Feasibility of cytological specimens for ALK fusion detection in patients with advanced NSCLC using the method of RT-PCR

Detecting ALK Rearrangement with RT-PCR: A Reliable Approach Compared with Next-Generation Sequencing in Patients with NSCLC

Background

Precise detection of anaplastic lymphoma kinase (ALK) rearrangement guides the application of ALK-targeted tyrosine kinase inhibitors (ALK-TKIs) in patients with non-small-cell lung cancer (NSCLC). Next-generation sequencing (NGS) has been widely used in clinics, but DNA-based NGS used to detect fusion genes has delivered false-negative results. However, fusion genes can be successfully detected at the transcription level and with higher sensitivity using RNA-based reverse transcription polymerase chain reaction (RT-PCR).

Objective

This study compared the performance of RT-PCR and NGS in the detection of echinoderm microtubule-associated protein-like 4 (EML4)-ALK fusion in Chinese patients with NSCLC.

Methods

Formalin-fixed paraffin-embedded tissues from 153 patients who were pathologically diagnosed as having NSCLC were collected from November 2017 to October 2019. Both DNA/RNA-based NGS and RNA-based RT-PCR were used to detect EML4-ALK fusion. For samples with discordant ALK status results, fluorescence in situ hybridization (FISH) or Sanger sequencing was used to further confirm the ALK status.

Results

In total, 124 samples were successfully analyzed using both NGS and RT-PCR. For 118 samples, results were consistent between NGS and RT-PCR, with 25 reported as ALK fusion positive and 93 as ALK fusion negative, achieving a concordance rate of 95.16%. Among the six samples with disconcordant results, five were positive using RT-PCR but negative using NGS, and one was positive using NGS but negative using RT-PCR. Four of six cases with disconcordant results (three RT-PCR positive and one NGS positive) were successfully validated using either FISH or Sanger sequencing.

Conclusions

Compared with NGS, RT-PCR appears to be a reliable method of detecting EML4-ALK fusion in patients with NSCLC.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40291-021-00532-8.

Impact of ALK variants on brain metastasis and treatment response in advanced NSCLC patients with oncogenic ALK fusion

Background

To investigate the impact of ALK variants on the features of brain metastases (BM), the outcome of chemotherapy and targeted therapy using crizotinib, as well as the progression pattern in patients with ALK fusion.

Methods

Patients with ALK fusion were retrospectively collected from January 2013 to July 2017 in Shanghai Pulmonary Hospital. ALK rearrangements were identified via ARMS-PCR. ALK variants were identified via Sanger Sequencing.

Results

A total of 135 patients and 41 with brain metastasis were identified. Radiological features showed that the patients with ALK variant 1 had a larger BM size compared with patients with ALK non-variant 1 (median tumor size: 16.89 vs. 11.01 mm, P=0.031). Similar time to treatment failure (TTF) was observed in patients with ALK variant 1 and non-variant 1 who received first-line crizotinib (median TTF: 15.7 vs. 13.8 months, HR =0.75, P=0.34). Patients with ALK variant 1 who had baseline BM had significantly shorter TTF than non-variant 1 with baseline BM when treated with first-line crizotinib (median TTF: 9.1 vs. 14.9 months, HR =2.68, P=0.037). In patients treated with chemotherapy, ALK variant 1 was associated with inferior TTF (median TTF: 5.6 vs. 8.1 months, HR =1.66, P=0.039). Progression pattern was similar between ALK variant 1 and non-variant 1.

Conclusions

Patients with ALK variant 1 and baseline BM had inferior TTF on first-line crizotinib treatment and presented with more aggressive radiological features. Patients with ALK non-variant 1 had better clinical outcome on first-line chemotherapy.

ALK and ROS1 rearrangement tested by ARMS-PCR in non-small-cell lung cancer patients via cytology specimens: The experience of Shanghai Pulmonary Hospital

BACKGROUND

Cytology specimens are the main samples used for the diagnosis of advanced lung cancer. The objective of our study was to assess anaplastic lymphoma kinase (ALK) and c-ros oncogene 1 receptor tyrosine kinase (ROS1) genes by an amplification refractory mutation system (ARMS)-polymerase chain reaction (PCR) using cytology specimens and to then evaluate the mutation frequency of ALK and ROS1 in non-small-cell lung cancer (NSCLC) patients.

