Testing for epidermal growth factor receptor mutations is an important step in the evaluation process for systemic therapy in patients with metastatic or recurrent non–small cell lung cancer according to updated recommendations issued by the American Society of Clinical Oncology and the National Comprehensive Cancer Network.
ASCO issued a provisional clinical opinion (PCO) on April 7 that patients with advanced non–small cell lung cancer (NSCLC) who are being considered for treatment with one of the tyrosine kinase inhibitors (TKIs) that target the epidermal growth factor receptor (EGFR) should undergo EGFR-mutation testing.
Oncologists have learned that NSCLC is "really a collection of genetically distinct diseases," ASCO’s PCO panel cochair Dr. Vicki L. Keedy of Vanderbilt-Ingram Cancer Center in Nashville, Tenn., said in a press release. The goal is to "treat patients with drugs that target the molecular drivers of their specific tumors rather than using a one-size-fits-all approach."
The NCCN earlier updated its clinical management guidelines to include a category 1 recommendation that EGFR testing should be undertaken after histologic diagnosis of adenocarcinoma, large cell carcinoma, or undifferentiated carcinoma.
The NCCN recommendation does not extend to patients with squamous cell lung cancer, because the incidence of EGFR mutation in this patient subgroup is less than 3.6%, Dr. David S. Ettinger said in March at the organization’s annual conference.
Both groups based their endorsements on studies demonstrating that mutations in two regions of EGFR gene appear to predict tumor response to chemotherapy in general, and to TKIs specifically.
Among the research priorities that were identified by ASCO, Dr. Keedy noted the trials that are designed to discern whether first-line treatment with a TKI in EGFR mutation–negative patients delays chemotherapy or affects outcome; whether chemotherapy prior to TKI treatment in EGFR mutation–positive patients affects outcome; and whether there are clinically significant differences between erlotinib (Tarceva) and gefitinib (Iressa) among EGFR mutation–positive patients.
The last question is of particular interest, because gefitinib is not Food and Drug Administration approved outside a special program in the United States, whereas erlotinib is currently approved as second-line therapy, she said.
Dr. Ettinger, chair of the NCCN’s NSCLC guideline panel and professor of oncology at Johns Hopkins University in Baltimore, cited findings from the landmark IPASS (Iressa Pan-Asia Study) investigation that compared progression-free and overall survival in 1,217 East Asian patients with advanced NSCLC that was treated with the gefitinib or standard carboplatin and paclitaxel chemotherapy.
IPASS demonstrated that EGFR mutation strongly predicted a lower risk of progression on gefitinib vs. chemotherapy (hazard ratio, 0.48), whereas wild-type EGFR predicted a higher risk of progression on gefitinib relative to chemotherapy (HR, 2.85) (N. Engl. J. Med. 2009;361:947-57).
Similarly, in a pooled analysis of clinical outcomes of NSCLC patients who were treated with erlotinib, EGFR mutations were associated with a median progression-free survival of 13.2 vs. 5.9 months (J. Cell. Mol. Med. 2010;14:51-69). Neither study demonstrated a difference in overall survival among treated patients with and without EGFR mutations, Dr. Ettinger said.
The updated NCCN guidelines also state that the sequencing of KRAS (a G protein involved in the EGFR-related signal transmission) could be useful for the selection of patients as candidates for TKI therapy. The KRAS gene can harbor oncogenic mutations that may render a tumor resistant to EGFR-targeting agents, Dr. Ettinger explained, noting that studies have shown that a KRAS mutation in patients with NSCLC "confers a high level of resistance" to TKIs.
Although the data – which primarily come from retrospective reviews with small sample sizes – are insufficient to make a determination about an association between KRAS mutation status and survival, he said, they are sufficient to warrant a category 2A recommendation for sequencing, as well as a recommendation that patients with a known KRAS mutation should undergo first-line therapy with an agent other than a TKI.
Individuals who test negative for EGFR and KRAS should also be screened for a mutation of the anaplastic lymphoma kinase (ALK) fusion gene, Dr. Ettinger said. "Patients who screen positive may not benefit from EGFR TKIs, but they may be good candidates for an ALK-targeted therapy," he said, noting that the investigational ALK-targeting drug crizotinib, in particular, has demonstrated positive results in early studies of NSCLC patients with echinoderm microtubule-associated proteinlike 4 (EML4)-ALK translocations (N. Engl. J. Med. 2010;363:1693-703).
With respect to first-line systemic therapy, patients with adenocarcinoma, large cell carcinoma, or NSCLC "not otherwise specified" who have an Eastern Cooperative Oncology Group/World Health Organization performance status grade of 0-4 and who test positive for the EGFR mutation prior to first-line therapy should be treated with erlotinib, according to the NCCN guidelines. Alternatively, the guidelines state that gefitinib can be used in place of erlotinib "in areas of the world where it is available."