Cancer is an ugly word that brings to mind all types of uncomfortable connotations. Most peoole have had exposure to people with malignant cancer and have seen the devastating effect the diseases can have. Unfortunately cancer is a common occurrence pets and we can luckily take major steps to prevent pain and suffering and it can be very well managed to enable excellent quality of life for the time left.
Benign vs. Malignant
At the thought of cancer, most people immediately think the worst. A cancer is essentially the result of a tissue cell dividing without control. Vets see an enormous amount of pets with low grade benign cancers such as lipomas (fat cell tumours) and papillomas (skin cell tumours) that whilst dividing uncontrollably, have no real impact on quality of life except for their physical presence and complications associated with this.
Issues to Consider
Causes
Causes of cancer are generally multi-factorial with a mixture of genetic and environmental factors playing roles. In a recent human study into cancer rates and causes in identical twins it was determined that generally cancer has a 25% genetic component and a 75% environmental component of causes. Pets are obviously very different and don’t live as long as humans thus reducing the influence of the environment however issues such has diet, activity, pollutants and exposure to chemicals play an important role amongst others.
The genetic issue is a bigger issue of dogs with specific breeds more commonly getting malignant cancers such as bone tumours in Rottweiliers and splenic tumours in German Shepherds. Whether these issues will be addressed in the way that hip, elbow and eye testing is done will be an issue for the future.
Onset and Symptoms
Whilst the speed on onset of clinical symptoms of cancer may vary depending on the cancer. It is the rapid onset cancers that are hardest emotionally to deal with because they come out of the blue.
The symptoms of cancer range from cancer specific problems (lameness with bone tumours, a skin lump, bloated abdomen with abdominal tumours) through to secondary problems (paraneoplastic symptoms) that can cause weakness, lethargy, weight loss, irritability and not eating. Furthermore some tumours cause other symptoms by stimulating other body systems e.g. testicular tumours can cause pigmentation and thickening of the skin, enlargement of the mammary glands and behavioural changes
Planning for Cancer
Assessment and planning are probably the most important steps in dealing with pets with cancer. From the first signs that something is not right it is important to enable the issue to be addressed to allow decisions to be made based upon good quality information.
The normal veterinary first steps are to get a detailed history including appetite, drinking, toileting and any other specific symptoms. Vets then perform a thorough physical examination which may or may not be able to pinpoint the exact problem however most cases generally require a little more investigation.
Further diagnostic work for cancers includes blood and urine testing, ultrasound, x-ray, tissue biopsy and analysis (either through cell analysis- cytology or complete tissue biopsy- histopathology, which is much more accurate) as well as more advanced techniques such as CT, MRI and nuclear scintigraphy.
Pathological Classification
When a tissue sample is taken for histological analysis, the pathologist will generally be able to tell you 4 things that provide enormous information that allow better decisions to be made.
· What is it called and thus what is it’s tissue origin
· Has it been completely removed
· Is it likely to regrow locally
· Is it likely to spread
Types and Sites
It’s hard to put every site and type of tumour down into an easy reference chart because cancers don’t always follow the same pattern. Generally cancer cells derive from the tissue of a body system such as skin, red blood cells, white bloods cells, bone, liver, kidney , neural tissue, connective tissue and glandular tissue to name a few.
The site of the tumour is not always consistent with its cell origin and therefore you can get lymphoma, a cancer of the lymphocyte white blood cell, growing in the skin. As far as determining where the site of the primary is and ruling out other new sites, “Staging” is also an important process in gathering useful information and determining if there are any unknowns lurking about in other parts of the body such as lymph nodes, lungs, liver tissue and blood.
Control and Treatment Options
In determining how to best approach dealing with pets with cancer, assuming that we already have a specific diagnosis, 3 issues are at commonly addressed.
· The nature of the cancer- this looks at the site of the tumour, the staging of the tumour, how aggressive it is, how likely it is to spread or recur and the nature of this tumour e.g. is it likely to cause pain, what are the statistical life expectancies of the cancer in question
· The Patient- what are the issues that need to be addressed in the pet. Is the pet well, pain free, is it concurrently sick from the tumour, has the tumour caused other problems that need to be addressed e.g. blood loss, anaemia. What other conditions does the pet have that need to be addressed? E.g. it would be questionable whether you would consider providing invasive treatment to a 16 year old dog with chronic kidney failure with a tumour that has a life expectancy of 3 months
· The Owner- what are the owners understandings and biases in dealing with cancers from previous experiences both human and animals, what are their attitudes towards chronic diseases, palliative care, life expectancies, costs and invasive treatment.
Treatment of pets with malignant cancer comes in 2 main categories with the first being conservative therapy. Providing good pain control and alleviating symptoms allowing pets to have a good quality of life is often a good decision. This ensures that the pet lives a slightly longer and happier life and a definitive decision to euthanase is made once this course of action is no longer appropriate. This approach, beyond euthanasia sooner than later, is a good option for older animals with concurrent diseases that are not in too much pain.
As far as invasive treatments go, the aim of these therapies is again to extend the life expectancy whilst maintaining good quality of life (THE MOST IMPORTANT THING)
· Surgery- the best thing for a cancer is to get rid of the visible disease with as much clear tissue margin as possible and surgery is usually the best method.
· Chemotherapy (chemo) - Depending on the type of tumour, chemo can be used alone or in conjunction with surgery. The aim of chemo is to kill as many of the rapidly dividing cancer cells as you can for as long as you can. Chemo in pets is rarely curative and only aims to increase good quality life expectancy.
Chemo varies in it applications from simple oral anti cancer drugs through to injectable agents. Not all cancers respond to chemo and the decision to treat depends on the whole picture and what is right for the dog.
· Radiation Therapy (RT) – this is becoming more accessible and thus more popular as ways of controlling tumours that cannot be surgically removed. In some cases of mouth tumours and non resectable benign tumours, RT can be curative. External beam radiation and nuclear medicine are both forms of radiotherapy that are used
· Ancillary treatments- much anecdotal information exists about ancillary cancer therapies that can help. Often the scientific proof may not be there but if it makes them feel better and not worse then it’s a consideration. Nutritional control and dietary assessment is important and some supplements may have benefit. Furthermore trials of herbs, organic materials, oils, monoclonal antibodies and anti cancer metabolites are in existence and can be considered with careful veterinary advice.
Whilst animal cancer is an unfortunate reality, significant advances have been made to ensure the best outcomes for our pets so they can live the happiest lives they can for the time they have with you.