A dog's nose has around 300 million scent receptors. Yours has about 6 million. In a 1,502-person trial in Bangalore, trained dogs detected early-stage cancer from breath samples with roughly 90% sensitivity. Then they did something nobody trained them to do. Tumors rewire cell metabolism, and that altered metabolism leaks volatile organic compounds into your blood, which diffuse into your lungs and exit in your breath. The concentrations are parts per trillion. Roughly one drop of scent in 20…