ALK Mutation and Crizotinib
The tyrosine kinase has been the target of cancer treatment. After finding success with the EGFR tyrosine kinase, scientists found another tyrosine kinase mutation, ALK, and a new drug, Crizotinib.
Crizotinib showed an impressive response rate of close to 60% of patients with an ALK gene abnormality. Like the EGFR patients, those with the mutation were primarily adenocarcinoma patients and non-smokers, or light former smokers. Early results indicate the profile and action of Crizotinibi to be similar to Tarceva and EGFR positive patients.
15.2 What is ALK
ALK stands for Anaplastic Lymphoma Kinase. Originally associated with lymphoma, “EML4-ALK is a fusion-type protein tyrosine generated in non-small-cell lung cancer as a result of a chromosome inversion” Soda (4). “ALK is a receptor tyrosine kinase that is normally not expressed in the lung.” Pao (17).
Chromosomal translocations and gene fusions play an important role in the initiation of tumorigenesis. Here, chromosomal rearrangements interrupt the ALK gene and fuse it with another gene result in the creation of an oncogenic, ALK fusion genes.
Translocation of ALK can result in fusion with the neighboring gene, EML4, in cancer cells. The fused genes then encode a fusion protein in which the intracellular tyrosine kinase domain of the ALK receptor is constitutively active.
15.21 Association with Other Cancers
ALK belongs to the insulin receptor subfamily of receptor tyrosine kinases. Aberrant ALK activity has recently been shown to be present in anaplastic large cell lymphoma, as well as in solid tumors. Zhang (14)
While translocations are seen in cancer, scientists associated them with hematological tumors and have only recently investigated their significance with solid tumors such as lung. Lin (11). Several studies showed that cell lines with ALK rearrangements underwent cell cycle arrest and apoptosis when treated with ALK-selective inhibitors. Lin (11).
15.22 The Model of Oncogene Addiction
The classic model of lung cancer was the development of one or more growth oncogenes and the failure of one or more tumor suppressor genes. See chapter one. However, some suggest that a single powerful mutation can spur cancerous behavior on its own.
These mutations occur in genes that encode signalling proteins
crucial for cellular proliferation and survival. Mutant
oncogenes drive tumour formation and also maintenance.
Thus, cancers might rely on the expression of these
single-mutant oncogenes for survival, even in the absence
of tumour-suppressor genes. This concept is also called
oncogene addiction. Pao (17)
Traditionally, lung cancer was a disease of middle-aged or elderly patients, as it was thought to take decades for multiple mutations to slowly develop. However, non-smokers with lung cancer appear to be younger, supporting the single mutation hypothesis.
15.31 Response rates
A response rate of close to 60% was reported with Crizotinib for patients with the ALK mutation. This response rate is similar to the response rate for Tarceva with EGFR positive patients. It appears that if the malfunctioning gene can be identified and appropriate treatment prescribed, impressive response rates can be seen. Interestingly , even with ALK positive patients there was a large group, 33% for which stabile disease, but no response was reported.
15.32 Animal and Cell Studies
Impressive results were also seen in cell and animal studies. In one study, mice developed adenocarcinoma nodules in several weeks. Inhibition of EML4-ALK activity with a small-molecule drug induced rapid death of the tumor cells. Soda (4). Tumors in the lungs of the transgenic mice changed to bullae or cysts after treatment with the ALK inhibitor, as revealed by CT scanning and pathology. Soda (4)
15.4 Prevalence of the ALK Mutation
15.40 Prevalence of the Mutation
A 2011 overview by Pao, a well-known researcher, states, the frequency of EML4-ALK translocation ranges from 3% to 7% in unselected NSCLC. Pao (17). If one targets particular patients more likely to have the mutation, such as non-smokers and/or adenocarcinoma patients, the percentage becomes higher.
