Effect of KRAS mutation on long-term outcomes of patients undergoing hepatic resection for colorectal liver metastases

282 Background: The impact of KRAS mutation on overall (OS) and recurrence-free (RFS) survival of patients with colorectal liver metastases (CLM) remains poorly defined. We sought to investigate the prognostic value of KRAS in a large cohort of patients undergoing liver resection for CLM. Methods: Between 2003 and 2013, 334 patients underwent hepatic resection for CLM at Johns Hopkins Hospital and met the inclusion criteria. Somatic mutations at codons 12/13 were evaluated through a sequencing analysis of the tumor samples. Clinicopathological characteristics, perioperative details, and outcomes were stratified by KRAS status (mtKRAS vs. wtKRAS) and analyzed. Results: Among 334 patients undergoing liver resection for CLM, mtKRAS was identified in 115 (34.4%) patients. Median CEA was 7.3 ng/dL; 40.4% of patients had a solitary tumor and median tumor size was 2.5 cm. At a median follow-up of 28.2 months, recurrence was observed in 59 (51.3%) patients with mtKRAS and 117 (53.4%) patients with wtKRAS (P=0.71); there was no difference in the pattern of recurrence (liver: mtKRAS, 39.0% vs. wtKRAS, 52.1%; lung: mtKRAS, 55.6% vs. wtKRAS, 64.3%; both P>0.05). While 5-year log-rank OS was comparable among mtKRAS (41.6%) vs. wtKRAS (48.5%), on multivariable Cox survival analysis mtKRAS was associated with worse OS(HR, 1.65; 95%CI, 1.07-2.54). Moreover, among patients who experienced a recurrence, 5-year OS was worse among those patients who had mtKRAS (mtKRAS, 28.1% vs. wtKRAS, 44.5%; P=0.004). After controlling for tumor factors, as well as receipt of chemotherapy, mtKRAS status remained independently associated with a worse outcome among patients who recurred(HR 2.07, 95% CI 1.31-3.27; P=0.002). Conclusions: mtKRAS was noted in one-third of patients with CLM. While KRAS status did not impact pattern of recurrence, mtKRAS was an independent predictor of worse OS among patients who experienced a recurrence following resection of CLM. mtKRAS was identified in 115 (34.4 %) patients. At a median follow-up of 28.2 months, recurrence was observed in 59 (51.3 %) patients with mtKRAS and 117 (53.4 %) patients with wtKRAS (P = 0.79); there was no difference in the pattern of recurrence (liver: mtKRAS 39.0 % vs. wtKRAS 52.1 %; lung: mtKRAS 55.6 % vs. wtKRAS 64.3 %; both P > 0.05). Although 5-year log-rank overall survival (OS) was comparable among mtKRAS (41.6 %) vs. wtKRAS (48.5 %), on multivariable Cox survival analysis and after adjusting for known predictors of OS mtKRAS was associated with worse OS (hazard ratio 1.65; 95 % confidence interval 1.07-2.54; P = 0.02). Among patients who experienced a recurrence, 5-year OS was worse among those patients who had mtKRAS (mtKRAS 28.1 % vs. wtKRAS 44.5 %; P = 0.004). After controlling for tumor factors and receipt of chemotherapy, mtKRAS status remained independently associated with a worse outcome among patients who experienced recurrence (hazard ratio 2.07; 95 % confidence interval 1.31-3.27; P = 0.002). mtKRAS was noted in one-third of patients with CRLM. Although KRAS status did not affect the pattern of recurrence and recurrence-free survival, mtKRAS was an independent predictor of worse OS. The effect was more pronounced among patients who experienced a recurrence after resection of CRLM.