A model for the behavior of β-hCG after evacuation of hydatidiform moles

Following an initial rapid drop in hCG after resolution of the mole, the patient should experience a slower drop associated with the dilution of residual hCG in the deep tissue reservoir. This is normal. The physical model suggests that even earlier detection of chemotherapy resistant persistent trophoblastic disease is possible if the patient's decrease in hCG is slower than a log-linear fit to the patient's previous data. The results also suggest an alternative approach to processing patient statistics in analysis of carcinomas with large variations in the tumor marker concentrations.