DNA image cytometric analysis of bronchial washings as an adjunct for the detection of lung cancer in a clinical setting

Background: DNA aneuploidy has a potential to become an adjunct to conventional cytology for diagnosis of lung cancer, but its value in bronchial washings has not been well evaluated.

Methods: We conducted a retrospective study on patients who underwent bronchoscopy and the bronchial washings were submitted for both cytology and DNA image cytometry (DNA-ICM) examination. The sensitivity and specificity of two methods and both in combination were compared. Analysis of clinical subgroups and DNA histogram were also performed.

Results: The study included 626 patients (326 patients with lung cancer and 300 patients with benign lung diseases). The sensitivity of cytology, DNA-ICM, and combination test for lung cancer were 53.3%, 62.3%, and 75.8%, respectively, and the sensitivity of DNA-ICM and combination test were superior to that of cytology (p < 0.05). A modest reduction of specificity was found in DNA-ICM compared with cytology (91.3% vs. 98.3%, p < 0.05). Subgroup analysis showed there was no significant difference in sensitivity of DNA-ICM between the visible tumor group and the invisible tumor group (66.5% vs. 56.9%, χ² = 3.114, p = 0.078). Among 101 patients with invisible endobronchial tumor, the positive rates for DNA-ICM of washing, cytology of washing, brushing and biopsy were 62.4%, 41.6%, 40.6%, and 45.5%, respectively. DNA-ICM in combination with the basic bronchoscopy techniques could increase the sensitivity from 67.3% to 87.1% (p = 0.000). The DNA histogram analysis showed 25.3% washing samples of lung cancer were diploid pattern, 49.4% were scattered aneuploid cells pattern, and 25.3% were aneuploid peaks pattern. Small cell lung cancer had the highest proportion of aneuploid peaks pattern (p < 0.05).

Conclusions: DNA-ICM could be used as an adjunct for the detection of lung cancer. The combination of DNA-ICM and basic bronchoscopy techniques could significantly increase the sensitivity, especially for the patients suspected of peripheral lung cancer, and contribute to select subjects for advanced bronchoscopy.