Vaccine-associated Sarcoma in Dogs
Vaccine-associated sarcoma in dogs is a rare occurrence, typically linked to specific injectable vaccines, including rabies vaccinations. Instances of sarcomas, cancerous masses originating from bone, cartilage, fat, or muscle, developing at vaccination sites have raised concerns about a possible correlation between vaccines and this reaction in some animals.
These tumors are characterized by their highly invasive, fast-growing, and malignant nature. Reports suggest metastatic rates ranging from 22.5 to 24 percent, with common sites of spread being the lungs, regional lymph nodes, and skin.
The exact cause of sarcoma development remains unknown, although it’s believed that local inflammation may play a crucial role in triggering the malignant growth. Initially, attention was drawn to vaccine adjuvants containing aluminum as potential culprits. However, the role of aluminum remains ambiguous as not all adjuvants associated with sarcoma formation in vaccines have contained this ingredient.
Symptoms
At the vaccination site, lesions emerge, persisting and potentially enlarging over time. In later stages, the lesions may become immovable and occasionally develop ulcers.
Causes
Administration of the rabies vaccine seems to be the primary trigger for this particular type of sarcoma. Furthermore, the likelihood of tumor development may rise with the frequency and quantity of vaccinations administered.
Diagnosis
A comprehensive history of your dog’s health, symptom onset, and any potential triggering incidents will be necessary. Your veterinarian will conduct a series of tests including a blood chemical profile, complete blood count, urinalysis, and electrolyte panel.
To evaluate the extent of cancer spread, X-ray imaging of the chest and abdomen will be performed. Additionally, computed tomography (CT) scans with contrast agents may be used to enhance visualization of the area, aiding the veterinarian in assessing the location, shape, and size of masses occurring at injection sites.
Any masses persisting for over three months, larger than two centimeters in diameter, or showing growth one month post-injection should undergo biopsy. Advanced lesions should also be biopsied prior to initiating definitive treatment.
Treatment
Achieving an effective treatment plan poses challenges, but radiation therapy administered before or after definitive surgery can significantly improve your dog’s chances of survival. It’s recommended to conduct a contrast CT scan prior to surgery, as it has been shown to prolong the time until sarcoma recurrence. However, chemotherapy has not been proven to increase survival rates in cases of this particular cancer.
Living and Management
Avoid over-vaccinating your dog. Vaccinate against rabies and other diseases no more frequently than every three years, unless specifically recommended by your veterinarian.