What is Cancer?
Cancer is a disease in which some of the body’s cells grow uncontrollably and spread to other parts of the body.
Cancer can start almost anywhere in the body, which is made up of trillions of cells. Normally, cells grow and multiply to form new cells as the body needs them. When cells grow old or become damaged they die and new cells take their place.
Sometimes this orderly process breaks down and abnormal or damaged cells grow and multiply when they shouldn’t. These cells may form tumors that can be cancerous or not cancerous (benign).
Cancerous tumors spread into nearby tissues and can travel to distant places in the body to form new tumors (a process called metastasis).
Benign tumors do not spread into other tissues. When removed, benign tumors usually don’t grow back, whereas cancerous tumors sometimes do.
Unfortunately, dog cancer is common. It is the leading natural cause of death in dogs. Approximately 50% of all dogs will be affected by a cancer in their lifetime; one report shows that 50% of dogs over the age of 10 will die from cancer. Cancer in cats is less common than cancer in dogs. It’s probably half the rate seen in dogs, but feline cancer tends to be a more aggressive form. Lymphoma is the most common cancer in cats, followed by oral squamous cell carcinoma and fibrosarcoma in the muscle, also known as injection-site sarcoma.
How do cancer cells differ from normal cells?
- grow in the absence of signals telling them to grow. Normal cells only grow when they receive such signals.
- ignore signals that normally tell cells to stop dividing or to die
- invade into nearby areas and spread to other areas of the body
- tell blood vessels to grow toward tumors to supply oxygen and nutrients
- hide from the immune system
- have changes in their DNA
- rely on different kinds of nutrients than normal cells
What causes cancer?
This is the million dollar question. While we don't have all the answers, we do know that there are contributing factors to cancer formation. Changes in the DNA within cells will cause cells to become cancerous. Known and suspected causes of cellular damage that can lead to cancer include:
- second-hand smoke
- radiation exposure
- environmental pollution
- chemical flame retardants in furnishings
- viral infections, particularly FIV and FeLV in cats
- genetic predisposition
- chemical additives and preservatives in food
- chronic stress
- chronic inflammation
What are some common forms of cancer?
There are more than 100 types of cancer. Types of cancer are usually named for the organs or tissues where the cancers form. For example, lung cancer starts in the lung, and brain cancer starts in the brain. Cancers also may be described by the type of cell that formed them.
- Carcinomas are the most common type of cancer. They are formed by epithelial cells, which are the cells that cover the inside and outside surfaces of the body. Adenocarcinoma is a cancer that forms in epithelial cells that produce fluids or mucus. Mammary, prostate, and colon cancers often fall into this category. Squamous cell carcinoma is a cancer that forms in squamous cells, which are epithelial cells that lie just beneath the outer surface of the skin. Squamous cells also line many other organs, including the stomach, intestines, lungs, bladder, and kidneys. Transitional cell carcinoma is a cancer that forms in a type of epithelial tissue called transitional epithelium. This tissue is found in the linings of the bladder, ureters, and part of the kidneys (renal pelvis), and a few other organs. Some cancers of the bladder, ureters, and kidneys are transitional cell carcinomas. Melanoma is a cancer of a pigmented skin cell called a melanocyte. It often occurs in the mouth or nail bed.
- Sarcomas are cancers that form in bone and soft tissues, including muscle, fat, blood vessels, lymph vessels, and fibrous tissue such as tendons and ligaments. Osteosarcoma is the most common cancer of bone. The most common types of soft tissue sarcoma are hemangiosarcoma, lymphoma, mast cell tumors, leiomyosarcoma, malignant histiocytosis, histiocytic sarcoma, and liposarcoma.
- Cancers that begin in the blood-forming tissue of the bone marrow are called leukemias. These cancers do not form solid tumors. Instead, large numbers of abnormal white blood cells build up in the blood and bone marrow, crowding out normal blood cells. The low level of normal blood cells can make it harder for the body to get oxygen to its tissues, control bleeding, or fight infections.
What are warning signs of cancer in pets?
- Any new lumps, bumps, or sores. If you examine your pet daily, you will notice if a new lump or bump suddenly appears. While many lumps and bumps are benign, many are not. Have your veterinarian look at the lumps and perform a needle aspirate (obtaining a few cells with a needle and syringe). Cells should be examined under the microscope to determine whether they may be cancerous.
- Any change in old lumps, bumps, or sores. If a mass has been present for a long time, but suddenly starts to grow, becomes ulcerated, seems painful when touched, or the pet is paying a lot of attention to it, the mass may need immediate removal. Sores that just won't heal may be a sign of skin cancer. Body maps can be used to chart lumps when you find them. Calipers can be used to measure the mass(es) to determine whether they are growing.
