There is growing evidence showing that the amount of muscle and fat one has in the body influences various aspects of cancer such as carcinogenesis (formation of cancer), response to chemotherapy drugs (to decide on the optimal dosage to the patient to destroy cancer cells while avoiding damage in other organs), death resulting from complications due to surgery, and overall survival outcomes. Conversely, cancer also causes loss of muscle mass. Accurate and easily available tools are thus needed to measure muscle and fat in an individual in the context of cancer treatment decisions. CT images are almost universally acquired in cancer diagnosis and treatment planning, and these directly show muscle and fat in the body. But in order to extract measurements, manual intervention (which is tedious) or automated tools are needed. We are developing a fully automated 3D method to measure the amount of muscle and fat from 3D CT images available in the cancer clinic. The availability of these measurements will enable correct chemotherapy treatment dosage to be determined for each individual based precisely on their body composition, resulting in better health outcomes.