The love dogs give us is priceless, but as our fur babies age, the risk of many diseases arise, including bone cancer. It’s a heavy subject, but awareness is key to early detection, improving survival chances.
This article takes you through the causes, types, and symptoms of bone cancer in dogs, as well as what you can do to treat the disease.
- The vast majority of bone cancers in dogs is osteosarcoma.
- Bone cancers have a very poor prognosis in dogs, with most not expected to survive one year.
- Most often, bone cancer has already spread by the time your dog is diagnosed.
- Surgery and chemotherapy together is the most effective treatment.
- Clinical research offers new hope, including immunotherapy treatment.
Types of Bone Cancer in Dogs
There are several types of bone cancer in dogs :
- Osteosarcoma is the most common type. This alone makes up 95% of bone cancer cases. Bone cancer and osteosarcoma are not interchangeable terms.
- Chondrosarcoma tumors are mostly made of cartilage-producing cells.
- Fibrosarcoma is defined as a cancer mostly made of collagen-producing cells, or fibroblasts.
- Hemangiosarcoma comes from the cells lining the blood vessels. These can include bone cancer if the tumor starts in a blood vessel serving a bone.
- Some bone cancers are known as secondary tumors, meaning they have metastasized (spread) from a cancer originally appearing somewhere else. Almost all bone tumors in dogs are primary tumors, however.
What Causes Bone Cancer in Dogs?
Risk factors of bone cancer in dogs include rapid growth, which is why larger breeds’ commercial puppy food is less energy-dense to extend the time to full growth. Metal implants to fix bone fractures and sterilization also increase the risk of dog osteosarcoma. The risk of osteosarcoma can be up to four times higher in dogs spayed or castrated before the age of one .
Don’t let this discourage you from sterilizing your dog, however. Although some studies show triple the risk of osteosarcoma in female dogs, this should be balanced against an 80-260 fold lower risk of mammary cancer. Male dogs have a lower risk of prostate and testicular cancer if they are sterilized, and these cancers are generally more aggressive .
Some breeds may gain protection from having been spayed or castrated. For example, male Vizslas have shown no risk of hemangiosarcoma anywhere in the body with castration before 12 months. Female Golden Retrievers are at a lower risk if they are sterilized before 12 months of age (1.8%) compared to after their first birthday (7.4%) .
Is Bone Cancer in Dogs Genetic?
Osteosarcoma is most common in large and giant breeds, such as the German Shepherd, Golden Retriever, Great Dane, Rottweiler and St Bernard. In fact, less than 5% of osteosarcoma appears in small-breed dogs under 33lbs (15kg), while 29% of cases appear in dogs over 88lbs (40kg) .
Additionally, certain genetic mutations are linked to osteosarcoma. They include altered P53 and RB genes, which are related to DNA repair. Scottish Deerhounds sadly have a 15% chance of developing osteosarcoma, with the CFA34 gene showing an association. Around 69% of osteosarcoma in this breed is genetic .
Signs of Bone Cancer in Dogs
Of course, your dog cannot tell you something’s wrong, so we must stay aware of any potential signs of illness. For osteosarcoma and other bone tumors, the typical warning signs of cancer in dogs are:
- An impaired ability to walk if the cancer is in a limb can be anything from mild to lameness.
- A visible lump, most often caused by it growing into other tissues.
- There may or may not be noticeable bone pain, such as if your dog yelps when you touch the area or tries to stop you .
- More severe cases can involve pathologic bone fractures, with no apparent cause as the affected limb was not injured. These are caused by the cancer destroying healthy bone tissue, which weakens its structural integrity .
It’s important to get a diagnosis and treatment as soon as possible, as osteosarcoma in dogs spreads rapidly . Currently, almost all dogs will have secondary tumors in regions such as their lymph nodes, lungs or other bones.
Diagnosis of Bone Cancer in Dogs
Diagnosing bone cancer in dogs involves a range of tests, both invasive and non-invasive.
An X-ray examination is the most accessible type in veterinary offices but not the most sensitive when it comes to imaging. Computed Tomography (CT) scans, Magnetic Resonance Imaging (MRI), and Positron Emission Tomography (PET) scans are more sensitive but cost more and require a general anesthetic.
Chest X-rays are commonly performed too, to see if there are tumors in other areas. Unfortunately, these generally spread long before they are detectable .
Bloodwork and Urinalysis
Blood levels of alkaline phosphatase play a key role in estimating a prognosis. This is an enzyme involved in bone turnover, with higher levels pointing towards greater bone destruction .
A biopsy is necessary to see what type of cancer your dog has by examining the type of cells. A vet can either do fine-needle biopsies or test the tumor once removed through surgery .
My Dog Has Bone Cancer: What Can I Expect?
How is bone cancer staged in dogs, and what is the prognosis?
Stages of Bone Cancer in Dogs
There are three main stages of osteosarcoma in dogs:
- Stage I describes a low-grade disease with no detectable spreading.
