Relationships between KRAS mutation status and baseline radiographic distribution of disease in patients with stage IV colorectal cancer

KRAS oncogene testing is recommended in all patients with metastatic colorectal cancer due to its impact on treatment selection, but we do not know if KRAS genotype affects extent or pattern of metastases. We investigated whether the initial radiographic distribution of disease varies by KRAS genotype in stage IV colorectal cancer. This retrospective study of 65 patients with stage IV colorectal cancer was derived from an institutional clinical trials database. Inclusion criteria required KRAS testing and pretreatment CT studies to be available. Disease burden was characterized by two radiologists. Univariate analysis showed that there was no significant difference in the initial distribution of disease between KRAS mutant and wild type tumors (P > 0.05). Exploratory analyses showed that patients with poorly differentiated histology had a statistically significant increase in hepatic metastases in the presence of KRAS mutations vs. KRAS wild type genotype (median 5.0 vs. 0.5, P = 0.02). No overall difference was found in the initial radiographic distribution of disease between KRAS mutant and wild type colorectal cancers. Patients with both poorly differentiated histology and KRAS mutations had more liver metastases in subgroup analyses.