Oncology

Author: MVDr. Renata Kratochvílová

Veterinary Oncology is a branch of veterinary medicine dealing with the diagnosis and treatment of cancer in animals - at our hospital mainly dogs and cats.

A tumor is any abnormal mass within the body resulting from unorganized cell growth. Tumors are divided into benign and malignant. Benign tumors are tumors that do not grow into tissues in their surroundings and do not spread. While malignant tumors grow into surrounding tissues or deep structures and spread through different pathways within the body, causing organ damage.

By improving the quality of veterinary care and changing the attitude of pet owners, dogs and cats live more often, and longer with cancer, along with other chronic organ diseases, These are a very common cause of animal health problems. According to available statistics, 50% of dogs and 30% of cats are affected by cancer throughout their lives. The exact cause of most forms of cancer has unfortunately, not yet been determined.

Some forms of cancer can be cured, while others can be treated to restore and prolong the quality of life - the patient is free of clinical signs or is not affected by treatment to such a degree that he or she is living a full life. Therefore, patients with cancer are treated similarly to patients with other chronic difficult-to-treat or incurable organ diseases such as heart disease, chronic renal failure or diabetes mellitus.

For each patient suspected of having cancer, we carry out careful diagnostics prior to initiating therapy, consisting of two parts:
1. tumor diagnosis - determining the type and extent of cancer.
2. assessing the patient's general health as they are mostly elderly individuals who may have several concurrent medical conditions.

To determine the type of tumor, we take samples for cytological or histopathological examination from skin/subcutaneous or altered thoracic/abdominal organs using a variety of biopsy techniques. The least invasive is the sampling for cytology, which does not require patient sedation or general anesthesia to identify the presence of cancer. Due to the limitations of this biopsy (obtaining single cells or small groups), it may be insufficient to diagnose some tumors. In such cases, we excise part of, or the whole tumor tissue using other biopsy techniques requiring sedation or general anesthesia. The tissue which is collected is sent for histological examination, which identifies the type of tumor and specifies its individual characteristics - this is called tumor grading.

Examples of Histology

Histology of Hemangiosarcoma of an ovary in a canine patient. This patient also had Cutaneous Hemangiosarcoma and Hemangiosarcoma of the uterus metastasizing to other organs, as well as Leiomyosarcoma.

Histology of Cutaneous Hemangiosarcoma in a canine patient. This patient also had Hemangiosarcoma of the ovaries and uterus metastasizing to other organs, as well as Leiomyosarcoma.

Histology of a Perianal Gland Carcinoma in a canine patient. The dog presented to our clinic with a small nodule located under the base of the tail. Upon excision and subsequent histopathology a Perianal gland carcinoma was diagnosed.

Histology of nail bed Melanoma in a canine patient.

© IDEXX Vet Med Lab Germany

In addition to determining the type of tumor, we also determine its extent - the so-called staging of disease or assessing the size of the tumor and the presence of metastases in the lymph nodes and various organs of the body. Part of tumor staging is a detailed clinical examination of the patient, focusing on the tumor itself, lungs, lymph nodes and the condition of the thoracic and abdominal cavities. We use imaging methods (X-ray, ultra-sonography, or endoscopic examinations) to evaluate less accessible tumors or tumors penetrating into deeper layers of surrounding tissues. In indicated cases for example, when the nervous system or nasal cavity is suspected, patients are referred to advanced imaging methods such as Computed Tomography (CT scan) or Magnetic Resonance Imaging (MRI scan).

Examples of Oncology Staging

Lung metastasis of a mammary gland tumor into the lungs of a canine patient. This patients owners observed him coughing for around 1 year, after which they decided to conduct diagnostics.

Lung and abdominal metastasis in a canine patient.

Fibrosarcoma in a cat, prior to surgical removal.

Blood and urine examinations are used to assess the patient's overall health, detection of complications associated with the presence of a tumor (so-called paraneoplastic syndromes) and diagnostics of other diseases that may impair the patient's ability to undergo the proposed therapy.

