48 hours at the IMPaCT symposium in Orlando: Part I

Most medical-scientific meetings that deal (at least in part) with prostate cancer are inhabited by academic scientists, clinicians, and various types of representative of commercial companies. Sightings of actual patients are relatively few and far between.

So what makes the IMPaCT meeting dramatically different is the fact that something like 15 to 20 percent of all the attendees at this meeting are prostate cancer patients, interacting directly with basic scientists and clinical researchers. Patients are session moderators. They get up and ask detailed scientific questions during the discussion sessions. And some even present posters themselves at the meeting.

The IMPaCT meeting takes place every two years, and is where all of the researchers who are given grants through the Prostate Cancer Research Program of the Congressionally Directed Medical Research Program (CDMRP) are required to come and present the results of their research to their peers and to the patient members of the peer review teams who participate in deciding who is to get such grants. (The CDMRP is the program that Senator McCain announced on Wednesday should be eliminated from the Department of Defense’s budget.)

Most of the research presented at the IMPaCT meeting is truly early stage research into everything from whether we can find new markers for early and late stage disease to whether specific biological pathways may be targets for the development of new types of treatment. Another focus is on issues underlying disparities between risk for prostate cancer and access to high quality therapy. However, one area is also on the earliest stages of clinical testing of possible new drugs, funded by the Prostate Cancer Research Program through the Prostate Cancer Clinical Trials Consortium. (On Thursday we reported early data from a Phase II clinical trial of cediranib, which is being carried out through the PCCTC.)

In addition to the presentation of completely new data, there are also discussions of issues that underlie new research. As an example of this type of presentation it is worth mentioning a presentation made this morning by Dr. Bob Vessella from the University of Washington.

We have known for years that some men who appear to have highly successful responses to first-line treatment with radiation or surgery, and who have undetectable PSA levels for years, may unexpectedly have disease recurrence 5, 10, or 15 years after their initial treatment (out to as long as 25 years). These men are said to have “dormant” forms of prostate cancer, with small numbers of prostate cancer cells identifiable in bone marrow, and Dr. Vessella and his colleagues have been trying to work out whether, among those patients who have such dormant cell groups in bone, who may be at greater or lesser risk for a recurrence.

Vessella is careful to differentiate between circulating tumor cells (CTCs) that are found in the bloodstream and disseminated tumor cells (DTCs) that are actually fixed in tissue (most commonly in bone). And it is valuable for patients to understand four things:

  • Even in men with apparently localized prostate cancer, as many as 50 percent or higher can be shown to have DTCs in bone based on bone marrow assays at the time of diagnosis and initial treatment.
  • Despite the presence of such DTCs in bone marrow, the majority of these men do not, subsequently, show any sign of metastatic disease, so these DTCs are not necessarily an indicator of clinically aggressive disease.
  • At present we have no good and standardized ways to identify and isolate DTCs from bone marrow in ar reliable and reproducible manner.
  • At present we have no way to be able to tell which men with which types of DTC in bone marrow can be told, with any degree of accuracy, whether they might or might not have recurrent disease after first-line treatment.

From the viewpoint of the individual patient today, however, what is important is the implications of this knowledge, and that is the following:

  • No one can tell you with certainty that you have been “cured” by any first-line or second-line treatment. There is always at least a small possibility that one or more dormant cells somewhere in your bone marrow could start to grow and metastasize years after successful treatment.
  • Regular PSA testing for at least 10 years from the time of your initial treatment is important, but after 10 years, if your PSA level is still very low and stable, it may be possible to stop regular PSA tests because your chances of recurrence are so low.
  • We have a long way to go in understanding the biology of prostate cancer if we are going to be able to prevent these types of late stage disease recurrence — and the earlier recurrences of the patients with more aggressive forms of this disease.

2 Responses

  1. “We have known for years that some men who appear to have highly successful responses to first-line treatment with radiation or surgery, and who have undetectable PSA levels for years, may unexpectedly have disease recurrence 5, 10, or 15 years after their initial treatment (out to as long as 25 years). ”

    Are there any data on the percentages of men experiencing recurrence after 5, 10, 15 years?

  2. Reuven:
    I am not aware of any reliable data from large, long case series that have attempted to assess new progressions at 5, 10, and 15 years post-surgery. There are probably only a few well documented case series from which it might be possible to extract such data. What I am sure about is that at 10 years and longer it is a very, very small percentage of patients. My guess would be that if your PSA is low and stable after first- or second-line therapy for 10 years, we are talking about well under 1% of such patients having a metastaic recurrence based on dormant DTCs in bone marrow.

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