Dogs can smell the chemical markers that indicate certain types of cancer, according to PedMD. The first suggestion of using dogs for detecting cancer was documented in a 1989 medical journal, and since then, there have been several research studies on the subject.
An English study suggested that dogs could determine which people had bladder cancer by smelling samples of their urine. In 2013, at the University of Pennsylvania's Working Dog Center, three dogs including a Labrador Retriever, a Springer Spaniel and a German Shepherd were being trained to use their excellent sense of smell to recognize the specific compound that is indicative of ovarian cancer. Based on this study and previous research, scientists hope to develop analytical instrumentation, such as an electronic sensor to assist in screening patients for ovarian cancer.
Three other studies have also demonstrated positive results for using dogs to detect lung cancer. However, two of these studies were preliminary and only included a small number of subjects. Some scientists believe that dogs may eventually be directly used in patient care, while others recommend that the ability of dogs to detect cancer would be best used in labs where gas chromatograph use could isolate the exact compounds that the dogs identified.