Has Tumor Profiling Caught Up to Cancer?

Non-small cell lung cancer (NSCLC) is one of the most aggressive and deadliest forms of cancer. For treatment to be effective, especially in the latter stages of the disease, oncologists must take a personalized, genetics-based approach, traditionally informed by tissue biopsy. But these procedures are invasive and can take up to four weeks to deliver results (1). For optimal treatment, speed is of the essence. In my opinion, the best way to realize the true potential of personalized therapy is with a blood-based liquid biopsy testing strategy that uses a droplet digital PCR (ddPCR)-based assay.

In 30 percent of lung cancer cases, oncologists cannot use genetic information from a tissue biopsy to create a personalized treatment regimen (2)(3). Some patients are ineligible for biopsies because the procedure is too risky; others simply yield too little tissue for analysis. And because the procedure can be highly invasive, physicians are often reluctant to perform multiple biopsies in a single patient – making it nearly impossible to monitor a tumor’s shifting genetic profile via traditional tissue-based testing.

ddPCR-based liquid biopsies, on the other hand, only require a minimally invasive blood draw, but can detect genomic biomarkers in blood-borne tumor DNA shed by dying cancer cells. Many patients who are ineligible for tissue biopsy can still undergo liquid biopsies, and blood can be drawn multiple times with little harm, which means physicians can more easily and comprehensively monitor their patients’ tumors over time.

In the clinic, ddPCR-based liquid biopsies also yield genetic data much faster than other commercially available tissue biopsy tests, which are primarily based on methods such as next-generation sequencing (NGS) (4)(5). Although NGS has thus far been considered the gold standard for profiling tumors’ genetic makeup, the quality comes with a downside: it yields so much data that pathologists may need up to three weeks to sort through it and deliver results (6). Consequently, 80 percent of the time, genetic data is not available to NSCLC patients by their first oncology consultation, and so a general chemotherapy regimen is started (7). And the delay in receiving more personalized treatment results in a worse patient outcome (4).

How do ddPCR-based tests deliver faster results? Unlike NGS-based liquid biopsies, they probe genetic hotspots directly linked to NSCLC, thereby providing only the information that immediately impacts a patient’s treatment. To test the speed of a ddPCR-based liquid biopsy, a working group of five cancer centers offered a liquid biopsy for patients with NSCLC to their physicians – and 95 percent received results within 72 hours (4)(8). With these turnaround times, physicians will almost always have patient data available in time to prescribe a personalized treatment regimen at the first visit.

Moreover, ddPCR-based liquid biopsies are more cost-effective than traditional lung biopsies (1). Navigational bronchoscopies can cost over US$8,200; CT-guided lung biopsies run about $4,000 (and, in the 15 percent of cases where complications arise, costs can soar to over $18,000). Liquid biopsies, on the other hand, do not involve surgical procedures, so any phlebotomist can procure samples, reducing costs to an average of about $800.

I see ddPCR as the future of personalized cancer therapies. Based on our cancer center’s successful experience with the technology, I believe it is only a matter of time before these kinds of blood-based liquid biopsies become an indispensable method for doctors to categorize a patient’s disease
and determine the best course of treatment.