Can CTC levels predict progression of hormone-sensitive prostate cancer?

The levels of circulating tumor cells (CTCs) — as evaluated using Cellsearch technology — is becoming accepted as a prognostic marker for disease progression among men with  metastatic castration-resistant prostate cancer (mCRPC), and may even be accepted soon as a surrogate marker for prostate cancer-specific mortality in clinical trials of new agents.

By comparison, there is very little good information about the potential value of CTC levels in the management of men with earlier stages of prostate cancer, most especially in men with micrometastatic and metastatic but hormone-sensitive prostate cancer.

Goodman et al. have now reported initial data on CTC levels in a small group of men with metastatic, hormone-sensitive prostate cancer (mHSPC). The data are based on a series of 33 consecutive patients, all of whom had mHSPC and were starting androgen deprivation therapy (ADT) at the Nevada Cancer Institute. The authors carefully tracked serial CTC values along with PSA levels and other recognized prostate cancer biomarkers from immediately prior to the initiation of ADT through to the evident onset of  metastatic, castration-resistant prostate cancer (mCRPC).

The results of this study are given below:

  • Baseline CTC levels correlated positively with levels of lactate dehydrogenase and alkaline phosphatase.
  • Baseline CTC levels were not related to serum levels of PSA and testosterone.
  • In univariate analysis, several individual biomarkers were predictive of progression to mCRPC, including
    • Baseline CTC level
    • Alkaline phosphatase
    • Lactate dehydrogenase
    • Serum testosterone
    • Follow-up CTC levels
  • In multivariate analysis, only baseline CTC levels retained independent predictive value.
  • The cutpoint CTC level that optimized specificity and sensitivity of the test was estimated to be 3 CTCs per 7.5 ml whole blood.
  • Baseline CTC levels also correlated well with benchmarks for nadir PSA values.

Goodman et al. conclude that baseline CTC values among patients with mHSPC are potentially predictive of the duration and magnitude of response to hormonal therapy, and may help to identify patients at risk of progression to mCRPC before initiation of ADT.

Clearly there is a great deal more work to be done, but it is possible that accurate enumeration of CTCs may make it possible to better project response to specific types of hormone therapy over time.

2 Responses

  1. Thank you very much for posting about this research. Those of us on long-term intermittent androgen deprivation therapy are naturally interested in knowing whether we are approaching a turning point where first-line therapy will no longer work, and it appears that CTCs may be an important indicator.

    I’m also thinking that CTCs may also help in comparing single, combined, and triple/maintained (5-ARI inhibitors) androgen deprivation therapy. I expect that CTCs would be less prominent for longer periods under triple therapy.

  2. I had/may still have high hope for the CTC test. I know one case doesn’t make or break the issue. My very good friend Bert had 0 CTC count a few weeks before dying of prostate cancer. It was disappointing to say the least … I wonder if someone botched that test.

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