Patterns of Metastatic Spread and Mechanisms of Resistance to Crizotinib in ROS1-Positive Non-Small-Cell Lung Cancer

Abstract

Purpose: The ROS1 tyrosine kinase is activated through ROS1 gene rearrangements in 1-2% of non-small cell lung cancer (NSCLC), conferring sensitivity to treatment with the ALK/ROS1/MET inhibitor crizotinib. Currently, insights into patterns of metastatic spread and mechanisms of crizotinib resistance among ROS1-positive patients are limited.

Patients and methods: We reviewed clinical and radiographic imaging data of patients with ROS1- and ALK-positive NSCLC in order to compare patterns of metastatic spread at initial metastatic diagnosis. To determine molecular mechanisms of crizotinib resistance, we also analyzed repeat biopsies from a cohort of ROS1-positive patients progressing on crizotinib.

Results: We identified 39 and 196 patients with advanced ROS1- and ALK-positive NSCLC, respectively. ROS1-positive patients had significantly lower rates of extrathoracic metastases (ROS1 59.0%, ALK 83.2%, P=0.002), including lower rates of brain metastases (ROS1 19.4%, ALK 39.1%; P = 0.033), at initial metastatic diagnosis. Despite similar overall survival between ALK- and ROS1-positive patients treated with crizotinib (median 3.0 versus 2.5 years, respectively; P=0.786), ROS1-positive patients also had a significantly lower cumulative incidence of brain metastases (34% vs. 73% at 5 years; P<0.0001). Additionally, we identified 16 patients who underwent a total of 17 repeat biopsies following progression on crizotinib. ROS1 resistance mutations were identified in 53% of specimens, including 9/14 (64%) non-brain metastasis specimens. ROS1 mutations included: G2032R (41%), D2033N (6%), and S1986F (6%).

Conclusions: Compared to ALK rearrangements, ROS1 rearrangements are associated with lower rates of extrathoracic metastases, including fewer brain metastases, at initial metastatic diagnosis. ROS1 resistance mutations, particularly G2032R, appear to be the predominant mechanism of resistance to crizotinib, underscoring the need to develop novel ROS1 inhibitors with activity against these resistant mutants.

Keywords: ALK; RET; ROS1; acquired resistance; crizotinib.

Fig 1.

Kaplan-Meier curves for progression-free survival (PFS) and overall survival (OS) of patients with ALK- and ROS1-positive non–small-cell lung cancer. (A) PFS for crizotinib treatment (any line of therapy). (B) PFS for crizotinib treatment in the second-line setting. (C) OS as measured from the time of crizotinib initiation. (D) OS as measured from the time of crizotinib initiation in the second-line setting.

Fig 2.

Frequency of (A) intrathoracic and (B) extrathoracic sites of malignant disease at initial metastatic diagnosis. (C) Frequency of brain metastases at initial metastatic diagnosis. (D) Frequency of any extrathoracic site of malignant disease at initial metastatic diagnosis.

Fig 3.

Cumulative incidence of brain metastases over time among (A) all patients with ALK- and ROS1-positive disease and (B) patients with ALK- and ROS1-positive disease with no known brain metastases at initial metastatic diagnosis.

Fig 4.

ROS1 resistance mutations in patients with ROS1-positive disease who progressed during crizotinib treatment. (A) Individual swimmer plots depict progression-free survival of crizotinib treatment and findings from postprogression biopsy specimens. (B) Frequencies and breakdown of ROS1 resistance mutations in postcrizotinib biopsy specimens. (*) Two patients continued crizotinib beyond progression and remained on crizotinib at the time of the resistance biopsy. MGH, Massachusetts General Hospital; WT, wild type.

Fig A1.

Progression-free survival (PFS) of ALK- and ROS1-positive patients with (A) M1a and (B) M1b disease.

Fig A2.

Breakdown of ROS1 resistance mutations in non–brain metastasis, postcrizotinib specimens (n = 14). WT, wild type.