Both biochemical recurrence and metastatic events in the RP group positively correlated to total CTC counts, as well as with AR-positive cells and phenotypic heterogeneity in CTC samples.

In their conclusion, the authors noted that these promising results might be unique to the Epic Sciences platform, and added that “[i]f confirmed in a larger cohort with longer follow-up, phenotypic and genomic characterization of CTCs pretherapy may provide an additional means of risk stratifying patients with newly diagnosed high-risk disease.”

Dr Morgan noted, however, that the “study focused on men with high-risk prostate cancer — that is, patients already known to have relatively aggressive cancer. In this context, the presence of CTCs looks like a promising approach to understanding future recurrence risk. Additional validation is absolutely needed before this is a test that should be used in men with localized prostate cancer.”

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The results may, however, help researchers rely on a specific platform when attempting to stratify patients by risk. The Epic Sciences platform, in particular, appears promising for determining which patients are likely to have recurrent disease, as another study published in The Journal of Urology suggested.4

Yet whether “liquid biopsies” — the general term used to describe analysis of CTCs and cell-free DNA in blood samples from patients with cancer — are, as a whole, a reliable tool for determining disease prognosis outside of prostate cancer is still unknown. One area of interest, for example, is whether CTCs may inform clinicians about the administration of immunotherapies across a variety of cancer subtypes, including lung cancer.

“LB [liquid biopsy] has many advantages since it is a noninvasive approach, repeatable, and allows us to get the results in a short time (mainly some genomic alterations, notably the status of EGFR mutations from circulating-free DNA),” Paul Hofman, MD, PhD, professor of pathology at Université Côte d’Azur in Nice, France, and director of the French OncoAge Consortium, wrote to Cancer Therapy Advisor in an email. He added, however, that “CTC measurements alone are not enough to give useful stratification in most of the solid tumors (notably in NSCLC [non–small cell lung cancer]).”

Dr Hofman recently coauthored a study in the Annals of Oncology on the utility of LBs when delivering immunotherapy to patients with NSCLC.5

When measured in tandem with cell-free DNA, CTCs appear to be a promising metric.

“cf [cell-free]DNA is certainly the best and most promising approach currently in patients treated by immunotherapy. Some next-generation sequencing panels are currently available too for the detection of genomic alterations, and, notably, the detection of mutations predictive of resistance to immunotherapies (ie, STK11 mutations, KEAP1 mutations, and others).

“However it would be certainly very useful to develop these analyses in house and not to send samples to referral centers, since the costs of these latter analyses are very expensive to date to be used in routine clinical practice.”

It appears, then, that as technology improves and researchers conduct more clinical trials, CTCs are likely to be very important in oncology, though it may be necessary to evaluate other elements of LB samples, including cfDNA. Ensuring that the platform used has been deemed effective for the clinical purpose in question — whether stratifying high-risk patients with prostate cancer or evaluating the efficacy of immunotherapy in lung cancer — is critical.

“LBs will be implemented widely in the coming years, at least as a complementary approach for tissue biopsies,” Dr Hofman said, adding that “all platforms need to participate to some quality controls program and need to validate externally their results.”

Disclosure: Some of the authors from the JCO paper reported financial relationships with medical companies. For a full list of disclosures, please refer to the original paper.

References

  1. Pantel K, Hille C, Scher HI. Circulating tumor cells in prostate cancer: from discovery to clinical utility. Clin Chem. 2019;65(1):87-99.
  2. Maas M, Hegemann M, Rausch S, Bedke J, Stenzl A, Todenhöfer T. Circulating tumor cells and their role in prostate cancer. Asian J Androl. 2017;21(1):24-31.
  3. Salami SS, Singhal U, Spratt DE, et al. Circulating tumor cells as a predictor of treatment response in clinically localized prostate cancer. JCO Precis Oncol [published online ahead of print May 30, 2019]. doi: 10.1200/PO.18.00352
  4. Friedlander TW, Welty C, Anantharaman A, et al. Identification and characterization of circulating tumor cells in men who have undergone prostatectomy for clinically localized, high-risk prostate cancer. J Urol [published online ahead of print June 19, 2019]. doi: 10.1097/JU.0000000000000393
  5. Hofman P, Heeke S, Alix-Panabières C, Pantel K. Liquid biopsy in the era of immune-oncology. Is it ready for prime-time use for cancer patients? Ann Oncol [published online ahead of print June 22, 2019]. doi: 10.1093/annonc/mdz196