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Bone Cancer in Dogs and Cats: Prognosis, Symptoms, and Treatment for Osteosarcoma

Bone tumor in a dog

It starts with innocent paw pain or lameness.

Then there is swelling in the area of ​​the joint, the pet becomes apathetic and refuses to walk.

Commonly used painkillers improve temporarily, but over the course of a month or two, they get worse.

In the clinic, an x-ray reveals a shocking truth - changes in bone suggestive osteosarcoma

  • What is osteosarcoma?
  • What are the causes of osteosarcoma?
  • Is my dog ​​at risk?
    • Predisposed breeds:
  • In which bones tumors are most often located?
  • Bone cancer symptoms
    • Signs of osteosarcoma in a dog
    • Signs of osteosarcoma in a cat
  • Is it really osteosarcoma?
  • Treatment of osteosarcoma
    • Surgery
    • Chemotherapy
    • Radiotherapy
    • Pain relief treatment
    • Biphosphonates
  • Prognosis of canine and cat osteosarcoma
    • The location of the tumor
    • Application of additional treatment
    • The occurrence of metastases to regional lymph nodes
    • Alkaline phosphatase activity
    • The degree of histological malignancy of the tumor
  • imagine

What is osteosarcoma?

Osteosarcoma (Osteosarcoma) is a malignant, very aggressive and highly metastatic bone tumor, harvesting its toll especially among large and giant breed dogs.

In these dogs, Osteosarcoma is approx 6% all malignant tumors.

It is less common in cats and has a lower ability to produce distant metastases.

What are the causes of osteosarcoma?

It is still unknown

Several theories have been put forward to explain why they develop in animals:

  1. In large and giant dog breeds, repeated injuries and small fractures of the bone tissue in the metaphysis area may occur. According to some researchers, the repair processes taking place in these regions may lead to the formation of cell clones with mutated genetic material.
  2. There are reports of the association of these malignant tumors with metal implants (used to stabilize bone fractures), with chronic osteitis or previous mechanical injuries.
  3. Radiotherapy. In dogs and cats, cases of osteosarcoma at pre-irradiation sites have been reported due to treatment of another tumor at this site.
  4. The genetic basis of the formation of osteosarcoma is the subject of intensive research, especially in relation to the fact that this tumor is a family history.
  5. Some studies show a strong correlation between early castration and bone tumors, especially in large and giant breed dogs.

Is my dog ​​at risk?

Golden retrievers are at increased risk

Most often, osteosarcomas are diagnosed in adult dogs of large and giant breeds.

Tumors appear at different ages (mean age 7 years), and are especially common in dogs 3 and 8 years old.

Unfortunately, cancer occurs even in animals younger than 6 months.

In cats, osteosarcomas are found at different ages (from 1 to 20 years), but most often in animals 8.5-10 years old.

There is no racial or gender predilection.

Predisposed breeds:

  • German Shepherds,
  • St. Bernardine,
  • great dane,
  • rottweilers,
  • setters,
  • dobermans,
  • Bernese Mountain Dogs,
  • golden retrievers,
  • boxers.

They get sick more often males than females (in the listed dog breeds).

Body weight and height they are even more important predictor factors than race.

It turns out that 29% of all osteosarcoma cases were found in dogs weighing over 40 kg, while 5% individuals weighed less than 15 kg.

Animals after orthopedic surgery are also more at risk, especially those in which, as a result of stabilization, e.g. fractures were left metal implants.

Dogs after orthopedic surgery are more at risk

In which bones tumors are most often located?

In dogs, neoplastic changes are most common peripheral skeleton (in 75%).

They usually sit in the area epiphyses of long bones.

In the case of limb bone tumors - 2 times more often they appear in the pectoral limbs than pelvic.

They are most often observed within:

  • distal epiphysis of the radius,
  • proximal part of the humerus,
  • less often in the distal part of the ulna,
  • proximal or distal segment of the femur or fibula ( "near the knee, far from the elbow "),
  • they are exceptionally found in the skeleton around the elbow, tarsus and wrist.

In 25%, osteosarcomas are located in axial skeleton (skull, jaw, zebra crossing, shoulder blades, circles) or in soft tissues.

Osteosarcoma within the skull bone has less metastatic potential compared to tumors located in the bones of the extremities, pelvis or ribs.

Rarely, there are multifocal changes (i.e. tumors in several bones at the same time).

In cats, the lesions are most often located in long bones, less often in the axial skeleton.