- Stage II involves a high-grade lesion without spread.
- Stage III osteosarcoma has spread to other areas.
Both Stage I and II are divided into category A if the tumor is only in the bone, and B if it has grown into other tissues nearby.
By the time most dogs are diagnosed with osteosarcoma, it is at Stage IIB.
How Fast Does Bone Cancer Spread in Dogs?
As written above, most dogs will have had bone cancer spread to other areas of their bodies before diagnosis.
Dog Bone Cancer Prognosis
Osteosarcomas are at a lower risk of spreading if they develop in the lower radius, which is the lower front legs’ bones closer to their feet. Cancers originating in the upper humerus or tibia and the lower femur are more likely to spread .
Prognosis is variable overall but currently falls between six months to a year. A 2010 article stated that around half of dogs treated with the standard of care could expect to live for one year, about 10% of an average lifetime . According to a 2014 review, the average survival time with amputation and chemotherapy is 284 days (just over 40 weeks) .
Bone Cancer in Dogs: Treatment Options
Similar to humans, current cancer treatment for dogs with bone cancer includes surgery, chemotherapy and radiation. Newer therapies, such as immunotherapy, are being developed.
Veterinarians and researchers often consider amputation to be the best treatment for osteosarcoma in dogs. It provides pain relief, prolongs survival by totally removing the tumor, and is even safer than limb-sparing surgery . However, amputation is understandably distressing for the dog and its family, and will cause irreversible disability.
Limb-sparing surgery only removes the tumor and includes reconstructing the missing bone with an implant. Both metal and bone implants have similar success rates, with over 80% of dogs keeping their limb function. However, up to half suffer infections, and 15-25% see their cancer return .
Radiation therapy is an effective palliative treatment for bone tumors, with 74-96% of dogs finding pain relief . It removes the source of the pain: tumor cells, inflammation and bone destruction through osteoclast activity, which are the cells that break down bone tissue, while osteoblasts rebuild it.
Combined with chemotherapy, radiation can improve survival time. A study of dogs undergoing palliative radiotherapy found the longest survival time with chemotherapy (307 days, or 44 weeks), and the shortest with radiotherapy and pamidronate (69 days, almost 10 weeks) .
Surgery alone is associated with poor survival rates. Some studies estimate that almost three-quarters of dogs die or are euthanized within 20 weeks because of metastases. Chemotherapy has fortunately been shown to improve survival in dogs with osteosarcoma. The most commonly used chemotherapy drugs are carboplatin, cisplatin and doxorubicin.
One study on carboplatin found that it more than doubled the survival time, from an average of 138 days (almost 20 weeks) to 307 days (almost 44 weeks).
In another, cisplatin increased survival from 138 days up to an average of 322 days (46 weeks), but didn’t prevent osteosarcoma from spreading. Doxorubicin, however, increased average survival to 366 days (52 weeks) and slowed the spread of cancer .
It is unclear how effective combined chemotherapy is for dogs with osteosarcoma compared to the use of a single drug. A 2016 study demonstrates a longer survival time with carboplatin alone (425 days, or one year and two months) than with alternating between carboplatin and doxorubicin (135 days) .
Clinical Trials for Dogs With Bone Cancer
To further improve survival, different types of drugs such as pamidronate, which is typically used for osteoporosis, and chemo-sensitizing substances like suramin have been tested.
Unfortunately, pamidronate, suramin and others have been unsuccessful in saving or extending dogs’ lives . If you are looking for a clinical trial that may benefit your dog, or pave the way to a brighter future for others, the Animal Health Studies Database may give you answers.
Immunotherapy is becoming more common as a cancer treatment. Types of immunotherapy include modifying white blood cells to better “see” the cancer, and drugs that unmask tumor cells. As of late June 2021, the Animal Health Studies Database, AAHSD lists 14 clinical trials as active for osteosarcoma in dogs, including several on immunotherapy :
- AAHSD005123 – Cryoablation with Immunotherapy to Treat Canine Osteosarcoma
- AAHSD005306 – Inhaled IL-15 and Autologous NK Immunotherapy for Treatment of Lung Metastases
- AAHSD005179 – A multi-center Phase I/II evaluation of the addition of perioperative and intercalating gefitinib to standard of care treatment for canine osteosarcoma
- AAHSD005260 – Defining the Pharmacodynamic Profile of STING Agonist Immunotherapy in Dogs with Solid Tumors
- AAHSD005174 – Histotripsy for treatment of canine appendicular osteosarcoma
- AAHSD005307 – COTC030: Evaluation of Inhaled recombinant-human IL-15 combined with Standard-of-Care in dogs with Osteosarcoma
Other Clinical Trials
Improvements in radiotherapy, chemotherapy and the use of other medicines, immunotherapy are being sought too. For osteosarcoma, current active trials are :
- AAHSD005166 – Dysbiosis Enhancing Linkage Towards Association with Canine Osteosarcoma (DEL-TACO)
- AAHSD005054 – GEM-IB/Docetaxel in Dogs: Safety and Effectiveness
- AAHSD005201 – XRADIOS: Improving radiation therapy for dogs with osteosarcoma
- AAHSD005051 – Evaluation of Flash Proton Radiation Therapy in Dogs with Appendicular Osteosarcoma
- AAHSD005262 – Pilot Study of High-Dose Ascorbate Combined with Carboplatin for Canine Osteosarcoma (OSA)
- AAHSD005265 – A Study to Explore the Effect of External Beam Radiation on the Strength and Histology of Long Bones in a Canine Model
- AAHSD005277 – K9 tumor And Blood sampling for Osteosarcoma and Oral Melanoma (KABOOM)
For the much rarer bone cancer, hemangiosarcoma, the following two studies are available:
- AAHSD005266 – Ethos Precision Medicine Umbrella Study for Hemangiosarcoma (Ethos-PUSH)
- AAHSD005063 – Clinical evaluation of propranolol in combination with doxorubicin for the treatment of hemangiosarcoma
Chondrosarcoma does not have active clinical trials listed on the AAHSD study search at this time. Fibrosarcoma only has one active study involving diagnostics, not treatment .
