Clinical effects of abiraterone acetate in the “real world”


It is well understood that drugs can demonstrate better results during the highly controlled, closely monitored setting of a clinical trial than they do in the “real world”. This seems to be the case for abiraterone acetate (Zytiga) — at least when the “real world” is Hong Kong and for patients who were chemotherapy-naive at the time of their treatment with abiraterone acetate.

A recent paper by Poon et al. in BMC Urology reports on the authors’ (and their patients’) experiences from the use of abiraterone acetate in Hong Kong between August 2011 and December 2014. Poon et al. reviewed the clinical records of men with metastatic, castration-resistant prostate cancer (mCRPC) treated with abiraterone acetate at all six public oncology centers in Hong Kong over that time period.

Here is what they found:

  • A total of 110 patients with mCRPC were treated with abiraterone acetate.
    • 58/110 patients (53 percent) were chemotherapy naive.
    • 52/110 patients (47 percent) had received chemotherapy prior to the abiraterone (post-chemotherapy).
  • Average (median) follow-up times were
    • 7.5 months for the chemotherapy-naive patients
    • 11.4 months for the post-chemotherapy patients
  • Average (median) overall survival times were
    • 18.1 months for all the the chemotherapy-naive patients
    • 15.5 months for all the the post-chemotherapy patients
    • 2.8 months for the chemotherapy-naive patients with visceral metastases
    • 18.0 months for the chemotherapy-naive patients with no visceral metastases
  • Average (median) progression-free survival times were
    • 6.7 months for the chemotherapy-naive patients
    • 6.4 months for  the post-chemotherapy patients
    • 2.8 months for the chemotherapy-naive patients with visceral metastases
    • 6.8 months for the chemotherapy-naive patients with no visceral metastases
  • Pain control was similar in both groups of patients.
  • The rates of common grade 3 toxicities (e.g., hypertestion and hyperkalemia) were similar in both groups of patients.
  • The occurrence of a PS response within the first 3 months of treatment (i.e., a ≥ 50 percent drop in a patient’s PSA from baseline) was associated with favorable overall and progression-free survival times in the chemotherapy-naive and the post-chemotherapy groups.

In the original clinical trial of abiraterone acetate in the pivotal clinical trial (COU-AA-302) in men with chemotherapy-naive mCRPC, the median overall survival was 34.7 months, so the 18.1-month median overall survival in the current cohort is 16.6 months (or 48 percent) shorter. On the other hand, for the men with post-chemotherapy mCRPC in clinical trial COU-AA-301, the median overall survival was 14.8 months, compared to 15.5 months in the current cohort.

There are several possible explanations for the difference in the outcomes among the chemotherapy-naive patients. The “real world” chemotherapy-naive patients treated by Poon et al. in Hong Kong could well, for example, have been less healthy than the theoretically comparable patients treated in the formal clinical trials of abiraterone acetate. It could also be that if the patients in Hong Kong were all (or mostly) of Chinese ethnic origin, and that this also had an impact on their outcomes in some way.

The bottom line is that we always need to be cautious about whether the results achieved in clinical trials will be replicated in the “real world” of day-to-day clinical practice. This becomes especially important when the benefit demonstrated in a clinical trial is small to begin with.

One Response

  1. Amen!

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