METHODS

A large cohort that consisted of 8180 NSCLC patients who were genetically tested using cytology samples or formalin-fixed and paraffin-embedded (FFPE) samples (tumor tissue or biopsy) from January 2015 to December 2018 were screened. The gene rearrangement ratio and clinical characteristics of the two sample groups were analyzed by SPSS software.

RESULTS

In our hospital, cytology specimens are the main resource used for gene testing in NSCLC. In most cases, an abundant quantity of nucleic acid was extracted from the residual liquid-based cell pellet for testing the ALK and ROS1 genes. In certain cases, when the residual cell pellet was insufficient for the gene testing, the cell block and liquid-based cell smear served as alternative options. In addition, we retrospectively analyzed our previous data, and the mutation ratio of the ALK/ROS1 rearrangements obtained by using the cytology samples (4.98%/1.80%) and the FFPE samples (6.06%/1.62%) was almost the same (P-value = .09/.634).

CONCLUSIONS

This study demonstrated that AMRS-PCR method can effectively identify ALK and ROS1 gene rearrangements and cytology specimens might be an excellent source for routine molecular testing in patients with advanced NSCLC.

ALK detection in lung cancer: identification of atypical and cryptic ALK rearrangements using an optimal algorithm

PURPOSE

IHC, FISH, and NGS are common methods of ALK evaluation in NSCLC. The purpose of this study was to investigate whether ALK false positives or false negatives occurred more often in daily routines. An approach to identify ALK fusion was then proposed.

MATERIALS AND METHODS

We analyzed 1815 cases of NSCLC, including 83 (4.6%) ALK IHC positives. Total 182 samples (62 ALK+ and 120 ALK-) were examined via FISH, RT-ddPCR, NGS, RT-qPCR and RNAscope to confirm ALK status.

RESULTS

One ALK FISH false negative was found, which harbored two genomic rearrangements involved in EML4-ALK (exon 13:exon 20) fusion. One ALK IHC false negative was confirmed depending on a rare ALK FISH-positive pattern and ALK RNAscope positive but ALK fusion was not found via NGS. In addition, an atypical ALK FISH-positive pattern was observed in an IHC-positive case with chromosome 2 inversion leading to EML4-ALK (exon 6:exon 20) fusion. EML4-ALK fusion was determined in one case with an atypical FISH patterns by RT-qPCR. Rare complicated genomic rearrangements involved in a novel ALK fusion of EML4-ALK (exon 7:exon 14) were distinguished in an ALK IHC and FISH double-positive case.

CONCLUSION

False negative of ALK IHC, FISH and NGS results were found in our cohort, but none was false ALK positive. False ALK negatives should be more concerned than false positives. ALK rearrangements with cryptic ALK fusion patterns could be identified using our algorithm. Non-squamous non-small cell lung cancer was recommended for priority detection.

High feasibility of cytological specimens for detection of ROS1 fusion by reverse transcriptase PCR in Chinese patients with advanced non-small-cell lung cancer

Purpose

Our previous study demonstrated that cytological specimens can be used as alternative samples for detecting anaplastic lymphoma kinase (ALK) fusion with the method of reverse transcriptase PCR (RT-PCR) in patients with advanced non-small-cell lung cancer (NSCLC). The current study aimed to investigate the feasibility of cytological specimens for ROS proto-oncogene 1, receptor tyrosine kinase (ROS1) fusion detection by RT-PCR in advanced NSCLC patients.

Patients and methods

A total of 2,538 patients with advanced NSCLC, including 2,101 patients with cytological specimens and 437 patients with tumor tissues, were included in this study. All patients were screened for ROS1 fusion status by RT-PCR. The efficacy of crizotinib treatment was evaluated in ROS1 fusion-positive NSCLC patients.

Results

Among 2,101 patients with cytological specimens, the average concentration of RNA acquired from cytological specimens was 47.68 ng/μL (95% CI, 43.24–52.62), which was lower than the average of 66.54 ng/μL (95% CI, 57.18–76.60, P=0.001) obtained from 437 tumor tissues. Fifty-five patients harbored ROS1 fusion gene that was detected by RT-PCR, and 14 of them were treated with crizotinib. The incidence of ROS1 fusion was 1.95% (41/2,101) in 2,101 patients with cytological specimens, similar to the rate of 3.20% (14/437, P=0.102) for the 437 patients with tumor tissue. Regarding crizotinib treatment, no statistically significant differences were observed in the objective response rate (ORR) (81.8% vs 100%, P=0.604) between the cytological and tissue subgroups of ROS1-positive patients.

