Senior Pets and Cancer: What to know and where to go if it happens

Dianne Larson of Valencia is spending as much quality time as possible with her 12 year old rescue dog, Tonka, who was recently diagnosed with spleen cancer. PHOTO BY MICHELLE SATHE

By Michelle Sathe

Dianne Larson has walked her dog Tonka at a Valencia park near their home every morning for 5 years. These days, those 20 minutes are a lot more precious to Larson.

That’s because Tonka, a sweet, handsome 12-year-old rescued Labrador Retriever, was recently diagnosed with cancer of the spleen during a routine veterinary exam.

“There were no signs, we don’t know how long the tumor has been there,” Larson said. “Tonka’s so low key and happy go lucky, you wouldn’t even know he was sick.”

This is a road Larson’s been down before. Her previous Labrador Retriever Lacey was 13 when she developed bone cancer after a small mass was misdiagnosed as benign. She passed away within 2 and a half months.

“It just seems like there’s a lot of cancer with pets nowadays. It used to be that an older pet would have their back end go out, but now, most of them get cancer,” Larson said.

Unfortunately, statistics bear this out.  According to the American Veterinary Medical association, almost half of dogs over the age of 10 will develop cancer. The AVMA also found that dogs get cancer at roughly the same rate as humans.

“If you think about it most humans are diagnosed with cancer in their 60’s and older, which in our dog and cat population are those 9 years and older,” said Dr. Evelyn Vega, owner of Happy Pets Veterinary Center in Valencia.

In Vega’s practice, the most common cancers for dogs include mast cell, lymphoma, spleen, and oral. For cats, it’s lymphoma in the intestines or masses in the abdomen stemming from an internal organ or lymph node.

Unfortunately, like Tonka, cancer symptoms may not be noticeable until a tumor grows to a large size, though sudden weight loss can be a sign.

“Weight loss in an older pet is always a concern to me, especially if nothing has changed in their diet or activity level,” Vega said.

Tumors related to the spleen can cause sudden anemia and weakness, while intestinal tumor can cause chronic vomiting or diarrhea in addition to weight loss.

X-rays, ultrasounds, and MRIs are the most common method to find a possible tumor, while a biopsy is the only way to determine if that tumor is benign or malignant.

If cancer is determined, Vega recommends a consultation with an oncologist. “This is their expertise and they are more knowledgeable about the options that are available for a specific type of cancer, the response rate and side effects of treatment, and how long of a remission to expect,” she said.


For older pets with late stage cancer, hospice care is certainly an option.

“The goal would be to keep them comfortable and pain free and measure their quality of life,” Vega said.

In those cases, Vega uses a common veterinary “quality of life” scale for pets with cancer.

“You measure hurt, hunger, hydration, hygiene, happiness, mobility, and whether there are more good days than bad days,” Vega said.

Larson is choosing the hospice path.

“I’m a colon cancer survivor and I know what treatment does to a human. It took a huge toll on me and I don’t want to put Tonka through that for maybe six more months of time with him. That’s not a good quality of life,” she said.

For now, Tonka is on gabapentin to help with pain and is comforted by the presence of his younger sister Ruby, a five year old rescued Labrador Retriever mix.

“It’s like she knows Tonka is sick. Ruby doesn’t engage him in play anymore, but just lays by his side and lets him put his head on her,” Larson said.

The Larsons created a bucket list for Tonka, including a trip to the beach and to In N Out for his first burger.

“It could be a month or three months, you just don’t know. We’re just loving him until he gives us a sign that it’s time,” she said.

They’ve had Tonka since he was 7, adopting the 106-pound dog after he was dumped in a shelter missing fur on a third of his body from a serious case of demodex mange.

“The last part of his life was way better than his first, so that gives me some peace,” Larson said.



  •         To help prevent mammary cancer, have your female pets spayed before they have more than one heat cycle
  •         For males, neutering helps prevent prostate and testicular cancers.
  •         Take your adult pets for an annual veterinary exam.
  •         Senior pets should have semi-annual veterinary exams that include bloodwork and X-rays.



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