Cancer in dogs: symptoms, signs and treatment

Cancer is the number one cause of mortality in dogs over 10 years old, and it can affect younger dogs, too. Unfortunately, around one-quarter of dogs eventually die as a result of cancer.

But there's good news: cancer treatment for dogs is much better than it used to be. It’s easier than ever to find the type of treatment your dog could benefit from most.

In this guide to treating cancer in dogs, we’ll look at the types of cancer that most frequently affect dogs, how cancer is diagnosed and treated, and how pet parents can afford such specialised care.

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Can dogs get cancer?

Sadly, yes. Dogs get cancer roughly at the same rate as us humans. Risk factors include age and obesity. Family history and breed play a big role, too. Some breeds, like Bernese Mountain Dogs, are very likely to get cancer.

We discuss the common dog cancer signs below.

Signs and symptoms of cancer in dogs

It's easier for vets to treat cancer when it's detected and diagnosed early. It's why you should know dog cancer symptoms and inform your vet as soon as possible.

Make an appointment with your veterinarian if you notice anything unusual with your dog, like:

• Abnormal patches of skin

• Coughing, sneezing, or difficulty breathing

• Diarrhoea or constipation

• Difficulty urinating or blood in the urine

• Lameness

• Lethargy

• New lumps or bumps, especially if they grow or change rapidly

• Pain

• Poor appetite

• Unexplained weight loss

• Unusual odours or discharges

• Weakness affecting the whole body or just one part

• Vomiting

Of course, symptoms like these aren’t always associated with cancer. Signs of cancer are broad, but it’s always best to talk to a vet just in case.

Common types of cancer in dogs

Some cancers are more common in dogs than others. Let’s look at some frequently diagnosed types.

Lymphoma

By itself, lymphoma accounts for up to 24% of cancer diagnoses in dogs. It is a cancer of lymphocytes (a type of white blood cell) and the tissues where they are commonly found. Canine lymphoma can affect lymph nodes, the spleen, the gastrointestinal tract, and other body parts.

Many dogs seem to feel pretty good early in the course of the disease. But without effective treatment, they eventually become lethargic, lose weight, and develop other symptoms of cancer based on where the disease is located. Pet parents often first notice swellings:

• Where a dog’s jaw meets the neck

• In front of the shoulders

• Behind the knees

Any dog can get lymphoma, but certain breeds are at increased risk. Breeds at high risk include Boxers, Golden Retrievers, Labrador Retrievers, German Shepherds, Rottweilers, and many more.

To diagnose lymphoma, a veterinarian will use a needle to take some cells from affected tissues or take a larger biopsy sample. A complete health workup, including sending tissue samples to a pathologist, blood work, a urinalysis, x-rays, and possibly bone marrow aspirates and other tests, will help the veterinarian determine the dog’s prognosis and plan the most effective treatment.

Lymphoma is usually treated with chemotherapy. Some pet parents choose simple, inexpensive protocols that can be expected to provide their dogs with several months of good quality of life. Others opt for more complicated and expensive protocols that can give them a couple of years of extra time with their canine companion.

Mast cell tumours

Mast cell tumours are the most common type of skin tumour in dogs. Dog owners most often notice a lump in the skin. Mast cell tumours may also develop in a dog’s spleen, liver, bone marrow, and intestines.

Dog lumps: when is it cancer?

Not all tumours are cancerous, which we've discussed in our dog tumour guide.

To diagnose a mast cell tumour, a veterinarian will use a microscope to look at a sample of cells from the tumour. It’s best to send a biopsy to a pathologist for grading (determining how aggressive the cancer is).

Lower-grade mast cell tumours may only require surgical removal, while dogs with higher-grade tumours often benefit from additional forms of treatment like chemotherapy or radiation treatment.

Any dog can be diagnosed with a mast cell tumour, but Boxers and Boston Terriers are at the highest risk.

Leukaemia

This is a type of cancer that affects the bone marrow and blood.