The aim of all of the above tests is to obtain information that is the basis for determining the prognosis of the disease and compiling an individual therapeutic plan that will lead to a patient's cure, or to improve and prolong the quality of life in a patient with an incurable tumor.

Tumor therapy depends on the type, local tumor control, systemic therapy, or a combination of several approaches. The most common methods of local tumor control are surgery and radiotherapy. Chemotherapy is a systemic treatment used to treat systemic cancer (eg, lymphoma, leukemia) or as a complementary therapy to surgery for tumors with high metastatic potential.

Surgery is the therapy of choice for most so-called solid tumors. In malignant tumors it is necessary to remove, along with the visible tumor, the normal-looking surrounding tissue to eliminate cancerous tissue completely and reduce the risk of relapse. Because extensive surgery can significantly affect the appearance of the patient, we consult the outcome with the owner in advance. We have experience with oncological surgery for skin tumors, subcutis, tumors affecting the locomotor system and organs of the abdominal cavity.

Cholangiocarcinoma of the liver in a canine patient.

Metastasis of Hemangiosarcoma of the uterus.

Radiotherapy can be used in different ways: as a separate therapeutic method in the treatment of some tumors (eg. nasal cavity or brain), as a complementary therapy to surgery for tumors that, due to their size or localization, cannot be completely removed and are at risk of relapse (eg. low grade mast cell tumor or sarcoma of the extremities, oral melanoma), or as a way to improve the quality of life in patients suffering from advanced cancer. Radiotherapy involves several short therapeutic doses of radiation, the number of which is influenced by the therapeutic plan. During the course of radiotherapy, only the tumor area is irradiated and irradiation of surrounding tissues or important structures that could be damaged by is avoided. The most common irradiation-related side effects are at the site of radiation and are skin manifestations, changes in the quality and character of the coat. These symptoms resolve with appropriate supportive therapy within 2-4 weeks after the end of therapy. Within the framework of providing comprehensive oncology therapy, we cooperate with domestic and foreign institutions, which have the necessary equipment and experience to provide this specialized oncological treatment.

More and more often, systemic oncology treatment is becoming the standard of care in patients - chemotherapy, which is the application of drugs (cytostatics). Most cytostatics are given by intravenous injection or by short infusion, some are given by the owners themselves as tablets. Cytostatics destroy rapidly dividing cells (tumor cells, mucous membranes of the gastrointestinal tract and bone marrow), resulting in general adverse effects occurring as possible complications of treatment. The most common are digestive problems persisting 3 - 5 days after drug administration, whose symptoms range from mild nausea, vomiting and diarrhea to severe conditions, where patients become weak and dehydrated, and require intensive supportive treatment. Another common side effect is bone marrow suppression manifested by varying intensities in the number of white blood cells which ensure the body's immunity. Therefore, patients suffering from a marked decrease in these blood cells may be at risk of bacterial infection and may require antibiotic therapy.

An integral part of systemic cancer treatment in our patients is supportive therapy such as special dietary recommendations, medicines for nausea or vomiting, and diarrhea medication. In indicated cases, we use infusion therapy including blood transfusion in patients with anemia, tendency to bleed or impaired immune systems. Most veterinary patients manage the administration of cytostatics without significant health problems - according to available statistics, about 1/3 of the patients treated and about 5% of patients have significant side effects requiring intensive supportive treatment.

In addition to classic cytostatics, specific drugs with a targeted effect (eg, masitinib) are used for specific types of tumors (eg, specific forms of mast cell tumors or gastrointestinal tumors). We also work with other alternative systemic cancer treatments such as immunotherapy, which may be more effective in some types of cancer than classic chemotherapy (eg, oral melanoma).

Cancer is one of the diseases of the elderly patient and its treatment can lead to some patients being cured, others to recover without any symptoms and to have a prolonged quality of life. We offer an individual approach to each patient, consisting of a detailed diagnosis and a treatment plan to improve the patient's life and extend the precious time that owners can experience with their beloved pet.

Motto: "Age isn't a diagnoses and cancer shouldn't always mean having to say goodbye to your pet."