Conclusion

This study shows that cytological specimens can be utilized as alternative samples for ROS1 fusion detection by RT-PCR in advanced NSCLC patients.

ALK testing methods: is there a winner or loser?

INTRODUCTION

Anaplastic lymphoma kinase (ALK) is one of the most attractive molecular targets for the treatment of patients with non-small-cell lung cancer. Treatment with ALK inhibitors is recognized as the standard-of-care for patients with ALK gene rearrangements, but it is important to appropriately select patients who will benefit from such treatment. Areas covered: In this article, we review the evidence regarding ALK testing. Immunohistochemistry (IHC), fluorescence in situ hybridization (FISH), and reverse transcription polymerase chain reaction (RT-PCR) are the representative methods for detecting ALK gene fusions. Among these diagnostic modalities, IHC in particular exhibits high sensitivity and specificity for the detection of ALK fusions when appropriately applied and interpreted. Expert commentary: Discrepancies have been reported between the results of IHC and FISH. However, it was revealed that patients with IHC-positivity and FISH-negativity may respond to alectinib, indicating that IHC can be used as a stand-alone method from a clinical standpoint for the identification of patients eligible for treatment with ALK inhibitors. In addition, differences between ALK variants have been reported to affect the prognosis and efficacy of ALK inhibitor-based treatments, and RT-PCR will likely increase in importance as a complementary tool.

Outcomes of Pemetrexed-based chemotherapies in HER2-mutant lung cancers

Background

HER2 mutation has been found to be an oncogenic driver gene in non-small cell lung cancers(NSCLC) and HER2-directed therapies have shown promising results in this unique population, while little is known about its association with outcomes of chemotherapy. The aim of this study was to investigate the efficacy of first line chemotherapy in patients with advanced HER2-mutant lung adenocarcinomas.

Methods

Patients with advanced NSCLC(N = 1714) initially underwent testing for EGFR, KRAS, BRAF mutations and ALK, ROS1 rearrangements, and negative cases were then assessed for HER2 mutations using the method of amplification refractory mutation system(ARMS). The efficacy of first line pemetrexed-based chemotherapy was investigated in patients with HER2-mutant and those with EGFR-mutant, ALK/ROS1-rearranged and KRAS-mutant advanced adenocarcinomas.

Results

HER2 mutations were detected in 29 of 572(5.1%) specimens from a selected population of EGFR/KRAS/BRAF/ALK/ROS1 negative patients. All of them are adenocarcinomas. Among patients with HER2-mutant lung cancers, 25 received pemetrexed-based first line chemotherapy. The objective response rate(ORR) was 36.0%. Their median progression free survival(PFS) was 5.1 months, which was similar with that of KRAS-mutant group (n = 40,5.0 months, p = 0.971), numerically shorter than that of EGFR-mutant group(n = 74, 6.5 months, p = 0.247) and statistically significantly shorter than that of ALK/ROS1-rearranged group (n = 39,9.2 months, p = 0.004). Furthermore, HER2 variants subgroup analysis showed that PFS was inferior in A775_G776insYVMA group compared with other variants (4.2 vs 7.2 months, p = 0.085).

Conclusions

Patients with advanced HER2-mutant lung adenocarcinomas showed an inferior outcome of first line pemetrexed-based chemotherapy compared to those with ALK/ROS1 rearrangements, which strengthen the need for effective HER2-targeted drugs in clinical practice.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4277-x) contains supplementary material, which is available to authorized users.

Analysis of Fusion Genes by NanoString System: A Role in Lung Cytology?

CONTEXT

- Patients with non-small cell lung cancer harboring ALK receptor tyrosine kinase ( ALK), ROS proto-oncogene 1 ( ROS1), and ret proto-oncogene ( RET) gene rearrangements can benefit from specific kinase inhibitors. Detection of fusion genes is critical for determining the best treatment. Assessing rearrangements in non-small cell lung cancer remains challenging, particularly for lung cytology.

