Comparison of ALK status between primary and corresponding lymph node metastatic tumors in lung cancer patients.

Background: The anaplastic lymphoma kinase (ALK) protein has recently become a promising target in the treatment of non-small cell lung carcinomas(NSCLC) patients with ALK translocation because of the high response rates obtained with an ALK inhibitor. ALK translocations are present in approximately 3-5% of NSCLC patients. According to the literature, little information about the relationship of ALK status between the primary tumor and metastatic sites has been reported. We intended to determine whether the ALK translocations of primary lung cancers are consistent with those in corresponding metastatic lymph node tumors. Materials and Methods: We analyzed ALK translocations from paired primary and metastatic lymph node tumors in 78 lung cancer patients who had not received TKI before the tissues were sampled. Results: Using fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) methods, all 45 patients with ALK translocation-positive primary lung tumors had translocations in the metastases. For 33 patients who were ALK negative in the primary tumors, 1 (3%) was ALK positive in their metastatic tumors. Conclusion: According to a paired t-test, there is no significant difference between primary lung tumors and metastatic sites. Analysis of ALK translocations in the primary lung tumor would be suitable for planning the use of a TKI for advanced NSCLC, but it would be better to detect metastasis specimens as ALK negative specimens if both primary and metastatic specimens have developed.