Mean ( SE ) @-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 @ to @ mm ( @ @ % vs. @ @ % ; hazard ratio for recurrence or metastasis , @ ; P = @ ) , and those with thick melanomas , defined as > @ mm ( @ @ % vs. @ @ % ; hazard ratio , @ ; P = @ ) .