Probably the word we most dread to hear, yet one that all of us who have wolfhounds are likely to hear at some time, since it is estimated that one in ten dogs will have some form of tumour. It is also a subject on which there are many misunderstandings and misconceptions, not only among owners but in the veterinary profession. The last is probably due to the fact that widespread treatment of cancer in animals is still relatively new and has only been included in the course of study at veterinary schools in the UK over the past three decades.
The proper name is neoplasia - literally "new growth" - and the features which define it are persistence/purposelessness/proliferation. There are two types of neoplasia: malignant which destroy, invade, and metastase (spread); and benign, which grow locally and by expansion rather than invasion. A benign tumour is like an egg, with well defined edges which can be felt around. It can usually be removed by surgery. Even a benign tumour, though, can cause problems through pressure, for example if it occurs in the brain. A malignant tumour has no clear edges and will ulcerate and spread. Since the boundary cannot be defined it is impossible to remove all the cancer cells by surgery. Malignant tumours metastase by lymphatic invasion, haematogenous route, or transcoelonic spread. Such metastasis in dogs is generally to the lungs but it can be to any part of the body. The only way to tell the difference between a benign and malignant tumour is to examine a sample under a microscope. Benign tumours can become malignant.
In dogs generally 50 per cent of all tumours are of the skin (of which about 40 per cent are malignant and 60 per cent benign), 20 per cent are of the mammary glands (which account for 58 per cent of tumours in bitches, of which about 50 per cent are benign), only 10 per cent are of the alimentary system (which is one of the prime sites in Man), 10 per cent of the lymphatic system, 5 per cent of the reproductive system, and 5 per cent others.
However, bone tumours are much more common in the large and giant breeds. They are most likely to occur at the ends of long bones in the growth plates but may occur on the skull, pelvis, etc. Bone tumours are mostly extremely malignant. Signs are swelling, pain, heat, and lameness (if the tumour is in a limb bone). However, although bone tumours on the forelimb (especially at the distal [lower] end of the radius/ulna - just above the knee joint and a favourite site) or those on the distal end of the tibia/fibula (just above the hock joint) on the hind leg are easy enough to detect, particularly when the typical hard swelling starts, those in other sites can be much more difficult to diagnose. This is especially so if they are on bones where there is heavy surrounding musculature, such as the shoulder-blade, upper arm, or thigh. These are all too likely to be diagnosed as pulled muscles, damaged tendons, arthritis, etc. Also, osteosarcoma (the most common form of bone cancer in these breeds) often starts up after some kind of trauma such as a collision or fall and is most likely to occur in the age range of 6 to 8 years, so the tendency is for a diagnosis of bruising, arthritis, etc. in any case.
Oral tumours are quite common and mostly malignant. One problem is that they are often well advanced before being noticed. Signs are bloody saliva, bad breath, difficulty in eating, or unwillingness to eat. Malignant melanoma are particularly dangerous and spread rapidly.
Nasal tumours are quite rare but mostly malignant. Signs are sneezing, difficulty in breathing, discharge from the nose, or nosebleeds. They do not spread quickly but cause much local damage.
Tumours of the gut are rare but usually malignant and generally well advanced by the time they are noticed. Spleen tumours are usually malignant with early secondaries. Signs of internal tumours are non-specific but include weight loss (sometimes rapid), diarrhoea or constipation, pain which may be shown by a stiffness of movement, passage of blood or vomiting of blood or "coffee-grounds", inappetance.
Tumours of the lungs (a prime site in Man) do not occur as primaries in dogs but frequently as secondaries. Signs are difficulty in breathing, particularly after exercise, coughing, and wheezing. This can often be misdiagnosed as lungworm.
Cancer of the lymph system is quite common and can involve a combination of lymph glands, bone marrow, circulating blood, and internal organs. Signs are enlargement of glands, depression, anorexia, and weight loss. These cancers include lymphosarcoma and leukaemia. There are two types of canine lymphoma: the multicentric which affects the whole body, and one which develops only in the alimentary, cutaneous, and thymic glands.
Skin tumours can vary from granuloma, which are pea-sized, to vast lumps. Not all lumps which appear on the skin are tumours. Sebaceous cysts are very common, particularly in the elderly dog, but are only blocked sebaceous glands and quite harmless, although they do sometimes burst. It is a good rule, though, to have any lump removed and tested.
The cause is generally unknown but some factors have been identified. Hormones affect the growth of some tumours such as mammary tumours, and perianal tumours which depend on male hormones. A virus which causes oral papillomas has been identified, and air pollution is important in the development of tonsil and lung tumours. Sunlight is believed to cause some skin tumours. At the BSAVA Hereditary Diseases Seminar in May, 1988, Professor Patterson mentioned that osteosarcoma in the giant breeds is due to a cancer gene. A possible cause of cancer is geopathic stress. Click here for more.
