1978
For the population of patients with melanoma levels III and IV significant differences in survival rate were associated with thickness ( less than 2 mm or greater than or equal to 2 mm ; p less than 0 , 001 ) , though not with level .
 None
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: GENE 
Text: {0} 
Answer:
 None