RESULTS: The three-year progression/recurrence-free survival rates for patients receiving Simpson grade 1, 2 or 4 resections were 95 %, 87 % and 67 %, respectively. Simpson grade 4 resections progressed/recurred at a significantly greater rate than Simpson grade 1 resections (hazard ratio [HR] = 3.26, P = 0.04), whereas Simpson grade 2 resections did not progress/recur at a significantly greater rate than Simpson grade 1 resections (HR = 1.78, P = 0.29).