RESUMO
Krebs von den Lungen-6 (KL-6) is a high molecular weight glycoprotein classified in the category of human MUC1 mucin. KL-6 has been reported to serve as a sensitive marker for interstitial pneumonia; however, recent studies have suggested that it can also be used as a tumor marker as its origin shows. To further elucidate the clinicopathological significance of circulating KL-6 in lung cancer, we monitored the circulating KL-6 levels in advanced nonsmall cell lung cancer (NSCLC) patients and analyzed the association between these levels and the clinical outcome of EGFR-TKI treatment. The pretreatment levels of circulating KL-6 were found to be significantly higher in progressive disease (PD) patients than disease-controlled (partial response (PR) and stable disease (SD)) patients. Multivariate analyses revealed the circulating KL-6 level to be an independent prognostic factor for overall survival as well as progression-free survival. In addition to these observations, we found that changes in circulating KL-6 levels at 2 weeks after the start of EGFR-TKI treatment from the baseline could quite precisely discriminate PD cases from PR or SD patients and the clinical outcome of EGFR-TKI in NSCLC patients. These results indicate that the monitoring of circulating KL-6 levels in NSCLC patients is effective for both selecting patients to be treated with EGFR-TKI and predicting the clinical outcome of EGFR-TKI. In addition, the findings suggest that the circulating KL-6 level could be used as a clinically relevant biomarker in patients with NSCLC, particularly those who are candidates for EGFR-TKI treatment.