Pp. 108-119 (12)
Pierre R. Band
The growth rates of solid tumors in experimental animals and in humans
were found to be exponential during their observable lifetime. It was concluded that
cancer develops over a long clinically undetectable phase, during which the probability
of occurrence of metastases is high. Solid tumors became viewed as frequently
disseminated at the time of clinical diagnosis, thus requiring a systemic therapeutic
approach in addition to the traditional loco-regional approaches offered by surgery or
radiation therapy. However, studies in experimental animal models in which tumor
growth can be measured over a wide range of doubling times have shown that solid
tumor growth rates best fit a Gompertz function, in which the tumor doubling times
continuously increase with increasing tumor size. Subsequent studies of the dynamics of
tumor growth revealed that tumors are composed of proliferative and non-proliferative
compartments, the latter consisting of cells that are able to proliferate again and cells
lacking this capacity. In addition to therapeutic implications drawn from the Gompertz
and cell-compartment models, experimental tumors characterized by a Gompertzian
growth were added to the in vivo systems used to screen for drug activity.
Tumor growth rate, exponential, Gompertzian, screening systems.
Faculty of Medicine, McGill University, Montreal, Quebec H3G 1Y6, Canada.