Analysis of EML4-ALK rearrangement in non-small cell lung cancer in Argentina.

INTRODUCTION: Identification of EML4-ALK rearrangement by FISH test has become standard in advanced NSCLC patients. There is limited information about the prevalence and clinical characteristics of ALK translocation in Latin America. The aim of our study was to evaluate this lung cancer subtype features in Argentinian patients and the factibility of FISH test with different methods used for obtaining tissue samples.

METHODS: Between August 2014 and February 2017, 183 non-squamous NSCLC patients were prospectively enrolled from five Argentinian institutions. Different techniques and procedures were used to obtained tissue samples material. ALK determination was performed by FISH and immunohistochemistry (IHC). Correlation with clinico-pathological information and different biopsy procedures was assessed.

RESULTS: From 183 non-squamous NSCLC samples, 131 could perform FISH test, finding 123 (93.9%) negative and 8 (6.1%) positive patients. Fifty-one samples were not evaluable by FISH, 35 because of technical problems and 16 due to not/weak signal. The difficulties in obtaining adequate FISH tests were observed significantly more frequently for fine-needle aspiration (FNA) and core-needle biopsy than for excisional and incisional biopsy (p = 0.009). Regarding the procedures, surgery was the most efficient, obtaining only 12.7% (10/79) of not evaluable samples for FISH, while CT guided biopsy and transbronchial biopsy (TBB) failed in 43.8% (21/48) and 41.3% (19/46) of patients respectively (p < 0.001). We observed a significant association between ALK translocation and never smoking habit (p = 0.004).

CONCLUSION: Our ALK rearrangements frequency (6.1%) was similar to the reports worldwide. One of the major determinants for the ALK FISH test success is the quality of the tissue sample obtained.