Life-Changing: Cancers Found In Big Dogs

May 27, 2024

It’s one of the worst words a dog parent will ever hear: cancer. Cancer is one of the most significant health challenges in dogs, particularly affecting large breeds with a greater frequency and often more severe outcomes. As dog parents, this disease affects the health and well-being of our best friends, but also tears at our hearts in the most gut-wrenching way. Especially for those of us who love bigger dogs– large breed dogs, with their unique genetic makeup and physical attributes, are predisposed to specific types of cancers. Some of these are more aggressive than in smaller breed dogs, and it’s important to know about how cancer cells affect large breed dogs.

Osteosarcoma in Large Breed Dogs

Osteosarcoma is the most common primary bone tumor in dogs, accounting for about 85% of all skeletal tumors. It primarily affects large and giant breed dogs, such as Rottweilers, Greyhounds, and Golden Retrievers, and tends to be more aggressive in these breeds due to their size and bone structure​.

Symptoms And Diagnosis Of Canine OsteosarcomaPhoto: A Greyhound looks at the camera.

The typical symptoms of osteosarcoma in dogs include limping or lameness, swelling at the tumor site, and pain. The tumors often occur in the long bones near the shoulder, wrist, and knee. A vet will typically confirm the diagnosis with an x-ray, which may show a characteristic “sunburst” pattern of bone growth at the tumor site. Sometimes, they’ll advocate for a biopsy for a definitive diagnosis, and this includes taking a sample of the tumor to be examined under a microscope.

Treatment Options and Prognosis For Canine Osteosarcoma

The primary treatment for osteosarcoma is surgical removal of the tumor, which often involves amputation of the affected limb to be sure that all cancerous cells are eliminated. Following surgery, your vet will typically recommend chemotherapy in case there was any microscopic cancer that might have spread before diagnosis. Although an amputation sounds like a drastic outcome, many, many dogs recover and adapt well to living without a limb and still maintain an excellent post-surgery quality of life. Addressing any microscopic disease that may have spread before diagnosis is typically recommended. While amputation might sound drastic, many dogs adapt well and maintain a good quality of life post-surgery. Sometimes, in advanced cases, there may be limb-saving surgeries or even custom implants, though this comes with the possibility of higher complication rates.

The prognosis for dogs with osteosarcoma varies significantly based on the stage of the cancer at diagnosis and the type of treatment they get. Early detection and aggressive treatment can improve outcomes, but because this cancer is so aggressive, many dogs may deal with significant challenges, including potential metastasis to their lungs and other areas. The extent of the disease influences the overall survival rates at the time of diagnosis and response to treatment, and survival times range from several months to over a year depending on various factors, including how well the dog responds to chemotherapy.

Hemangiosarcoma in Large Breed Dogs

Description and Common Sites

Hemangiosarcoma (HSA) is a malignant endothelial cell cancer that lines your dog’s blood vessels. This aggressive tumor predominantly affects large breed dogs such as Golden Retrievers, Labrador Retrievers, and German Shepherds. The most common sites for HSA are the spleen, heart (specifically their right atrium), and liver, but it can develop almost anywhere in the body because its origins are vascular.

Early Signs and Diagnostic Methods

Hemangiosarcoma is often called a “silent killer” because it may not show noticeable symptoms until the disease is too advanced. When symptoms do appear, they can include sudden collapse, weakness, lethargy, pale gums, and abdominal bloating and distension, which is often due to internal bleeding from the tumor. Diagnosing HSA can be really challenging; it typically involves imaging such as ultrasound or CT scans to identify internal tumors. That’s then usually followed by a biopsy to confirm the diagnosis. Unfortunately, because these tumors bleed, routine needle biopsies just might not be super effective, though, and your dog may need more invasive diagnostics for a definite diagnosis.

Available Treatments and Survival Rates

The primary treatment for HSA is surgical removal of the tumor, but that can be challenging depending on the location of the tumor (e.g., heart, liver, spleen). Post-surgery, chemotherapy is commonly recommended to manage the disease, with doxorubicin being the most commonly used drug. Despite aggressive treatment, the prognosis for dogs with HSA is just not that great, especially for those with tumors in critical organs like the heart or spleen. Average survival times vary. When it’s splenic HSA, a dog may live up to 6 additional months with surgery and chemo. When they’re more aggressive in internal HSA situations, the survival time without chemo may be as short as a few weeks to a few months, if lucky.

There’s ongoing research into new treatments, including immunotherapy and molecular targeted therapies, which researchers hope to improve outcomes for dogs with gut-wrenching disease. However, these are still under investigation and not widely available, and like many canine cancers, research is difficult because finding subjects for the study during such an emotional and sensitive time in the dog’s life.

Lymphoma in Large Breed Dogs

Types of Lymphoma Prevalent in Large Dogs

Lymphoma in dogs typically shows up in different forms. The most common is multicentric lymphoma, and this affects their lymph nodes. This type accounts for the majority of lymphoma cases in dogs. Other types include alimentary lymphoma, which affects their gastrointestinal tract, and mediastinal lymphoma, which impacts the area around their lungs and heart. Extranodal lymphoma, which can occur in any organ, including the skin, kidneys, or eyes, is less common but still impacts significantly.

