Summer 2015

Radiation to the Rescue 

Lab treated for rare cancer

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Annabelle is cancer-free and back to her old self. Photo: Matthew Healey

When Ryan Ehlinger, V09, found a lump during a rectal examination of Annabelle, a middle-aged Labrador retriever, the Connecticut veterinarian acted quickly. Within days, the rescue dog underwent surgery to remove the suspected cancer.

The post-op pathology report confirmed Annabelle had anal sac adenocarcinoma, an uncommon malignancy of the scent glands near a dog’s rectum. It also showed that some cancer cells remained.

“Humans don’t have anal sacs, but this disease does behave quite similarly to rectal cancer in people,” says Michele Keyerleber, the Cummings School radiation oncologist to whom Annabelle was referred. As in human cases, “there’s a lot of important normal anatomy nearby, limiting how wide a surgical excision you can do,” she says. “So although you often can remove the bulk of the tumor, there’s frequently microscopic disease left behind that can lead to regrowth of the tumor.”

Anal sac adenocarcinoma is aggressive. Studies show the cancer travels to neighboring lymph nodes in 40 to 90 percent of dogs and to such distant sites as the spleen, liver or lungs in up to 30 percent of cases.

To contain the cancer, Annabelle underwent daily radiation therapy for four weeks at the Foster Hospital for Small Animals. Radiation works like a super-powerful X-ray. Focused on the cancer and nearby lymph nodes, which often lie too close to major blood vessels to be removed safely, “the X-rays damage both healthy and cancerous cells in a tightly mapped area,” says Keyerleber. “But unlike normal tissues, cancerous cells are very poor at rebuilding afterward.”

Annabelle’s owners drove up from East Hampton, Connecticut, on Monday morning for the start of each week’s radiation treatments, visited every Wednesday and brought her home every weekend. “Everyone there loved her,” says the dog’s owner, Mark Sieczkowski.

Once she finished her radiation treatments, Annabelle received five doses of chemotherapy to kill any cancerous cells that might be lingering.

Now, more than two years after her diagnosis, the black Lab is cancer-free and back to her old self. “She always wants to go for a ride or a walk,” says Sieczkowski. “Her favorite thing in the whole world is to go exploring.” —Genevieve Rajewski

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