Thursday, April 9, 2015

Liquid Biopsy: The “Holy Grail”?

Circulating tumor cells (CTCs), tumor cells that are shed from primary tumors in the body and carried through the circulation, were discovered some 140 years ago.  Researchers have struggled to create an efficient way of capturing these elusive and rare cancer cells, and perform genetic analysis to learn about their growth characteristics and molecular evolution.

I’m inspired and encouraged by the work of Dr. Bert Vogelstein, at Johns Hopkins.  Dr. Vogelstein is credited with having proved that damaged DNA causes cancer.  Nearly every type of cancer sheds DNA into the bloodstream, so Vogelstein and his colleagues are trying to prove that cancer can be diagnosed much earlier -- perhaps decades earlier -- using a procedure called "liquid biopsy."

But the technology isn't clinic-ready yet, and the screening process is still too expensive.  We are nowhere near the reality of liquid biopsy being used in, for instance, your annual check-up.  Making such screening a routine practice in medicine will be challenging.  One challenge is that while the test may detect the presence of cancer DNA in the body, doctors might not know where the tumor is, how dangerous it is, or even whether it is worth treating.  

In a recent MIT Technology Review article, Dr. Daniel Haber, Director of the Massachusetts General Hospital Cancer Center was quoted, “We have to be cautious about how we talk about that.” He believes the DNA blood tests are “far from ready” and says very large studies will be needed to prove that they are useful. “There is a huge bar to get over,” he says.

Dr. Haber, Mehmet Toner, PhD, and their research team at MGH have developed a microfluidic chip called the CTC-iChip, used to isolate the minute numbers of tumor cells circulating in the blood. The CTCs can then be analyzed to reveal critical information about cancer growth and the effectiveness of different treatments. Researchers believe the technology may revolutionize the way oncologists detect, monitor and treat cancers.  Janssen Diagnostics is working with the Mass General team to transform the iChip into a “next-generation CTC-analysis platform”.

In the long term, the goal would be to use the technology for early detection.  This will involve much larger clinical trials and, of course, large-scale funding. Says Toner, “But that would be the Holy Grail - where we could isolate CTC cells early, and monitor certain mutations over time, particularly for cancers we know tend to become aggressive.”

Eventually, “in the very long term,” CTC technology might be used to screen the general population, Toner suggests. “The screening could be included in the blood analysis when you go for an annual checkup with a primary care physician, just like a CBC [complete blood count].”

This is why cancer research funding is so critical.