The rate of cancer among dogs and cats is similar to the rate of cancer among humans. Cats seem to get cancer a little less frequently than humans while dogs seem to develop cancer slightly more frequently than humans. For most species, the chance of cancer occurring goes up with age. For example, cancer is more common in pets 10 years old or older. Among dogs aged 10 or more, just under half of the deaths are due to cancer. However, even young animals can develop cancer; age is not the only factor involved in cancer development.