It is significant that in this species of animals, in about 1/3 of osteosarcomas, the lesions originate from extra-skeletal soft tissues:

  • mammary gland,
  • eyeball,
  • interscapular area.

In the latter case, they are considered as post-vaccination sarcomas. You can learn more about them in the article "Cancer after vaccination in a cat: post-injection sarcoma "

Bone cancer symptoms

What are the symptoms of osteosarcoma?

Signs of osteosarcoma in a dog

It usually comes to the fore in osteosarcomas of the limbs pain (most often the metaphyseal part of the bone) and to varying degrees lameness, which gets worse over time.

It may be visible deformation, which gets bigger, gets warmer and covers more and more limb area.

The longer the pathological process lasts, the more the animal becomes relieves the sick paw, muscle tissue it fades away.

Sometimes it also comes to enlargement of nearby lymph nodes.

It also happens that at the site of the appearance of the neoplasm it occurs pathological bone fracture.

In the case of a tumor located within the axial skeleton, the symptoms may vary and depend on the localization site.

As a rule, the noticeable is smaller or larger deformation within the skull, pelvic girdle, scapula or ribs.

Osteosarcomas of the mandible or jaw can cause:

  • salivation,
  • swallowing disorders,
  • lack of appetite,
  • exophthalmia,
  • inability to close the jaws or problems with opening them.

With cancers of the sinuses and nasal cavity, it comes to respiratory disorders, discharge from the nose (initially serous, but usually blood-stained or purulent).

With the involvement of the bones of the skull or vertebrae - possible nervous symptoms different types and of varying intensity.

With the coexistence of lung metastases, respiratory problems in the form of breathlessness, cough or exercise intolerance.

It happens that these symptoms are the main reason for consultation at a veterinary office even before the presence of the primary tumor is confirmed.

Signs of osteosarcoma in a cat

They depend on location and are usually similar to dogs.

As a rule, however, it is deformation occupied area and to varying degrees lameness and soreness in the limb.

Is it really osteosarcoma?

Diagnostics at osteosarcoma

To fully confirm that we are dealing with osteosarcoma, careful examination should be performed clinical trial and additional research.

It plays a key role here x-ray examination the affected area.

On suspicion osteosarcomas execution is also necessary chest x-rays in order to exclude or confirm the presence of metastases.

Osteosarcoma in 90-98% cases metastasize to lung tissue.

It is of particular importance in determining the exact extent of the neoplastic process computed tomography if magnetic resonance imaging, especially when considering a limb-sparing surgery.

The diagnosis should always be confirmed histopathological examination primary tumor excision (core needle biopsy or surgical excerpt).

In the case of lymphadenopathy, it is performed fine needle aspiration biopsy to confirm the presence of metastases.

In the case of planned chemotherapy should do:

  • thorough morphological examination,
  • blood chemistry (with particular emphasis on the activity of alkaline phosphatase),
  • urine test,
  • cardiological examination,
  • abdominal ultrasound.

Treatment of osteosarcoma



The primary treatment for osteosarcoma in dogs and cats is surgical procedure, consisting of amputation of a diseased limb.

For many owners, this is a shock, especially if the disease affects a large or giant breed dog.

They believe that the pooch will not be able to move around, that it will tire.

Indeed, there are several serious contraindications for avoiding such a radical procedure. These are:

  • massive lung metastases,
  • serious neurological and / or orthopedic problems in other limbs (e.g. we will not perform an amputation of the front limb in St. Bernardine with advanced hip dysplasia),
  • in very obese individuals.
In other cases, the limb removal procedure is performed is always recommended, even in very large and heavy individuals.

It has many advantages, namely:

  • it is relatively short, uncomplicated,
  • is burdened with a low risk of complications and contamination of the surgical field with neoplastic cells (compared to other surgical techniques), and thus a low risk of recurrence due to incomplete excision,
  • allows you to quickly relieve pain,
  • is a relatively inexpensive procedure,
  • the recovery period is quite short.

In the case of tumors located in the axial skeleton, the treatment is also based on surgery, e.g. maxilectomy (resection of part or all of the jaw bone), mandibuletkomia (removal of a fragment of the lower jaw) or removal of the ribs occupied by the tumor.

In neoplasms located in the scapula or pelvic bones, the removal of these bones with or without amputation of the associated limb is used.


Chemotherapy is an additional treatment for osteosarcoma that slows down the development of metastases.

