I found the link to this article in The Cancer Blog from inside my feedreader browsing headlines of Engadget.com. Engadget is a part of the Weblogs, Inc. Network – a network of more than 70 blogs, and there is a lot of (non pet-related) neat articles and topics.
They say the research is exciting because if dogs can really find out things (like cancer) that technology and human testing could not find out, well perhaps a lot of sick people might be treated sooner. Dogs have a high sense of smell. The theory, is that cancerous cells emits a slight odor. Put the two together and ~voila~.