Incidence and impact of K-ras mutation in colorectal cancer (CRC) in a minority population.

Abstract

e14690 Background: K-ras mutation in CRC is known to occur in around 40% of the general population. It implies a poor prognosis, and resistance to anti- EGFR monoclonal therapy. The incidence of Kras mutation in African American (AA) patients with CRC is not known. Methods: Records of patients treated for CRC at Kings County Hospital and Downstate Hospital; in Brooklyn from 2005-12 were reviewed. Results: Of 116 patients’ records, 90 were informative for presenting stage, K-ras expression or both; all but one were AA, and 60 of 90 (67%) were male. Their ages ranged from 36 to 86 (median 64) years. The stages at presentation were known in 76; 3% were stage I, 17% stage II, 35% stage III and 45% stage IV. Follow-up periods ranged from 14 to 2381 days (median 409). K-ras mutation analysis was performed by a single commercial laboratory in 68 patients who had, or were suspected of having advanced disease. Codons 12 and 13 in K-ras exon 2 were analyzed. Of these 68 patients 31 (45%) bore K-ras mutations. K-ras mutation status was known in 9 stage I and II pts, and 6 of 9 pts (67%) bore mutations. After 233-967 days follow-up (median 474) 8 of 9 patients were alive. The 3 pts with wild type K-ras were a median of 70 years of age, 67% were female, and all were alive at median of 266 days (range 239-122-) follow up. Of the 16 stage III patients whose K-ras was analyzed, 7 (44%) were mutated. These 7 pts were a median of 66 years of age, and 86% were male. After 398 days median follow up 57% had relapsed and 45% had died. The 9 stage III pts with wild type K-ras were a median of 70 years of age and 78% were male. After a median follow up of 600 days, 2 were relapse-free, 7 had relapsed and 6 had died. Of the 34 stage IV pts, K-ras was analyzed in 29 and mutated in 12 (41%). Of the mutated patients, 83% were female and the median age 57. Their median survival was 557 days (56-1627). The 17 pts with wild type K-ras were 67% female with a median age of 59. Their median survival was 711 days (25-2040). The presenting CEA levels were similar in wild type and mutated patients. Conclusions: The prevalence of K-ras mutations, and the better prognosis of wild type K-ras in advanced CRC in AA patients, is similar to that of the general American population. The relapse rate of stage 3 AA patients seems higher in both wild type and mutated pts.