Understanding “cell-free DNA analysis” in cancer diagnosis and management


We have probably all heard terms like “liquid biopsy” and “genetic screening” and “cell-free” DNA analysis over the past few years. These are all terms related to the use of genetic and genomic information to “personalize” cancer diagnosis and its management. And they are potentially a huge big deal. But, … at the moment we are still in the early stages of knowing how to use these types of genetic/genomic test in the diagnosis and management of cancer in general and prostate cancer in particular.

In a newly published paper in the New England Journal of Medicine this week, there is a truly excellent review article by Corcoran and Chabner entitled “Application of cell-free DNA analysis to cancer treatment“. Your sitemaster has been able to read the full text of this article. Unfortunately this is not freely available on line, but we would encourage interested readers, support group leaders, and other prostate cancer educators and advocates to try to get themselves a copy of this article if trhey can do so because it provides a thorough but reasonably accessible explanation of just how we may be able to use cell-free DNA analysis (most particularly using blood samples, but also using other liquid samples like urine, saliva, cerebrospinal fluid, etc.) over the next 20 years or so, in the diagnosis and management of almost all known types of cancer.

Because the article has been written primarily for primary care physicians (as opposed to cancer specialists) it is very focused on avoiding all the technical language often associated with papers on cancer genetics, and deals in a very straightforward manner with the following potential areas of clinical application of cell-free DNA analysis:

  • Diagnosis and molecular profiling (and whether the use of cell-free DNA analysis can now be used in this setting with a high degree of accuracy)
  • Tracking of therapeutic responses to specific type of therapy
  • Monitoring of the development of resistance to specific types of treatment and the importance of tumor heterogeneity (i.e., the fact that not all types of prostate cancer or other cancers are exactly the same)
  • The detection of residual disease after first-line therapy (with a particular focus on post-surgical residual disease)
  • Early detection of specific types of cancer

It is worth noting that, with respect to the last item, the authors state the following:

The holy grail of liquid biopsy applications is the potential for early cancer detection through a simple blood test in  otherwise healthy, asymptomatic persons. At present, no mature technology exists to achieve that goal …

So, we do still have to temper our expectations of the possible, but just because something isn’t possible yet doesn’t mean that it won’t be possible in the future. Jules Verne imagined sending a man to the Moon in a spaceship in 1865. It only took 104 years to make that happen. My suspicion is that the speed of progress of development of genetic risk profiling will be a good deal faster, and that we may be able to diagnose at least some very specific types of risk for clinically significant prostate cancer within 20 years. Whether we will be able to afford to use such a test as a method to screen for prostate cancer risk is a rather different question. The cost may still be prohibitive.

4 Responses

  1. At SWOG we call is circulating tumor DNA or ctDNA. But we are a long way away from a usable “biopsy”.

  2. There are so many genetic tests out there, what is one of the best DNA health analysis test available for patients to purchase?

  3. Dear Robert:

    That rather depends on what you are trying to find out. Most of the consumer-directed tests (like 23&Me and Ancestry, for example) don’t actually provide a great deal of useful, health-specific information, particularly when it comes to something like prostate cancer (because in most cases this is not a genetic disorder like, for example, hemophilia). See this recent commentary on this topic.

  4. Thank you, Sitemaster.

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