There is a significant decrease in the incidence of mammary tumours in bitches which are spayed before their second season. Tumours of the uterus and ovaries are prevented by spaying, and testicular and perianal tumours by castration. Retained testicles are prone to tumour formation and should be removed before tumours occur. Oral warts (papillomas) can be prevented by avoiding contact with affected dogs. Since tumours of the digestive tract are not common in dogs, it is unlikely that diet can be used as a preventative measure (as it can in Man), although anyone who had several dogs suffer such tumours should perhaps review their feeding methods. (This is a conventional veterinary view. In my opinion diet does more than affect the digestive system; it affects the whole body) Lines prone to suffer osteosarcoma should be avoided in breeding programmes.
Not all types of cancer are treatable (nasal tumours, for example, are not) but many are and there are several different types of treatment which can be used. Some will actually effect a cure, in other cases the tumour will not be cured but may be controlled and the effects of the tumour (e.g. pain) alleviated.
Benign tumours can generally be cured by surgery and surgery remains the major form of treatment in most cases of cancer. Although surgery does not address the problem of very invasive tumours, because of the difficulty of removing all the cancer cells, it can still be used in conjunction with other forms of treatment.
Other methods of treatment are radiotherapy, chemotherapy, cryosurgery, and hyperthermia, although there are new methods of cancer therapy starting to come into use, such as gene therapy for osteosarcoma.
At one time in the UK the favoured treatment for osteosarcoma was radiotherapy but now it seems to be amputation of the affected limb together with chemotherapy. Radiotherapy did not cure but does remove the pain and slow down the rate of growth of the tumour. A high proportion of bone tumours metastase to the lungs; radiotherapy does not prevent metastasis but nor does amputation. Amputation only removes the primary tumour and radiotherapy does much the same while leaving the dog with all four limbs. The main danger with radiotherapy is pathological fracture but the danger is reduced the earlier treatment is begun. If treatment is not carried out early, or if the tumour is very aggressive and fast growing, a large part of the bone may have been invaded by cancer cells and, when these are killed by radiation, there is obviously going to be a narrower than normal portion of bone. Fractures of bones treated with radiation will not heal, so that if a fracture occurs the only alternatives are amputation or euthanasia.
Radiotherapy in dogs does not cause the awful side effects that it does in humans. This is partly because it is not used for widespread neoplasia or for tumours in major organs, and partly because of the dosage and frequency of treatments. It is not true that radiotherapy treatment will cause a dog to suffer the most appalling side effects which will make the few weeks of added life a misery. The only side effects likely to occur in a dog are loss of hair over the treatment site (which generally grows back white) and sometimes an effect on the skin over the treatment site similar to sunburn. Neither effect bothers the dog in the slightest. It is not true, either, that radiotherapy will give only a few weeks extra life. If a dog is accepted for radiotherapy it is impossible to say how long it will have as this depends so much on how long the tumour has been there, how aggressive it is, and how quickly it metastases, but the likelihood is that the extra lifespan will be measurable in months rather than weeks. The factors involved are, in any case, involved in exactly the same way with any other therapy. However, radiotherapy for dogs is not available everywhere.
Dr. Stephen Withrow, chief of the Comparative Oncology Unit at the Colorado State University Veterinary Teaching Hospital started a new treatment protocol (reported in the Cornell Newsletter of April/May, 1987) for osteosarcoma using a combination of radiation, chemotherapy, and surgery in an effort to avoid amputation of affected limbs. The procedure was to treat the tumour with chemotherapy and radiation to halt the spread of the tumour at its margins, then the cancerous bone was removed and replaced with a bone graft. After this procedure, limb function was good to excellent, especially when the forelimb was involved. Cancer control was achieved in about 90 per cent of treated dogs and the incidence of tumour spread greatly reduced. One year after treatment, fewer than half the dogs treated had died of metastatic tumours compared with the 85 per cent that die within one year after being treated by amputation alone.
At a Cornell seminar, Dr. Claudia Barton of Texas A & M University reported that remission of lymphosarcoma can be achieved in 9 out of 10 cases that are detected early - that is, before the bone marrow, blood, and liver are affected. Even when the disease has progressed to the stage where these sites are involved and the dog has stopped eating and become lethargic and depressed, remission can usually still be obtained, although the length and cost of chemotherapy and the risk of adverse side effects are greatly increased. A dog in an advanced stage of the disease before treatment begins tolerates the drugs poorly. Untreated dogs live on average only 30 to 60 days.
