KRAS mutations in patients with colorectal cancer as detected by high-resolution melting analysis and direct sequencing.

Direct sequencing (DS) has often been used for detection of v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations. High-resolution melting analysis (HRMA) is another method to detect mutations by using a light scanner, and is more rapid, lower in cost, and more sensitive than DS. We confirmed correspondence between DS and HRMA for KRAS mutation detection in colorectal cancer (CRC). From 102 patients with CRC, intended to receive cetuximab treatment at the National Cancer Center Hospital between September 2008 and July 2009, formalin-fixed paraffin-embedded tissues were retrospectively analyzed for KRAS status using HRMA and DS. Cetuximab efficacy was evaluated. Success rates of analysis by DS and HRMA were 100 out of the 102 patients (98.0%) and 99 out of the 102 patients (97.1%), respectively. The cases which failed by one method were analyzed by the other. KRAS mutant-type was detected by DS in 47 out of 100 samples (47.0%), and by HRMA in 45 out of 99 samples (45.5%). The concordance between the two methods was 94.8%. Forty-six out of the 53 patients with wild-type KRAS, as detected by DS received cetuximab and the response and disease control rates were 19.6% and 63.0%, respectively. With a median follow-up of 8.8 months, the median progression-free survival was 5.6 months and median overall survival was 11.1 months. The efficacy of two discordant cases which received cetuximab showed that the best responses were stable disease and progressive disease in one each, progression-free survival was 2.9 and 1.1 months and overall survival was 5.3 and 1.2 months, respectively. HRMA is a useful optional method for detection of KRAS mutations in CRC in light of accuracy, cost performance and rapidity.