One Senior Maltese, a Very Rare Cancer, and 19 Months of Disease Control
Chemotherapy for dog cancer does not always follow a fixed script. A case report published in Frontiers in Veterinary Science shows that adjusting a chemo schedule to fit one dog’s needs may make a real difference. In this case, a senior Maltese with a rare colorectal cancer that appeared to spread to the liver was kept stable for more than 19 months — after the treatment plan was tailored to what the dog could tolerate.
This is a report of a single dog, so it does not set a new treatment standard. But it offers a useful example of individualized cancer care — and a reminder that oncology vets have tools to adapt when standard approaches need to change.
What Is Colorectal Extramedullary Plasmacytoma?
Most dog owners have never heard of this condition. Here is what it means in plain terms.
“Colorectal” refers to the large intestine and rectum — the last section of the digestive system. “Plasmacytoma” is a tumor made up of plasma cells. Plasma cells are a type of white blood cell your dog’s immune system uses to fight infections. When these cells grow out of control and form a tumor, it is called a plasmacytoma.
Most plasmacytomas in dogs appear on the skin and are easy to remove. Finding one in the colon or rectum is much rarer. These tumors are harder to fully remove, and in this dog’s case, the cancer was also suspected to have spread to the liver after surgery — making it even more complex to treat.
What Is Melphalan and Why Was It Modified?
Melphalan is a chemotherapy drug — a medicine used to kill or slow the growth of cancer cells. It belongs to a class of drugs called alkylating agents, which work by damaging the DNA inside cancer cells so they cannot divide and multiply.
In standard “pulse-dose” therapy, melphalan is given at a high dose for a set number of days in a row. The problem is that some dogs struggle to tolerate this. Side effects can become too severe.
For this Maltese, the veterinary team shortened the duration of each pulse — giving smaller bursts of the drug rather than the full standard course. This reduced the burden on the dog’s body while still delivering enough of the drug to target the cancer.
Think of it like adjusting a garden hose. Instead of one long, forceful blast, you use shorter, controlled bursts. The water still reaches the plants, but with less stress on the hose.
What the Results Showed
After surgery to remove the primary tumor and the start of the modified chemotherapy, two important things happened:
The liver lesions shrank. The suspected cancer deposits in the liver got smaller. This suggested the chemotherapy was working — the cancer cells were responding to the drug.
Disease control lasted more than 19 months. This means the cancer did not visibly progress for at least 19 months from the time treatment began. For a rare, spreading cancer like this one, that is a meaningful result.
The dog also tolerated the regimen better than it might have with the unmodified schedule, according to the report.
Signs of Gastrointestinal Cancer in Dogs to Know
Colorectal tumors in dogs are rare, but they do occur — and they can be easy to miss. The signs often look like common digestive issues. It is worth knowing what to watch for:
- Straining to defecate or changes in stool shape (narrow, ribbon-like stools can be a warning sign)
- Blood or mucus in the stool
- Unexplained weight loss
- Reduced appetite
- Vomiting that keeps coming back
None of these symptoms alone means cancer — many things can cause them. But if your dog has ongoing or worsening digestive problems, a vet visit is always the right call. Early evaluation gives more options.
What This Case Means for Dog Owners Facing Cancer Treatment
Chemotherapy Can Be Adjusted
If your dog is going through chemotherapy and struggling with side effects, this case is a reminder: the schedule is not always set in stone. Veterinary oncologists can and do modify regimens based on how a dog responds.
Talk openly with your vet or veterinary oncologist if your dog seems to be having a hard time with treatment. There may be ways to adjust the approach without giving up on the goal.
Rare Cancers Deserve Specialist Evaluation
Colorectal plasmacytoma is uncommon enough that most general-practice vets may never see a case. If your dog is diagnosed with an unusual or rare cancer, a veterinary oncologist — a specialist in animal cancers — can offer the most up-to-date guidance on options. Referral to a specialty clinic is always worth asking about.
19 Months Is Not a Cure
It is important to be realistic. The goal of treatment for spreading cancer is usually to control the disease and maintain quality of life — not necessarily to eliminate the cancer entirely. In this case, the dog’s disease was controlled for more than 19 months, which is a significant outcome. But this is one dog, and outcomes vary widely depending on the type of cancer, how far it has spread, and how the individual animal responds to treatment.
What This Single Case Cannot Tell Us
A case report involves just one patient. That makes it valuable for documenting rare situations and helping other vets recognize and manage similar cases — but it cannot prove that this modified approach will work for all dogs, or even for most dogs with this type of cancer.
The dog’s breed, age, overall health, and the specific details of its cancer all likely played a role in how things unfolded. A different dog in a similar situation might need a different plan entirely.
Larger studies would be needed to know whether this modified chemo schedule is consistently better — or better for certain types of patients — than the standard approach.
The Bottom Line
A case report in Frontiers in Veterinary Science describes a senior Maltese with a rare colorectal cancer that appeared to spread to the liver after surgery. By modifying the chemotherapy schedule — shortening each dose pulse to improve tolerance — the veterinary team achieved shrinking of liver lesions and more than 19 months of disease control.
This is one case. But it shows that individualized chemotherapy for dog cancer can lead to meaningful results even in rare and challenging situations. If your dog faces a difficult cancer diagnosis, know that treatment plans can often be adapted — and that specialist care can open up more options.
This article summarizes peer-reviewed research for educational purposes. Always consult with your veterinarian for personalized advice about your pet’s health and behavior.