Leukaemia in dogs symptoms include:

• Diarrhoea

• Enlarged lymph nodes

• Enlarged abdomen

• Fever

• Increased urination

• Increased water consumption

• Lethargy

• Loss of appetite

• Vomiting

• Weight loss

Treatment for leukaemia will depend on the severity of the condition and the vet's view; it's why early detection is so important.

Options can include:

• Chemotherapy

• Immunotherapy

• Medications to suppress the immune system

Osteosarcoma

Osteosarcoma is by far the most common type of bone cancer in dogs. It primarily affects larger breed dogs like Rottweilers, Great Danes, St. Bernards, Irish Setters, Irish Wolfhounds, Doberman Pinschers, German Shepherds, Rhodesian Ridgebacks, and Golden Retrievers. 

Common symptoms include persistent lameness and swollen, painful areas affecting the legs or other bony parts of the body. Unfortunately, osteosarcoma spreads rapidly so other symptoms can develop quickly.

A veterinarian may have a high degree of certainty that a dog has osteosarcoma based on an x-ray of the affected area. But other diagnostics, including a bone biopsy, may be needed for a definitive diagnosis. A complete health workup will be performed to determine a dog’s prognosis and best treatment options. 

Common treatment of cancer can include:

• Aggressive use of pain medications (osteosarcoma is very painful)

• Chemotherapy

• Possible amputation

• Radiation treatment

• Surgery

Prognosis varies, but with early detection and aggressive treatment, some dogs can live for up to two years after developing osteosarcoma.

Melanoma

Melanomas arise from cells that produce the pigment melanin, so they usually (but not always!) appear as a raised mass that is dark in colour. They most commonly occur in the skin, in the mouth, and around the base of toenails but can be located elsewhere in the body too. Any dog can develop melanoma, but those with dark skin pigmentation are at higher risk.

Melanomas can be benign or malignant. A vet will take a sample of cells to diagnose the condition. A biopsy may also need to be sent to a pathologist. Melanomas in the mouth and around the toenails tend to be malignant and carry a worse prognosis than melanomas affecting hairy skin.

Surgery is necessary to remove the mass. Dogs with malignant melanomas will need additional treatment with chemotherapy, radiation therapy, and/or immunotherapy (a melanoma vaccine for dogs), which can also be beneficial. A complete health workup is necessary to determine a dog’s prognosis and the best form of treatment.

Mammary gland carcinomas

There are several different types of mammary gland tumours in dogs, but carcinomas are the most frequent. About half of mammary gland tumours in dogs are benign, while the other half are more aggressive, malignant mammary tumours. Female dogs who are not spayed or were spayed after they were two years old are at the highest risk for developing mammary gland tumours as they get older.

Pet parents will often first notice one or more lumps in their dog’s mammary chain. A veterinarian will take a sample of tissue and perform a complete health workup to determine if the lumps are cancerous and then make a plan of action. Benign tumours and low-grade malignant tumours are often treated through surgical removal and spaying the dog.

Additional treatment for more aggressive tumours in dogs may include chemotherapy and radiation therapy. A dog’s prognosis depends on the type of mammary carcinoma involved and how widespread it is at the time of diagnosis.

Hemangiosarcoma

Hemangiosarcomas is an aggressive type of cancer that arises from cells that line blood vessels. They can occur anywhere in the body, but the most common sites are the spleen, liver, heart, and sometimes the skin. The most common symptoms of internal hemangiosarcomas relate to sudden bleeding and include weakness, lethargy, pale gums, rapid breathing, and collapse.

Any dog can develop a hemangiosarcoma, but Golden Retrievers, Labrador Retrievers, and German Shepherds are at higher than average risk. A tissue sample is necessary to diagnose a hemangiosarcoma and determine its aggression. A full health workup will help guide the treatment process, which may include surgery, chemotherapy, and radiation therapy. If the tumour can be completely removed before it spreads, a dog’s prognosis is good. However, hemangiosarcomas tend to spread quickly, and even with appropriate treatment, dogs often only survive for a matter of months.

