Veterinary medicine has made great strides in treating pets with cancer. Advances in Veterinary Oncology, Radiation Oncology, and Radiation Therapy (RT), are applied using state-of-the-art equipment including CT or CAT scans and Linear Accelerators, along with chemotherapy and surgery, to combat tumors and cancer in pets. Expertise + equipment + compassion can treat, cure, or provide quality time to pets with cancer.
Cancerous tumors are made up of aggressive cells that have already beaten the immune system, allowing them to invade the surrounding tissue, or spread (metastasize) to other organs. Often resistant to chemotherapy, more than one medical weapon (i.e. surgery, immunotherapy, radiation therapy, hyperthermia and photodynamic therapy) may be needed to turn the tide against cancer. For example, surgery may remove the primary tumor, but radiation therapy can kill off any microscopic cancerous cells left behind. Radiation therapy is an effective weapon that can cure your pet’s cancer, but it may also be used as palliation radiotherapy to relieve cancer-related discomfort and provide more quality time for pets. In human medicine, over half of all cancer patients undergo radiation therapy as part of their treatment.
Cancer, what is it and how we treat it…
Cancerous tumors are made up of aggressive cells which have already escaped the body’s first line of defense – the immune system – allowing them to invade the local surrounding tissue, or spread (metastasize) to other organs, creating secondary points of attack.
Often resistant to the chemotherapy used against them, more than one medical weapon (i.e., surgery, immunotherapy, radiation therapy, hyperthermia and photodynamic therapy) may be needed to turn the tide against cancer. For example, surgery may be successful alone in treating cancer, but in some cases the tumor cannot be completely resected (surgically removed) and additional therapy is needed to eliminate the cancerous cells left behind. This is often done with radiation therapy.
What is radiation therapy?
Radiation therapy uses high energy x-rays to kill cancerous cells while preserving as many normal surrounding cells as possible. Radiation therapy is an effective weapon and can mean a chance to cure your pet’s cancer. In human medicine, over half of all cancer patients undergo radiation therapy as part of their treatment.
Palliation radiotherapy – used to relieve cancer-related discomfort – is also widely used for human patients and is becoming more common in veterinary medicine. Palliation therapy may be recommended for patients with advanced spread of cancer or other terminal medical condition and is particularly effective in alleviating bone pain in bone cancer.
Whether intended for tumor control or simply to relieve discomfort, radiation therapy has the potential to improve the quality of life of the cancer patient – your pet. The end result being more quality time.
How radiation therapy works:
Using radiation therapy to kill tumor cells without needlessly harming the normal cells surrounding them requires a very high level of precision. Using x-rays, ultrasound, CT-scan, and/or other diagnostic methods, the radiation oncologist determines the treatment area, as well as the appropriate dose and protocol. These decisions are critical in gaining control of the tumor without causing unnecessary damage or complications.
Different tissues (and the cells that compose them) have varying tolerances to radiation, but all cells – normal and cancerous – are capable of repairing some of the damage caused by radiation. Radiation induced damage will often cause the cell to die when it attempts to divide. If the damage is repaired before this division, the cell will survive. Cells with a longer proliferation (division) cycle are more likely to repair themselves than those with a short proliferation cycle. Tumor cells tend to have a very short cycle, making their demise following radiation much more likely.
The goal of radiation therapy is to eliminate the cancerous cells while not saturating the normal surrounding cells with more damage than they can repair. By correctly gauging treatment doses and intervals to allow for maximum repair and cell survival, many of the longer cycle cells can be spared. This greatly reduces the chance of complications that would otherwise make radiation therapy unsafe. For this and other reasons, radiation therapy is given by administering multiple small doses of radiation rather than a single large dose. Known as fractionation, these multiple doses allow the slowly proliferating cells to receive and tolerate a higher total dose of radiation than they otherwise could, thus increasing our ability to achieve good tumor control.
