Another Tool Against Cancer
By Gail D. Mason,
DVM, MA, DACVIM
www.pvesc.com
The mainstay of cancer treatment in veterinary medicine involves surgery, radiation therapy, chemotherapy, or a combination of these modalities. Treatment choice is based on several factors including the tumor type, tumor location, feasibility of complete removal, and the likelihood of metastatic disease (spread within the body).
In some patients, complete removal of a tumor is not possible due to its size, aggressive tendencies, or location within the patient. In other patients, the tumor has been removed, but some tumor cells were likely left behind due to the tumor’s size and anatomic location. Radiation therapy is certainly an option, but can be logistically difficult, costly, and current access is limited to out-of-state locations. Electrochemotherapy (ECT) is a cancer treatment modality that combines chemotherapy with electrical impulses to enhance the delivery of chemotherapy directly into tumor cells. It is a minimally invasive procedure used to treat various cutaneous, mucocutaneous, and subcutaneous malignancies in dogs and cats.
What is it?
ECT is a mode of treatment that enhances the delivery of certain chemotherapy drugs (bleomycin or cisplatin) directly to the interior of the cancer cell through the local application of short and intense electric pulses. Performed under a relatively brief sedation or anesthesia, the electric pulses cause the cancer cell membranes to be transiently permeable to chemotherapy, thereby increasing local absorption of the drug by up to a thousand-fold over that given intravenously. This usually results in "targeted high-dose" treatment of the tumor, sparing the surrounding normal structures. Its second effect is instantaneous interruption of the blood flow to the treated tumor. This not only traps the drug within the tumor but also results in tumor starvation and cell death. The patient's immune system is activated by this process and offers a third assault on tumor cells. The process may involve one or more treatments, based on the size of the original tumor or surgical scar.
What types of tumors can be treated with ECT?
ECT can be used for local tumor control to improve quality of life, or as a potential cure. It can be used for primary or metastatic tumors of virtually any type if a first-line treatment is otherwise unavailable. Nasal, oral, or limb tumors (not bone cancer), or incompletely removed (or nonsurgical) tumors (sarcomas, melanomas, squamous cell carcinomas, plasma cell tumors, low-to-intermediate grade mast cell tumors, plus perianal and rectal tumors) are potential candidates for this therapy.
How is it performed?
The patient is heavily sedated or anesthetized briefly. The dose of chemotherapy administered is calculated based on the tumor size (if present), or surgical scars size (if done postoperatively), or body weight (if the drug is given IV). The drug may be given partially intravenously and partially into the tumor itself. Each treatment lasts about 20 minutes, and overnight hospitalization is not required. Multiple areas can be treated during the same session and treatments can be repeated weekly as necessary. Typically, 3 sessions are needed for 5 cm. lesions or greater.
What are the side effects of treatment?
There is a very small, but inherent risk associated with sedation/anesthesia. The procedure, which is typically performed by an oncologist is fully supervised by skilled, dedicated oncology technicians +/- an anesthesiologist as deemed necessary. Local tumor site reactions include redness, swelling, and loss of some affected skin tissue. Your pet may be prescribed medication for pain control and/or infection. Full healing is expected in a few weeks. Treatments may be repeated as necessary, which makes this an attractive option for dogs with multiple tumor sites. It is considered safe, effective, and affordable.