DNA hypermethylation analysis in sputum of asymptomatic subjects at risk for lung cancer participating in the NELSON trial: argument for maximum screening interval of 2 years.

Aims: Lung cancer is the major contributor to cancer mortality due to metastasised disease at time of presentation. The current study investigated DNA hypermethylation of biomarkers RASSF1A , APC , cytoglobin, 3OST2, FAM19A4, PHACTR3 and PRDM14 in sputum of asymptomatic high-risk individuals from the NELSON lung cancer low-dose spiral CT screening trial to detect lung cancer at preclinical stage.
Methods: Subjects were selected with (i) lung cancer in follow-up (cases; n=65), (ii) minor cytological aberrations (controls; n=120) and (iii) a random selection of subjects without cytological aberrations (controls; n=99). Median follow-up time for controls was 80 months. Cut-off values were based on high specificity to assess diagnostic value of the biomarkers.
Results: RASSF1A may denote presence of invasive cancer because of its high specificity (93% (95% CI 89% to 96%); sensitivity 17% (95% CI 4% to 31%), with best performance in a screening interval of 2 years. The panel of RASSF1A, 3OST2 and PRDM14 detected 28% (95% CI 11% to 44%) of lung cancer cases within 2 years, with specificity of 90% (95% CI 86% to 94%). Sputum cytology did not detect any lung cancers.
Conclusions: In a lung cancer screening setting with maximum screening interval of 2 years, DNA hypermethylation analysis in sputum may play a role in the detection of preclinical disease, but complementary diagnostic markers are needed to improve sensitivity.
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