Treating lymphoma can be difficult because it is a systemic cancer. It affects a large portion of the body by spreading through the bloodstream, so some of the other options for treating localized cancers aren’t always as effective in treating lymphoma. A common cancer treatment that can be used with various presentations of the disease is radiation therapy—also known as radiotherapy.
To answer that question, we first have to discuss what radiation is. Basically, radiation is a type of energy. It is naturally produced by the sun and earth, and can be artificially recreated by machines. A common way that radiation is used outside of radiotherapy is through X-rays; X-ray machines use low dose radiation to create images of the inside of the body.
Radiation therapy then is a treatment method that uses a high dose of radiation to specifically target and destroy cancer cells. Because cancer cells rapidly divide, being able to damage the replicating DNA will kill the cancerous cells, and radiation therapy targets that gene. If used efficiently, radiation therapy is capable of shrinking or even completely destroying a tumor.¹
For dogs with tumorous cancer, radiation therapy can be used as a treatment on its own or, commonly, with other treatments, like chemotherapy or surgery. Radiation therapy targets a localized region and is therefore typically used for more localized type of cancers. But when a dog has lymphoma—a systemic cancer—choosing to treat with radiation therapy is not typically the first choice.
Radiation therapy is most often administered while the dog is under an anesthetic. This prevents them from moving and will keep the radiation targeted directly at the area that the cancer is localized. Some patients with tumors will need to go through multiple treatments where they are anesthetized to treat the tumor with radiation.
To mark the tumor’s location and minimize the number of healthy cells that are impacted by the treatment, the patient will often go through a CT scan prior to the start of therapy. Because radiotherapy is meant to target specific areas, knowing where the tumor is located minimizes the number of healthy cells that may be damaged.¹
Why is radiation not the most common for dogs with lymphoma? While radiation therapy can be effective on its own for tumorous cancer, lymphoma patients need a combination of chemotherapy with the support of radiotherapy. This creates a slightly more effective, and, in turn, a more toxic treatment.²
The thing to remember is that radiation itself is quite toxic—we don't want healthy cells to be exposed to that kind of treatment. Unlike other cancers, lymphoma is a systemic disease, which means it spreads throughout the body and is not localized to a single area. As a result, radiotherapy for a lymphoma patient would involve administering radiation to the entire body. While this would certainly target all of the cancerous cells, there would also be an impact on the dog's healthy cells.
The most effective way to use radiation therapy for dogs with lymphoma is to use it after chemotherapy treatment has already been completed, as well as using a half body radiation therapy treatment.
Half body radiation works exactly how it sounds. Rather than localizing the radiation therapy to a single area, the treatment is applied to half of the dog's body at a time. This treatment is then done in two different sessions to address the whole body. The treatment will start with marking around the midsection to separate the dog’s body in half, from their nose to the center line and from the center line to their tail.
The treatment covers one half, usually starting with the nose half of the body. The patient is put under anesthesia and receives radiation treatment to the half of the body scheduled for the day. After the initial treatment, there is an average of a two-week gap before the next treatment, during which time the owners are asked to maintain the mark splitting the center of their dog to make it easy to identify the remaining half for the patient’s next treatment. Recently, a newer form of therapy, called stereotactic radiation therapy (SRT), is being adapted in veterinary medicine. The advantage of the technique is that the toxicity is reduced by excluding normal tissue compared to conventional radiation therapy.³
The addition of radiation therapy to chemotherapy may increase the remission and survival times in canine lymphoma patients. The technique has been known to make a more impactful change to high stage B-cell lymphomas, and not have as great of a cost-to-reward ratio on T-cell lymphoma.⁴
Radiation therapy can be added to a treatment plan when a B-cell lymphoma patient has not seen a great response to chemotherapy protocols, as it gives an additional push towards remission.
Often, veterinary oncologists work to get the best initial treatment for your pet so as to not put the strain of radiation therapy on their body. Radiotherapy has one of the highest levels of toxicity to the patient’s body and is more likely to impact their quality of life post-treatment than an effective chemotherapy treatment. But when a patient is not responding positively to chemotherapy treatments, radiation therapy can be the difference between a remission and a sad goodbye.
Because radiation therapy is not often the first choice for lymphoma patients, being able to identify the most effective chemotherapy treatment for a patients’ individual lymphoma can make a huge difference in the time that it takes to find the treatment that will work for the patient and help them to achieve remission.
ImpriMed works with your vet to receive a sample of your pet’s live cancer cells and then uses artificial intelligence and our advanced labs to test your dog’s live cancer cells against 300 different concentrations and combinations of chemotherapy drugs to find the most effective treatment plan for your pet.
In a process that takes only 7 days, ImpriMed uses the information found through their AI programs to develop a Personalized Prediction Profile that helps to explain the predictions of efficacy and remission times to you and your veterinary oncologist, and allows you to make a more educated treatment plan for your dog, rather than using a trial and error method.
Finding the right treatment is half the battle when it comes to treating lymphoma, take the guesswork out by working with ImpriMed. To learn more about how our system works you can take a look at our blog post going over the Future of Testing for Lymphoma.