KRAS mutation detection by high resolution melting analysis significantly predicts clinical benefit of cetuximab in metastatic colorectal cancer

Background: Anti-EGFR monoclonal antibodies are restricted to KRAS wild-type (WT) metastatic colorectal cancers (mCRC), usually identified by direct sequencing, that may yield false negative results because of genetic heterogeneity within the tumour. We evaluated the efficiency of high resolution melting analysis (HRMA) in identifying KRAS-mutant (MUT) tumours. Methods: We considered 50 mCRC patients scored as KRAS-WT by direct sequencing and treated with cetuximab-containing chemotherapy, and tested the correlations between HRMA findings and response rate (RR), progression-free (PFS) and overall survival (OS). Results: Aberrant melting curves were detected in 4 (8%) cases; gene cloning confirmed these mutations. RR of HRMA KRAS-WT patients was 28.3%. There was no response in HRMA KRAS-MUT patients. Disease control rate (responsive plus stable disease) was 58.7% in HRMA KRAS-WT patients and 25% in HRMA KRAS-MUT patients. There was no correlation between HRMA KRAS status and RR (p=0.287) or disease control (p=0.219). Median PFS (5.1 versus 2.5 months; HR=0.34, p=0.04) and OS (11.3 versus 3.2 months; HR=0.11, p=0.03) were significantly longer for HRMA KRAS-WT than for HRMA KRAS-MUT patients. Conclusions: HRMA identified 8% more KRAS-MUT patients not responding to cetuximab-containing regimens, suggesting that HRMA may be more effective than direct sequencing in selecting patients for anti-EGFR antibodies.