Tumor Volume Measurements in Animal Experiments: Current Approaches and Their Limitations

Animal experiments are often used in cancer research as an alternative to clinical trials to determine the effect of various drugs and other biological conditions on tumor behavior. The tumor volume measurement is necessary in these experiments. The operation of imaging devices is expensive, and it is necessary to anesthetize the animals during the measurement. Anesthesiology induces stress and deviation from homeostatic functioning, which greatly affects the results of the experiment. To address these problems, the digital caliper method, which is safe and cost-effective, is applied to measure tumor volume during in vitro studies. However, it is only rarely possible to accurately measure the volume of the tumor with a digital caliper. It is, therefore, important to examine how we can estimate the three-dimensional volume of the tumor from measurements carried out with a digital caliper. This study summarizes the approximation formulas used in the literature and their scope of use and analyzes the advantages and disadvantages of digital caliper measurements. We aim to highlight the importance of creating a noise model in cancer research that generally describes the difference between real tumor volumes and those measured with calipers.