Sarcomas

There are very few of us within the Sighthound world who have not been affected by cancer, either personally or within our circles of Sighthound families and friends. Through our Sarcoma Awareness Campaign we want to help raise awareness of these potentially devastating cancers, especially osteosarcoma. Not only does osteosarcoma account for approximately 85% of bone tumors in dogs, it is also the eighth most common cancer in children. By treating and investigating dogs with cancer, veterinarians gain important insights into improving treatments for humans and often consult with physicians. Though all larger breeds are at higher risk for osteosarcoma, like Mastiffs and Irish Wolfhounds, the risk for osteosarcoma in retired racing Greyhounds is 17 times higher than in mixed breed dogs. Moreover, osteosarcoma represents the most common cause of death in Greyhounds from racing blood lines and yet is relatively uncommon in AKC bloodlines.

Most sarcomas arise spontaneously but because we don’t really understand what causes them, there is no proven way to prevent sarcomas. As a general rule, all cancers are genetically determined and research in progress is aimed at identifying specific cancer genes in Greyhounds and Irish Wolfhounds with osteosarcoma. As for all cancers, early detection and treatment are the best ways to address these tumors — knowing what to look for and keeping a vigilant eye out for those signs will give you a better chance at identifying the disease in it’s early stages, which can improve the prognosis.

What is a Sarcoma?

Sarcomas are malignant tumors of connective tissue that can originate on a variety of tissues, from blood vessels and bone to cartilage, from muscles and organs to nerves and lymphatic tissues. There are many different sarcomas in dogs and, combined, these account for roughly 15% of all canine cancers, making sarcomas approximately 5x more prevalent in dogs than humans. About 15% of skin lumps and 7% of subcutaneous (under the skin) lumps in dogs are soft-tissue sarcomas. Some of the most common ones in dogs are (listed alphabetically):

Fibrosarcoma   •   Hemangiosarcoma  •   Liposarcoma   •   Lymphangiosarcoma
Neurofibrosarcoma   •   Osteosarcoma  •   Schwannoma  •   Synovial cell sarcoma

Symptoms To Watch Out For

Unfortunately, signs can be hard to spot, when they’re present at all. Sarcomas usually grow slowly and some can metastasize (spread to other parts of the body) after the primary tumor has become well established. The liver and lungs are the most common sites of metastasis and, in some sarcomas, micro-tumors are often present even before the primary tumor is detected. Osteosarcoma most frequently occurs in the long bones of large dogs’ legs, though it can also arise on ribs and spinal bones. A dog with osteosarcoma in the leg may start to limp for no reason or the owner may notice a hard lump on the dog’s leg. It’s not unusual for the dog to show no clinical signs until it develops a spontaneous fracture (break) at the spot where the bone has been weakened by the tumor. You should consult with your vet for any new lump, especially if it is hard or irregular, and feels “fixed in place” or if it continues getting larger. Other sarcomas may have different signs: tumors in the GI tract can cause vomiting, diarrhea, inappetence, and anemia, whereas a tumor in the mouth or throat could cause difficulty eating or swallowing and bad breath. Sarcomas that are not outwardly visible (arising on internal organs) often go undetected for extended periods and can therefore be well advanced before the dog starts showing any signs — and may occasionally only be diagnosed posthumously.

Treatment Options

Diagnosis involves either cytological (fine needle aspirate) or histopathological (biopsy) evaluation. Because these tumors can be locally invasive (meaning that the primary tumor spreads out into surrounding tissue, not to other parts of the body as with metastatic cancers), diagnostic tests such as CT scans may help to identify the extent of the mass and whether it has “well-defined margins”, meaning there is a clear delineation between cancerous and non-cancerous cells with a better chance of removing all of the bad cells surgically. If the tumor does not have well-defined margins, then more of the surrounding tissue may need to be removed, if possible, to get as much, if not all, of the cancerous cells. The primary goal of the surgery is to get rid of 100% of the tumor cells. Radiation may be recommended before surgical removal, especially if the tumor is located in an area that isn’t easily accessible for the surgeons, or after, if there are no clean margins and surgery is not thought to have gotten 100% of the cancerous cells. As in humans, chemotherapy is available for dogs with highly aggressive tumors, such as osteosarcoma, hemangiosarcoma, and high grade sarcomas, or those that already have metastatic disease. A number of different drugs, including carboplatin and doxorubicin, have been used with varying degrees of success to treat osteosarcoma in dogs. And, no, dog’s hair doesn’t fall out from the chemo.

The prognosis for dogs with sarcomas varies almost on an individual basis: location, the type and grade of the sarcoma, the aggressiveness/invasiveness, how advanced it is, evidence of metastasis and even the age and overall health of the dog are all factors in determining the prognosis. Dogs with metastatic osteosarcoma at the time of diagnosis usually have a poorer prognosis. In low-grade soft tissue sarcomas, local injection of chemotherapy may be effective in preventing tumor regrowth.

Osteosarcoma Metastatic Vaccine

The immune system plays an important role in identifying and killing cancer cells in the body. Dr. Mason and her team at the University of Pennsylvania School of Veterinary Medicine developed a vaccine that aims to stimulate the body’s immune system to recognize and kill bone cancer cells to prevent metastasis (the development of secondary cancerous growths in other parts of the body after the removal of the primary tumor). In their pilot study, researchers evaluated 18 dogs with primary tumor removal and gave them 4 doses of carboplatin chemotherapy followed by the new canine osteosarcoma vaccine every 3 weeks for 3 doses. The median survival rate in dogs given the vaccine was 956 days compared with 423 days in a historical control group.

Aratana Therapeutics was granted a conditional license by the US Department of Agriculture (USDA) based on the efficacy data from that 18-dog study. After getting the conditional license, Aratana announced that the osteosarcoma vaccine will undergo an extended field study as part of the USDA’s requirement to progress from a conditional license to a full license, at which time it will become commercially available. Approximately 24 veterinary oncology practice groups across the United States will be able to purchase the vaccine if they participate in the study [need list of participating locations].

Do You Need Help With Your Diagnosis or Treatments?

Whether you’ve already consulted with a veterinary oncologist and are looking for a second opinion, or if you’re struggling to find an oncologist in your area, Dr. Guillermo Couto, our Founder, does remote consultations with you and your vet. For more information, please see his website here. If you need financial help for your dog’s cancer treatment or surgery, please see the list of resources we’ve compiled here.

Final Word

Though a great deal is still unknown about cancer, researchers are making progress every day both on furthering their understanding of what causes sarcomas and what the best treatment options are. There are ongoing research studies in the US that have shown promising results, some focusing on bolstering the dog’s own immune system to help fight cancer. The Greyhound Health Initiative is raising funds to both promote awareness of the different types of sarcomas and to support research projects we think are both clinically relevant and that have shown positive early results, such as those being undertaken by Dr. Mason. Your donations will directly support these education and research initiatives.