When the cancer occurs in the mouth, it is not the result of sunlight exposure – the cause is unknown, though for cats it has been associated with household smoke. In cats, the disease is particularly aggressive and generally not curable. Surgery can be done, but must be aggressive. For dogs, the prognosis can be better, and for some, cure is a likely outcome.

Your veterinarian will advise you on how best to commence diagnosing and treating your pet’s tumour. At some point, a specialist opinion may be helpful to offer advice, or to commence treatment.

If the risk is low, there are 3 types of treatment available for your pet:

1. The most effective treatment is surgery, however this must be aggressive to have any chance of cure. In many cases this may mean removal of nearby structures, and for limb tumours, amputation may be required.
2. Less aggressive surgery not intending to cure can be followed by daily at-home metronomic therapy. This is a relatively new approach which targets the blood supply to the tumour and may also make the tumor more visible to the immune system. Recurrence will occur but hopefully after several years; this treatment therefore may be most useful for older pets. Alternatively, radiation therapy can be used to ‘mop up’ cancer left behind following surgery.
3. Injections of chemotherapy into the tumour. The advantage of this technique is that very high concentrations of drug are placed into the tumour, however very little diffuses out into the patient. Chemotherapy side effects therefore do not occur. Success rates are lower than with surgery.

If the tumour is classed as high grade, the potential for spread becomes very high. In this instance it is preferable to follow removal of the tumour with medical treatment aimed at removing remaining cancer cells elsewhere in the body. This should result in your pet having a significantly longer period of normal quality life. These medications generally will not make your pet ill.

Chest x-rays are often taken prior to surgery. If the tumour can be seen in the chest (about a 10% chance), then treatment aims to restore quality of life for up to a year . If there is no tumour visible in the chest, this means that the cancer is not advanced (but will almost certainly be hiding there) and that cancer treatment has a greater likelihood of achieving long term control. Unfortunately, if surgery is the only treatment, most dogs will not live more than 3 or 4 months. With cancer therapy, about half of dogs will live 16 months or more, and about 1 in 5 will be cured. Cancer therapy therefore obtains good control of the disease and importantly in most dogs causes no side effects: 70% of the time our treatments have no side effects at all, and another 25% produce only brief, mild problems. Only one dog in 20 will have a serious reaction to the medication, which is almost always successfully and rapidly controlled.

Because of the nature of the drugs used to treat osteosarcoma, you should be referred to a veterinary oncologist.

Thanks to new medications, dogs with biopsy-proven osteosarcoma can now have effective treatment WITHOUT needing surgery. Medical-only treatment is not as reliable or as durable as standard treatment (surgery plus medication) and therefore should only be used in circumstances where the patient is not expected to cope with amputation (due to severe arthritis in other limbs, for example). It employs a combination of chemotherapy and either a new bone drug called pamidronate or radiation.

Costs can be very high with these sorts of treatment. Surgery may cost up to several thousand dollars, and medical cancer treatments can cost the same again. The cancer therapy is given via a drip, every 2 to 3 weeks on up to 6 occasions, and does not require overnight hospitalisation. It is important to remember that all the treatment for this disease is designed to restore quality of life, and to then provide as much time as possible. Quality of life is the primary objective.

1. Surgery. This is the best first-line therapy, and is usually successful in preventing the tumour growing back at the same site. Unfortunately, there are no tests available that detect the tumour elsewhere until the disease is very advanced. In general, if the tumour appears malignant at the laboratory or occurs in a dog’s mouth or cat’s eye, it usually has already spread elsewhere in the body, and most often to the lungs, even though it may not be visible on x-rays for some time.
2. Intralesional chemotherapy. Injecting chemotherapy drugs into the tumour reduces the tumour to the micropscopic level at its original site in about half of all cases. The doses used are too small to cause any side effects, and generally only require sedation and local anaesthetic. Most commonly, 4 treatments are given, each a week apart. Not all patients are suitable for this treatment.
3. Systemic chemotherapy. This form of chemotherapy is used to treat the whole body and hence fight cancer wherever it has spread to. The way in which this is done in animals results in no serious side effects in most patients. On average, treatment lasts 2 months.
4. Vaccination. There is now a vaccine available in the USA which can help dogs with malignant melanoma. Its success is variable but it does appear to result in a durable period of control for many dogs. It works by training the immune system to fight the cancer. It is not available at present outside the USA.
5. Nutritional changes and pain control. There are several changes that can be tailored to individual patient’s diets to improve quality of life. Pain control can be helpful in animals with advanced disease even if they do not show signs of pain.

Initially, a diagnosis must be made. A sample of tissue will need to be sent to the laboratory to determine how aggressive the tumour is. Generally, the cancer will be given a grade, where grade I tumours are low grade and generally harmless, and grade III tumours are high grade and spread rapidly. All of them however tend to burrow deeply into the surrounding tissue such that the visible mass is no more than the ‘tip of the iceberg’. The surgeon therefore will take as much tissue as possible around the cancer to decrease the odds of leaving any microscopic cancer behind. Often, only surgery will be necessary to effect a cure. For tumours of grade II or III severity, and especially if the location prevents aggressive surgery from being performed (e.g. the leg or face), further treatment may be helpful – both radiation and chemotherapy have been shown to be effective. The majority of dogs with mast cell tumours can be cured, though the chance reduces the higher the grade or stage.