Similar to EGFR mutations, the frequency of EML4-ALK fusions is
increased in people with adenocarcinomas, in young adult
patients, and in people who have never smoked (<100 cigarettes
in a lifetime) or who are light smokers. Pao (17)
Kwak’s study found "predominantly" adenocarcinoma patients with the mutation. Article at 1696. Another article found adenocarcinoma patients almost exclusively. Eighteen of the 19 EML4-ALK tumors were adenocarcinomas. Pao likewise notes the prevalence of adenocarcinoma patients. Pao (16).
15.42 Squamous Cell Cancers
While he found predominantly adenocarcinomas patients with the mutation, Kwak found one squamous cell patient with the mutation. Inamura found none in 48 tumor cells sampled in his study (Inamura (10). The possibility of squamous patients having the mutation appears small but not nonexistent. If a squamous cell patient asked, is there anything else that can be done, even if is a 1/100 chance, perhaps the physician should mention testing.
15.43 Large Cell and other types
Kwak categorizes tumors as adenocarcinoma, squamous cell carcinoma, and other. She found two classified as other. Kwak (1). In contrast, Inamura found no positive samples among 3 large cell and 21 small cell tumor samples.
Younger patients were more likely to have the mutation
15.45 Smoking History
Most of the ALK positive patients were non-smokers or light former smokers. The results mirror those with EGFR positive patients. Most However, the study found "five patients had a history of more than 10 packyears including three who had smoked for at least 35 packyears." One could not exclude smokers and testing may make sense for these group.
15.46. EGFR and ALK
EGFR is the other prominent tyrosine kinase. However, the groups appear to be different. The patient population harboring EGFR mutations did not overlap with that harboring the EML4–ALK fusion gene, showing that EML4–ALK-positive cancer is a novel subclass within NSCLC. Soda (2)
15.5. FDA Status and Testing for the ALK Fusion Mutation
15.50 Application Pending
The manufacturer is apparently seeking expedited FDA approval of the drug. Many predict approval will be forthcoming.
15.51. Commercial entities performing testing
In clinical trials for Crizotinib patients are tested for the mutation. The studies provide a strong argument for testing at least adenocarcinoma patients. Whether insurance will cover this, whether surgical tissue is needed, the ease and cost of testing, are open questions.
The need for genetic testing is becoming increasingly recognized,
The emergence of new targeted therapies and clinical trials demonstrating differing efficacy and toxicity of treatments according to specific histological subtypes of NSCLC, has resulted in an increasing need for improvements in pathological diagnosis. With the emergence of selective kinase inhibitors targeting epidermal growth factor receptor (EGFR) and anaplastic lymphoma kinase (ALK), there is a corresponding need to identify the subset of NSCLCs harbouring specific genetic mutations associated with sensitivity to these agents… In this review, the importance of accurately subtyping NSCLC is discussed, along with a suggested approach for distinguishing histological subtypes in small biopsy specimens. The significance of EGFR and ALK mutations in NSCLC and the impact of these genotypes on pathology and clinical practice are also reviewed.
Various companies are publicizing testing methods. See www.responsegenetics.com (discussing ALK test; our mention of companies is not intended as an endorsement or evaluation). Another study suggests that routine laboratory testing may be able to detect the mutation:
Low levels of ALK protein expression is a characteristic feature of ALK- rearranged lung adenocarcinomas. A novel, highly sensitive IHC assay reliably detects lung adenocarcinomas with ALK rearrangements and obviates the need for fluorescence in situ hybridization analysis for the majority of cases, and therefore could be routinely applicable in clinical practice to detect lung cancers that may be responsive to ALK inhibitors. Knutsen (6)
A skilled professional may be able to use existing testing methods to identify the mutation . “Detection methods include reverse-transcriptase PCR, fluorescence in-situ hybridisation, and immuno histochemistry.” Pao (17).
