Use of tumor diameter to estimate the growth kinetics of cancer and sensitivity of screening tests.

A statistical method has been developed that is useful for studying the relationship between the growth kinetics of malignant tumors and the detection probability either through symptoms or by screening. Mathematical models that describe the distribution of pathological variables in malignant tumors, detected after various histories of screening, are derived and parameters for detection probabilities and the growth kinetics are then estimated by the maximum likelihood procedure. By this method the probabilities of detection through symptoms as well as by screening can be estimated as functions of pathological variable(s) such as tumor size. The growth rate of tumor can also be estimated from the distribution of pathological variables. The present method was applied to gastric cancer in Japan, where an annual screening program for the disease exists. The detection probability for the indirect X-ray used as the screening test was estimated to be 0.323 x (diameter)2/[1 + 0.323 x (diameter)2]. The doubling time of gastric cancer was estimated to be 2.90 months.