A meta-analysis by Liang et al. found an association between CXCR4 overexpression and lymph node metastasis, distant metastasis, and OS [15]; however, the patient population was quite heterogeneous (i.e. included stage I-IV patients as well as small cell lung cancer patients), making comparison to our patient population difficult. Here, CXCR4 is linked to small cell lung carcinoma.