Other recently conducted clinical trials, listed on the Comparative Oncology Trials Consortium (COTC), include a study of the mTOR inhibitor rapamycin (COTC021) and a modified Listeria monocytogenes featuring a receptor found on cancer cells (COTC026) .
How To Manage a Dog With Bone Cancer at Home: Palliative Care
When symptomatic relief is the only choice, we must look at palliative treatment, which aims to improve quality of life. Palliative care options that can be administered at home for dogs with bone cancer include anti-inflammatory and opioid drugs.
Tumor cells produce inflammatory prostaglandins, which cause pain in a wide range of conditions. Non-steroidal anti-inflammatory drugs (NSAIDs) relieve bone pain by blocking their production. This may also directly slow cancer growth and the development of blood vessels to feed the cancer.
Additionally, opioids are given at a range of doses as effective pain relief. Tramadol is one drug given to relieve cancer-related pain, which also increases serotonin, a mood-lifting neurotransmitter.
You may also be given bisphosphonates for your dog. They only have a mild anti-cancer effect, but it is enough for pain relief .
When Is It Time to Euthanize a Dog With Bone Cancer?
When or if you euthanize a dog with osteosarcoma or another bone cancer is a personal decision. General guidelines for consideration include profound loss of appetite, extreme weakness or inability to endure mild physical activity. In cases of a medical emergency, immediate decisions must be made, such as if your dog collapses .
Dealing with bone tumors or any type of cancer is devastating–below, we answer some of the most commonly asked questions.
What Percentage of Dogs Get Osteosarcoma?
It all depends on the breed. While it is rarely seen in small breeds, around 15% of Scottish Deerhounds are expected to develop osteosarcoma .
What Can You Do for a Dog With Bone Cancer?
Besides giving them the love and support they deserve, it’s best to avoid hesitation around treatment. Current cancer therapies’ side effects may be brutal, but they are often better than allowing the cancer to spread.
Does Bone Cancer in Dogs Spread Quickly?
Sadly, yes. By the time of diagnosis, 90% of dogs will have had their cancers spread, even though only a small percentage of these secondary tumors are detectable. This is largely why survival rates and average life expectancy after diagnosis are so poor.
Veterinarians expect 80% of dogs with osteosarcoma to die of secondary cancers in the lungs .
How Long Can a Dog Live With Bone Cancer?
While some dogs have been known to live five or more years with bone cancer, the mean survival time is still estimated to be around seven months. Some studies on chemotherapy drugs report average survival times of approximately a year .
How Long Can Dogs Live With Osteosarcoma Without Treatment?
With no treatment, dogs usually don’t survive more than a few months once osteosarcoma is noticeable. Even with amputation as the sole treatment, life expectancy is less than five months .
Bone cancer in dogs is a heavy, emotionally draining subject to discuss. However, it is a necessary conversation, as early detection and treatment are crucial to maximizing survival.
Chemotherapy after surgery is your best bet, but new treatments are being developed. As bone cancer has such poor survival statistics in dogs, don’t hesitate on treatment and consider clinical trials. Shout out to our trooper G-Money, a brindle Galgo Greyhound who sadly lost her battle with bone cancer.
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- Boerman, Ilse, et al. “Prognostic Factors in Canine Appendicular Osteosarcoma – a Meta-Analysis.” BMC Veterinary Research, BioMed Central, 15 May 2012, bmcvetres.biomedcentral.com/articles/10.1186/1746-6148-8-56
- “AVMA Animal Health Studies Database.” AAHSD Study Search, ebusiness.avma.org/aahsd/study_search_results.aspx.
- Amber LaRock. “When To Euthanize A Dog With Hemangiosarcoma & What To Watch For.” Emergency Vets USA, 15 June 2021, emergencyvetsusa.com/euthanize-dog-with-hemangiosarcoma/