Cancer can be a devastating disease for both humans and their animal companions. At the Las Vegas Veterinary Specialty Center’s oncology service, we will strive to provide your pet with the best possible cancer care. We feel that a big part of our job is to educate our clients (pet owners) about cancer itself, the principals of treatment, and the numerous options that may be available for the management of your pet’s cancer. Through our guidance, education and discussion we hope that you will be able to make the best decisions for your pet. This hand-out is designed to compliment our discussions and provide additional information about each treatment option that is available. As always, do not hesitate to ask us if you have any questions or concerns about any aspect of your pet’s cancer management regimen.
What is cancer and what does it do?
Cancer is a complicated disease that involves the loss of regulation of cellular replication. Since every tissue in the body is comprised of cells, cancer can theoretically arise in any site in the body. When the normal mechanisms of control of replication are lost, cells begin to replicate and divide in an uncontrolled fashion. After many cycles of such replication, a mass (tumor) may form. Two things make cancerous tumors different from benign growths like warts. The first is their ability to invade the local tissues in their environment. The second problems is the ability of cancer cells to shed from the primary tumor, spread to other sites in the body, and grow to form other tumors in those secondary sites. This latter process is called metastasis. The combination of local invasion and metastasis makes cancer both a devastating disease and a troublesome foe in the fight for a cure. The word malignancy is synonymous with cancer.
How do the different types of cancer arise?
The different types of cancer arise from each of the different cell types in the body. Thus, when lymphocytes undergo a malignant change they cause a cancer called lymphoma (or leukemia). When a cell in a woman’s breast epithelium undergoes a malignant change, breast cancer forms. When a cell in a bone undergoes such a change osteosarcoma may form. These three different examples are just a few of the many types of cancer that may form from all of the body’s cells.
How is cancer diagnosed?
The diagnosis of cancer can range from being a relatively simple task to a very complex multi-faceted project. In general terms, this involves identification of the cell type that gave rise to the cancer. Fortunately, in most instances, cancer can be routinely diagnosed via either aspiration cytology or a tissue biopsy. For more complicated situations we may occasionally recommend the utilization of molecular techniques for which tissue samples are sent to labs across the country for evaluation, diagnosis and prognosis.
Aspiration cytology involves the insertion of a needle into the tumor (with appropriate analgesia if needed) followed by the application of suction. The cells that are sucked into the needle are then sprayed onto a slide and visualized under a microscope. In some instances such analysis can provide a definitive (absolute) diagnosis. More commonly such an evaluation helps to determine whether a growth is inflammatory or malignant. Occasionally, aspiration cytology does not provide any information at all and more detailed (and invasive) techniques may be required. Fortunately aspiration cytology often provides very useful information and can be performed and evaluated on the same day in our hospital or within a few days at a nearby laboratory.
Tissue biopsies involve the removal of a piece of tissue from the patient’s body (with appropriate analgesia and/or anesthesia) and can be performed in many different ways depending on the size and location of the growth. The ultimate choice of biopsy technique will be made by your referring veterinarian or by the doctors at LVVSC. In most instances such a biopsy provides a definitive diagnosis. Unfortunately, biopsies take 2-7 days to evaluate and in some instances they fail to provide a diagnosis. In the latter situation we may need to perform even more elaborate testing to reach a diagnosis.
What is staging? Is this necessary?
Once cancer has been confirmed by the diagnostic tests described above, we recommend the process of staging. Staging is the diagnostic assessment of a patient to determine how advanced a cancer is within their body. Typically this involves a detailed assessment of the size and invasiveness of the primary tumor in the local area and a more general assessment for evidence of cancer in other sites in the body (metastasis). Sometimes we may also recommend diagnostic evaluation for other concurrent diseases (e.g. liver disease, kidney disease, heart disease, and other cancers) to ensure that a patient’s health status is fully understood before embarking upon aggressive treatment measures.
Evaluation of the primary site for superficial tumors usually involves simply making measurements and feeling the tumor’s invasiveness into surrounding tissues. For tumors arising in deeper locations, diagnostic imaging techniques (e.g. ultrasound, radiographs (X-rays), computed tomography (CT), magnetic resonance imaging (MRI)) may be more useful.
The second aspect of staging is to assess for evidence of metastatic disease. This can be a complicated process because cancer is not always predictable in the time-course or sequence of metastasis. Thus staging can involve diagnostic imaging with radiographs, ultrasound, CT, MRI, nuclear scintigraphy or other methods. Additionally, we may recommend tissue aspiration or biopsy of key locations to complement the findings of imaging your pet. Fortunately, we have all of the appropriate equipment present at our hospital (or nearby) for providing the most accurate evaluation of pets with cancer.
Ultimately, staging is critical for determining how advanced your pet’s cancer is. This has tremendous implications for determining the most appropriate course of therapy and for providing a more accurate prognosis. During the course of our detailed evaluation of your pet’s condition our doctors will discuss the findings of staging with you and their impact in much more detail.
What treatments are available for pets with cancer?