The medical treatment itself is usually intravenous injections, which are quick and largely painless. Most dogs will receive 8 or 10 treatments over 12 to 16 weeks.  The drugs most commonly used are Vinblastine and lomustine. A new medication called imatinib is available which can cause dramatic reduction in the tumour. It is unfortunately quite expensive and should be used over a long period of time.

Radiation therapy protocols range from a few doses at weekly intervals with palliative intent, to 3 times per week over a month and are generally done under a general anesthetic.

Fortunately, testicular cancer in dogs is usually much less aggressive than in man. For the majority of dogs, surgical removal of the tumour is curative. Whilst many people are uncomfortable with the idea of castrating a pet, we all have a duty to safeguard our pet’s health, and castration is kinder than cancer. In general, this surgery will not change your dog’s behaviour other than reducing dominance aggression (but not territorial or protective aggression). Castrated dogs only put on weight if overfed. In most instances, referral is not required; your own veterinarian is usually the best person to perform this procedure.

In some instances, these tumours can spread elsewhere. Evidence of lymph node enlargement or the results from the laboratory that examine the tumour after surgery may suggest that more than surgery is necessary. In this case, your veterinarian will advise referral to an oncologist to discuss treatment of the cancer. Medication can do a lot to keep your dog comfortable and generally doesn’t cause any illness itself.

Finally, some testicular cancers can produce the female hormone, oestrogen. This produces skin changes and hair loss, but can also cause serious damage to the bone marrow that may be irreversible. A blood test will detect the marrow injury rapidly.

Prostate cancer

Prostate cancer is the most common reason for a castrated dog to have a large prostate. Castration does not prevent prostate cancer in dogs, and does not slow it down once it has developed. Prostate cancer in dogs can respond very well to cancer drugs. The result is not cure, but often a dog with normal quality of life for another year or two. Surgery can sometimes help but will cause urinary incontinence; any benefits are for the short term as the cancer has usually spread before detection. There are several ways that many of the symptoms of prostate cancer in dogs can be eased with various medications.

The disease is rapidly fatal. Most dogs succumb within 2 months of diagnosis if treatment is not initiated promptly. This is an average figure – some dogs will have less aggressive forms and live for 6 or 7 months, whilst some will decline within days. Most dogs develop the high-grade (aggressive and rapid) form. Treatment can be either palliative or can aim to reduce the cancer burden directly. Palliative therapy is generally corticosteroid (“cortisone”, prednisone) tablets, which can produce a dramatic short-term benefit in about half of all patients. Length of life is not improved, but quality of life is often much better. The only therapy proven to be very effective in pets is chemotherapy. Drugs are used to kill large numbers of cancer cells (well over 99%), which places the patient into remission. Remission means that the tumour cannot be detected, and is unable to cause any symptoms. Hence your pet will have normal quality of life. For the majority of patients there exists a therapeutic “window” such that medication can result in complete remission for good periods of time, with ZERO side effects. With all treatments, there exists a risk, and around 1 in 20 patients will have serious reactions to the medication.

The patients that do best with treatment tend to have less advanced disease, are not showing signs of obvious illness at the time of diagnosis, and do not have the beginning of treatment delayed. For most, the age of the patient does not seem to alter success.

Treatment can be given in many different ways. The most effective therapy uses many different drugs in rotation, with the aim of delaying the development of resistance within the cancer. Around 85% of dogs that receive treatment go into remission, and typically within days or weeks. Dogs receiving therapy have a 50% chance of still being alive 12 months after treatment first started and around a 15% chance of cure. The drugs are used in such a way that quality of life is more important than length of life. This lowers the cure rate, but means that however long they live, they enjoy that period of time. Treatment is generally given for 6 months. Other treatments are available that are simpler, and these may only require as little as 5 treatments over 15 weeks. The longer-term success with these shorter treatments is not as good, however.

The other 2 forms of treatment involve the use of medications. Medical treatment is available that results in significantly longer periods of normal quality of life following surgery. Whilst not every patient responds, most experience a good 6 to 12 months or longer, with a 10% chance of cure. The treatment is given in such a way that side effects are uncommon. Treatments are generally given from every 3 weeks to every week for up to 15 treatments. Costs can be high, with medical cancer therapy treatments costing from several hundred dollars per treatment.

Alternatively, there is treatment available that can prevent blood vessel growth leading to a halting of tumour growth overall. Treatments aimed at preventing blood vessel growth are given at home, and require visits as often as fortnightly initially, but less often later. Treatment costs are much lower.  Ideal therapy at present uses both treatments.

Uterine Tumours: Fortunately for most dogs with this rare tumour, the problem is benign and cured by surgery. For cats however, the tumours are typically advanced at diagnosis, and have spread. The most common symptom in both species is the presence of vaginal fluid. Surgery is required in all cases.

Vaginal Tumours: These tumours can grow to be very large, but fortunately are mostly benign. Surgery therefore is typically successful in curing the patient. Occasionally, cancerous tumours will appear in this location. Your veterinarian may suggest referral in this instance.

Your veterinarian will advise you on how best to commence diagnosing and treating your pet’s tumour. At some point, a specialist opinion may be helpful to offer advice, or to commence some of the therapies listed above.