Boxers are very prone to a whole host of cancers. One of the most common is mast cell cancer. Boxers frequently recover from this form at a greater rate than many breeds. Many boxers that get benign tumors like fatty lipomas and histiocytomas will never get a more malignant form of cancer.
The bad news is that boxers do get lymphoma, fibrosarcoma, osteosarcoma, mast cell cancer, and virtually every other cancer known to the canine world. Boxers also get a brain tumor that seems to be specific to the breed. Breeders of many of the longer-lived lines often say that their boxers live until a certain age, then die of a brain tumor or some other fast-acting cancer. Many, if not most, boxers go out of this world because of cancer.
Spaying or neutering your boxer will help reduce the incidence of cancer if done while your boxer is quite young. All male dogs with one undescended testicle (monorchids) or whose testicles never descended at all (cryptorchids) should be neutered shortly after six months. The undescended testicle is at a great risk of becoming cancerous. A male with one or more undescended testicles should never be bred.
Boxers and other bracycephalic, or short-nosed, breeds have the highest incidence of a type of brain tumor known as gliomas. These tumors start in the glial cells (supporting cells) within the brain. As they grow, they cause compression and death of the surrounding brain tissue. The tumors can vary in malignancy from slow-growing, relatively benign tumors to high-grade, aggressive tumors known as globastoma multiforme. These latter tumors are resistant to current forms of treatment. They tend to occur in older boxers.
Symptoms of glioma include seizures, behavioral changes (including sudden unprovoked aggression), circling, and general clumsiness, an indication of damage to the forebrain. A tumor in the brain stem could trigger head titling, nystagmus (rapid flicking of the eyes), difficulty swallowing, and unsteady walking.
There are almost as many options for cancer treatment these days for dogs as for people, including surgery, tumor-inhibiting drugs, and radiation. There are holistic approaches to feeding. You can attempt to avoid lines of boxers that displayed a tendency to develop cancer in them. Unfortunately, cancer is kind of a wild card in life. While you can take all sensible precautions, there may be nothing you can do to avoid it.