title: Clinical Implications of Variant ALK FISH Rearrangement Patterns.
abstract: BACKGROUND
  Break-apart fluorescence in situ hybridization (FISH) is the FDA-approved assay for detecting anaplastic lymphoma kinase (ALK) rearrangements in non-small-cell lung cancer (NSCLC), identifying patients who can gain dramatic benefit from ALK kinase inhibitors. Assay interpretation can be technically challenging, and either splitting of the 5' and 3' probes or loss of the 5' probe constitute rearrangement. We hypothesized that there may be clinical differences depending on rearrangement pattern on FISH.
  
  
  METHODS
  An IRB-approved database of NSCLC patients at Dana-Farber Cancer Institute was queried for ALK rearrangement. Clinical characteristics and response to crizotinib were reviewed. Immunohistochemistry (IHC) and targeted next-generation sequencing (NGS) were obtained when available.
  
  
  RESULTS
  Of 1614 NSCLC patients with ALK testing, 82 patients (5.1%) had ALK rearrangement by FISH: 30 patients with split signals, 25 patients with 5' deletion, and 27 patients with details unavailable. Patients with 5' deletion were older (p = 0.01) and tended to have more extensive smoking histories (p = 0.08). IHC was positive for ALK rearrangement in all 27 patients with FISH split signals, whereas three of 21 patients with FISH 5' deletion had negative IHC (p = 0.05). Targeted NGS on two of three cases with discordant FISH and IHC results did not identify ALK rearrangement, instead finding driver mutations in EGFR and KRAS. Patients with 5' deletion treated with crizotinib had a smaller magnitude of tumor response (p = 0.03).
  
  
  CONCLUSIONS
  Patients with 5' deletion on ALK FISH harbor features less typical of ALK-rearranged tumors, potentially indicating that some cases with this variant are false positives. Corroborative testing with IHC or NGS may be beneficial.
authors.affiliation: *Brigham and Women's Hospital, Boston, Massachusetts; and †Dana-Farber Cancer Institute, Boston, Massachusetts.
authors.forename: Xin
authors.initials: X
authors.lastname: Gao
authors.forename: Lynette M
authors.initials: LM
authors.lastname: Sholl
authors.forename: Mizuki
authors.initials: M
authors.lastname: Nishino
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Heng
authors.forename: Pasi A
authors.initials: PA
authors.lastname: Jänne
authors.forename: Geoffrey R
authors.initials: GR
authors.lastname: Oxnard
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics* / Q000473:pathology; D000077547:Crizotinib; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence / Q000379:methods*; D008175:Lung Neoplasms / Q000235:genetics* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D047428:Protein Kinase Inhibitors / Q000008:administration & dosage / Q000627:therapeutic use*; D011720:Pyrazoles / Q000008:administration & dosage / Q000627:therapeutic use*; D011725:Pyridines / Q000008:administration & dosage / Q000627:therapeutic use*; D055815:Young Adult
chemical_list: D047428:Protein Kinase Inhibitors; D011720:Pyrazoles; D011725:Pyridines; D000077547:Crizotinib