In Dog World (the American version) of March 1987 there was a report on a "glimmer of hope for dogs afflicted with osteosarcoma". Dr. Gregory MacEwen, oncologist at the University of Wisconsin-Madison Veterinary Medical Teaching Hospital, Dr. Isaiah J. Fidler of the Tumor Metastasis Branch of the National Cancer Institute, and the Swiss pharmaceutical company Ciba-Geigy had been collaborating on a project to produce multilamellar vesicles (MLV) to stimulate the body's immune system to fight cancer. The idea was to utilise the cells called macrophages, which are located in the walls of blood vessels and loose connective tissue, and which act as "garbage men" by clearing the system of foreign substances. The macrophages can be stimulated by immuno-stimulant drugs such as muramyl dipeptide and muramyl tripeptide, which are derived from a tuberculosis vaccine, combined with liposomes to form a MLV which keeps the drug from floating freely in the body and, as a foreign body, attracting the attention of the macrophages.
This technique was combined with amputation of the affected limb and only increased the survival time from 3 or 4 months to 6 or 7 months but it had no side effects and possibly could be used in a combination treatment with radiation, chemotherapy, or surgical techniques.
Radiotherapy: in radiotherapy the ability of radiation to damage tissue has been harnessed to disrupt cancer cells in tissues so that they cannot replicate. The difficulty is in destroying the cancer cells and not normal tissue. One large dose of radiation would kill the cancer but it would also kill the normal tissue, so, as the normal tissue has a greater power to regenerate than do tumour cells, small doses are given at intervals so as to gradually kill the tumour while allowing normal tissue to recover. The daily doses used in human cancer are not feasible in animals because the animal has to have a general anaesthetic for each treatment and there is a limit to the amount of anaesthesia an animal can stand. The usual dosage regime for radiotherapy in dogs is a couple of doses a week for a period of four to five weeks. This type of treatment is used mainly for tumours which are not suitable for surgery, such as bone tumours, but also in conjunction with surgery to kill the cancer cells which could not be removed, as in mammary tumours, etc. It does not prevent metastasis.
There are two types of radiation therapy. The first is teletherapy or external beam therapy, which is given by machine and is the kind mostly used. Of the machines used, the main one is the cobalt unit. The disadvantage of this is that it cannot be switched off and so wears out over a period of years and is expensive to replace. It is also dangerous. The second type is the electrical machine; a small x-ray machine which is restricted to superficial tumours such as skin tumours. The third type of machine is the megavoltage machine or linear accelerator.
The second type of radiation therapy is brachytherapy or interstitial therapy in which anodes are implanted into tissues and give off radiation gradually to kill the tumour. The problem with this type of treatment is that, whilst the implant is in place, the dog is a radiation hazard and has to be kept in a special area.
Tumours appropriate for radiation therapy are mainly those where surgery is impractical, such as on the upper jaw, on bone, or other major structures. However, radiation therapy is also used in conjunction with surgery to kill off those cancer cells it is not possible to remove. Tumours vary in sensitivity to radiation and some do not respond well to radiation alone.
In the UK, radiation therapy is available at the Cambridge Veterinary School and the Animal Health Trust in Newmarket. I believe these are the only centres in Western Europe at which radiotherapy for animals is possible. Radiotherapy is available at some centres in the U.S.A.
Chemotherapy: cytotoxic drug therapy uses drugs such as Endoxana, Oncovin, Lytosar, etc. It is used mainly for widespread cancers such as canine multicentric lymphona (lymphosarcoma or pseudo Hodgkins disease). The drugs used damage dividing cells and to minimise toxicity a variety of drugs are used to spread the different side effects so as not to have more than minimal damage to normal tissues.
Body surface area is used to calculate dosage rates. As low a dosage as possible is given to minimise side effects. The usual regime is to give eight weeks of intensive treatment and then one week of treatment and one week off. The expectation is that the dog will go into remission for from three months to twenty-four months. The low dosage given to dogs does not cure the cancer but only controls it, as a high enough dose to kill the cancer would make the dog ill.
It is not known why there is so much difference in the period of remission but it is possibly due to there being different types of lymphona. Drug therapy has not proved much good at treating tumours of the bone, although it is used in conjunction with amputation to treat osteosarcoma.
Animals on chemotherapy have to be monitored closely by taking blood samples at monthly intervals. Possible side effects are suppression of bone marrow making the dog more susceptible to infection, heart problems, and irritation of the bladder but dosing is individually geared to causing as little side effects as possible. With the latest range of cytotoxic drugs, the treated dog has to be hospitalised for the actual treatment because of the dangers of the drugs themselves.
Hyperthermia: a technique of using high temperature to kill the tumour cells but, in fact, it only raises the temperature to around 44 degrees C, which is like a hot bath. Probes are put into the tumour to monitor the temperature so that overheating can not occur and burn the patient. The method of heating is an applicator using microwaves which is aimed into the tumour. When the required temperature is reached, the applicator is left on for 30 minutes. Hyperthermia is usually used in conjunction with radiotherapy; normally giving two doses of hyperthermia and four of radiation.
