Modeling of sequentially measured volumes of rat tumors treated with single- or multiple-fraction radiotherapy, with or without hyperthermia.
This paper describes a model for the response of the volume of a tumor to a single treatment or a series of identical treatment fractions. The model is built on three assumptions: a fixed proportional cell killing for each treatment fraction, a constant removal rate of dead cells and a constant growth rate of the remaining clonogenic cells. For each individual tumor these parameters may be estimated from sequential tumor volume measurements. The model is applied to volume measurements of 173 rhabdomyosarcoma tumors implanted in the flanks of female rats after single or fractionated radiation with total doses between 0 and 90 Gy, with or without hyperthermia. Although the assumptions on which the model is built are evidently too strong, the model serves as an acceptable first-order approximation. A comparison between fitted and measured volumes showed the best fits for single radiation treatments in the period between treatment and regrowth to about the original volume. The overall shape of the fitted and observed growth curves of tumors exposed to fractionated radiation or combined treatment with hyperthermia were similar but, especially in the period of volume reduction, the fit was moderate. The model offers the opportunity for an alternative computation of growth delay and other parameters for the effect of treatment, and for the efficient planning of experiments based on the treatment of a few animals.
van Putten
W L
WL
Department of Statistics, Dr. Daniel den Hoed Cancer Center, Rotterdam, The Netherlands.
de Ru
V J
VJ
D000465:Algorithms; D000818:Animals; D002455:Cell Division; D003131:Combined Modality Therapy; D005260:Female; D006979:Hyperthermia, Induced; D008433:Mathematics; D008954:Models, Biological; D011878:Radiotherapy / Q000379:methods*; D011879:Radiotherapy Dosage; D051381:Rats; D011919:Rats, Inbred Strains; D012208:Rhabdomyosarcoma / Q000473:pathology / Q000532:radiotherapy / Q000628:therapy*; D013997:Time Factors