Retraction: Prognostic and predictive value of carcinoembryonic antigen and cytokeratin-19 fragments levels in advanced non-small cell lung cancer patients treated with gefitinib or erlotinib. Yonsei Med J 2012;53:931-9.

Dear Editor

We deeply regret to inform you that our paper was submitted twice to two different Journals, and was already published in another Journal1; therefore, we are requesting to retract our paper that has been published in YMJ.2 We mistakenly submitted our paper to the other journal. As the corresponding author, I will take full responsibility for this error and respectfully request for the retraction of our paper from YMJ.