Practical Oncology for the Practicing Veterinarian
Highlights from the 2026 AAHA Oncology Guidelines
“The goal is not simply treating cancer—it is optimizing patient quality of life while extending meaningful survival whenever possible.”
Cancer remains one of the most common diagnoses encountered in small animal practice. Current estimates suggest 1 in 4 dogs and 1 in 5 cats will develop cancer during their lifetime, with prevalence increasing dramatically in older patients.
For the practicing veterinarian, oncology cases often present a combination of diagnostic uncertainty, client expectations, financial limitations, and evolving treatment options. The AAHA Oncology Guidelines provide a framework to approach these cases systematically—from diagnosis and staging through treatment selection and monitoring.
Free AAHA Oncology Guidelines Takeaways Download
Most Common Cancers Encountered in Small Animal Practice
While oncology encompasses hundreds of tumor types, a smaller group accounts for the majority of cases seen in general practice.
Dogs
Common diagnoses include:
• Lymphoma
• Mast cell tumors
• Osteosarcoma
• Soft tissue sarcoma
• Splenic hemangiosarcoma
• Mammary tumors
• Oral malignant melanoma
Cats
Common cancers include:
• Lymphoma
• Mammary carcinoma
• Squamous cell carcinoma
• Soft tissue sarcoma
• Mast cell tumors
Recognizing these patterns helps guide early diagnostic decision-making.
When Cancer is Suspected, Start the Diagnostic Process
“Suspicion of cancer should mark the beginning—not the end—of the diagnostic process.”
One of the most important clinical principles emphasized in the guidelines is that suspicion of cancer should mark the beginning—not the end—of the diagnostic process.
Too often, clinicians and clients assume that identifying a mass immediately leads to referral or palliative care. In reality, the most important next step is obtaining a diagnosis that informs treatment decisions.
Whenever feasible, pursue:
• Fine needle aspiration for cytology
• Tissue biopsy when cytology is inconclusive
• Histopathology with grading when appropriate
Without a confirmed diagnosis, treatment options and prognostic discussions remain limited.
The Role of Collaboration in Oncology Cases
“Teleconsultation and specialist collaboration are increasingly valuable tools for expanding access to oncology expertise, particularly for practices without local specialty hospitals.”
Managing oncology cases in general practice often involves balancing diagnostic thoroughness with client expectations and financial limitations.
Collaboration with veterinary oncologists can assist with:
• Interpreting staging diagnostics
• Developing treatment protocols
• Navigating newer therapies
• Client communication and expectations
Teleconsultation and specialist collaboration are increasingly valuable tools for expanding access to oncology expertise, particularly for practices without local specialty hospitals.
Grade vs Stage: Both Matter
Two concepts are fundamental when managing oncology cases:
Tumor Grade
Tumor grade describes the microscopic appearance and biologic aggressiveness of the cancer cells.
Tumor Stage
Tumor stage describes the extent of disease within the body, including local invasion and metastatic spread.
Both factors influence:
• Prognosis
• Treatment recommendations
• Monitoring intervals
• Client expectations
For example, a high-grade mast cell tumor with metastasis carries a vastly different prognosis and treatment plan compared with a low-grade localized tumor.
Staging Diagnostics: Tailor to the Tumor Type
“Appropriate staging tests will vary based on the specific cancer diagnosis and should be chosen based on the pet’s needs and client’s priorities and limitations.”
Appropriate staging varies significantly depending on tumor type and clinical suspicion. Common components of staging include:
Baseline diagnostics
• CBC
• Chemistry panel
• Urinalysis
• Viral testing in cats
Metastatic evaluation
• Regional lymph node cytology
• Thoracic radiographs
• Abdominal ultrasound
Advanced imaging
• CT
• MRI
Additional diagnostics
• Flow cytometry
• Immunohistochemistry
• PARR testing
These tests help determine whether disease is localized, regionally metastatic, or systemic, which ultimately guides therapeutic planning.
Treatment Modalities: Multimodal Therapy is Common
Veterinary oncology frequently involves combination therapy, with treatment plans tailored to tumor biology, patient status, and client goals.
Surgery
For many solid tumors, the first surgical attempt offers the best opportunity for cure.
Key surgical principles include:
• Wide margins in all directions
• Consideration of fascial planes
• Submission of all excised tissue for histopathology and margin evaluation
Incomplete initial excision can significantly complicate future treatment.
Chemotherapy
Conventional chemotherapy (maximally tolerated dose protocols) targets rapidly dividing cells and is typically administered weekly to every three weeks.
Common adverse effects include:
• Myelosuppression
• Gastrointestinal upset
• Alopecia
Neutropenia remains the primary dose-limiting toxicity, requiring routine monitoring during treatment.
Targeted Therapies
Targeted therapies are becoming increasingly common in veterinary oncology. A detailed summary of all the new therapies is included in our free 2026 AAHA Oncology Guidelines Top Takeaways.
Examples include:
• Tyrosine kinase inhibitors (TKIs)
• Monoclonal antibodies
• Cancer vaccines
Toceranib (Palladia) remains the only FDA-approved TKI for cancer treatment in dogs in the United States.
These therapies target specific cellular signaling pathways involved in tumor proliferation.
Immunotherapy
Immunotherapy approaches aim to stimulate the patient’s immune system to recognize and destroy tumor cells.
Examples include:
• Oncept melanoma vaccine
• PD-1 monoclonal antibody therapies
While promising, many immunotherapies still require further clinical validation.
Monitoring Response to Therapy
Regular monitoring of oncology patients is important and rechecks should be scheduled based on the tumor’s behavior/grade, stage and treatment protocol.
Objective response criteria help clinicians determine whether treatment is effective.
Responses are categorized as:
Complete remission (CR)
No detectable disease.
Partial remission (PR)
≥30% reduction in tumor size.
Stable disease (SD)
No sufficient change to qualify as PR or PD.
Progressive disease (PD)
≥20% increase in tumor size or new lesions.
These criteria guide decisions regarding continuation or modification of treatment protocols.
Safety Considerations for Veterinary Teams
Handling chemotherapeutic drugs requires strict safety protocols to minimize occupational exposure.
Recommended precautions include:
• Double chemotherapy gloves
• Impermeable gowns
• Eye and respiratory protection
• Closed drug transfer systems
• Hazardous drug spill kits
Human healthcare data demonstrates increased risks of reproductive complications and malignancy among personnel exposed to hazardous drugs, underscoring the importance of proper handling procedures.
Client Communication Considerations
“Providing a safe space for discussion and education regarding diagnosis, treatment options and expectations helps to make sure everyone is on the same page. ”
It is important to educate owners about possible side effects that can include myelosuppression, alopecia and GI upset. Preventative medications are commonly sent home with owners to have on hand “just in case” side effects occur after hours. Preventing side effects is important in maintaining a patient’s quality of life.
Added precautions should be taken when handling any urine, feces, vomit, or saliva for the first 72 hours after a patient receives chemotherapy due to concern there could be active drug present. Gloves and mask should be worn if handling any of these and immunocompromised or pregnant women should avoid contact.
Final Clinical Takeaway
Veterinary oncology continues to evolve rapidly. For clinicians in general practice, a systematic approach to diagnosis, staging, and treatment selection remains essential.
The goal is not simply treating cancer—it is optimizing patient quality of life while extending meaningful survival whenever possible.