Bone Marrow Cancer in Cats

Various types of cancer can occur in the bone marrow, but the symptoms and clinical signs are similar. Left unchecked, the cancerous cells will continue to overproduce and can cause serious and even fatal issues with the cat’s blood, immune system, and kidney performance. Cancer can also spread to other organs, resulting in damage and eventual organ shutdown. Early detection provides the best chance for successful treatment and recovery. If symptoms associated with bone marrow cancer are present, seek medical treatment as soon as possible.

Bone marrow cancer is a serious medical condition that requires veterinary treatment. It occurs when one type of bone marrow cell begins to reproduce or clone itself at a rapid rate. Cancerous cells overpopulate the bone marrow, reducing the production of other necessary cells and interfering with normal bodily functions. 

Bone marrow cancer will result in various symptoms, including localized pain, signs of bone weakness, signs of blood disorders, and potentially other issues if cancer has metastasized and spread to other parts of the body. Several clinical signs may also be present in the cat’s blood work. 

Symptoms Include:

• Weakness
• Lethargy
• Behavior changes including depression
• Loss of appetite
• Weight loss
• Fever
• Pain usually marked by vocalization
• Increased thirst and urination
• Favoring one or more limbs
• Partial paralysis
• Loss of bladder control
• Blood in urine or feces
• Difficulty breathing
• Behavior changes
• Vision loss
• Unexplained bleeding from the eyes or nose
• Seizures

Clinical Signs Include:

• Anemia
• Abnormal blood count
• Thickening of the blood
• Kidney issues or failure

Types

There is more than one type of cancer that can occur in a cat’s bone marrow. The type differs based on which kind of cell cancer starts to develop in. The common causes of bone marrow cancer in cats include:

• Lymphoma – this type of cancer affects the cells in the lymphatic system and can originate in lymphoid tissues found in bone marrow. 
• Myeloma – this type of cancer affects plasma cells, which begin their life in the bone marrow
• Metastasized Cancers – this occurs when cancer from other portions of the body spreads to the bone marrow.

The specific cause of bone marrow cancer in cats has not been determined. Recent research has shown there may be a genetic tendency, as cases have been observed in multiple cats from the same family line. In humans, bone marrow cancer has been linked to tobacco smoke, inhaled toxins, and emissions from refineries and other industrial processes. These causes could also affect cats and other companion animals. Feline risk factors for developing bone marrow cancer include the prevalence of similar cancers in their genetic line, sex, as males are statistically more likely to have it, and age as it is most often found in cats over the age of seven. The symptoms and clinical signs related to bone marrow cancer are caused by an overgrowth of malignant cells. The cancerous cells reproduce or clone themselves rapidly, reducing the body’s ability to produce healthy cells. 

Diagnosing bone marrow cancer will require numerous examinations and testing. Be prepared to discuss your cat’s medical history, any symptoms you have observed, and the timeframes associated with those symptoms. Many of the signs associated with bone marrow cancer could also be related to various other conditions, so veterinary staff will need to rule out other potential causes by testing your pet for infections and toxins. Blood will be drawn, and a full blood panel and analysis will be required. In addition to testing your pet’s blood for other issues, the veterinarian will look for signs of an overabundance of one type of blood cell, plasma lymphocytes for example, which is common in myeloma. Too much of any one type of blood cell is a sign of overproduction, a common cause of bone marrow cancer. Thickening of the blood and the presence of proteins released from cancerous cells will also aid in a diagnosis. 

If bone marrow cancer is suspected, additional testing will be required. A urinalysis, or analysis of the cat’s urine, for a protein known as the Bence-Jones protein will be required. The presence of this protein in the urine is a sure sign of cancer in the bone marrow. A vet may use X-rays or other imaging to look for changes in bone structure and to locate other organs that may have been affected by metastasizing, or spreading, of the cancer is also necessary. A sample of the bone marrow, obtained through a process called aspiration, will confirm the diagnosis.

Treatments for bone marrow cancer are similar to treatments used for other types of cancer. Your veterinarian will determine the best treatment plan for your pet’s condition based on several factors, including the cat’s overall health, the location of the bone marrow cancer, and whether cancer has begun to spread into other systems. Your veterinarian may refer you to a veterinary oncologist who specializes in handling cancer in cats and other companion animals. Hospitalization may be required initially, however, if your pet responds well to treatment, outpatient options are available. Treatments for bone marrow cancer may include:

• Analgesics: This category of drug is used to treat pain and reduce inflammation. This treatment does not affect the cancerous cells but is symptomatic or used to treat symptoms. If your cat is experiencing pain, a common symptom, they may be given this type of painkiller. Your veterinarian will determine the appropriate dose for your pet’s size to reduce the risk of potential side effects. 
• Chemotherapy: This common cancer treatment is used in humans and animals. The treatment is taken orally or administered through intravenous (IV) fluids. It works by combatting cancer cells throughout the body, making it especially effective for cancer that is spreading from the bone marrow to other organs or tissues. Chemotherapy treatments can cause side effects like nausea, lack of appetite, and weakness or lethargy. In some cases, this treatment can be used on an outpatient basis with routine follow-up visits to monitor your cat’s progress. 
• Radiation: Another common cancer treatment for both humans and animals, radiation therapy targets cancerous cells helping to diminish their production and provide symptom relief. This treatment is more targeted than chemotherapy, which makes it less effective against cancer that is spreading. It is often used in conjunction with chemotherapy and other treatments. The treatment can weaken your pet, so monitoring is required during and after treatment. 
• Antibiotics: Both cancer and its treatments can weaken your pet’s immune system, making them more susceptible to illness and infection. A course of antibiotics may be prescribed to prevent or treat secondary infections. 
• Surgical Removal: In some situations, surgery may be performed to remove the source of the cancerous cells. A full amputation may be required. This treatment is only an option if the affected bone marrow is located in a limb or extremity. This method of treatment has become less popular as chemotherapy and radiation therapy have proven relatively effective in combatting cancer. 

Your cat may be able to return to your home during treatment if it does not require supportive care. Continue to monitor your pet closely for new or worsening symptoms. Follow all of your veterinarian’s instructions, including providing doses of medication, recommended dietary changes, and follow-up visits. During follow-up visits, veterinary staff will draw blood for analysis and may continue to use imaging or other diagnostic methods to monitor the cancer. Treatment plans may be modified if your pet’s condition is not improving. Treatment can last for many months before the cancer is successfully put into remission. Even if your cat goes into remission, monitoring at home and returning for regular check-ups is necessary because it is highly likely cancer will return in the future. Your cat will require plenty of attention and support as they recover. Avoid stressors like changes to their environment, travel, or boarding while your pet is undergoing treatment.