Before too long you’ll be able to get cancer screening involving only laying down on an examination table while a dog sniffs about you for a few minutes. I’ve read claims that a trained dog can even detect melanoma before there are any outward manifestations.
Dogs can also detect some forms of internal cancers on the breath.
http://www.dogsdetectcancer.org/dogs-detect-cancer-blog/can-dogs-smell-cancer
Sounds good, but I doubt it’s ready for mass distribution. Now if you replace the dog with a cat... Cat Scanning is a pretty widely accepted modality...