Distribution and therapeutic outcomes of intergenic sequence-ALK fusion and coexisting ALK fusions in lung adenocarcinoma patients.

INTRODUCTION

Patients with ALK rearranged non-small-cell lung cancer (NSCLC) show survival benefits from tyrosine-kinase inhibitor (TKI). Widely application of DNA sequencing revealed various rearrangement pattern in addition to single EML4-ALK fusion. Here, we retrospectively analyzed the distribution and coexistence of ALK rearrangement and therapeutic outcome of patients with ALK rearranged NSCLC.

METHOD

ALK positive NSCLC patients were screened at West China Hospital. NGS was performed on pre-treatment samples. Clinical characteristics and therapeutic outcomes were collected to retrospectively analyzed.

RESULTS

Among the 89 patients with 22 ALK rearrangements, fusions of intergenic sequences with ALK were found in 15 (16.85 %). Non-EML4-ALK fusions were present in 18 patients (20.22 %). Coexistence of rearrangements were present in 16 patients (17.98 %). Intergenic sequence-ALK and non-EML4-ALK fusions occurred at higher rates in patients with at least two fusions (62.5 % versus 6.85 % for intergenic sequence-ALK, 62.5 % versus 10.96 % for non-EML4-ALK). There were 40 ALK-rearranged NSCLC patients receiving the first-line crizotinib. The median progression-free survival (PFS) was 9.7 months when excluding three lost patients. In the seven patients who had at least two fusions, the median PFS was 11.9 months, compared with 9.0 months among those with single (p = 0.336). No significant difference in median PFS was found between patients with and without intergenic-ALK fusion (12.0 months versus 9.6 months, p = 0.989). The median PFS was 9.0 months in patients harboring a single EML4-ALK fusion versus 13.0 months in those with other ALK alterations (P = 0.890). The PFS of patients with single intergenic sequence-ALK fusion reached to 2.9 months, 27 months, and 28.9 months respectively.

CONCLUSION

Our study reports the distribution of intergenic sequence-ALK and coexisting fusions in ALK-rearranged NSCLC. Intergenic sequence-ALK and non-EML4-ALK are prone to coexist with other fusions. Neither intergenic sequence-ALK nor coexistence of fusions had a significant effect on the therapeutic benefit of treatment with crizotinib.