A simple mathematical model applied to describing tumour marker data

The blood levels of tumour markers (alpha-foetoprotein and human chorionic gonadotropin) were determined and serial chest X-rays were obtained from 11 patients with germ cell tumours to study the growth of the tumours. Assuming an exponential growth pattern, the tumour marker levels and diameters of lung metastases were analysed. The use of a simple model made it possible to describe the time course of the change of tumour marker levels in blood before and during treatment. The analysis provided estimates of doubling times for marker-positive subpopulations, which were generally in accordance with the doubling times for lung metastases. The estimated doubling times had a log-normal mean value of 21.3 days, in agreement with the 19.5 days for embryonic tumours obtained in other studies.