Bronchial mucus properties in lung cancer: relationship with site of lesion

To compare the biophysical properties of mucus from the left and right mainstem bronchi in patients undergoing diagnostic bronchoscopy because of a unilateral radiological abnormality. It was hypothesized that abnormalities in the properties of mucus would be greater on the side with the lesion and that this would be most obvious in patients with unilateral lung cancer.

Bilateral paired samples of bronchial mucus were taken from 38 nonatopic patients (aged 59.8+/-12.6 years) including 16 nonsmokers, 14 current smokers and eight exsmokers (more than one year). Twenty of the 38 patients had a radiologically defined unilateral abnormality. Eight of these 20, including one nonsmoker, had lung cancer. The viscoelastic properties of the collected mucus were determined by magnetic microrheometry, and the analysis was carried out without knowledge of the histological diagnosis or source.

The rheological properties of mucus strongly suggested which was the abnormal side. Within the group of 20 patients with a unilateral radiological abnormality, mucus from the side of the lesion had a lower value of the loss tangent, tan d100 (P=0.004), indicating greater mucus recoil. This is consistent with poor mucus cough clearability on the lesion side. All eight cancer patients fit this mucus rheological pattern with a lower value of tan d100 on the affected side (P=0.007). Four of the five other patients with a similar mucus abnormality were categorized as high cancer risk by other criteria, while six of seven patients with mucus that did not have this abnormality were considered to be lower risk. Based on the mucus analysis done at the time of the bronchoscopy, two of the 'noncancer' patients initially designated as high risk had cancer detected after several months of follow- up. Only two of the 18 patients without a defined unilateral lesion fit the mucus 'cancer pattern'.

These findings are consistent with the hypothesis that either abnormalities in mucus properties may represent a risk factor for the development of lung cancer or that bronchial mucus abnormalities may be associated with products secreted by the tumours that, in turn, may suppress mucus clearance.