While this is not a pleasant subject, we feel that it is one that needs to be addressed. Cancer is the leading cause of death in dogs. This is why we recommend the spaying or neutering of all dogs not intended for breeding purposes.
Some breeds seem to be more susceptible to a certain forms of cancer.
If you are considering purchasing a puppy please discuss this issue with the breeders that you contact. From many discussions with people that have been through it, and our own limited experience, we know that when it happens it can be heartbreaking. The decisions are tough and very personal. The treatment of cancer can be very expensive and while sometimes it does work and the dog will live many more happy productive years, sometimes it does not and the dog may spend it's last few months in pain and sick, either from the disease or the treatment. Only you can decide what to do for your situation.