The most commonly used drugs in chemotherapy (in various combinations) are:

  • cisplatin,
  • carboplatin,
  • doxorubicin.


Radiation treatment, especially before surgery, it is used to minimize the risk of postoperative recurrence.

It should be noted, however, that it did not substantially extend the survival time in dogs with osteosarcoma.

More commonly used as palliative treatment for the relief of pain in untreated animals with osteosarcoma.

Pain treatment

They are used in advanced situations or in the event that the owner does not consent to surgery non-steroidal anti-inflammatory drugs, such as:

  • carprofen,
  • meloxicam,
  • piroxicam.

They can be used in conjunction with opioid drugs.


These are drugs that show potential benefits in dogs with osteosarcoma.

Namely, by inhibiting osteoclasts (cells that have the ability to dissolve and resorb bone tissue), they reduce bone resorption.

This group includes, among others:

  • alendronate,
  • pamidronate,
  • zoledronic acid.

Prognosis of canine and cat osteosarcoma

Prognosis of dog osteosarcoma

It is difficult to answer this question unequivocally.

The prognosis depends, inter alia, on:

The location of the tumor

The main factor determining further prognosis is the possibility of complete tumor removal.

  • Left untreated, osteosarcomas of the limbs lead to death or euthanasia within most animals 3 months from the diagnosis, 90% of which is caused by the presence of lung metastases.
  • When amputation is the only treatment, lung metastases (less commonly to bone) occur around 72%. The median survival time is approx 5 months, not all 2% patients are still going through 2 years.
  • Tumors of the skull or mandible are less able to metastasize and therefore do better prognosis compared to limb bone tumors.
  • Extremely poor prognosis they give extra-skeletal osteosarcomas - here the average survival time from diagnosis is approx 28 days.

Application of additional treatment

In the case of enhancement of surgery with chemotherapy, the percentage of patients surviving 2 years reaches 26%.

The occurrence of metastases to regional lymph nodes

As can be expected, the prognosis in such cases is poor.

Alkaline phosphatase activity

Dogs with high levels of this enzyme have a shorter survival and disease-free period.

The degree of histological malignancy of the tumor

The higher it is, the worse the prognosis.

In cats, the treatment of osteosarcomas of the limbs is satisfactory when completely removed by surgery. In some cases, you can get a full recovery.

In such cases, the average survival rate is 24-49 months (even without additional therapy).

In the case of tumors located in in the axial skeleton, the prognosis is usually poor.

It is very important to realize how aggressive and painful is this cancer.

Contrary to popular belief, pets do not squeal from pain or vocalize.

They get used to chronic suffering day after day, slowly slowing down their activity.

Often, caregivers are confused when I ask them if they see any obvious pain symptoms in their pet.

They answer no, just the lameness, nothing else

Lameness it is a symptom of pain. Reduced appetite it is a symptom of pain. Reluctance to get up and move are symptoms of pain.

This should not be taken lightly!


To make you aware, dear Reader, how much an animal with osteosarcoma suffers, I will now tell you about a beautiful female Great Dane, known as the Brave Shina.

Shina was diagnosed with osteosarcoma in the left thoracic limb.

The girl did not want to walk, she was apathetic and clearly suffering.

The decision was made to amputate the paw.

It was risky because our patient had been diagnosed earlier advanced cardiomyopathy.

However, everyone, including Shina, was determined to fight back.

The surgery was done.

On the second day, we received information that the brave doggy in the nose has medical recommendations and is happily jumping on three legs all over the garden.

Imagine how much the tumor must have hurt to see post-amputation pain was virtually unnoticeable?

According to the owner of Shin, she acted like a puppy, regained the joy of life, completely ignoring the fact that she had been deprived of one limb.

Dog limb amputation - why we are so afraid of it?

Paw amputation raises a lot of controversy among owners, but it is not so scary.

In the vast majority of cases, it is this procedure that improves the comfort of our patient's life, removes pain and gives a chance for a longer, suffering-free life.

Animals get used to walking very quickly on three legs.

We humans have the most resistance to accepting our pet's disability. Completely wrong, because even such large breeds as Great Danes do very well.

For them, the most important thing is that it finally stopped hurting.

And whether a life devoid of pain and suffering is the most important determinant of its quality?

You have questions related to osteosarcoma in animals? Or maybe you are just struggling with this nasty cancer?

Let me know in the comment below, I will be happy to explain your doubts.

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