A comparative study of telomerase activity in sputum, bronchial washing and biopsy specimens of lung cancer.

The potential of telomerase, the ribonucleoprotein enzyme, as a non-invasive screening marker was studied in pre-bronchoscopy sputum (S), bronchial washings (W) and bronchoscopic biopsy (B) samples from individuals under evaluation for lung cancer. Out of the 52 cases studied, 42 were clinically suspected primary lung cancer patients and 10 had pulmonary disorders but had no clinical evidence of lung cancer. Fifteen (39.5%) S samples, 24 (63.1%) W samples and 32 (84.2%) B samples, which were cytologically/histopathologically positive were also positive for telomerase activity. Interestingly, 16 (42%) S samples, 20 (52.6%) W samples and 20 (52.6%) B samples, initially reported cytologically/histopathologically negative, showed detectable telomerase activity. Lung cancer was finally confirmed in these cases by repeat cytology/histopathology. However, telomerase activity was detected in 31 (81.6%) S, 26 (68.4%) W and 33 (86.8%) B samples of suspected lung cancer patients. Telomerase activity was negative in S, W, and B of four of the suspected cases, which ultimately turned out to be negative for lung cancer. Cytopathology/histopathology alone (including repeat attempts) identified 15 (39.5%) cases of sputum, 24 (63.1%) cases of bronchial washings and 32 (84.2%) bronchoscopic biopsy samples. Out of 10 controls, low telomerase activity was detected in only one (10%) of the bronchial washings, which later turned out to be due to large number of inflammatory cells. Telomerase activity assay of sputum carried sensitivity, specificity and diagnostic accuracy of 81.6, 100 and 86.5%, respectively, while that for bronchial washing was 68.4, 100 and 76.9%, respectively, and for bronchoscopic biopsy samples was 86.8, 100 and 88.1%, respectively. A positive correlation (P<0.01) was seen between age and telomerase activity in sputum, bronchial washing and biopsy samples but no significant correlation was seen between sex and telomerase activity or duration of smoking and telomerase activity. A significant positive correlation was observed between staging and telomerase activity in sputum (P<0.01), bronchial washing (P<0.01) and biopsy samples (P<0.01). Our findings indicate that telomerase is a specific marker for malignant lung disease and can complement cytology/histopathology in the diagnosis of lung cancer. Sputum telomerase assay holds the potential for early and non-invasive diagnosis of lung cancer.