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Systematic Review: Anti–Epidermal Growth Factor Receptor Treatment Effect Modification by KRAS Mutations in Advanced Colorectal Cancer

BACKGROUND
KRAS mutations have been extensively investigated as predictive biomarkers for treatment of advanced colorectal cancer with the anti-epidermal growth factor receptor (EGFR) antibodies cetuximab and panitumumab.


PURPOSE
To summarize whether KRAS mutation status modifies effects of anti-EGFR-based treatments for patients with advanced colorectal cancer and whether KRAS status predicts clinical outcomes among such patients.


DATA SOURCES
MEDLINE and 2 curated genetics databases (through 24 March 2010) were searched for observational studies. MEDLINE, the Cochrane Central Register of Controlled Trials, the Cochrane Database of Systematic Reviews, and the Database of Abstracts of Reviews of Effects (through 1 September 2010) were searched for randomized, controlled trials. No search was restricted by language.


STUDY SELECTION
Three reviewers screened titles and abstracts to identify published studies assessing KRAS mutations as predictors of overall and progression-free survival or treatment failure for patients who received anti-EGFR-based therapy for metastatic colorectal cancer.


DATA EXTRACTION
Three investigators extracted data on population and study-design characteristics, including quality items, and on outcomes of interest. Random-effects meta-analyses were done on nonoverlapping studies.


DATA SYNTHESIS
In 4 reanalyses of randomized trials of anti-EGFR-based therapy versus best supportive care or cytotoxic chemotherapy, no significant benefit was found for overall or progression-free survival from anti-EGFR-based treatment among KRAS-positive patients (hazard ratio [HR], 1.0). However, evidence favors anti-EGFR therapy among KRAS wild-type patients; the relative HR across KRAS-positive and wild-type patients was 1.30 (95% CI, 0.95 to 1.78) for overall survival and 2.22 (CI, 1.74 to 2.84) for progression-free survival by random-effects meta-analysis. In 13 cohorts of patients who received anti-EGFR antibodies, the summary HR for overall survival was 1.79 (CI, 1.48 to 2.17), with better survival in wild-type patients. The corresponding HR for progression-free survival was 2.11 (CI, 1.74 to 2.55 [16 cohorts]). In random-effects bivariate meta-analysis of 22 studies, the summary sensitivity of KRAS mutations for predicting lack of response was 0.49 (CI, 0.43 to 0.55), and summary specificity was 0.93 (CI, 0.87 to 0.97).


LIMITATIONS
Limited evidence from randomized studies exists. Patient-level data are needed to assess modifiers of the mutation-by-treatment interaction. Publication bias could be a concern.


CONCLUSION
KRAS mutations are consistently associated with reduced overall and progression-free survival and increased treatment failure rates among patients with advanced colorectal cancer treated with anti-EGFR antibodies.


PRIMARY FUNDING SOURCE
Agency for Healthcare Research and Quality.