The impact of KRAS mutation on radioembolization in the treatment of unresectable liver predominant metastatic colorectal cancer.
664 Background: Radioembolization with either Yttrium-90 labeled resin or glass microspheres is an FDA approved treatment for hepatic metastases from primary colorectal cancer. Y-90 therapy is used almost exclusively in unresectable liver metastases. However, radioembolization is only an optional part of the treatment process along with first-line, second-line, and salvage chemotherapy. KRAS is a known proto-onco gene that has typically been studied as a negative prognostic factor in the chemotherapeutic treatment of metastatic colorectal cancer (mCRC). KRAS is a known marker for resistance to anti-EGFR antibodies and generally have a poorer prognosis. The aim of this study is to begin to shed light on the impact of KRAS status on the outcome of patients undergoing radioembolization for the treatment of unresectable liver predominant metastatic CRC, regardless of their chemotherapy regimens. Methods: This is a retrospective analysis of 18 subjects treated with radioembolization for liver predominant metastatic CRC. KRAS status and treatment outcomes were followed for each patient up to the study close date of 9/15/13. Statistical analysis was performed using the Mann-Whitney U test. Results: Of the 18 subjects included in the study, 5 were found to have KRAS mutant oncogene. The remaining 13 were found to have the KRAS wildtype. Overall, those subjects with KRAS mutant were found to have a statistically significant difference in median time to progression of intrahepatic metastatic disease burden when compared to KRAS wildtype even when liver-directed therapy was utilized (2.0 vs. 6.4 months). Differences in median time to progression of extrahepatic metastatic disease burden and overall survival were not found to be statistically significant at this time. Conclusions: KRAS mutant patients are exceedingly difficult to treat due to both intrahepatic and extrahepatic disease recurrence/progression.