Medical Policy: 02.04.20
Original Effective Date: October 2008
Reviewed: March 2017
Revised: March 2017
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This Medical Policy document describes the status of medical technology at the time the document was developed. Since that time, new technology may have emerged or new medical literature may have been published. This Medical Policy will be reviewed regularly and be updated as scientific and medical literature becomes available.
Cetuximab (Erbitux®, ImClone Systems) and panitumumab (Vectibix®, Amgen) are monoclonal antibodies that bind to the epidermal growth factor receptor (EGFR), preventing intrinsic ligand binding and activation of downstream signaling pathways vital for cancer cell proliferation, invasion, metastasis, and stimulation of neovascularization. Some individuals with colorectal cancer have tumors with a Kirsten rat sarcoma viral oncogene homolog (KRAS) mutation that may affect tumor response to these EGFR inhibitors.
The RAS-RAF-MAP kinase pathway is activated in the EGFR cascade. RAS proteins are G-proteins that cycle between active (RAS-GTP) and inactive (RAS-GDP) forms, in response to stimulation from a cell surface receptor such as EGFR, and act as a binary switch between the cell surface EGFR and downstream signaling pathways. The KRAS gene can harbor oncogenic mutations that result in a constitutively activated protein, independent of EGFR ligand binding, rendering antibodies to the upstream EGFR ineffective. KRAS mutations are found in approximately 30-50% of colorectal cancer tumors and are common in other tumor types. KRAS and BRAF mutations are considered to be mutually exclusive.
Cetuximab and panitumumab are approved in the treatment of metastatic colorectal cancer (mCRC) in the setting of refractory disease. Data from randomized controlled trials have consistently shown a lack of clinical response to cetuximab and panitumumab in patients with mutated KRAS, with tumor response and prolongation of progression-free survival observed only in patients with wild-type KRAS mutations. KRAS mutation analysis using polymerase-chain reaction (PCR) methods is commercially available as a laboratory-developed test in a CLIA-licensed laboratory.
Clinical trial data show that patients with KRAS-mutated metastatic colorectal cancer do not benefit from cetuximab (Erbitux®) or panitumumab (Vectibix®) when given in combination with other treatment regimens or when used alone.
The National Comprehensive Cancer Network (NCCN) guidelines (v2.20156 on the treatment of colon cancer, and the guideline on rectal cancer (v.1.2016) recommend that tumor KRAS gene status testing be performed for all patients with metastatic colorectal cancer. Testing should be performed on archived specimens of primary tumor or a metastasis at the time of diagnosis of metastatic disease. The guidelines indicate that cetuximab and panitumumab are appropriate only for patients with tumor that expresses the WT KRAS gene.
Current NCCN guidelines (v 4.2016) indicate that KRAS mutational status may be prognostic of survival and predictive of therapeutic efficacy from EGFR-TKIs, specific recommendations are not made with regard to the use of KRAS mutation testing in the selection of TKI and anti-EGFR monoclonal antibody therapies for NSCLC.
In 2015 NCCN guidelines for both colon and rectal cancer were updated to include the addition of RAS mutation analysis which includes both KRAS and NRAS gene testing in the workup for all patients with metastatic colorectal cancer. The guidelines state that cetuximab and panitumumab are only indicated for patients with tumors that express the wild-type KRAS/NRAS gene.
NCCN guidelines for colon cancer state that patients with a BRAF V600E mutation appear to have a poorer prognosis. Evidence is insufficient to guide the use of anti-EGFR therapy in the first-line setting with active chemotherapy based on BRAF V600E mutation status.
NCCN guidelines for melanoma, version 3.2016, recommend vemurafenib, dabrafenib, and trametinib “only for patients with V600 mutation of the BRAF gene, as documented by an FDA-approved or CLIA-approved facility.” Vemurafenib and dabrafenib both have category 1 recommendations as preferred regimens for advanced or metastatic melanoma. Trametinib (monotherapy) has a category 1 recommendation as an “other active regimen”.