OBJECTIVE

- To examine the possible application of the multiplex, transcript-based NanoString system (NanoString Technologies, Seattle, Washington) in the evaluation of fusion genes in lung adenocarcinoma samples.

DATA SOURCES

- This study is a narrative literature review. Studies about NanoString, gene fusions, and lung adenocarcinoma were collected from PubMed (National Center for Biotechnology Information, Bethesda, Maryland). We found 7 articles about the application of the NanoString system to detect fusion genes on formalin-fixed, paraffin-embedded tumor tissues and one article evaluating the adequacy of lung cytologic specimens for NanoString gene expression analysis.

CONCLUSIONS

- To maximize the yield of molecular tests on small lung biopsies, the NanoString nCounter system has been suggested to detect fusion genes. NanoString fusion gene assays have been successfully applied on formalin-fixed, paraffin-embedded tissues. Although there are only a few studies available, the application of NanoString assays may also be feasible in lung cytology. According to available data, the NanoString system could strengthen the routine molecular characterization of lung adenocarcinoma.

Comparison of ALK status between primary and corresponding lymph node metastatic tumors in lung cancer patients

Background

The anaplastic lymphoma kinase (ALK) protein has recently become a promising target in the treatment of non-small cell lung carcinomas(NSCLC) patients with ALK translocation because of the high response rates obtained with an ALK inhibitor. ALK translocations are present in approximately 3-5% of NSCLC patients. According to the literature, little information about the relationship of ALK status between the primary tumor and metastatic sites has been reported. We intended to determine whether the ALK translocations of primary lung cancers are consistent with those in corresponding metastatic lymph node tumors.

Materials and Methods

We analyzed ALK translocations from paired primary and metastatic lymph node tumors in 78 lung cancer patients who had not received TKI before the tissues were sampled.

Results

Using fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) methods, all 45 patients with ALK translocation-positive primary lung tumors had translocations in the metastases. For 33 patients who were ALK negative in the primary tumors, 1 (3%) was ALK positive in their metastatic tumors.

Conclusion

According to a paired t-test, there is no significant difference between primary lung tumors and metastatic sites. Analysis of ALK translocations in the primary lung tumor would be suitable for planning the use of a TKI for advanced NSCLC, but it would be better to detect metastasis specimens as ALK negative specimens if both primary and metastatic specimens have developed.

A comparison of ALK gene rearrangement and ALK protein expression in primary lung carcinoma and matched metastasis

AIMS

The 2013 College of American Pathologists, the Association for Molecular Pathology and the International Association for the Study of Lung Cancer guideline for EGFR and ALK testing in lung carcinoma indicates that either the primary tumour or the metastasis is suitable for testing. The heterogeneity of gene mutations has been studied extensively, while similar reports on gene rearrangements are limited. The aim of this study was to determine if ALK status between primary tumour and matched metastasis differs.

METHODS AND RESULTS

Fifteen ALK fluorescence in-situ hybridization (FISH) rearranged and 19 non-ALK FISH rearranged adenocarcinomas were collected retrospectively based on availability of tissue from a matched metastatic site. Sixty-eight samples were tested by ALK FISH (Vysis ALK break-apart FISH kit) and ALK immunohistochemistry (IHC) (Ventana ALK D5F3 CDx assay). Overall agreement of FISH and IHC was 88%, with IHC showing 100% specificity and 71% sensitivity. Concordance between primary site and metastasis by ALK FISH was seen in 30 cases (88%), and in 32 cases (94%) by ALK IHC. Five discordant cases were found (15%). Three ALK FISH discordant cases had low percentage of ALK FISH-positive tumour cells (average 23%, range: 18-31%) and all were negative by ALK IHC. One IHC discordant case had a high percentage of ALK FISH-positive tumour cells (67%), and was ALK IHC-negative. One FISH discordant case showed ALK FISH- and ALK IHC-positive primary tumour, but ALK FISH- and ALK IHC-negative metastasis.

CONCLUSIONS

ALK FISH results show more frequent discordances between primary tumour and matched metastases than ALK IHC, due probably to technical challenges and sample quality. This observation indicates that the quality of sample and technical expertise of the laboratory should guide the decision about ALK testing in clinical practice.