The reactivity to CK5/6 antibody in tumor cells from non-small cell lung cancers shed into pleural effusions predicts survival

Lung cancer, especially adenocarcinoma and large cell carcinoma, tends to spread to the pleural cavities. Once an effusion develops, the prognosis is generally dismal. Immunocytochemistry is frequently applied to effusions for diagnostic purposes, but the prognostic value of markers in malignant effusions have thus far attracted less attention. Dakopatts CK 5/6 antibody was applied to ethanol-fixed fresh cytospin preparations from malignant pleural effusions originating from 18 patients (11 men and 7 women) with a previously or later verified non-small cell lung carcinoma (NSCLC). In three cases, CK5/6 reactivity was found in part of the malignant population, whereas 10 cases showed reactivity in most tumor cells. The lack of reactivity in malignant cells was only seen in five effusions. Females showed significantly lower reactivity rates, with all negative effusions coming from female patients, whereas 9/10 effusions with reactivity in most malignant cells originated from males. CK5/6 reactivity was significantly correlated to survival, with a median survival time of 18 days for patients with CK5/6-negative tumors, and 212 days for those with positive tumors. The strong relationship between CK5/6 reactivity and survival, and the observed gender difference, warrants larger studies aimed at the clinical utility of CK5/6 as a prognostic marker in metastatic NSCLC, the possible functional role of CK5/6 in cell adhesion in advanced NSCLC and its possible hormonal control.