Symptoms to Watch For With Lymphoma In Large Dogs

The symptoms of lymphoma can be wildly different, depending on the type. The most noticeable signs for multicentric lymphoma are swollen lymph nodes, which can be felt under the neck, in front of the shoulders, or behind the knees. Alimentary lymphoma might cause symptoms related to gastrointestinal distress, such as vomiting, diarrhea, and weight loss. Mediastinal lymphoma may show up in breathing difficulties or cough, due to a mass in the chest area​.

Treatment Protocols and Efficacy

Treatment for lymphoma in dogs typically involves chemotherapy, which is the general standard of care. The CHOP protocol (cyclophosphamide, doxorubicin, vincristine, and prednisone) is what’s commonly used. It can lead to high remission rates, particularly in cases of B-cell lymphoma, which tend to respond better than T-cell lymphomas. This is also dependent upon the stage of diagnosis, or course.

Treatment efficacy varies; for example, dogs with B-cell lymphoma may have an average survival time of about 12 months with successful treatment, while those with T-cell lymphoma might expect shorter survival times. Some newer therapies, including targeted drugs and immunotherapy, are also being explored as part of ongoing research efforts to improve outcomes​.

Mast Cell Tumors in Large Breed Dogs

General Information and Occurrence in Big Dogs

Mast Cell Tumors (MCTs) are among the most common skin tumors in dogs and can also affect other areas like the spleen, liver, gastrointestinal tract, and bone marrow. These tumors arise from mast cells, which are a type of white blood cell that’s involved in allergic responses. Large-breed dogs can develop MCTs, although they are not limited to any specific breed or size. Certain breeds like Boxers, Bull Terriers, and Boston Terriers, though, are known to be more predisposed​ (BetterPet)​​ (BluePearl Pet Hospital)​.

Identifying Symptoms Of A Mast Cell Tumor In Dogs

The symptoms of MCTs vary depending on the tumor’s location but often include a visible lump on the skin that may change in size, redness, and itching around the lump. If the tumor is more aggressive, it might release histamines that cause systemic effects like stomach ulcers, vomiting, and shock-like signs like severe lethargy and collapse. Dogs with MCTs may also show decreased appetite and changes in their activity levels​​.

Treatment Outcomes and Management: Chemo And Radiation Therapy

The treatment and prognosis of MCTs depend significantly on the tumor’s grade, size, location, and whether it has metastasized. Surgical removal of the tumor is typically the first line of treatment, and it’s often followed by chemotherapy or radiation therapy, especially if the tumor is of a higher grade or has spread. The prognosis for mast cell tumors varies; low-grade tumors that are completely removed surgically often have a good prognosis, but higher-grade tumors that have metastasized require more aggressive treatment and have a less optimistic prognosis. Early detection may help in outcome statistics.

Rare Cancer in Large Breed Dogs: Histiocytic Sarcoma

Photo: A Bernese Mountain Dog looks happily at the camera.Understanding Histiocytic Sarcoma

Histiocytic Sarcoma (HS) is a particularly aggressive form of cancer that’s predominantly found in certain large breed dogs, including Bernese Mountain Dogs, Rottweilers, and Golden Retrievers. It begins from the histiocytes, which are a type of immune cell, and show up in either localized or disseminated forms. The localized form tends to occur within specific tissues like bones or skin, and the disseminated form affects multiple organs simultaneously.​

Signs and Symptoms Of Histiocytic Sarcoma Specific to Large Breeds

The symptoms of HS can vary significantly depending on whether the disease is localized or disseminated. Common signs include lethargy, decreased appetite, weight loss, and visible lumps or swelling if the tumor affects the skin, bones, or joints. More severe symptoms like difficulty breathing, vomiting, and diarrhea can indicate broader organ involvement, particularly in the disseminated cases. Pale gums and weakness may occur due to anemia, especially in dogs with the hemophagocytic form of the disease.​

Diagnostic Challenges Of Histiocytic Sarcoma In Dogs

Diagnosing HS can be challenging because it looks like other cancers in dogs. A definitive diagnosis usually requires a biopsy or tissue aspirate, followed by microscopic examination and possibly additional molecular testing. Your dog may even need advanced imaging like CT scans or MRIs to look at the disease’s extent and make the best treatment plan.

Treatment Avenues and Research Directions

The unfortunate thing for the large-breed dogs who are prone to this is that treatment options are different based on the stage and form of the cancer, but it’s pretty aggressive. When the HS is localized, surgery is the first line of treatment to remove what they can, and then chemotherapy and/ or radiation often follow to make sure the disease hasn’t spread. Sadly, the disseminated HS is almost always treated with systemic chemotherapy due to how much it’s spread. And despite best efforts, the prognosis is often poor, with many dogs surviving less than a year after their diagnosis.

The good news is that more and more vets are realizing this is a devastating cancer that needs more research. Recent research has focused on genetic and molecular studies to better understand and treat this cancer. In addition, new and promising therapies, including targeted drugs and immunotherapy, are being explored to improve outcomes​, but again, finding subjects for one of the most innovative studies out there has proven challenging.

There’s hope as long as research advances, with ongoing clinical trials and genetic studies to improve diagnostic accuracy and treatment efficacy. The hard part is finding subjects to study and pave the path for future canines to be saved from the devastating effects of cancer.

The Veterinary Cancer Society estimates that nearly 50% of dogs experience cancer. With statistics like this, it’s likely you’ve either experienced a cancer path with your best friend, or you may one day. The more we can do to help find earlier diagnoses and cures, the better for us all.

If your best friend or a dog you love is dealing with cancer, and you believe you may be able to participate in research to help them and all dogs after them, you can contact some of these organizations for more information.



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