A novel non-invasive “liquid biopsy” that scans the entire landscape of circulating tumor cells (CTCs) may help guide individualized treatment decisions for patients with cancer, according to an early study to be presented this week at the 2016 Genitourinary Cancers Symposium.1
CTCs are malignant cells released by solid tumors both from the site of the original tumor and from metastatic sites into the bloodstream.
This new experimental blood test utilizes special dyes to distinguish CTCs from normal blood cells. A machine then analyzes the various features of the CTCs, allowing the researchers to choose a particular cell of interest in order to analyze the genetic abnormalities of that cell.
“Not all men respond equally to either enzalutamide or abiraterone, and some men don’t respond at all. If the test is validated, it could be used to help select the treatment to which a patient is more likely to respond, sparing the toxicities that may result from one that is ineffective,” said lead study author Howard I. Scher, MD, a medical oncologist and chief of the Genitourinary Oncology Service at the Memorial Sloan-Kettering Cancer Center in New York, NY.
“In addition, unlike a tissue biopsy, blood samples are easily obtained at any time so that treatment adjustments can be made sooner.”
For the study, investigators tested a total of 221 blood specimens from 179 patients with metastatic prostate cancer who were about to initiate therapy with enzalutamide, abiraterone, or taxane chemotherapy.
Results showed that patients with a higher heterogeneity score, meaning there was more variation in CTC appearance and genetic make-up, had shorter survival times on abiraterone and enzalutamide but not docetaxel or cabazitaxel.
“Single CTC morphology, protein, and genomic characterization is feasible and can be used to assess tumor heterogeneity,” Dr Scher concluded. “A non-invasive liquid biopsy that enables the characterization individual cells from a patient with metastatic cancer can be used to guide treatment selection.”
Of note, this novel test still needs to be thoroughly validated in a clinical trial to determine how well the test results predict outcomes in these patients.
“Though this is an early study, it’s an exciting one,” said Sumanta Pal, MD, ASCO spokesperson. “It’s remarkable that a blood test could help us profile cancers in real time, gleaning insights that directly affect patient care decisions. Eventually, we may be able to spare some men with prostate cancer the significant side effects of hormone therapy.”
- Scher HI, Graf R, Louw J, et al. Single CTC characterization to identify phenotypic and genomic heterogeneity as a mechanism of resistance to AR signaling directed therapies (AR Tx) in mCRPC patients. J Clin Oncol. 2015:34;(suppl 2s; abstr 163).