 |
By Christine Anderson, DVM, MS, DACVIM (Oncology), DACVR (Radiation Oncology)
Radiation therapy is an essential component of comprehensive cancer care. Angell has been providing radiation therapy services since 1997, and we are upgrading our linear accelerator in order to continue to provide state-of-the-art-care. Installation and commissioning of our new Varian 2100 C/D linear accelerator will be completed in October 2010.
Radiation therapy uses high energy ionizing radiation to kill cancer cells by damaging DNA resulting in cell death or the inability to replicate. Radiation therapy can be performed with either curative or palliative intent. Curative intent radiation therapy is used when there is a reasonable chance of long term tumor control with treatment. Depending on the tumor type and location, 15 to 20 treatments are administered Monday through Friday for 3 to 4 weeks.
Palliative radiation therapy is preferable when there is little hope of long term control either due to presence of metastatic disease, inherent radioresistance of a particular tumor type, or serious concurrent illness. In these cases, the goal of treatment is to improve quality of life by decreasing pain or inflammation associated with the tumor. Treatments are usually administered once weekly for 3 to 6 treatments.
One limitation of radiation therapy is the effect on normal tissues located near the tumor bed and, consequently, in the treatment field. During or shortly after treatment we can see temporary but potentially painful acute side effects including moist desquamation of the skin, mucositis of the oral cavity, KCS and conjunctivitis of the eye. Late complications occur at least 6 months, but more typically 1 year, after treatment is completed and are permanent and possibly life-limiting. Late complications include cataract formation, blindness, bone necrosis, and in the case of the spinal cord, paralysis. Because late complications are progressive and irreversible, great care is taken in treatment planning to keep the risk of late complications extremely low.
The new linear accelerator has both photon and electron capability and will allow us to treat deep-seated tumors such as brain tumors or medial iliac lymph nodes with deeply penetrating 6 MV photons, and most skin or subcutaneous tumors with more superficially penetrating electron beams. Electron beam radiation allows delivery of a high dose of radiation to a superficial tumor site, but the radiation does not penetrate very far into tissue. This is critically important for body wall tumors such as mast cell tumors or sarcomas which overlie the thorax, abdomen, or cranium to allow effective sparing of deeper normal tissues such as lungs, heart, kidneys, spinal cord and brain.
In addition, the new linear accelerator is equipped with a 120 leaf, multi-leaf collimator, which when combined with our 3- dimensional computerized treatment planning system, will allow conformal shaping of the radiation beam to block critical structures located near the tumor bed. This is particularly important, for example, to spare the eye and brain when treating nasal or skull tumors, the heart when treating tumors located within the thorax or abdomen, and tumors near the spinal cord.
Tumor types that can be effectively treated with radiation therapy include soft tissue sarcoma, mast cell tumor, nasal carcinoma and sarcoma, melanoma, and localized lymphoma.
For more information about Angell Animal Medical Center’s Oncology service, please visit www.angell.org/oncology. Our oncology team, Christine Anderson, DVM, MS, DACVIM (Oncology), DACVR (Radiation Oncology), Carrie Wood, DVM, DACVIM (Oncology), and Jennifer Mahoney, DVM, are available for consult via phone or e-mail (oncology@angell.org). To contact the Angell oncology team by phone or to refer a patient, please call 617-541-5136.
