NEW YORK (GenomeWeb) – A recent study led by researchers from Integrated Diagnostics sheds light on the clinical utility of the company's proteomic Xpresys Lung cancer test for evaluating indeterminate pulmonary nodules.
Published online in the journal Lung in September, the study found that with use of the test, 32 percent of surgeries and 32 percent of invasive procedures (surgeries plus biopsies) could be avoided. At the same time, the test was roughly equivalent to standard clinical practice in terms of the percentage of patients with malignant nodules it triaged to a regime of CT surveillance.
The 32 percent reduction in surgeries and invasive procedures is 5 percent higher than in previous studies of the test, Indi Co-founder and CSO Paul Kearney told GenomeWeb, noting that the company has seen fairly consistent results across studies." Launched in 2013, Xpresys is intended to aid doctors in identifying lung nodules detected via CT scans that are likely benign. The test uses multiple-reaction monitoring mass spec to quantify the levels of 11 proteins in patient blood samples.
The rationale for Xpresys is that by identifying nodules that are likely benign, physicians can more comfortably put patients on a regimen of watchful waiting. A noninvasive test like Xpresys is desirable due to the expense and significant risks of the invasive procedures currently used for determining lung cancer status, like fine needle aspiration and thoracotomies.
Kearney said that the patient cohort in the study matched well with the types of patients the company has seen since launching the test in 2013, with the exception that "in actual practice the patients are slightly older than in this published data."
The Lung study combined a retrospective analysis of 377 patients with pulmonary nodules between 8 millimeters and 20 millimeters, taken from 18 different outpatient pulmonary clinics, with a prospectively collected group of 353 patients enrolled at 12 sites across the US.
In the retrospective analysis, the patients were evaluated using standard clinical measures, while in the prospective analysis, they were evaluated using clinical measures and the Xpresys test.
Of the 353 prospectively enrolled patients participating in the study, 287 were diagnosed with non-small cell lung cancer, and 66 were diagnosed with a benign nodule, using a variety of invasive procedures. One hundred one were diagnosed using either a CT-guided needle aspiration or bronchoscopy, which identified 16 benign nodules and 85 cases of NSCLC. Two hundred fifty-two patients had a surgical lung biopsy, which identified 50 benign nodules and 202 cases of NSCLC.
Looking at the 66 cases identified as benign by invasive procedures, the researchers determined that 21, or about a third, would have been identified as likely benign by the Xpresys test, meaning that the test could have decreased the number of patients with benign disease undergoing invasive procedures by nearly 32 percent.
On the flip side, the test would have classified as "likely benign" 69 of the 287 patients, or 24 percent, who were ultimately diagnosed with NSCLC. Under current guidelines, these patients would have been moved to regular surveillance with CT scans.
This 24 percent misclassification rate was similar to that found in the 377-patient retrospective analysis, where 23 of the 94 patients, or about a quarter, who were eventually diagnosed with NSCLC were first put on CT surveillance.
One factor complicating that comparison, the authors noted, is the fact that while the retrospective cohort included only nodules between 8 millimeters and 20 millimeters, the prospective cohort, to which the Xpresys test was applied, included nodules between 8 millimeters and 30 millimeters.
Regarding this comparison, Anil Vachani, a pulmonologist at the University of Pennsylvania and that first author of the study, told GenomeWeb that "in general, if Xpresys was limited to 8 millimeter to 20 millimeter nodules, it would steer [fewer] patients with lung cancer into observation, as the rate of cancer among 21 millimeter to 30 millimeter  nodules is higher than in those [between 8 millimeters and 20 millimeters.]"
However, he added, "I think it is very difficult to estimate the effect of false negative results based on a retrospective comparison group" as was done in the Lung study.
"A prospective study will allow a better assessment of exactly how many procedures are avoided and a better estimate of how many false negatives will occur," Vachani said.
Because Penn is one of the sites collecting patients for a prospective study Indi is putting together to further evaluate Xpresys, Vachani and his colleagues have thus far held off on using the test in their actual practices.
"Given our involvement [in the trial], we choose to not use the test clinically, but only in the context of the trial, where we are blinded to the results," he said.
Kearney declined to release sales or revenue numbers for the test, saying that the company is "very pleased with the level of physician interest in the test."