Translation: "There was no statistically significant increase in cancer detected." However, that's less meaningful than you might think as detecting even a 2x increase in cancer among mice is a lot harder than say showing in increased population lifespan.
The real question is what was their power to detect an X-fold increase in cancer. Probably quite low, as that was not the purpose of this particular study.
http://onlinelibrary.wiley.com/doi/10.1002/emmm.201200245/fu...