Download UPDATES IN VETERINARY ONCOLOGY Lorin Hillman, DVM

Technician
UPDATES IN VETERINARY ONCOLOGY
Lorin Hillman, DVM, DACVIM (Oncology)
Veterinary oncology is a diverse, rapidly changing field. Cancer is diagnosed more frequently as
health care improves and pets are living longer lives. Owners are interested in treatment options
that can help their pets live longer with a good quality of life. A good quality of life is the most
important goal of veterinary oncology. Treatments are similar to those utilized in human
oncology but we try to minimize side effects as much as possible. It is important to have an
understanding of cancer terminology and treatment options so you can assist your owners
through a difficult diagnosis.
Cancer is defined as uncontrolled division of abnormal cells in a part of the body. Cancer usually
indicates a malignant tumor or growth. Most malignancies can invade regional tissues and
metastasize to other parts of the body. Some malignancies are actual solid tumors such as
osteosarcoma (malignant cancer of bone) or mast cell tumors (malignant skin cancer). Some
malignancies affect the blood such as acute leukemia or chronic lymphocytic leukemia. Some
tumors are benign, indicating a less aggressive behavior without metastasis. Benign tumors may
still cause morbidity in a patient due to physical characteristics. For example, a large lipoma on a
limb that affects a pet’s ability to ambulate normally.
Basic tumor types include carcinomas and sarcomas. Carcinomas originate from tissues that
cover a body surface, line a body cavity, or make up an organ. Examples include mammary
adenocarcinoma that develops from mammary glands and transitional cell carcinoma that
develops from the uroepithelium in the bladder. Sarcomas arise from mesenchymal tissue that
connects, supports, or surrounds other tissues and organs. Examples include fibrosarcoma that
develops from fibrous connective tissues and hemangiosarcoma that develops from cells that
support blood vessels. Lymphoma, also called lymphosarcoma, is a cancer of solid lymphoid
tissue such as lymph nodes or spleen. Leukemia includes cancers of blood cells and blood
forming tissues.
Cancer can be diagnosed by cytology or histopathology. Cytology involves obtaining a sample of
cells with a needle aspirate. Histopathology involves obtaining a piece of tissue with a biopsy.
Grading is a histological diagnosis made by a pathologist and the grading scale depends on
tumor type. Stage is a clinical assessment made through diagnostic tests to allow us to determine
the best treatment plan for an individual pet. Staging tests include bloodwork, urinalysis, thoracic
radiographs, abdominal ultrasound, lymph node aspirate or biopsy, bone marrow aspirate, CT or
MRI, FeLV/ FIV testing, and tumor biopsy. The necessary staging tests are determined by the
specific tumor type.
There are several abbreviations used in veterinary oncology literature and one of the most
important to understand is MST or median survival time. The median survival time is the point
where half the patients live longer and half the patients live a shorter amount of time. Other
abbreviations include: CR- complete remission, PR- partial remission, SD- stable disease, PDprogressive disease, DFI- disease free interval, DOR- duration of response, and DLT- dose
limiting toxicity.
Technician
There are several types of cancer treatments including surgery, radiation therapy, chemotherapy,
and novel therapeutics including targeted therapies (small molecule inhibitors, monoclonal
antibodies) and vaccines. Surgery still remains our most effective treatment for most types of
cancer. Many tumors can be completely removed with surgery or the majority of the tumor can
be removed allowing for efficacy of adjuvant treatments. Radiation therapy and chemotherapy
can be used as primary or adjuvant treatments depending on the tumor type.
Chemotherapy is frequently used in practice and safety is of utmost importance. Personal
protective equipment (PPE) should be utilized at all times when preparing and administering
chemotherapy. PPE includes gloves (chemotherapy rated nitrile, no powder), mask, gown, and
face/ eye protection. Both a vertical laminar flow biological safety cabinet (BSC II) and closed
drug transfer system are recommended (and likely soon to be required) for chemotherapy
preparation and administration. It is important to counsel owners on handling chemotherapy at
home if necessary and to discuss risks of chemotherapy present in urine, feces, vomit, blood, and
saliva after administration. Chemotherapy administration should be a positive and safe
experience for each pet. Sedatives may be necessary. Some breeds may have a genetic mutation
(ABCB-1 gene mutation, formally MDR1) that causes increased sensitivity to certain drugs and
chemotherapeutics. The Clinical Pharmacology Lab at Washington State performs the test for
this mutation and more information is available at https://vcpl.vetmed.wsu.edu/.
Novel therapeutics are being developed in veterinary oncology and several will be discussed
including Palladia® 1, Oncept melanoma vaccine 2, monoclonal antibodies 3, B cell lymphoma
vaccine 4, and the feline IL-2 immunomodulator vaccine for fibrosarcomas 5. Current and
developing treatment options for common cancers will be discussed including lymphoma, mast
cell tumors, melanoma, and feline fibrosarcomas.
Contact email for questions: [email protected]
1
Palladia, Zoetis, Parsippany, New Jersey
Oncept canine melanoma vaccine, Merial, Duluth, Georgia
3
Blontress and Tactress, Aratana, Leawood, Kansas
4
Canine B cell lymphoma vaccine, Merial, Duluth, Georgia
5
Feline IL-2 Immunomodulator, Merial, Duluth, Georgia
2