Frequency of Brain Metastases and Multikinase Inhibitor Outcomes in Patients With RET–Rearranged Lung Cancers

Introduction: In ret proto-oncogene (RET)–rearranged lung cancers, data on the frequency of brain metastases and, in particular, the outcomes of multikinase inhibitor therapy in patients with intracranial disease are not well characterized. Methods: A global, multi-institutional registry (cohort A, n = 114) and a bi-institutional data set (cohort B, n = 71) of RET-rearranged lung cancer patients were analyzed. Patients were eligible if they had stage IV lung cancers harboring a RET rearrangement by local testing. The incidence of brain metastases and outcomes with multikinase inhibitor therapy were determined. Results: The frequency of brain metastases at the time of diagnosis of stage IV disease was 25% (95% confidence interval [CI]: 18%–32%) in all patients from both cohorts. The lifetime prevalence of brain metastasis in stage IV disease was 46% (95% CI: 34%–58%) in patients for whom longitudinal data was available. The cumulative incidence of brain metastases was significantly different (p = 0.0039) between RET-, ROS1-, and ALK receptor tyrosine kinase (ALK)–rearranged lung cancers, with RET intermediate between the other two groups. Although intracranial response data was not available in cohort A, the median progression-free survival of multikinase inhibitor therapy (cabozantinib, vandetanib, or sunitinib) in patients with brain metastases was 2.1 months (95% CI: 1.3–2.9 months, n = 10). In cohort B, an intracranial response was observed in 2 of 11 patients (18%) treated with cabozantinib, vandetanib (± everolimus), ponatinib, or alectinib; the median overall progression-free survival (intracranial and extracranial) was 3.9 months (95% CI: 2.0–4.9 months). Conclusions: Brain metastases occur frequently in RET-rearranged lung cancers, and outcomes with multikinase inhibitor therapy in general are suboptimal. Novel RET-directed targeted therapy strategies are needed.