Our commitment, and yours…
Multiple treatments require a great deal of commitment from both the radiation oncologist and you, the owner. Palliation radiotherapy (to alleviate symptoms) requires only a few treatments with a large time interval between each one. Pets receiving radiation therapy for tumor control rather than just palliation require several weeks of treatment, with the therapy being given three to five times per week.
Boarding your pet with us during the week is one option that can lessen the frustrations of multiple appointments, work schedules, and rush hour traffic. This would still allow you quality time with your pet on the weekends.
The use of anesthesia is vital to precisely target the treatment area, and your pet must be well-fasted before each anesthesia. (Originally, the number of weekly treatments were limited to minimize the stress of anesthesia, however with newer anesthetic agents, daily anesthesia can now be safely administered.)
Normal tissues have certain tolerance levels to radiation. Exposing them to more than these levels causes tissue damage and serious complications. If the course of radiation treatments is interrupted, the tumor cells will continue to divide, quickly regaining any loss in tumor size that had been gained through the initial radiation therapy. It is not possible to “catch up” by giving additional doses because the accumulated radiation would be greater than the normal tissue tolerance level. Therefore, it is critical that no treatments be missed unless absolutely unavoidable.
If your pet requires multiple types of treatment, they must be well-coordinated to achieve the maximum effectiveness of each one. This would include chemotherapy appointments as well as surgery and radiation therapy.
Although limited as much as possible, some side effects from radiation are unavoidable. It is important to closely monitor the treatment area when your pet returns home. Depending on the type of treatment, your pet may temporarily lose its hair in the treated area, and may experience a “sunburn” effect. Since irradiated tissues are more fragile, they may require more healing time, and your pet must be discouraged from scratching, licking, and biting the area so it doesn’t worsen.
What to expect after radiation treatment
Following the treatment the radiation oncologist will want to see your pet in the next 2 to 4 weeks to evaluate the treatment area and healing process. Other follow-up examinations will be scheduled at your convenience to monitor the area and assure there is no recurrence, spread of tumor, or new tumors (for most patients this will be 3, 6, and 12 months after therapy).
Following radiation therapy, your veterinarian will receive a referral letter including all pertinent information so that he/she can be thoroughly familiar with your pet’s condition. A duplicate of all follow-up information from our records will be sent to your regular veterinarian’s office.
Cancer in pets traditionally evokes thoughts of terminal disease, cosmetic disfigurement and painful death. Progressive advances in surgery, chemotherapy, and radiation therapy have allowed better care for pets with cancer. At the Regional Veterinary Referral Center we use a regimented approach to cancer in pets which has allowed a cure in many patients, and marked improvement in quantity and quality of life in many others through early detection and aggressive therapy.
General Principles of Surgical Oncology
Presurgical biopsy to determine prognosis and surgical dose required for cure.
Complete staging of patient using radiography, lymph node biopsy, and other imaging. We have a CT scan in house which allows us to better characterize loco-regional disease.
Aggressive surgery using appropriate dose. Experience in surgical oncology allows a cure of local disease in many patients without over dosing patients with surgery, thereby reducing postoperative complications.
Marking and assessing surgical margins. This is the best predictor of local recurrence and helps determine weather radiation therapy or other surgery is required. We achieve clean surgical margins in 95% of patients on which we operate.
Radiation therapy or repeated surgery if margins are incomplete. We have a state-of-the-art linear accelerator for admission of optimal radiation therapy with minimal side effects.
Chemotherapy if survival benefit has been demonstrated. We have a medical oncologist, a board certified internist with a special interest in oncology, and a radiation oncologist who can facilitate administration of chemotherapeutics to patients who need them.
Routinely performed oncologic surgical procedures:
Limb salvage surgeries for osteosarcoma otherwise requiring amputation
Thoracotomies for mediastinal masses and primary lung tumors
Adrenalectomies for adrenal adenomas, adenocarcinomas & pheochromocytomas, including those invading the vena cava
Craniotomies for brain tumors
Maxillectomies and mandibulectomies for tumors of the oral cavity and rostral cranium
Orbitectomies for tumors of the eye or boney orbit