PCR test for circulating DNA may allow early lung cancer detection

Quantifying free circulating DNA by PCR could represent a useful noninvasive method for early lung cancer detection, according to a report published in the November 1st issue of the Journal of Clinical Oncology.

Previous reports have shown that plasma DNA levels are increased in lung cancer patients. Still, there has been a need for an assay that can accurately determine these levels.In the new study, Dr. Ugo Pastorino, from Istituto Nazionale Tumori in Milan, Italy, and colleagues evaluated the sensitive and specificity of a PCR assay that quantified plasma DNA levels by testing for amplification of the human telomerase reverse transcriptase gene (hTERT). The test was applied to samples obtained from 100 non-small-cell lung cancer patients and from 100 controls matched by age, sex, and smoking status.Although hTERT expression has been linked to lung cancer, in the present study, the authors used it simply as an indicator of total circulating DNA.The median amount of circulating DNA in cancer patients was nearly eight times higher than the amount seen in control subjects, the researchers note. Moreover, the highest DNA levels were associated with an 85.5-fold increased risk of lung cancer compared with the lowest levels.The sensitivity and specificity of the assay in detecting lung cancer depended on the cutoff point used. The maximum sensitivity and specificity attained with the various cutoff points were 97% and 99%, respectively. “These results highlight a potential value of this DNA-based plasma test for early detection of lung cancer in high-risk individuals, and particularly former heavy smokers,” the researchers state. A study is currently underway to see if the test can improve the accuracy of spiral CT in detecting early lung cancer, they add.In a related editorial, Dr. Paul A. Bunn, Jr., from the University of Colorado Cancer Center in Denver, comments that while the current findings are encouraging, “much needs to be done in validation, and much larger series must be completed before [tests like this] are ready for prime time.”(Source: J Clin Oncol 2003;21:3891-3893,3902-3908: Reuters Health: November 20, 2003: Oncolink)