OPRM1-ROS1 Fusion Detected by Next-Generation Sequencing with Circulating DNA in a Patient with EGFR Mutated Advanced NSCLC: A Case Report

Abstract

ROS1 comprises a small molecular subset of NSCLC, and several fusion partners have been discovered. Concomitant mutations of EGFR and ROS1 in NSCLC have been occasionally reported, while no clear standard of treatment has been revealed. Here we report a case with metastatic lung adenocarcinoma detected to have EGFR 21 exon L858R mutation at diagnosis, who responded to first-line gefitinib and second-line osimertinib treatment. Next-generation sequencing during the treatment course revealed multiple alterations, including an OPRM1-ROS1 Ointergenic: R36 fusion. We reviewed the related literatures but found no report of this fusion type previously. The application of ctDNA detection results in the finding of new alterations, which need further confirmation.

Introduction

Great progress has been achieved in molecular targeted therapy for lung adenocarcinoma. The targetable driver genes include mutant EGFR, BRAF, HER2, and MET, rearrangements in ALK, ROS1, RET, and so on [1]. Molecular genotyping has been routinely conducted in clinic to determine the therapeutic regimen with the development of sequencing technology, and novel mutations are being identified which may lead to more treatment opportunities.

EGFR mutation and ROS1 rearrangement occur in about 50% and 2–3% of Asian patients with advanced lung adenocarcinoma, respectively [2, 3]. There were 2.8% of patients harboring EGFR mutations who carry additional alterations, among which KRAS mutations (31.7%) and ALK rearrangement (17.5%) were relatively common, while EGFR/ROS1/KRAS was rare (0.13%) [4]. In patients with ROS1 rearrangement, the incidence of concomitant mutations involving EGFR were detected as 0–24% [5, 6, 7]. With the popularization of next-generation sequencing (NGS), more and more fusion gene partners of ROS1 have been reported, including CD74, EZR, SLC34A2, TPM3, SDC4, LRIG3, FIG(GOPC)1, CCDC6, CLTC, KDELR2, LRIG3, TPD52L1, CEP72, TMEM106B, ZCCHC8, and WNK1 [3, 8, 9, 10, 11, 12, 13]. We report a novel OPRM1-ROS1 Ointergenic: R36 fusion concomitant with EGFR mutations in a patient with stage IV lung adenocarcinoma.

Case Report

A 66-year-old male never-smoker was diagnosed as stage IV lung adenocarcinoma of the left lower lobe with extensive metastases (multiple ribs and vertebras, pelvis) in May 2016 (Fig. 1a). The biopsy specimen obtained by fiber bronchoscope was tested for EGFR and ALK using ARMS-PCR and FISH, respectively, and the tumor was found to be positive for EGFR 21 exon L858R mutation and negative for ALK rearrangement.

Fig. 1.

Lung computed tomography scans during the treatment course.aPET/CT scan before treatment (May 2016).bA computed tomography scan after treatment with gefitinib for 1.5 months (June 2016).cA computed tomography scan after treatment with gefitinib for 11 months (March 2017).dA computed tomography scan after treatment with osimertinib for 2 months (May 2017).eA computed tomography scan after treatment with 2 cycles of pemetrexed and cisplatin (Dec 2017).fA magnetic resonance scan after treatment with 2 cycles of pemetrexed and cisplatin (Dec 2017).

He received gefitinib as first-line therapy and had a stable disease (Fig. 1b) until progression occurred after 11 months, presenting with aggravating pain in the waist and left iliac region (Fig. 1c). CT scan showed enlargement of primary lesion and new lesions of bone metastasis. We did ctDNA multiplex genotyping analysis using NGS with peripheral blood (Burnig Rock, Guangzhou, China), and the results showed EGFR 21 exon L858R (abundance 36.62%), EGFR 20 exon T790M (7.95%) and OPRM1-ROS1 Ointergenic: R36 fusion (15.81%), EGFR, HER2, and BRAF amplification (copy number [CN] 2.69, 3.07, and 2.63, respectively). He received osimertinib as second-line therapy with palliative radiotherapy for vertebral lesions (30 Gy/10 fx) and had a stable disease (Fig. 1d). Progression was confirmed with CT scan after 7 months. Using NGS, we detected EGFR exon 18 L718Q (abundance 0.79%), 20 exon T790M (5.04%), C797S (0.11%), 21 exon L858R (24.58%), and OPRM1-ROS1 Ointergenic: R36 fusion (6.11%), HER2 amplification (CN 2.66). He received pemetrexed and carboplatin as third-line therapy for 2 cycles, with multiple bilateral pulmonary nodules on CT scan and multiple new intracranial lesions on MR (Fig. 1e, f). Repeated NGS showed EGFR exon 18 L718Q (abundance 1.09%), 20 exon T790M (2.43%), 21 exon L858R (13.80%), OPRM1-ROS1 Ointergenic: R36 fusion (3.97%), and EGFR amplification (CN 2.25), HER2 amplification (CN 2.26) (the genetic alterations detected by NGS are listed in supplementary table 1; see www.karger.com/doi/10.1159/000507980). He refused further treatment and died 3 months later without re-evaluation.

Discussion

This is the first report of co-existing OPRM1-ROS1 fusion and EGFR mutation in NSCLC. OPRM1 (opioid receptor mu 1) gene occupies a 200-kb region on the 6q25.2 (genecard.org) and encodes mu-opioid receptor, which is a transmembrane receptor regulating the analgesic response to pain [14]. ROS1 gene is located on the 6q22 [15]. OPRM1 is located near EZR (6q25.3), and the fusion may be generated from intra-chromosomal inversion similar to EZR-ROS1. ROS1 receptor has no known ligand, and the downstream oncogenic pathway differs with different fusion partners. The most reported breakpoints are exon 32, 34, and 35 [16]. The breakpoint of ROS1 in this case was exon 36, which encodes the transmembrane domain of ROS1 together with exon 35, and the reserved ROS1 kinase domain is sufficient to drive carcinogenesis independent of partners [17]. There were several limitations with this case. ROS1 detection was not performed at baseline. The patient did not receive crizotinib and the function of the fusion could not be proven. The detection of EGFR T790M after treatment with gefitinib, C797S, and L718Q after osimertinib were in accordance with the course of EGFR TKI treatment [18, 19], confirming that EGFR mutation was a definite driver. Generally, pemetrexed-based chemotherapy is favorable in patients with ROS1 arrangements [20], while in this case there was no response to pemetrexed. Many other alterations were also present in this case, for the use of NGS may result in a higher ratio of concomitant mutations. The dynamic monitoring of mutation was carried out with blood, while repeated biopsy for FISH was lacked because of the unwillingness of the patient. The function of this fusion needs further illustration.

In conclusion, a new ROS1 rearrangement was found, which was concomitant with EGFR mutation and should be further examined for the oncogenicity. NGS is a feasible method to detect novel types of gene arrangement and concomitant mutations, while the treatment standard needs further studies.

Statement of Ethics

The patient provided written informed consent to publish his case including the NGS results and images.

Conflict of Interest Statement

All the authors declare that there is no conflict of interests.

Funding Sources

There was no funder involved.

Author Contributions

Sicai Zhang drafted the manuscript, Zhiyong Xu reported the case, and Weimin Zhang revised manuscript. All the authors reviewed and approved the submitted article.

Supplementary Material

Supplementary data