underestimation of prostate cancer volume (by about two-thirds). This information is not common knowledge to all clinicians and their patients, and needs to be shared with them.

    Dr. Reiter at UCLA has gone so far to say that mpMRI is inadequate for use to monitor patients on active surveillance and that prostate biopsies will continue to be needed. The mpMRI/TRUS fusion prostate biopsies could still be potentially helpful in targeting specific areas of interest for biopsy.

    Hopefully, more really useful prostate cancer diagnostic tests will be available in the near future, as they are sorely needed.

  2. Dear Walter:

    It would be naive of anyone to think that:

    (a) mpMRIs are 100% accurate in determining the prognosis of all patients. They aren’t. We have known this for years now.
    (b) mpMRIs could replace biopsies completely in the monitoring of men on active surveillance. They can’t. This is also widely understood.

    mpMRIs offer an additional set of data in the evaluation of patients who either have or are suspected of having prostate cancer. They need to be used together with all of the other data that is traditionally collected in assessing risk: DRE data, PSA levels, PSA doubling times, biopsy data, Gleason grades (or grade groups), genomic data, you name it.

    No one that I am aware of has ever suggested that the use of mpMRIs (or any other form of scan) can be used to replace biopsies. The question of who needs to have repeat biopsies and with what level of frequency is still not well established — although I would point out that even Johns Hopkins has stopped giving all their patients on AS an annual biopsy (which is an unnecessary form of cruel, unusual, and risky punishment for a man with very low-risk prostate cancer). At the other end of the scale, there are patients on AS for intermediate-risk forms of prostate cancer who would be wise to consider annual MRI/TRUS fusion-guided biopsies together with traditional systematic 12-core biopsies (which can all be done in one biopsy session).

    With regard to the fact that “in the US, PSMA PET/CT scans are only available on a research basis”, we are well aware of this. The regulatory system here in the US is very different to the ones used in Europe and Australia, and that is why these forms of scans are still in research here in the US. Whether that is a good idea or not is something you would need to take up with the US Food and Drug Administration.

    It is my understanding that ASCO is currently developing new guidelines on the application of imaging tests in the management of advanced prostate cancer, and some of these issues will undoubtedly be addressed in those guidelines.

  3. Thank you for your reply. We are gifted to have a resource that truly understands prostate cancer diagnosis and treatment issues. The challenge is to educate patients sufficiently so they can make intelligent decisions for themselves.

    The reason this comment was made is that there may be variance in the use of mpMRI in AS, as demonstrated in a recent case review video on UroToday and an advisement in a recent Stanford University whole mount study that doctors need to warn patients that a negative MRI-guided biopsy does not totally rule out prostate cancer because of the MRI’s low sensitivity.

    Let’s face it, when you get a MRI, it is normal to expect that it will be able to reliably show if there is cancer as this is usually the case; in prostate cancer, this is not the case, unfortunately, and the average person could get a false sense of security. Making this exception well known would be of help to everyone, including patient and doctor, as it could make patients more receptive to repeat bxs when recommended.

    The PSMA PET/CT and other types of PET/CT scans could be a game changer in the diagnosis and staging of prostate cancer patients and is already being utilized for these purposes outside of the US. In the US, studies are ongoing in prostate cancer patients to plan radiation treatment and deliver radiation therapy like radioactive iodine is used to treat thyroid cancer.

    We can all look forward to this site keeping us up to date on this kind of progress. Thank you for the great job you are doing.

  4. Dear Walter:

    In fact, the belief that if you have an MRI it will always or nearly always find the cancer in association with the diagnosis of other forms of cancer is just as misguided as it is with prostate cancer. Multiple factors affect the ability to use MRIs to accurately identify any form of cancer in specific individuals. MRIs are not specific and there are all sorts of reasons why a specific tumor might not show up on a particular scan, three of which are scan, location, and interference of differing types with the quality of the image. On top of that, there is the matter of how well trained the radiologist is.

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