Predictive Biomarker Testing in Lung Cancer (ALK, ROS1, PDL1, EGFR, KRAS, BRAF, MET and RET)
Principle of Examination
Non-Small Cell Lung Carcinomas (NSCLC) account for around 85% of lung cancers and includes predominantly adenocarcinoma and squamous cell carcinoma. Depending on the patients’ medical status and stage of disease, treatment options include surgery, radiation therapy and chemotherapy. Although cytotoxic chemotherapy remains an important part of treatment, targeted therapies based on genetic alterations in the tumour are appropriate for selected cases. Identifying disease-causing variants in oncogenes associated with NSCLC can help determine which patients are more likely to benefit from a targeted therapy.
Anaplastic Lymphoma Kinase (ALK) Testing
Rearrangements of the gene encoding anaplastic lymphoma kinase (ALK) have been linked to abnormal proliferation and NSCLC (most commonly adenocarcinoma). The most common ALK rearrangement in NSCLC is EML4-ALK, which arises from fusion between the 5’ end of the EML4 gene and the 3’ end of the ALK gene on chromosome 2p23. Patients with ALK rearrangements are younger than most patients with NSCLC. EML4-ALK rearrangements are also more common in adenocarcinomas of light or non-smokers. In addition, ALK gene rearrangements are rarely coincident with EGFR, HER2 or KRAS variants, indicating it is a distinct disease subtype.
Patients with ALK rearrangements may be considered for therapy targeting the activated receptor tyrosine kinase (TKI) that results from EML4-ALK and other ALK fusions.
ROS1 Testing
The ROS1 gene makes a protein that is involved in sending signals in cells and in cell growth. Mutated forms of the ROS1 gene and protein have been found in some types of cancer, including non-small cell lung cancer (NSCLC), a type of brain cancer called glioblastoma multiforme, and cancers of the bile duct, ovary, stomach, colon, and rectum. The protein made by the ROS1 gene is a type of receptor tyrosine kinase#.
Less than 2% of people with NSCLC have ROS1-positive advanced NSCLC. The ROS1 oncogene is thought to be found almost exclusively in non-squamous NSCLC, mainly in tumours with adenocarcinoma histology. In the absence of any targeted therapy until now, ROS1-positive advanced NSCLC is treated with cytotoxic chemotherapy that can cause unpleasant side effects. Crizotinib is now recommended for use within the Cancer Drugs Fund as an option for treating ROS1-positive advanced NSCLC in adults. ROS1 status should be tested upfront in all non-squamous NSCLC, testing for ROS1 status in all newly diagnosed nonsquamous NSCLC is recommended in line with testing for other types of tumour expression in NSCLC##.
PD-L1 Testing
Responses to anti-PD-1 and anti-PD-L1 agents are enhanced in patients whose tumours express high levels of PD-L1 compared with those expressing low or no tumour PD-L1. As such, reliable testing assays are required to inform treatment choices. Broad access to high-quality PD-L1 testing will help clinicians to identify the most appropriate treatment option for individual patients with NSCLC, including chemotherapy versus anti-PD-1/PD-L1, and single-agent anti-PD-1/PD-L1 versus combination immunotherapy regimens.
Current data indicate that PD-L1 expression predicts survival outcome in lung cancer patients treated with PD-1 antibodies.
ALK, ROS1 and PDL1 are tested via IHC in-house and are currently validated on FFPE tissues only. These are requested on EPIC by the pathologist via MDT. Results of these are then added as supplementary reports to the patient record. All non-small cell non-squamous lung cancers are reflex tested for ALK mutation following reporting of the patient’s cytology or histology.
Epidermal Growth Factor Receptor (EGFR) Testing
This one of the most frequently mutated genes in non-small cell lung cancer (NSCLC), resulting in constitutive activation of cellular signalling pathways that induce and sustain tumorigenesis. By testing for EGFR mutations, personalised treatment can be employed using established targeted kinase inhibitors to preferentially kill malignant cells.
KRAS Testing
RAS alterations are the most common activating lesions in human cancers, and KRAS is the most common oncogene-driven form of NSCLC, accounting for one-quarter of these cancers. In lung cancer, driver alterations in KRAS are predominantly G12X (most commonly G12C).
BRAF Testing
BRAF mutations have been reported in about 4% of non-small cell lung cancers (NSCLC). They are most common in adenocarcinoma non-small cell lung cancer. BRAF V600E mutations specifically occur in about 1-2% of non-small cell lung cancer patients. Most patients with BRAF V600E tend to have a smoking history.
All non-small cell non-squamous lung cancers are reflex tested for EGFR, KRAS and BRAF mutations following reporting of the patient’s cytology or histology.
RET Testing
RET rearrangements occur in approximately 2.5-10% of sporadic Papillary thyroid cancer (PTC) (Ref N° 5) and 1-3% of NSCLC. The most prevalent fusions are KIF5B exon 15 – RET exon 12 and KIF5B exon 16 – RET exon 12, which represent over 75% of RET fusions.
METexon14 skipping Testing
Although many cases of METex14 alterations are found in lung adenocarcinomas, these events have a much higher incidence in pulmonary sarcomatoid carcinomas. Approximately 20% to 30% of sarcomatoid carcinomas harbour METexon14 alterations.
All non-small cell non-squamous lung cancers are reflex tested for RET and MET following reporting of the patient’s cytology or histology.
Please use the request form located on the right side of this page for sending samples to the Royal Devon and Exeter Hospital for testing.
More than or equal to 10% neoplastic cell content is required for predictive biomarker testing on FFPE samples; for PD-L1 testing a neoplastic cell content of at least 100 cells is required. This will be determined in house but if you require advice on sample suitability please contact Dr M. Powari, Consultant Histopathologist, RDE manish.powari@nhs.net or on 01392 402999.
Specimen Labelling Procedure
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