The Application of Cell Survival Theory to High Dose-rate Intracavitary Therapy

Abstract

Carcinoma of the cervix is treated using a high dose-rate intracavitary unit which delivers dose-rates 100 times greater than those obtained using the Ra technique. Cell survival theory was applied to the existing Ra treatments to estimate the levels of damage produced in the tumor and in the surrounding healthy tissue structures. An attempt was made to predict regimes of fractionated treatment at the high dose-rate, which will as nearly as possible match the effect of the Ra treatment on the tumor and which will produce less damage to the surrounding healthy tissue structures. The structures irradiated were divided into 2 types. Type 1 structures are defined as structures with cell cycles sufficiently long to prevent complete repopulation occurring between consecutive doses of radiation, which consequently have a cumulative effect. Type 2 structures are defined as structures capable of rapid cell division and which consequently restore their cell populations to normal between 1 dose and the next, provided the 1st dose is not sufficiently large to denude the structure of viable cells.