Mean ( SE ) 10-year disease-free survival rates were significantly improved in the biopsy group , as compared with the observation group , among patients with intermediate-thickness melanomas , defined as 1.20 to 3.50 mm ( 71.3 1.8 % vs. 64.7 2.3 % ; hazard ratio for recurrence or metastasis , 0.76 ; P = 0.01 ) , and those with thick melanomas , defined as > 3.50 mm ( 50.7 4.0 % vs. 40.5 4.7 % ; hazard ratio , 0.70 ; P = 0.03 ) .