Abstract
IntroductionPreclinically, high epidermal growth factor receptor 1 (FGFR1) messenger RNA (FGFR1-MRNA) and FGFR1 amplification (FGFR1-AMP) predicted sensitivity to fibroblast growth factor receptor inhibitors in non–small-cell lung cancer and small-cell lung cancer cell lines. KRAS mutations did not preclude sensitivity. Patients and MethodsMetastatic EGFR- and ALK-negative lung cancers were screened for FGFR1-MRNA by in-situ hybridization (ISH) and FGFR1-AMP by silver in-situ hybridization (SISH). Patients with positive findings were offered ponatinib, a multi–kinase inhibitor of FGFR1-4. Differences in overall survival (OS) between cohorts were assessed by the log-rank test. Association of FGFR1 positivity with clinicopathologic features were assessed by Fisher exact test and Kruskal-Wallis rank sum test. ResultsA total of 171 cases were prescreened: 9 (7.3%) of 123 SISH+; 53 (42.1%) of 126 ISH+; and 6 cases concordantly positive for SISH and ISH. SISH+ cases had fewer coincident KRAS mutations (P = .03) than SISH− cases, and ISH+ cases had worse OS (P = .020) than ISH− cases. Data distributions suggested a distinct higher positivity cut point for FGFR1 ISH (≥ 20%), occurring in 29 (23%) of 126 cases, was associated with small-cell lung cancer histology (P = .022), soft tissue metastases (P = .050) and shorter OS (P = .031). Four patients received ponatinib on study: All ISH+ by the initial cut point, 2 of 4 by higher cut point, 1 of 4 SISH+. Tolerability was poor. The best response for the 2 higher ISH cases was stable disease and progressive disease for the 2 lower ISH cases. ConclusionElevated FGFR1-MRNA is more common than FGFR1-AMP and associated with worse OS. Higher FGFR1 mRNA expression may be associated with a specific phenotype and is worthy of further exploration. Ponatinib's poor tolerance suggests further fibroblast growth factor receptor exploration in ISH+ cases should utilize more selective FGFR1 inhibitors.
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