Sputum Test May Boost Accuracy Of CT Scans For Lung Cancer

Issue 25 Summer/Fall 2015


Genetic 'Biomarkers' In Patients’ Sputum Could Show If Nodules Are Malignant Or Benign

As reported elsewhere in this issue of Cancer Prevention, lung CT scans are gaining acceptance as a noninvasive means of spotting lung cancer early, when it is most treatable.

Currently, patients whose scans show a suspicious lung nodule might be subjected to invasive biopsies, radiation or surgery that would prove unnecessary if the anomaly turns out to be benign.

However, a new trial funded in part by the U.S. National Cancer Institute suggests that a noninvasive test based on coughed-up sputum might someday distinguish benign lung nodules from malignant ones.

The experimental test relies on a panel of three types of cellular microRNA – a form of genetic material – that is often present at abnormal levels in cancer patients.

Using this trio of genetic “biomarkers,” a team led by Dr. Feng Jiang of the University of Maryland said they were able to identify cancerous lung nodules with more than 80 percent accuracy.

However, any test used in a clinical setting would require accuracy that’s closer to 100 percent. The goal, then, is to expand the range of the biomarker panel “to generate a test with high efficiency that can be practically used in clinical settings for lung cancer early detection,” Jiang said.

The study involved three groups of patients whose lung CT scans showed evidence of a lung nodule. In one group of 122 patients, 60 were confirmed to have a malignant nodule via traditional, invasive testing methods. Jiang’s team used the new sputum test to accurately identify cancers almost 83 percent of the time [“sensitivity”], and correctly identify benign nodules nearly 88 percent of the time [“specificity”].

Similar results were found in two other similarly sized groups of patients with lung nodules detected by lung CT scan. Jiang’s group reported the findings earlier this year in Clinical Cancer Research.

While heartening, the test’s sensitivity and specificity are still “not high enough for the three-biomarker panel to be used in the clinic,” Jiang said in a news release from the American Association for Cancer Research.

“Because the specificity is only 87 percent, we cannot be certain enough that a patient does not have lung cancer,” he said. So, “before these results can be translated into the clinic, we need to identify other biomarkers to add to the existing panel, to increase its sensitivity and specificity.”

That type of enhanced screening panel would then have to be tested in a prospective clinical trial, Jiang explained.

If successful, use of CT lung scans and a sputum-based diagnostic test in combination might save patients from unnecessary procedures, worry, and later-stage diagnosis, Jiang and colleagues said.

This type of diagnostic tool, “would improve the ability to detect lung cancer in smokers at its early stage, where therapeutic interventions have a curative potential,” the researchers wrote.