Objectives: RET rearrangements represent one of the newest molecular targets in non-small cell lung cancer (NSCLC). However, the prevalence, clinical characteristics, and outcome of patients with RET-rearranged lung adenocarcinoma in metastatic disease remain uncertain.
Materials and methods: Multiplex reverse transcription-polymerase chain reaction (RT-PCR) was used to detect KIF5B-RET and CCDC6-RET fusions from specimens of malignant pleural effusion (MPE) in patients with metastatic lung adenocarcinoma. The demographic data and outcome of patients with RET-rearranged tumors were compared with those with EGFR-mutant, KRAS-mutant, EML4-ALK-rearranged, and quadri-negative tumors.
Results: Of the 722 patients with MPE of lung adenocarcinoma screened, 17 (2.4%) had RET-rearranged tumors. The detected RET rearrangements comprised 11 (65%) KIF5B-RET and 6 (35%) CCDC6-RET fusions, including 2 novel fusion variants identified. The presence of RET rearrangements was not associated with age at diagnosis, gender or smoking history, but predominantly seen in solid histological subtype. None of patients with RET-rearranged tumors had received kinase inhibitors with activity against RET kinase. The median overall survival was 22.4 months (95% CI, 8.8-36.0) for the 17 patients with RET-rearranged tumors, compared with 21.3 months (95% CI, 18.7-23.9; P=0.57) for the 451 patients with EGFR-mutant tumors, 5.4 months (95% CI, 2.7-8.1; P=0.002) for the 13 patients with KRAS-mutant tumors, 18.9 months (95% CI, 10.7-27.1; P=0.82) for the 51 patients with EML4-ALK-rearranged tumors, and 12.0 months (95% CI, 9.0-15.0; P=0.07) for the 190 patients with quadri-negative tumors.
Conclusion: Multiplex RT-PCR from specimens of MPE is feasible for the screening of RET rearrangements in NSCLC. Metastatic RET-rearranged lung adenocarcinoma patients with MPE might have favorable survival comparable to those with metastatic EGFR-mutant tumors.
Keywords: CCDC6–RET fusions; EGFR; KIF5B–RET fusions; Lung adenocarcinoma; NSCLC; RET rearrangements.
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