DETECTION OF K-RAS ONCOGENE MUTATIONS IN BRONCHOALVEOLAR LAVAGE FLUIDFOR LUNG-CANCER DIAGNOSIS

Background: Lung cancer is the leading cause of cancer deaths in the U nited States, A long-standing goal of cancer researchers has been to d evelop tests that would facilitate earlier diagnosis and treatment of lung cancer and thereby decrease mortality from this disease, Because cancer results from the accumulation of a variety of genetic events (e .g., mutations, rearrangements, and deletions) in genes controlling ce ll growth and differentiation, these changes might serve as diagnostic ally useful molecular markers, Activation of the K-ras oncogene by poi nt mutations in codon 12, which occurs in many cases of lung adenocarc inoma, may serve as one such clinically useful molecular marker, For d etection of K-ras point mutations in bronchoalveolar lavage fluid, in which small numbers of malignant cells are mixed with a population of predominantly genetically normal cells, the sensitivity of commonly us ed assays for ras mutations risks false-negative results, Purpose: By applying a highly sensitive assay, we investigated whether detection o f K-ras codon 12 mutations in samples of bronchoalveolar lavage fluid could be clinically useful in diagnosing lung cancer, Methods: We deve loped a highly sensitive assay for detecting K-ras codon 12 mutations based on an enriched polymerase chain reaction (PCR) technique, This t echnique was applied to 87 specimens of bronchoalveolar lavage fluid s pecimens that were obtained from 86 patients, and associated tumor bio psy specimens obtained from 35 of these patients who underwent diagnos tic bronchoscopy for clinically suspected lung cancer, Lavage fluid sp ecimens were also obtained from nine patients undergoing nondiagnostic bronchoscopy, Statistical comparisons mere performed by using the two -tailed Fisher's exact test, Results: Of 52 patients with confirmed lu ng cancer, samples of bronchoalveolar lavage fluid from 16 patients co ntained K-ras codon 12 mutations, including 14 (56%) of 25 patients wi th lung adenocarcinomas, one (33%) of three with bronchoalveolar carci nomas, one (20%) of five with large-cell carcinomas, and none of the 1 4 with squamous cell carcinomas, Mutations were detected in four addit ional cases in which cancer was suspected but had patients all yielded the identical K-ras codon 12 genotype found in the corresponding samp les of bronchoalveolar lavage fluid, No mutation was found in any samp le from 30 patients with diagnoses other than non-small-cell lung canc er, Thus, for those cases in which tissue was available and tested, th e sensitivity and specificity of detecting K-ras mutations in bronchoa lveolar lavage fluid for diagnosing Kras mutation-positive lung cancer were both 100%, For nine patients, K-ras mutations were detected in b ronchoalveolar lavage fluid obtained during otherwise nondiagnostic br onchoscopies, Conclusions: Our data demonstrate that sensitive detecti on of K-ras codon 12 mutations can serve as an important adjunct to cy tology in the diagnosis of lung cancer, Implications: Detection of the se mutations could lead to earlier cancer diagnosis and less need for invasive diagnostic procedures.