Cancer is a common problem. 1 in 4 animals will get some sort of tumour in their life & maybe 43% of dogs over 10 years of age may die from cancer. However many forms of cancer are curable if treated quickly.
Certain giant breeds seem to have a genetic susceptibility that may be due to rapid growth characteristics. However truly hereditary cancers are rare in dogs.
Treatment is very much worth doing as soon as possible, giving the animals a return to excellent quality of life. Forms of chemotherapy used on animals seem to avoid the unpleasant side effects of nausea, vomiting & diarrhoea.