OR has been well applied in medical science field particularly in healthcare planning, cancer diagnosis, Alzheimers and optimization of radiotherapy treatment plan. I am sure there are more evidences of its application in a number of areas within medical science. You can find some evidence in the following book

Brandeau, M. L., Sainfort, F., & Pierskalla, W. P. (Eds.). (2004). Operations research and health care: a handbook of methods and applications (Vol. 70). Springer Science & Business Media.

OR has also been quite successful in the search for matching donors to patients (for organ transplants), as well as sophisticated OR models for the cure of cancer, using external or internal radiation of several different kinds.This field is growing very quickly, and there are also successful companies inventing new treatment machines. Parts of the design of medical trials is another application of operations research. 

OR has applied to medical science through formulating some model and simulating it