Just like in humans, cancer can be devastating for dogs. Cancer is the leading cause of death in dogs, and the American Veterinary Medical Association estimates that nearly half of canines over the age of 10 will develop the disease.
Previous studies have shown that certain breeds of dogs have a higher risk of developing cancer throughout their lives. Common breeds in the United States with an above-average lifetime cancer risk include Bernese Mountain Dogs, Boxers, French Bulldogs, Golden Retrievers, Great Danes, Mastiffs, Rottweilers, Smooth-Coated Retrievers, German Shepherds, and Retrievers. farmer.
The question of why some breeds experience higher rates of cancer is difficult to answer definitively.
“It’s challenging to pinpoint a factor that makes some breeds of dogs more prone to cancer than others,” said Jill Rafalko, a researcher at PetDx, a biotech company located at the University of California, San Diego’s Center for New Therapeutics. , and Andi Flory, the firm’s chief medical officer, said news week.
“Like cancer in people, the cause is multifactorial, including genetic and environmental influences. Certain breeds may harbor genetic variants that increase the risk of developing certain types of cancer,” Rafalko and Flory said.
Most common cancers in dogs and symptoms
The most common cancers in dogs, as defined by the American Animal Hospital Association, are anal sac adenocarcinoma, hemangiosarcoma, lymphoma, malignant melanoma, mammary gland carcinoma, mast cell tumor, soft tissue sarcoma, and osteosarcoma.
Below are some of the typical signs and symptoms in each case.
- Anal sac adenocarcinoma: Discomfort in the area around the anus, anal discharge, sliding on the floor, licking in the anal area, difficulty pooping, constipation.
- Lymphoma: enlarged lymph nodes, decreased appetite, swelling in the face or extremities, increased thirst and urination.
- Malignant melanoma: enlarged lymph nodes, abnormal concentrations of the pigment melanin in parts of the body.
- Mammary Gland Carcinoma: Firm swelling of the mammary glands, lethargy, decreased appetite and weight loss, weakness, cough.
- Mast cell tumor: a new skin mass, a known mass that has changed in size or color, an unexplained allergic reaction that can be potentially serious, swelling and redness in the affected area.
- Soft Tissue Sarcoma: Large, diffuse mass of soft tissue usually in skeletal muscle.
- Osteosarcoma: signs of lameness, inflammation of the soft tissues of the extremities, asymmetry of the extremities, decreased appetite, pain in the extremities, elevated heart rate, dehydration, neurological signs.
Study on the median age of diagnosis of cancer in dogs
Rafalko, Flory, and their colleagues at PetDx have just published a study in the peer-reviewed open access journal PLUS ONE, which investigated the average age at diagnosis of cancer in dogs. One of the goals of the study was to determine the age at which individual dogs should begin screening for cancer.
“Cancer is a huge problem in dogs; in fact, it is the most common cause of death in dogs and, unfortunately, it is often diagnosed late in the course of the disease, when treatment options are limited,” they said. .
“Until recently, cancer screening in dogs relied primarily on a physical examination and routine laboratory tests at a dog’s annual or semi-annual wellness visit to screen for disease, however this paradigm cannot detect cancer. early in most dogs.
In 2021, the PetDx lab developed a new “liquid biopsy” test called OncoK9 that uses next-generation sequencing (NGS) that can detect 30 different types of cancer with a simple blood draw, enabling early detection of cancer in dogs. .
“With the widespread availability of NGS-based liquid biopsy tests and the knowledge that certain breeds of dogs are diagnosed with cancer earlier than others, it was important to determine the age at which individual dogs should start being screened. to try to detect the disease early — ideally when there may be more treatment options and the treatments may be more successful,” the scientists said.
In it PLUS ONE In the study, PetDx researchers examined more than 3,000 dogs with cancer to determine the typical age at which the disease was diagnosed.
They also looked at the typical age at cancer diagnosis based on the dogs’ breed, weight, sex and type of disease.
The scientists found that across all dogs in the study, the typical age at cancer diagnosis was 8.8 years, while they also identified other trends.
“On average, larger dogs were diagnosed with cancer at younger ages than smaller dogs, and certain breeds were diagnosed with cancer at earlier ages than others,” Rafalko and Flory said. “With this information, we were able to make evidence-based recommendations for when to start cancer screening in individual dogs, based on their breed or weight.
“We know that cancer develops over time, so it is reasonable to start cancer screening two years before the typical age at which cancer is diagnosed. In short, this means that all dogs should start screening for the cancer at age 7, but some large dogs and dogs belonging to specific breeds may benefit from starting screening at age 4.”
Breeds that may benefit from starting cancer screening before age 7 include Boxers, Great Danes and Mastiffs (start screening at age 4), Bernese Mountain Dogs (start screening at age 5), and Golden Retrievers , French bulldogs, and Rottweilers (Start testing at age six).
At 11.5 years, the Bichon Frize had the oldest median age of diagnosis. Meanwhile, female dogs were generally diagnosed at later ages than males, and dogs that were neutered were diagnosed later than intact dogs.
Pet owners and veterinarians can use the OncoK9 Cancer SAFE (Screening Age for Early Detection) site to find a recommendation on the most appropriate age to start cancer screening for an individual dog, including mixed-breed dogs.
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