Confirming that saliva is just as accurate as biopsied tissues to detect treatable cancer mutations is a major step forward in the field of salivary diagnostics. Collecting and analyzing saliva is a non-invasive, inexpensive method in the early detection of many types of cancer. Lung cancer patients can particularly benefit from this method as lung cancer tends to be diagnosed in advanced stages and may be mistaken for other problems.
Researchers from the UCLA School of Dentistry and their collaborators performed a double-blind study on 37 people who have non-small cell lung cancer at three lung cancer centers in Chengdu, China. For each person, pre- and post-biopsy samples were collected for tissue and saliva cells. The researchers began by cataloging the biopsied plasma cells (from the lungs) using digital polymerase chain reaction. Next, the team cataloged the saliva cells using a proprietary UCLA-developed technology, called electric field-induced release and measurement (EFIRM) liquid biopsy, to see whether they could detect the same mutations as they did with the plasma cells.
They were looking for epidermal growth factor receptor (EGFR) mutations, which are early cellular signals for cancer. More specifically, they were looking for epidermal growth factor receptor L858R and exon 19del — two types of cancer mutations.
The team found saliva detection correctly predicted the mutations in all 37 pre- and post-surgery saliva samples with 100 percent accuracy. The biopsied tissue predicted mutations with 70 percent accuracy. Furthermore, they found that the mutation signals in saliva were cleaner than in the biopsied tissue for L858R; and the tissue and saliva samples had clean separation for exon 19del.
“This study has confirmed the performance of EFIRM liquid biopsy using as little as 40 microliters of saliva for detecting EGFR mutations,” said Dr. David Wong, lead author on the study and the associate dean for research at the UCLA School of Dentistry. “We are confident that EFIRM liquid biopsy is just as effective at detecting cancer mutations as the current dPCR method of testing tissue. The results from this study show that we are even closer to using saliva to detect cancer mutations; and that saliva can be just as accurate as tissue.”