Bone cancer in dogs:
Let’s talk about one of the most occurring bone cancer in dogs. In dogs, bone cancer also can occur as a primary or metastatic disease. Still, in contrast to humans, the most common form of bone cancer seen in dogs is osteosarcoma, according to a study in the U.S. Bone cancer is a common cancer form in dogs, especially in large and giant breeds.
Approximately 85 percent of canine bone tumors are osteosarcomas, osteo means bone, and sarcoma means cancer. Osteosarcomas are highly aggressive tumors, which include painful bone destruction where the tumor grows. Osteosarcoma mostly affects the limbs of dogs but can also occur in other parts of the body, such as the skull, ribs, vertebrae, and pelvis.
Small dogs also get affected by it but less as compared to larger ones. In about 80 percent of cases, cancer will spread to the lungs. The biological behaviour, prognosis, and treatment of bone tumors depend on
- tumor type
- primary location
- the extent of disease spread
and for diagnostics, Various diagnostic tests such as X-rays, blood tests, and sometimes a biopsy are required to determine the most appropriate treatment.
What is bone cancer?
Bone cancer is a disease in which unusual cells grow out of control in your bone. It destroys normal bone tissue. It may start in your bone as a primary disease or spread there from other parts of your body, called metastasis.
Bone cancer is a rare form of cancer. Most bone tumors are benign, which means they aren’t cancer and don’t spread to other areas of your body. But still, harm and weaken your bones and lead to broken bones or other problems. There are a few common types of benign bone tumors:
- Osteochondroma: it is the most common. It often happens in people under age 20.
- Giant cell tumor: it is usually in your leg. In rare cases, these can also be cancerous.
- Osteoid osteoma: often happens in long bones and usually in your early 20s.
- Osteoblastoma: it is a rare tumor that grows in your spine and long bones, mostly in young adults.
- Enchondroma: it usually appears in the bones of your hands and feet. It often shows no symptoms. It’s the most common type of hand tumor.
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Bone marrow cancer in dogs:
Every year many dogs are diagnosed with cancer, and sadly this is the major cause of death in dogs that are above the age of 10. White blood cells, plasma, or B cells are present in the blood, and they originate from bone marrow. Bone marrow cancer affects these cells. This disease is also called “myeloma.” It is another type of bone cancer in dogs.
In this condition, dogs have an overproduction of immunoglobulins (antibodies), which are produced by the continuously dividing plasma cells. Myeloma is not very common in dogs like osteosarcomas, and it makes for less than 1% of cancer cases.
Symptoms of bone marrow cancer:
It can show severe symptoms. The following are some symptoms of bone marrow cancer.
- renal dysfunction
- loss of eyesight
- neurological complications
Often the animal’s death happens from the occurrence of secondary infections. Multiple myeloma is uncommon cancer that is derived from a colonial population of cancerous (malignant) plasma cells in the bone marrow. It is not presently curable because it’s relatively uncommon in canines and has successful treatment options in the future. If your dog is suspected of having Multiple Myeloma, a Veterinary Oncologist would be the best to perform definitive diagnosis and treatment of your dog.
Multiple myeloma is not gender or breed-specific. The average age of diagnosis is between 8 to 9 years old.
Diagnosis of bone cancer in dogs
The following are some criteria from which doctors commonly choose the diagnosis process.
Radiographic evidence of osteolysis (bone destruction): With multiple myeloma, bones often show a lytic or patchy appearance on radiographs. Bones commonly affected by multiple myeloma include the spine, pelvis, ribs, skull, and proximal extremities.
>20% of plasma cells in bone marrow aspiration or biopsies: Bone marrow analysis is essential for diagnosing multiple myeloma. Doctors do an aspiration and take core marrow biopsies from areas of bone destruction. If multiple myeloma is present, cytologic evaluation of the bone marrow predicts that plasma cells constitute more than 20% of all nucleated cells.
Monoclonal gammopathy on serum protein electrophoresis: Hyperproteinemia (elevated protein) and elevated globulin, which is also the type of protein found in the blood, levels are detected on routine bloodwork.
Bence-Jones proteinuria: This is a particular type of protein found in the urine in patients of multiple myeloma.
How can it be treated?
Myeloma in canines is treated in the following ways.
Chemotherapy: it aims to decrease tumor cell numbers with the treatment of the secondary systemic effects. Chemotherapy helps reduce bone pain and aids in bone healing while decreasing serum immunoglobin levels of through chemicals.
Radiotherapy: it is very effective in the treatment of multiple canine myelomas as it destroys the tumor with radiations and also relieves the pain.
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Symptoms of bone cancer in dogs:
The symptoms of bone cancer in dogs can appear instantly without any sign of sickness. Most commonly, it affects the long bones of the legs. But with the rear legs, jaw, facial bones, ribs, and vertebrae can all be affected, as well. However, symptoms may differ according to the bone, which is affected.
The following are some symptoms of bone cancer.
- Lameness or limping
- Signs of pain, often severe
- Swelling, usually on the legs but can be on the ribs or spine. It is the most common symptom.
- Broken bones near the site of the tumor
- Swollen jaws which are indicated by difficulty in eating
- Difficulty eating
- Loss of appetite
- Signs of pain when opening the mouth
- Nasal discharge
- Respiratory distress
- Neurologic signs, such as seizures or a wobbling, with the skull or spinal/vertebral tumors
The most common sign is swelling and painful bone, and with time these signs increase like irritability, weight loss, aggression, sleeplessness, and no physical exercise. Some dogs need to visit the veterinarian due to a fracture caused by the weakening of the affected bone. Other symptoms may vary according to the primary site and involvement of underlying structures.