Bowel cancer

Bowel cancer is relatively uncommon in dogs, but it's important to catch this early, so we've decided to discuss it here. You must seek advice from a vet as soon as you spot signs.

Symptoms of bowel cancer in dogs include:

• Abdominal pain

• Bloating

• Blood in stool

• Decreased appetite

• Diarrhoea 

• Pale mucous membranes

• Vomiting

• Weight loss

Treatment depends on the tumour, cancer, size, location and other factors:

• Chemotherapy

• Non-steroidal anti-inflammatory medications (NSAIDs)

• Radiation therapy

• Special diets or other medications

• Surgery

Throat cancer

Throat cancer is, again, uncommon, but worth discussing as spotting this cancer early is important.

Signs of throat cancer in dogs include:

• Breathing issues

• Bark changes or loss of voice

• Bluish mucous membranes

• Coughing

• Depression

• Drooling

• Eating issues, like regurgitation and difficulty swallowing

• Lethargy or weakness 

• Smelly breath

• Weight loss

For treatment, your vet will likely need to remove the rumour and some surrounding tissue while preserving throat function.

Radiotherapy, generally, isn't too effective, so surgical intervention is common.

It's another reason why early detection is so important as throat cancer is particularly life-threatening.

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Cancer diagnosis

Even if there are strong signs of cancer in dogs, an accurate diagnosis is essential before treatment. This process starts with a thorough health history followed by a complete physical examination.

However, there isn’t a single type of cancer that can be accurately diagnosed without some laboratory testing.

• Veterinarians often begin by using a needle to collect a small sample of cells from a lump or bump and then look at it under the microscope.

• Basic blood work combined with urinalysis is a simple way to evaluate a dog’s overall health and how their internal organs are functioning.

• X-rays and ultrasounds are widely available, noninvasive ways to look inside a dog’s body.

• Other diagnostic tests to detect cancer and determine how far it has spread in the body include endoscopy, CT scans, MRIs, and specialised laboratory tests.

The best combination of diagnostics depends on a dog’s symptoms, and what types of cancer are most likely.

In many cases, the veterinarian will want to biopsy (surgically remove a piece) the abnormal tissue and send it to a pathologist for review.

Pathologists who specialise in cancer can confirm the diagnosis and often provide more detailed information that will be used to guide treatment. An early diagnosis will give your dog the best chance of receiving effective treatment.

Dog cancer treatment

Every dog with cancer deserves treatment, but the right form can depend on many variables, including the dog’s overall health and age, how advanced or aggressive the cancer is, and their caretaker’s desires and financial constraints. As is the case with human medicine, there are many new and cutting-edge cancer treatments available for your dog.

Your vet may recommend referring you to a veterinary oncologist or other specialists.

The following options can be used alone or in combination to help dogs with cancer.

Palliative care and euthanasia

In extreme cases, immediate euthanasia may be in a dog’s best interest. If suffering can’t be adequately controlled and treatment is unlikely to provide much in the way of benefit, helping a dog to pass peacefully can be a gift.

However, palliative care — treatments aimed at improving a dog’s quality of life, not directly addressing the underlying disease — can often make a dog comfortable when pet owners need to make informed decisions.

Palliative care can include:

• Assistance with urination and defecation

• Fluid therapy

• Helping pets move around safely

• Keeping pets clean and well-groomed

• Maintaining engagement with family life

• Nutritional support

• Pain-relieving medications

• Symptom management

Palliative care should always be integrated into euthanasia decisions, and the forms of treatment used to fight a dog’s cancer.

Surgery

Surgery plays a big role in the treatment of many different types of cancer. Sometimes one or more cancerous tumours can be completely removed with surgery, and no further treatment is necessary. At other times, surgical intervention can significantly reduce the amount of cancer in a dog’s body, which has a positive effect on their quality of life and other forms of treatment.

