Are there imaging characteristics associated with lung adenocarcinomas harboring ALK rearrangements?

5% of lung adenocarcinomas harbor rearrangements of the anaplastic lymphoma kinase (ALK) gene. This study compared computed tomography (CT) imaging features in patients with ALK rearrangements and those with EGFR mutations.

30 patients with ALK rearrangements were studied. 97 patients with epidermal growth factor receptor (EGFR) mutations were used as controls. Features assessed included size and location of thoracic lymphadenopathy, and the size, contour, consistency and location of the primary tumor.

127 lung adenocarcinomas were examined. 30 (24%) tumors harbored ALK rearrangements, 97 (76%) tumors harbored EGFR mutations. ALK tumors had larger thoracic lymphadenopathy than the control group (p=0.005). Both readers identified 17 (57%) patients in the ALK group with lymph nodes >1.5cm. Reader 1 identified 19 (20%) patients in the EGFR group with lymph nodes >1.5cm, and reader 2 identified 18 (19%) (kappa 0.969). Patients with ALK rearrangements were more likely to have multifocal lymphadenopathy. Reader 1 identified 22 (73%) ALK patients versus 35 (36%) EGFR patients with multifocal thoracic nodal enlargement, while reader 2 identified 20 (67%) ALK patients versus 30 (31%) EGFR patients (kappa 0.953). 92% of ALK positive lesions were solid.

ALK positive lung adenocarcinomas are more likely than EGFR mutant lung adenocarcinomas to be associated with larger volume, multifocal thoracic lymphadenopathy. While routine testing for ALK should be standard, the presence of such characteristics in a solid tumor should further prompt testing for ALK rearrangement.