Diagnosis and staging of bone cancer in dogs:
The diagnosis is based upon the symptoms and all the tests and biopsies etc. following are the techniques that can be used.
- The initial step is that your vet will take an X-ray and perform a physical and orthopaedic examination to rule out other causes of lameness.
- To obtain an effective diagnosis and determine the best treatment plan for your dog, any problem areas identified in the X-ray will be biopsied.
- Chest X-rays or a computed tomography (CT) scan, blood tests, and a urinalysis will be performed to overview your dog’s overall health and determine if cancer has spread.
- In 90–95% of dogs, the tumor will have already metastasized at the time of diagnosis; osteosarcoma most commonly spreads to the lungs.
Advanced CT imaging is often recommended for osteosarcoma tumors of the limbs because it provides better information for a veterinary surgeon to determine if surgery is possible and the extent of surgery necessary to achieve a positive result.
Types of osteosarcoma:
There are three most common types.
- Osteoblastic: In which tumor cells produce large amounts of tumor osteoid
- Chrondoblastic: in this condition, tumor cells produce cartilage in addition to some osteoid
- Fibroblastic: where tumor cells are predominantly fibroblasts and can produce both collagen and tumor osteoid.
This disease is actively metastatic and can also spread to lymph nodes and intraabdominal organs.
Treatment of bone cancer:
Osteosarcoma is the disease in which the limb is the most affected part, so amputating the limb followed by chemotherapy is the most useful treatment. The following is the treatment criteria.
Limb sparing surgery:
It is a process in which the tumor is removed, and the bone is replaced with another bone, but this process depends upon the location of the tumor and the size of the tumor at the time of diagnosis. The complication rate, especially infection in this kind of surgery, is high. When it is not useful, stereotactic radiation can be done.
When the affected bone is not destroyed much, then this type of treatment can replace the bone amputation. This latest and accurate type of treatment includes killing and destroying the osteosarcoma cells with high doses of radiation. This therapy has the following advantages.
- Maximum damage to the cancerous cells and minimum damage to the neighbouring healthy bone cells
- It needs fewer treatment sessions as compared to conventionally fractioned radiation therapy. The patient only needs 1 to 3 sessions, which means less risky events and disturbance in routine.
- Quick recovery with fewer side effects
- Treat tumors that were once considered untreatable.
It works as an addition to primary surgery and radiation treatment. It basically slows down the rate of metastasis, which is high in the case of bone tumors. It cannot cure cancer, but it can increase the life span. The most commonly used drug is an injectable medication called carboplatin, which is given once every three weeks in a total of four sittings.
Most dogs tolerate chemotherapy well, but some dogs can experience mild, self-limiting side effects such as depressed appetite, nausea, occasional vomiting, and diarrhea for a few days. Less than five percent of dogs will experience severe side effects needing hospitalization. If severe side effects occur, the dosages of these drugs can be lessened in the subsequent treatments.
Survival and life expectancy:
The prognosis for bone cancer in dogs depends on the severity and spread of the disease and on the treatment you choose. Dogs with limb osteosarcoma that receive SRS and chemotherapy have a median survival time of about one year, similar to the survival time for dogs treated with amputation and chemotherapy. Up to 16–28% of dogs are alive at two years.3 The median survival time for dogs with amputation alone is about three months.
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How common is osteosarcoma in dogs?
Osteosarcoma is much more common in dogs than in people. According to an estimation, 10,000 diagnoses are made yearly, mostly in large and giant breed dogs, and it is seen only rarely in cats.
Osteosarcoma accounts for approximately 85% of bone tumors in dogs. The median age at diagnosis is eight years; also, a bit of this is seen in animals less than three years. Still, when the effect of body mass is taken into account, the overall risk for any dog to develop primary osteosarcoma is not broadened with increasing age.
Dogs heavier than 90-lb account for almost 1/3 of cases, and most tumors in this group occur in the limbs. Dogs under 30-lb account for less than 5% of cases, and at this age, most osteosarcoma occurs in the axial skeleton. In cats, it has no relation with size or breed, and the frequency of axial tumors is about the same as skeletal tumors.
What causes bone cancer in dogs?
The causes of bone cancer in dogs are still not well identified. But there are many risk factors which can lead to cause it. The following are some causes.
Genetic factors: this can be one of the major factors. Body mass and size are the main indicators for this factor.
Environmental factors: following are environmental factors that can be a cause of this cancer.
Metallic implants to fix fractures
Males tend to have bone cancer more often, as compared to dogs who are spayed or neutered before turning one year old. Males have 20% to 50% more risk.
Large dog breeds tend to develop bone cancer more often.
And there is some evidence that suggests dogs who have suffered broken bones, had orthopedic implants surgically placed, or suffer from other bone disorders may be more at risk for bone cancer.
Bone cancer in dogs is a serious kind of threat. It is not like a stomach or gastrointestinal upset. It is a life-threatening condition. And in this regard, osteosarcoma is the most occurring cancer in dogs. It damages the bones but can also occur in other parts. You have to acquire the proper medication and serious treatment for your pets, as described above. I hope this article helped you