Methylation assay for the diagnosis of lung cancer on bronchial aspirates:: A cohort study

Purpose: Recent studies have detected aberrant promoter methylation of adenomatous polyposis coli promoter 1A (APC), cyclin-dependent kinase inhibitor-2A (p16(INK4a)),retinoic acid receptor beta 2, and RAS association domain family protein 1 (RASSF1A) in bronchial aspirates and suggested their use as biomarkers for lung cancer diagnostics. The purpose of this study was to validate these candidate marker genes in a retrospective cohort study. Experimental Design: Bronchial aspirates collected from a cohort comprising 247 patients with suspected lung cancer were investigated retrospectively regarding aberrant promoter methylation using a quantitative methylation-specific real-time PCR (QMSP). Results: Eighty-nine patients were diagnosed with primary lung cancer, 102 had benign lung disease, and 56 showed miscellaneous other conditions. A panel consisting of APC, p16(INK4a), and RASSF1A emerged as useful combination. This panel detected aberrant methylation in bronchial aspirates of 22 of 35 (63%) and 21 of 44 (44%) centrally and peripherally located primary lung cancers, respectively. Bronchial aspirates also showed aberrant methylation in 5 of 7 (71%) patients with a recurrent lung cancer and in 8 of 30 (27%) cases without tumor recurrence. In contrast, only 1 of 102 patients with benign lung disease displayed a (false) positive test result. Rarely, aberrant methylation was found in patients with other malignancies (3 of 16). The QMSP assay correctly confirmed lung cancer in 8 of 12 (67%) cases with an ambiguous cytology. Moreover, it disclosed 9 of 26 (35%) of peripheral tumors lacking simultaneous cytologic or histologic diagnosis of malignancy. Conclusions: Our findings suggest that the QMSP assay could be applied as a reflex test in cases of suspected lung cancer that defy a definite diagnosis by conventional methods. Thus, the assay could be a useful diagnostic adjunct especially regarding peripheral tumors.