A New Surveillance Algorithm After Resection of Colorectal Liver Metastases Based on Changes in Recurrence Risk and RAS Mutation Status

Background: The optimal surveillance strategy after resection of colorectal liver metastases (CLM) is unknown. We evaluated changes in recurrence risk after CLM resection and developed a surveillance algorithm. Methods: Patients undergoing CLM resection during 1998 to 2015 were identified from a prospectively compiled database and analyzed if they had the potential for follow-up longer than the longest observed time to recurrence in this cohort. Changes in recurrence risk and risk factors for recurrence were evaluated. All statistical tests were 2-sided. Results: Among 2,105 patients who were initially identified and underwent CLM resection, the latest recurrence was observed at 87 months; 1,221 consecutive patients from 1998 through 2011 with the potential for at least 87 months of follow-up were included. The risk of recurrence was highest at 0 to 2 years after CLM resection, lower at 2 to 4 years after CLM resection, and steadily lower after 4 years after CLM resection. Factors associated with increased recurrence risk at the time of surgery were primary lymph node metastasis (hazard ratio [HR], 1.54; 95% CI, 1.21-1.97; P<.001), multiple CLM (HR, 1.31; 95% CI, 1.06-1.63; P=.015), largest liver metastasis diameter >5 cm (HR, 1.64; 95% CI, 1.23-2.19; P<.001), and RAS mutation (HR, 1.29; 95% CI, 1.04-1.59; P= .020). In patients without recurrence at 2 years, the only factor still associated with increased recurrence risk was RAS mutation. In those patients, the recurrence rate at 4 years was 59.3% in patients with RAS mutation versus 27.8% in patients with RAS wild-type (P=.019). Conclusions: For patients who have undergone CLM resection, we propose surveillance every 3 to 4 months during years 0 to 2, every 3 to 4 months (if mutant RAS) versus every 4 to 6 months (if RAS wild-type) during years 2 to 4, and every 6 to 12 months if recurrence-free at 4 years.