What we have learned from radiolabeled choline PET/CT scanning to date

A newly published paper in the Journal of Urology provides additional data on the role of sophisticated, modern scanning methods in the management of men with recurrent prostate cancer after first-line surgical treatment.

Specifically, the paper by Sobol et al. reports on data from the use of [11C]choline PET/CT scanning and multiparametric MRI (mpMRI) scanning at the Mayo Clinic — from 2008 to 2015 — in 202 men who had recurrent prostate cancer after surgery alone (i.e., no additional adjuvant or salvage radiation therapy, no hormone therapy, etc.). A media release from the Mayo Clinic also discusses this paper. These 202 men are just a subset of the nearly 2,500 men who have had an [11C]choline PET/CT scan for suspicion of prostate cancer recurrence during the same time frame.

  • Among these 202 men
    • 118/202 (58.4 percent) had their positive lesion(s) identified by both mpMRI and [11C]choline PET/CT.
    • 15/202 (7.4 percent) had their positive lesion(s) identified only by mpMRI.
    • 69/202 (34.2 percent) had their positive lesion(s) identified only by [11C]choline PET/CT.
  • When broken down by category of recurrence:
    • 68/202 men (33 percent) showed local-only recurrence.
    • 45/202 men (22 percent) showed local and metastatic recurrence.
    • 89/202 men (45 percent) showed metastatic-only recurrence.
  • Pelvic node node-only relapse was observed in 39/202 men (19 percent).
  • The patients’ average (median) PSA levels at the time of a positive scan were
    • 2.3 ng/ml for all 202 patients combined
    • 2.3 ng/ml for the 68 patients with local-only recurrence
    • 2.2 ng/ml for the 45 patients with local and metastatic recurrence
    • 2.7 ng/ml for the 89 patients with metastatic-only recurrence
  • The median times from PSA relapse to visualization the recurrent tumor were
    • 15.0 months for all 202 patients combined
    • 33.5 months for the 68 patients with local-only recurrence
    • 15.0 months for the the 45 patients with local and metastatic recurrence
    • 7.0 months for the 89 patients with metastatic-only recurrence
  • On multivariable analysis, the time from biochemical recurrence to positive imaging was independently associated exclusively with local-only
    recurrence (odds ratio = 1.10 for every 6-month increase, p = 0.012).

In their conclusion, the authors state that:

Combined choline positron emission tomography and multi-parametric magnetic resonance imaging evaluation of biochemical recurrence after prostatectomy reveals an anatomically diverse pattern of recurrence. These findings have implications for optimizing the salvage treatment of patients with prostate cancer with relapse following surgery.
 Now that is a fair conclusion, but what those implications may be for any particular patient are harder to discern. [11C]choline PET/CT scanning is available at only one site in America. Thus, a key question is going to be whether other forms of sophisticated scanning technique (e.g., the new Axumin-based PET/CT scan and others currently in development), when combined with mpMRI, can be more accessible for more patients and produce even better results.
Having said that, it is fair to point out that this study does clearly confirm some other conclusions:
  • Recurrence of what was originally thought to be a localized prostate cancer does not necessarily proceed in some type of stepwise fashion (i.e., in the prostate bed, and then the lymph nodes, and then to true metastatic disease) — but we already had many good reasons to understand that.
  • Recurrence of localized prostate cancer can be fast — and a great deal faster than the average of 8 years proposed many years ago by Pound et al. (in 1999), based on a subset of the highly selected patients treated by Walsh at Johns Hopkins, many of whom would probably be considered as good candidates for active surveillance today.

We are getting better at knowing how best to treat men with recurrent disease after their first-line treatment for presumed localized prostate cancer. The [11C]choline PET/CT scan has helped to contribute to that knowledge, but it is not going to be the answer that helps the majority of patients because access to this test is so restricted. We are going to need much better ways to identify, with accuracy, the location of early recurrent prostate cancer lesions so that we can treat them with a high degree of accuracy. And we may need to be able to use some of those tests in the work-up of higher-risk patients prior to any form of first-line treatment, because there is not much point in just removing someone’s prostate as first-line treatment if they already have a tiny metastatic lesion that is not visible on a bone scan or an mpMRI in somewhere like their bone marrow.

One Response

  1. I think you put your finger on it when you wrote that we need better ways of identifying the location of early recurrent cancer [emphasis mine]. The problem with [11C]choline PET/CT is that it isn’t very good at detecting cancer when PSA is less than 2 ng/ml. This was already too late for two-thirds of the men in their study. We know that outcomes are better when treated earlier. But salvage radiation therapy is futile if the cancer is already micrometastatic or detectably metastatic (M1). Patients can’t wait for PSAs to rise to search for distant metatasis with any PET scan, even fluciclovine, 68Ga-PSMA, or any of the other experimental ones. Of course, they must look for them anyway. It is frustrating, but a fact of life, that we will probably never have an imaging tool that can rule out all distant metastases at the time the patient must make the decision.

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