Small tumours are easier to remove, which increases the effectiveness of surgery and reduces the chances of complications during and after the procedure. Dogs with large tumours may first need other treatments — like chemotherapy or radiation therapy — to shrink the mass and make surgery as safe and effective as possible. Don’t wait to get your pet checked out by a veterinarian if you notice something unusual!

Chemotherapy

Pet parents tend to have an understandably negative reaction to the thought of putting their dog through chemotherapy. But it’s important to remember that the word chemotherapy can mean many different things. Some chemotherapy drugs are very safe, while others do have potentially serious side effects associated with them. However, veterinarians often treat cancer less aggressively than human medical doctors do, which lessens the risk and severity of side effects like bone marrow suppression or vomiting.

There are many situations where chemotherapy can be an essential part of cancer treatment in dogs, including:

• When cancer has originated in or spread to multiple parts of the body

• When a dog has an aggressive type of cancer that has probably already spread

• When other forms of treatment, like surgery, might be too dangerous for the dog or are unlikely to have a significant positive effect on the dog’s quality of life

• To shrink a tumour before surgery or other forms of treatment

Different chemotherapy drugs are administered in different ways — orally, intravenously, intramuscularly, topically, subcutaneously, or even directly into a tumour or body cavity. In other words, you have choices! If you don’t want to bring your dog to the clinic frequently, perhaps an oral form of chemotherapy you can give at home is available.

Radiation therapy

Radiation therapy is most often used for cancers that are in locations where surgery would be very difficult or would lead to unacceptable outcomes. It can also shrink a mass before it is surgically removed or kill cancer cells left behind after surgery. Sometimes the primary goal of radiation therapy is pain relief.

Most veterinary schools and some veterinary speciality practices can provide radiation therapy for dogs. Protocols vary depending on the cancer involved and the goals of treatment. Typically, dogs are treated anywhere from daily to once a week for around three to four weeks. They will need to be anesthetised during the procedure, so they don’t move.

Emerging forms of treatment

New cancer treatments for dogs are quickly being developed. Immunotherapy is a great example. A vaccine to help treat melanoma in dogs is currently available, though it seems to work best in combination with other forms of treatment. Other vaccines that stimulate the immune system to fight a dog’s cancer and novel gene therapies are also in development. The American Veterinary Medical Association maintains a searchable database of clinical trials that are looking into new forms of treatment for a variety of diseases.

Complementary care

Everything we’ve touched upon so far in this article falls under the heading of “traditional” veterinary medicine. But complementary care can also be beneficial, particularly when used in combination with rather than instead of traditional techniques like surgery or chemotherapy. This combined approach to veterinary medicine is often called integrative or holistic care. Examples of potentially useful forms of complementary medicine for the management of canine cancer include:

• Acupuncture

• Some herbal therapies

• Nutritional intervention and supplements

• Physical therapy

To avoid complications, ensure your dog’s entire healthcare team is aware of all the treatments your dog is receiving.

How long can a dog live with cancer?

Quality of life is key.

No matter how a dog’s cancer is treated, the primary focus must always be on their quality of life. A short-term compromise may be necessary to achieve a long-term gain. Still, when a dog is suffering, and there is no reasonable expectation that their quality of life will improve with continued treatment (including an increased level of palliative care), euthanasia may be the best thing you can do for your dog. Talk to your veterinarian about what you can do if your dog is experiencing significant and consistent decreases in their ability to:

• Eat and drink

• Urinate and defecate

• Move safely around their environment

• Experience some joy each day

Cost

We haven’t yet touched on one important aspect of cancer treatment in dogs: cost. There’s no way around it; treating cancer can be very expensive, but of course, there is a huge range depending on the specifics of a dog’s case.

For example, dogs with lymphoma can be treated with prednisone, a form of chemotherapy that only costs a few cents per pill. Their symptoms will generally go into remission for several months, after which time euthanasia often becomes necessary.

On the other hand, more advanced treatment protocols can extend that remission up to a year or two but may cost many thousands before all is said and done.

Purchasing dog insurance (before your pet is sick!) will allow you to make decisions about your dog’s treatment without worrying about its cost.

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