As described above, the results of tissue biopsy and staging provide our health care team with the information necessary to formulate a cancer treatment plan for your pet. As is the case in human medicine there are often many different available therapies at our hospital. Since each patient and their family are individuals, we constantly try to provide a range of options to ensure that we are providing the most appropriate treatment for each individual pet. Generally our treatments can be divided into palliative and definitive approaches. Palliative care is the more conservative approach in which we generally target the clinical signs of the cancer rather than the cancer itself. This is a common approach for patients with more advanced (incurable) cancers, for patients that may not tolerate frequent hospital visits due to age or temperament, or for owners that do not wish to pursue more aggressive therapies. When palliating cancer we attempt to avoid side-effects from therapy at all costs, focusing on the provision of quality of life as the major goal. Definitive therapies are more aggressive by nature as they attempt to cure the cancer entirely. Such therapies may or may not be feasible for an individual pet’s cancer. This often depends very heavily on the stage of the cancer (as described above). With definitive therapies side-effects may be somewhat more frequent, however, in each instance we will talk with you about the potential risks and benefits of any therapy that is provided.
At the Las Vegas Veterinary Specialty Center we utilize state of the art treatments to provide some of the best cancer care available for your pet. Treatment modalities that we routinely recommend for both palliative and definitive benefit include surgery, radiation therapy, chemotherapy, immunotherapy, physical therapy, or other measures. Fortunately, most of these techniques can be provided within our hospital, allowing our doctors and staff to provide the best possible care for veterinary cancer patients within one facility. Additionally, if you prefer, we can consult with your referring veterinarian to facilitate the provision of treatments and/or diagnostics at their practice, closer to your home.
It must be stressed that cancer is unpredictable and cancer therapy can have variable effects on different individuals. Thus, some patients with advanced cancers can have dramatic responses to therapy while others with minimal cancer can have dramatic progression in spite of therapy. Likewise, while most patients do not develop any side-effects from certain treatments, other patients can have serious, even life-threatening, complications. Due to the inherent variability of cancer and its treatment, we closely monitor our patients to attempt to avoid side-effects and to ensure that we are maintaining a good quality of life throughout treatment and afterwards. In all instances we will discuss with you the potential benefits and risks of a proposed treatment before it is pursued. Questions are welcomed at all times.
How is surgery used in the treatment of cancer? What are the risks and side-effects?
By definition surgery is an invasive form of treatment. Because of this, surgery is usually used more for definitive therapy rather than palliation. Generally surgery is appropriate for patients that do not have evidence of metastasis at diagnosis. In such instances, wide surgical resection can be curative for many forms of cancer. Unfortunately, “wide” resection may require the removal of large amounts of surrounding normal tissue to ensure that clean margins are obtained. Since this can provide a cure in some instances, surgery may still be in a pet’s best interest, in spite of the risks and side-effects of such an approach. Nonetheless, each and every surgery can involve the risk of bleeding, infection, damage to normal surrounding tissues, and other complications depending on the exact site. Our surgeons will talk with you extensively prior to the operation to ensure that you understand all of the risks of the procedure. Fortunately, most of the complications are of short duration and pets usually recover within a few days following the operation.
Unfortunately, surgery is not always a good option for some pets with cancer. Many tumors arise in locations in which wide surgical excision would result in dramatic cosmetic and/or functional consequences that reduce the pet’s quality of life. Also, some forms of cancer may already have metastasized at diagnosis, making surgery less helpful. In these instances we may recommend alternative therapies like radiation therapy or chemotherapy in addition to, or instead of, surgery.
How is radiation therapy used in the treatment of cancer? What are the risks and side-effects?
Because a patient’s entire body cannot safely receive large quantities of radiation, radiation therapy is normally used to treat tumors in a limited local area. This therapy can be used for the treatment of isolated tumors in two very different ways.
1) Palliative radiation therapy uses low doses of radiation to reduce the pain, inflammation and swelling associated with a tumor without causing substantial side-effects in most instances. Such radiation is provided in either 5 daily doses for a week, or on a once a week basis for a month. The exact protocol depends on the type of cancer being treated and on the radiation therapist’s preference.
2) Definitive radiation therapy involves the provision of many small doses of radiation on a daily basis over a month-long period. Such treatments can be used to cure cancer (or control it for long periods) in a local area. Radiation is often combined with surgery to maximize the benefits of each approach. In other instances radiation therapy is used alone in locations in which surgery is not possible or not beneficial (e.g. brain tumors, nasal tumors). For some cancers radiation therapy may provide the only chance of a cure. Unfortunately, the side-effects of definitive radiation therapy can be very substantial. While these side-effects usually last for two to four weeks, they can occasionally (<5% of the time) be permanent. We will talk to you about the potential side-effects for your pet in great detail before pursuing such therapy.
How is chemotherapy used in the treatment of cancer? What are the risks and side-effects?
Chemotherapy is a word that creates an instant emotional response in everyone. Chances are that you, or someone you know, has undergone chemotherapy for the treatment of cancer. The reality of chemotherapy for animals is generally different from that of human cancer patients. Most people are pleasantly surprised at how well their pets feel while undergoing chemotherapy.
Chemotherapy can be used in many ways for the treatment of cancer. Because most chemotherapeutics are given orally or intravenously they travel throughout the body targeting cancer in all areas. For this reason, chemotherapy is the primary treatment used for cancers that have already metastasized at diagnosis. Chemotherapy is also given following surgery or radiation therapy for cancers which have a high likelihood of occult (not-visible) micro-metastasis (very small deposits of cancer elsewhere in the body). Finally, chemotherapy can be given for large, invasive tumors that are not amenable to surgery or radiation therapy.
Each chemotherapy drug is quite different in its potential for side-effects and effectiveness for different cancers. We have individual hand-outs for each of the drugs that we will give you depending on the treatment that is recommended for your pet.