An easy model for prediction of human renal clear cell carcinoma：curve fitting for three kidney tumors observed for over 10 years

The current researches on natural history of small renal masses show that small renal tumors grow slowly,and few metastasize.1-4 As the length of follow-up is short in these studies （the longest mean follow-up time is 48 months）,changes in tumor size in vivo cannot be observed enough.In addition,the growth model of tumor is linear,and the average growth rate is used to reflect tumor growth in these studies.However,most malignant tumor growth curves were not linear.It may not be correct to assess the growth of tumors by linear models.