Responses to crizotinib in a patient with c-ros oncogene 1, receptor tyrosine kinase-positive advanced lung adenocarcinoma: A case report

Efficacy of crizotinib and pemetrexed-based chemotherapy in Chinese NSCLC patients with ROS1 rearrangement

Background

ROS1 rearrangement is a novel molecular subgroup of non-small-cell lung cancer (NSCLC). This study aimed to investigate the efficacy of crizotinib and pemetrexed-based chemotherapy in Chinese NSCLC patients with ROS1 rearrangement.

Results

A total of 2309 patients received ROS1 fusion detection and 51(2.2%) patients had ROS1 rearrangement. There was no significant difference between ROS1 fusion-positive and fusion-negative cohorts in demographic data. For the ROS1 fusion-positive patients, crizotinb-treated group had a higher overall response rate (ORR, 80.0%), disease control rate (DCR, 90.0%) and longer progression-free survival (PFS, 294 days) compared with the rates in pemetrexed-treated group (ORR, 40.8%; DCR, 71.4%; PFS, 179 days) and non-pemetrexed-treated group (ORR, 25.0%; DCR, 47.7%; PFS, 110 days). Besides, ORR, DCR and PFS were similar in three major ROS1 fusion partners. For the first-line treatment, patients received pemetrexed had a significant longer PFS than those received non-pemetrexed chemotherapy (209 vs. 146 days, P = 0.0107). In pemetrexed-treated cohorts, ROS1-positive patients with low TS expression had a statistically significant longer PFS than those with high TS expression (184 vs. 110 days, P = 0.0105).

Materials and methods

We retrospectively identified patients with NSCLC who were screened for ROS1 fusion using multiplex reverse transcription-polymerase chain reaction (RT-PCR) from October 2013 to February 2016. The thymidylate synthase (TS) mRNA levels were tested using quantitative real-time RT-PCR.

Conclusions

Crizotinib was also highly active at treating Chinese NSCLC patients with ROS1 rearrangement. TS expression could predict the efficacy of pemetrexed-based therapy in ROS1 fusion-positive patients.

Testing for ROS1 in non-small cell lung cancer: a review with recommendations

Rearrangements of the ROS1 gene occur in 1-2 % of non-small cell lung cancers (NSCLCs). Crizotinib, a highly effective inhibitor of ROS1 kinase activity, is now FDA-approved for the treatment of patients with advanced ROS1-positive NSCLC. Consequently, focus on ROS1 testing is growing. Most laboratories currently rely on fluorescence in situ hybridisation (FISH) assays using a dual-colour break-apart probe to detect ROS1 rearrangements. Given the rarity of these rearrangements in NSCLC, detection of elevated ROS1 protein levels by immunohistochemistry may provide cost-effective screening prior to confirmatory FISH testing. Non-in situ testing approaches also hold potential as stand-alone methods or complementary tests, including multiplex real-time PCR assays and next-generation sequencing (NGS) platforms which include commercial test kits covering a range of fusion genes. In order to ensure high-quality biomarker testing, appropriate tissue handling, adequate control materials and participation in external quality assessment programmes are essential, irrespective of the testing technique employed. ROS1 testing is often only considered after negative tests for EGFR mutation and ALK gene rearrangement, based on the assumption that these oncogenic driver events tend to be exclusive. However, as the use of ROS1 inhibitors becomes routine, accurate and timely detection of ROS1 gene rearrangements will be critical for the optimal treatment of patients with NSCLC. As NGS techniques are introduced into routine diagnostic practice, ROS1 fusion gene testing will be provided as part of the initial testing package.