15.52 Where is Testing Done
Sophisticated genetic testing is the type of procedure where the large research hospital frequently shows its superiority. They may routinely utilize such a procedure based upon recent research, whereas the local hospital and general oncologist may not utilize such tests, particularly for use with a drug which has not yet been FDA approved. (As of May, 2011, Crizotinib had not been approved). Those who may potentially have the mutation may want to utilize a major research facility, at least a Comprehensive Cancer Center, which has the resources to evaluate and perform such testing.
15.53 Tissue or sample needed
Generally a tissue is secured through a biopsy which is a surgical procedure carrying some risk and some discomfort. Studies are looking at less intrusive alternatives, For example, one study looked at obtaining EGFR mutation results from pleural fluid which would be more easily obtained. Knutsen suggests standard testing may be able to detect the mutation. (3)
15.54 Crizotinib’s Use for ALK negative patients
Whether Tarceva, an anti-EGFR drug is effective with EGFR negative patients has been debated here and elsewhere. There may be similar discussion of Crizitonib, and whether this gene plays any role in patients without the ALK rearrangements.
15.7 Other Treatments for the ALK Mutation
With the model of Tarceva and those of other tyrosine kinases, targeting ALK would appear to be the primary treatment, in early 2011 as this was written. Sadly, resistance arises in many patients, as the cagey tumor finds ways of restoring its aberrant signaling and abnormal replication. For those experiencing resistance and others, other treatments are being evaluated.
An initial study of Crizotinib showed it provided a higher response rate for ALK positive patients than Alimta. Alimta may be superior to other drugs in treatment of ALK positive patients and Camidge in a 2011 study found Alimta superior to other drugs for ALK positive patients. (Camidge) (16).
More research is needed. Overall, one study found only limited benefit to adding Alimta to conventional chemotherapy. Smit (19) The question of whether Alimita should be combined with chemotherapy for patients overall or ALK patients in particular, or substituted on its own continues to be investigated.
15.721 Side Effects and Limits
According to the Eastern Cooperative Oncology Group, “the FDA has approved the use of pemetrexed in combination with cisplatin for patients with locally advanced or metastatic NSCLC other than predominantly squamous cell histology.” (20)
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7. Sakari, EML4-ALK Fusion Gene Assessment Using Metastatic Lymph Node Samples Obtained by Endobronchial Ultrasound-Guided Transbronchial Needle Aspiration, Clinical Cancer Research October 2010 16; 4938
8. Clinical Features and Outcome of Patients With Non–Small-Cell Lung Cancer Who Harbor EML4-ALK, Journal of Clinical Oncology, August 10, 2009.
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10. Inamura, EML4-ALK Fusion Is Linked to Histological Characteristics in a Subset of Lung Cancers, Journal of Thoracic Oncology, January 2008 - Volume 3 - Issue 1 - pp 13-17
11. Lin, Exon Array Profiling Detects EML4-ALK Fusion in Breast,
Colorectal, and Non–Small Cell Lung Cancers, Mol Cancer Res 2009;7(9). September 2009
12. Wong, The EML4-ALK Fusion Gene Is Involved in Various Histologic Types of Lung Cancers From Nonsmokers With Wild-type EGFR and KRAS,
13. Martelli, EML4-ALK Rearrangement in Non-Small Cell Lung Cancer and Non-Tumor Lung Tissues, American Journal of Pathology. 2009, 174:661-670.
14. Zhang, Fusion of EML4 and ALK is associated with development of lung adenocarcinomas lacking EGFR and KRAS mutations and is correlated with
ALK expression, Molecular Cancer 2010,
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19. Smit, Randomized Phase II and Pharmacogenetic Study of Pemetrexed Compared With Pemetrexed Plus Carboplatin in Pretreated Patients With Advanced Non–Small-Cell Lung Cancer, J. Clin Onco., Vol. 27, No. 12, April 20, 2009
20. Eastern Cooperative Oncology Group Report, Randomized Phase III Study of Maintenance Therapy with Bevacizumab, Pemetrexed, or a Combination of Bevacizumab and Pemetrexed Following Carboplatin, Paclitaxel and Bevacizumab for Advanced Non-Squamous NSCLC