Cryosurgery: uses intense cold, such as liquid nitrogen, to destroy the tumour cells. It is used on tumours of the skin and mouth and its side effect is to de-pigment hair at the treatment site.
There is a body of opinion which considers it unethical to treat cancer in animals. One reason put forward is that all the efforts at cancer treatment ought to go into treating humans, but, not only is there no overlap between veterinary hospitals and ordinary hospitals, but work on cancer in animals helps towards a greater knowledge of cancer in people.
Another reason given is that it is cruel to subject animals to the awful side effects of cancer treatment. However, dogs do not in most cases suffer unpleasant side effects from treatment because the treatments are geared towards avoiding them by not in most cases killing the cancer but only slowing it down. Whether the side effects of losing a limb to amputation are too unpleasant to inflict on a dog can only be considered by those involved in individual cases.
There is seldom any reluctance to treat other severe conditions, such as kidney failure or heart disease, or even arthritis, despite the fact that such treatment frequently gives less quality of life (and often quite severe side effects) than does cancer treatment.
A third reason is that cancer treatment is not worth while because such a short period of extra life is gained. Certainly treatment is a gamble, because no-one can predict with any certainty how long the tumour will be suppressed or how long it will be before metastasis occurs. It might be only a few weeks or months, but it could be two years or longer and, in the case of many tumours, it could be several years because the tumour turns out to be benign.
Whether to have ones dog treated should be an individual decision, but it is a decision which should be based on all the facts. I have heard of vets who have refused to refer patients for treatment, or have told clients no treatment is possible or available, because they (the vets) have believed it unethical to treat a dog for cancer, or that it causes severe side effects, or gains such a short extra life-span as not to be worthwhile. I do not believe any vet has the right to make such a decision.
In most cases it is as well to get a referral to an oncologist from your own vet. Cases must be investigated thoroughly before it can be said which treatment, if any, can be used and what is the prognosis, and a specialist is the best person to do that and advise on what can be done. It may not even be cancer. One case diagnosed as bone cancer by the local vet turned out to be osteoarthritis when investigated at Cambridge, and another diagnosed as lymphosarcoma turned out to be an abscess.
If your hound is diagnosed as having osteosarcoma, no treatment is possible or worthwhile if metastasis has already occurred. Osteosarcomata vary enormously in rate of growth and metastasis. Some are exceedingly aggressive and grow very quickly; others may grow more slowly but may metastase early. Each case has to be judged on its individual merits. When I was taking Moppet to Cambridge for radiotherapy, another hound started treatment at the same time and with the cancer at much the same level of growth. However, within three weeks of starting radiotherapy, his cancer had metastased to the lungs and he had to be euthanased. Moppet went on for eighteen months and even then had no metastases.
Whether amputation is a reasonable procedure must be looked at from each individual viewpoint. It is entirely possible that some hounds just could not cope; and it is also entirely possible that some owners could not. It has to be a matter of personal choice.
Some cancers seem to have responded to home treatment with flax seed oil given with cottage cheese - about a tablespoonful of flax seed oil to two to three tablespoonfuls of cottage cheese. The cottage cheese is necessary for the full assimilation of the flax seed oil. It is important to get only a good quality flax seed oil; one that has been cold-pressed, excluding light and oxygen, is in a dark coloured bottle, has a short shelf life (a use-by date no more than six months from date of pressing) and which is stored in a refrigerator or freezer (freezing extends the shelf life safely to one year).
Curcumin (found in turmeric, a root used in Asian cookery) has been found to work well against some cancers. It also has anti-inflammatory effects. Much research has been and is being undertaken to study the effects of curcumin. See the links (below) for more details.
The Irish Wolfhound Foundation (see Links below) has a report on a Study on the use of Fosomax for the palliative treatment of osteosarcoma in wolfhounds and, although the Study is now closed, information on the use of this therapy and the most cost-effective ways to obtain it can be obtained via the website.
There is a book, entitled Help Your Dog Fight Cancer by Laurie Kaplan, and a website (see Links below) which gives lots of advice on treatments, nutrition, etc., details of research studies, support groups and lots more.
Written March 10th, 2006
|The website of the Veterinary Cancer Society|
|Article entitled "Canine Osteosarcoma" on the CancerQuest.org website|
|Article on the VetContact website - Osteosarcoma in Dogs - Current Treatment Protocols|
|The page for Animal Cancer: Natural Healing on shirleys-wellness-cafe website|
|The site for Help Your Dog Fight Cancer (Laurie Kaplan)|
|The Irish Wolfhound Foundation home page|
|LifeExtension Magazine, July 2002 - report on Curcumin's anti-cancer effects|
|Article on Turmeric for Dogs on the Dogs Naturally Magazine website|