Suicide gene therapy for prostate cancer: some VERY early data


Data from a small, distinctly esoteric, Phase II clinical trial of a form of prostate cancer suicide gene therapy along with radiation therapy have suggested that such treatment may be able to stop the development of some early stage forms of prostate cancer (but such data need to be interpreted with great care).

Freytag et al. enrolled 44 patients who had been diagnosed with intermediate-risk, localized prostate cancer into this Phase II clinical trial, and the patients were randomly assigned to one or other of two forms of treatment:

  • Patients in Group A (n = 21) were initially treated with oncolytic adenovirus-mediated cytotoxic gene therapy (OAMCGT) and then with intensity-modulated radiation therapy (IMRT).
  • Patients in Group B (n = 23) were treated with IMRT alone.

The primary trial endpoint was acute toxicity in response to treatment (within ≤ 90 days). However, secondary endpoints were also evaluated and included quality of life (QOL), prostate biopsy (12-core) positivity at 2 years, freedom from biochemical/clinical failure (FFF), freedom from metastases, and survival.

Here are the core study findings:

  • Patients in Group A had a higher incidence of low-grade influenza-like symptoms, transaminitis, neutropenia, and thrombocytopenia than men in Group B.
  • There were no significant differences in gastrointestinal or genitourinary events or QOL between the two study groups.
  • Prostate biopsies were obtained from 37/44 patients (84 percent) at 2 years post-treatment.
    • 33 percent of men in Group A were biopsy-positive.
    • 58 percent of men in Group B were biopsy positive.
    • There was a relative reduction in biopsy positivity of 42 percent in the investigational arm (P = 0.13) — but this was an absolute reduction in positivity of only 25 percent.
    • There was a relative reduction in biopsy positivity of 60 percent in the investigational arm in men with < 50 percent positive biopsy cores at baseline (P = 0.07).
  • To date, 1 patient in each study group has exhibited biochemical failure.
  • No patient developed hormone-refractory or metastatic disease, and none has died from prostate cancer.

The authors conclude that:

Combining OAMCGT with IMRT does not exacerbate the most common side effects of prostate radiation therapy and suggests a clinically meaningful reduction in positive biopsy results at 2 years in men with intermediate-risk prostate cancer.

Some additional information is available on the Science Daily web site.

According to the trial information on the ClinicalTrials.gov web site, this trial was to be converted from a Phase II to a Phase II/III clinical trial enrolling some 260 patients. However, the current status of this trial seem to be rather vague, and whether it is actually enrolling all these patients is therefore less than clear.

While The “New” Prostate Cancer InfoLink does find these data interesting, they are a long way from being able to prove that this type of investigational therapy can actually cut the risk of progressive prostate cancer over a really significant time frame (10, 15, or 20 years) in men being diagnosed with intermediate-risk prostate cancer.

5 Responses

  1. A POTENTIAL SUCCESS BOOSTER AS AN ALTERNATIVE OR COMPLEMENT TO ADT

    Research has suggested that ADT is not as successful with intermediate-risk patients receiving IMRT as it is with higher-risk patients, though intermediate-risk patients generally have better results, as we would expect. It is encouraging to learn that there is another potential tool for further boosting success rates for intermediate-risk patients.

  2. LINK TO CLINICALTRIALS.GOV FAULTY — WONDERING ABOUT EXTENDED FOLLOW-UP

    I read the Science Daily article — thank you for the link, but the other link did not work. I’m wondering if further follow-up of these patients is underway. It would be useful to eventually see at least 5-year follow-up results,.

  3. USE IN HIGH-RISK CASES?

    As a high-risk guy who had 39 sessions for 78 Gy plus a pelvic boost (46 Gy) and 18 months of triple ADT in support (fourth round of ADT since 1999), I’m thinking this suicide gene therapy would likely also help high-risk men undergoing radiation as a complement to ADT. It’s probably much too early for research on that, but I’m wondering if there has been any buzz about that prospect. I’m thinking that well-done radiation + ADT for high-risk guys seems to have about an 80% success rate long-term, and that leaves a fairly substantial area for improvement, especially if the added side-effect burden is low.

  4. Link fixed … sorry.

  5. Jim:

    You’re doing an awful lot of speculating based on a 25% potential success rate over just 2 years on 21 treated patients! I think there’s a good deal of very basic work to be done before most of this speculation is worth the effort.

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