The International Association for the Study of Lung Cancer and the Association for Molecular Pathology published evidence-based guidelines addressing molecular testing to select individuals with lung cancer for treatment with EGFR and alkaline phosphatase TKI therapy. Based on a category B rating (good quality evidence), the authors do not recommend KRAS mutation testing as a sole determinant of EGFR TKI therapy. The guideline states: The significance of KRAS mutational analysis may become increasingly important with the further development of new therapies targeting downstream RAS pathways, such as PI3K/AKT/mTOR and RAS/RAF/MEK, but at this time, the absence of a KRAS mutation does not add clinically useful information to the EGFR mutation result and should not be used as a determinant of EGFR TKI therapy.
Summary of recommendations: The Evaluation of Genomic Applications in Practice and Prevention (EGAPP) Working Group (EWG) found that, for patients with metastatic colorectal cancer (mCRC) who are being considered for treatment with cetuximab or panitumumab, there is convincing evidence to recommend clinical use of KRAS mutation analysis to determine which patients are KRAS mutation positive and therefore unlikely to benefit from these agents before initiation of therapy. The level of certainty of the evidence was deemed high, and the magnitude of net health benefit from avoiding potentially ineffective and harmful treatment, along with promoting more immediate access to what could be the next most effective treatment, is at least moderate.
The EWG found insufficient evidence to recommend for or against BRAF V600E testing for the same clinical scenario. The level of certainty for BRAF V600E testing to guide antiepidermal growth factor receptor (EGFR) therapy was deemed low.
Another RAS gene is the neuroblastoma RAS viral (v-ras) oncogene homolog, or (NRAS). NRAS mutations are found in 2-7% of CRCs and occur most commonly in codon 61 rather than codon 12 or 13. NRAS mutations are mutually exclusive from KRAS and NRAS mutation testing should be performed when KRAS is wild-type. The presence of NRAS mutations is associated with lack of response to cetuximab therapy. NRAS, another member of the RAS family of protooncogenes, which can harbor mutations in codons 12, 13, and 61. Thus, the NRAS oncogene also may have an impact on outcomes of anti-EGFR treatments for CRC. Compared with KRAS, NRAS mutations are extremely rare. Although NRAS mutations account for approximately 15% of all RAS mutations, they are found in perhaps 2% to 7% of all CRC.
BRAF (also known as serine/threonine-protein kinase B-Raf, v-raf murine sarcoma viral oncogene homolog B1) encodes a protein kinase which is implicated in intracellular signaling and cell growth and is a direct downstream effector of KRAS.
The presence of the V600E BRAF mutation in tumors is associated with a poor prognosis in colorectal cancer, colon cancer, and several other cancer types. V600E BRAF mutation is linked to a poor response to anti-EGFR therapies and shorter survival independent of anti-EGFR therapies. The published literature does not yet clearly define the role of BRAF status in response to EGFR inhibitor therapy. It is still unclear to what extent the lack of response in individuals with KRAS wild-type is solely due to BRAF mutations. The determination of BRAF mutation analysis within the NCCN guidelines in 2016 for colon and rectal cancer is the first step in the treatment algorithm.
The EGFR signaling system is quite complex which may explain the modest objective response rates that have been achieved with clinical trials of EGFR inhibitors to date, as well as the disparities observed between clinical and preclinical findings. Metastatic colorectal predictive algorithms to identify additional patients with metastatic colorectal cancer who are unlikely to respond to treatment with an EGFR-targeted monoclonal antibody are being developed. These algorithms include the addition of BRAF, expression to NRAS/KRAS analysis. BRAF testing is included in the 2016 NCCN guidelines under principles of pathologic review.
KRAS and NRAS mutation analysis may be considered medically necessary to predict nonresponse to cetuximab and panitumumab in the treatment of metastatic (Stage IV) colorectal cancer. Testing must be done prior to initiation of therapy.
Testing for the BRAF V600E mutation may be considered medically necessary to further stratify those patients with KRAS wild type tumors and to guide treatment for colorectal cancer. Testing must be completed prior to therapy.
BRAF mutation analysis with a diagnosis of stage IIIC or IV (metastatic or unresectable) metastatic melanoma to predict nonresponse to vemurafenib, dabrafenib, or trametinib may be considered medically necessary. Testing must be completed prior to therapy.
KRAS, NRAS or BRAF mutation analysis for all other indications, including but not limited to the following, is considered investigational:
KRAS, NRAS, or BRAF is considered investigational for routine testing at initial diagnosis.
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