Luna's Battle with Lymphoma

When Luna, a five-year-old Scottish Terrier, went in for a routine wellness exam last April, her family mentioned they had noticed a few small “lumps” near her shoulders. What began as a simple checkup quickly turned serious when her primary care veterinarian performed a cytology test (a needle sample used to examine cells) and diagnosed Luna with lymphoma.

“Luna was originally diagnosed with lymphoma via cytology  by her primary care veterinarian when her family reported ‘lumps’ (enlarged lymph nodes) in front of her shoulders during a wellness appointment,” explained Dr. Jessica McCall, oncology resident at Iowa Stat University’s Hixson-Lied Small Animal Hospital. “On further evaluation, they noted many enlarged lymph nodes under her jaw, in front of her shoulders, and behind her knees. They then referred her to the oncology service at Iowa State University’s Hixson-Lied Small Animal Hospital.”

At ISU, Luna met Board-Certified Veterinary Oncologist, Dr. Meg Musser, who confirmed the diagnosis and assessed the extent of her disease. “When Luna was diagnosed in April, she was overall feeling well still (which makes her ‘substage a’),” said Dr. Musser. “She had very enlarged lymph nodes under her jaw, in front of her shoulders, in her groin, and behind her knees. The largest of these was over six times normal size!”

Despite the seriousness of the diagnosis, Luna’s overall good health meant there was reason to be hopeful. She began chemotherapy on April 22,  just a few weeks after her initial diagnosis. “Luna was 5 years old when diagnosed in early April , began treatment on 4/22. She has since turned 6 years old,” said Dr. McCall. “The median age of diagnosis for canine lymphoma is 6–9 years old.”

To give Luna the best possible outcome, Dr. Musser and Dr. McCall recommended the CHOP chemotherapy protocol, which has been used for decades in both human and veterinary oncology. “‘CHOP’ is the acronym for multi-drug chemotherapy protocols containing the drugs cyclophosphamide (C), doxorubicin (H-the chemical name is Hydroxydaunorubicin), vincristine (O-the brand name is Oncovin), and prednisone (P),” explained Dr. McCall.

She added, “CHOP chemotherapy has been a part of standard of care in lymphoma treatment in humans since the 1970s, and veterinary species since the 1990s. There are different variations of CHOP protocols. These vary in number of doses of vincristine [a chemotherapy drug] and spacing between doses.”

This specific version of the CHOP protocol involves four, four-week cycles, each including three weeks of chemotherapy followed by one week of rest and bloodwork. “Prednisone is administered at a tapering dose during the first cycle of treatment,” Dr. McCall said.

Dr. Musser emphasized why this treatment approach remains the gold standard. “CHOP chemotherapy is the standard of care for canine multicentric lymphoma, with the most published scientific data and longest survival outcomes,” she said. “For perspective, average survival times of dogs undergoing no chemotherapy (palliative alone with steroids) are less than 3 months.”

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Throughout Luna’s treatment, communication between the ISU oncology team and her primary care veterinarian played a key role.

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“Collaboration with primary care veterinarians is an important part of treatment for our lymphoma patients especially,” Dr. McCall explained. “After the first cycle of treatment, we often dispense the cyclophosphamide medication (oral capsules) during week 1 (vincristine) visits. The following week patients will visit their primary care vet for a vitals check and complete blood count, forward the results to us, and we call the patient’s family to let them know if it is safe or not to administer the chemotherapy that week or if we need to delay the treatment protocol for 1 week.”

That collaboration proved especially helpful for families like Luna’s who traveled long distances for appointments. “If clients have to travel long distances to ISU for treatment, they will also often have bloodwork performed with their primary care veterinarian the day prior to their ISU chemotherapy appointments,” Dr. McCall said. “That way, based on their cell counts, we can determine if it is safe to proceed with chemotherapy the next day with less travel burden for families.”

As Luna progressed through her treatment, she handled chemotherapy well, but she still experienced some expected side effects. “In lymphoma, we are using chemotherapy to kill cancerous white blood cells, but normal white blood cells can be affected too,” explained Dr. Musser. “A known and expected side effect of chemotherapy is mild immune suppression, and occasionally this is significant enough that it is not safe to administer chemotherapy, and treatment needs to be delayed (often ~1 week) to allow a patient’s bone marrow to recover.”

Those treatment delays didn’t hold Luna back , and may have even been beneficial. “Luna had several instances of mild neutropenia (reduced white cells) that required dose delays, making her CHOP protocol about 5 weeks longer than ‘standard,’” Dr. Musser said. “This is not uncommon, and there is even some data indicating that dogs who experience mild neutropenia can potentially have better outcomes with treatment.”

Like many Scottish Terriers, Luna also experienced one of the unique side effects of chemotherapy. “Most dogs do not have significant effects to their fur from chemotherapy the same way humans’ hair is affected,” said Dr. Musser. “However, dogs with more ‘hair-like’ fur or continuously growing coats (some terriers, poodle breeds, etc.) can have more significant effects. Luna, being a Scottish Terrier, initially had a ‘beard’ and ‘Scottie clip’ when she first presented to ISU. During her chemotherapy protocol, she had significant thinning of the hair on her face, and so her family chose to get her a fresh new short haircut over the summer! Now that her chemotherapy is finished her fur should slowly fill back in.”

After months of dedication, Luna’s treatment came to a successful close. “Luna finished chemotherapy in remission, which we confirmed by sampling one of her lymph nodes,” said Dr. Musser. “Now that she has graduated, she will be monitored monthly for potential relapse.”