Firstly, cancer is a syndrome, not a final diagnosis. Cancer can be divided into benign (slow to spread and producing a few inflammatory proteins) and malignant (faster to spread and infiltrating surrounding tissue, often producing inflammatory proteins that affect the rest of the body). The inflammatory proteins, known as cytokines, cause weight loss, changed appetite, vomiting and blood changes among others, and often affect the body more than the actual cancer itself.
Within the group of malignant cancers, some will spread and grow slowly, some are very chemo sensitive, some are radiation therapy (RT) sensitive and some can be easily cured with surgery, while there are others where we are unable to change their clinical course. Therefore, it is very important to take the diagnosis further than just ‘cancer’. To define the cancer further, we need to get either fine needle aspirates (FNA) or histopathology from biopsies or other diagnostic tests, like radiographs (x-rays), to define the cancer further. This is especially important if it is in bone, so as to get to an exact cancer type.
We also need to determine if the cancer has spread (metastasis). This process is called staging. Cancer is staged by looking for spread to distant regions, using ultrasound (often of the abdomen, but can be of the chest or the lumps themselves), radiographs with three to four views of the chest and often FNA of organs. Pathology sections of the mass give an indication of its rate of growth and other changes to architecture, or one can request special markers. All these can give an indication of the level of malignancy. Finally, there are blood tests to look for paraneoplastic changes (changes in the blood caused by the presence of cancer). Some cancers start as, or become leukaemia, and can be diagnosed on blood smears. Certain cancers have always spread at the time of diagnosis, but one must still look for how far it has spread and how much it has affected other organs (like the bone marrow or lungs), as this will affect the type of treatment chosen and affect the prognosis and quality of life of the patient.
We have diagnosed the type of cancer, what now?
Once we know that there is cancer, we need to decide on a directed therapy (if there is a therapy that will work!). This decision requires knowledge of how the dog is doing:
- Metabolically – have any other organs been affected.
- In terms of age – cancer usually occurs in older pets who have co-morbidities, such as renal disease or osteoarthritis, that we need to identify and take into account.
- In terms of how much, how far and where the cancer has spread.
- ‘As a dog’ – clinically, sick pets are sub-staged afor healthy or b for sickly; in some cancers, the prognosis is months longer for sub-stage a
Is the cancer chemo, surgery, or RT responsive?
Many cancers are commonly diagnosed, so your vet will know how to handle that specific diagnosis and in many cases they will be equipped to do so. However, referral to a specialist facility means that the care giver aiding you and your pet is more likely to have the latest info and access to more advanced treatment modalities (if needed). Referral is always preferred in clinically ill animals.
- Google is your friend, if you put in the right search terms.
- Search words needed:
- Name of cancer& dog or cat & client info
- by putting in the term client infoyou get specialist information and less personal experience/opinion, which the internet is riddled with and which is often incorrect
- Discuss your findings, miracle cures and concerns with your vet and ask the questions that arise in your searches.
What is chemo?
Conventional chemotherapies target the cancer cells using medicines that work to change the ways cells divide. Through years of trial, we have ascertained which of these medications work best for which groups of cancer. The chemo drugs are dosed either alone (single agent therapy) in a weekly to three to four-weekly schedule, or in combination chemo protocols.
For instance, in lymphoma therapy, we like to use the Wisconsin protocol which uses a mixture of cortisone, vincristine, cyclophosphamide and doxorubicin in four to eight-week cycles over a six-month period. In conventional chemo, one uses the highest dose that has been proven to cause the least side effects and still kill the most cancer cells, and repeat it within the shortest time period (of recovery) between doses. This knocks back the cancer repeatedly, to keep the cancer from growing. Remission is achieved if one achieves 100% control of observable cancer, or partial remission is achieved if cancer is partially controlled.
Metronomic chemo is medication that if one simplifies its function, is used to target the cancer’s new blood vessel formation. These blood vessels are needed so that the cancer can grow. Unlike conventional chemo which is dosed at the highest dose with the shortest interval, metronomic chemo is dosed daily at a low dose to suppress new blood supply and thus aims at stunting the cancer’s growth. The two forms of chemo use a different mechanism to kill cancer. Conventional and metronomic chemo are often synergistic.
Note – this is a simplified report of what chemo entails to make it accessible to non-medical persons