- Constant licking at one toe or any other specific area. Pets try to heal themselves by licking areas that are painful or infected. Constant chewing or licking at only one toe can be a sign of a nail bed tumor. Constant licking at the anal area could indicate an anal gland tumor. Pets with bladder tumors may lick in the groin area.
- Bloody discharge from anywhere, whether that is nose, mouth, penis, vulva, or rectum. Nose bleeds are not common in pets and should always be a warning sign to have the pet checked. Many pets with dental disease will have malodorous saliva, but pets with serious cancers in the mouth may have a lot of blood in the saliva. While blood in the urine or urinary openings may signify a urinary tract infection, it may also signify something worse, like a transitional cell carcinoma of the bladder or prostate cancer in males. Rectal bleeding may be associated with colitis, but can also occur with tumors in the bowel. Dark, black, tarry stools are an indication of bleeding higher in the digestive tract and may indicate a bleeding mass in the stomach or small intestine.
- Weight loss without a diet change. Some pet owners associate weight loss with aging changes. However, the weight loss may signify something much worse. Your pet should be weighed at each veterinary visit and any significant change should be noted and the cause determined.
- Bloated abdomen. Bleeding tumors of the spleen or liver can cause abdominal distention. Hemangiosarcoma is a big culprit with this. However, tumors of the liver will often be accompanied by fluid in the abdomen, called ascites. A sample of the fluid can often reveal the underlying cause.
- Loss of appetite. If your pet starts turning up his nose at the usual meals that he loves, something has changed. If they turn down treats or goodies, get them seen!
- Straining to urinate or defecate. While straining to urinate may indicate an infection, it may also indicate a tumor in or around the bladder. I recently had a patient that started leaking urine and the problem turned out to be a huge hemangiosarcoma sitting above the bladder putting pressure on the bladder. Pets that strain to produce very small or flattened stools may be trying to pass stool around a mass blocking the bowel (either in the bowel or compressing it from outside the bowel as in prostate cancer).
- Weakness or loss of energy. If your normally playful, energetic pet is now refusing to go for walks or play with their favorite toy, something has changed. This could be due to pain of arthritis, pain of cancer, a metabolic problem like diabetes or Cushing's disease, or general weakness. Time for a check up.
- Foul odor. This usually indicates an infection somewhere. But that infection may be secondary to an underlying cancer. Many cancerous masses will have dying cells that release a "dead" odor. Cancers do have a specific odor, as evidenced by dogs used to sniff out bladder cancers in urine samples.
- Behavior changes. If your pet is hiding more, doesn't want to be petted or involved in the activity of the household, or is becoming snippy or rude, these are signs he isn't feeling well and wants to be left alone. He may be struggling with pain.
- Pale gums. This is a sign of bleeding or anemia. Chronic illness will lead to anemia. Blood-based tumors like hemangiosarcoma can rupture and bleed into the chest or abdomen.
- Coughing. That dry, harsh cough that just won't go away. Usually non-productive or only a little phlegm is spit out. Respiration may become labored or rapid. This can be a sign of spread of tumors to the chest. Will usually be made worse with exercise.
How is cancer diagnosed in pets?
Screening tests can be performed for dogs by VDI Labs to determine if your pet is at risk for cancer. Cancer is a form of inflammation; tests that show evidence of chronic inflammation can be used to assess risk. VDI labs also offers cancer risk assessment testing for dogs.
Semi-annual blood tests including a complete blood count (CBC) and full chemistry panel to assess organ function and electrolyte and mineral imbalances should be performed. A urinalysis should be included in testing. It is important to know what normal values are for your pet; if test results change, comparisons can be made.
More specific tests for cancer in dogs include the NuQ test which has a high success rate for early diagnosis of lymphoma and hemangiosarcoma, but may indicate other cancers such as histiocytic sarcoma and mast cell cancer.
VDI labs offers a canine cancer panel that can be used to diagnose the presence of cancer and to monitor disease progression or therapy outcomes. Common use includes diagnosis of lymphoma, abdominal masses, solid tumors, mast cell tumors (stage II), hypercalcemia found on blood work that may be associated with malignancy, chemotherapy management, and metastatic disease. The test is not recommended for skin masses, stage I mast cell tumors, or brain tumors. Tests include TK1 and C-Reactive Protein.
VDI labs also offers a feline gastrointestinal lymphoma panel which is very useful to help differentiate GI lymphoma from inflammatory bowel disease.
Some disease problems may interfere with cancer testing. Inflammatory diseases such as immune mediated disease, systemic inflammation, sepsis and trauma can also cause elevated nucleosome and inflammation levels. Tests may not differentiate between sick patients with systemic inflammatory mediated illness and cancer. For this reason, it is not recommended to run the tests in patients that could have these types of diseases. However, the test may be run in dogs without systemic inflammation but with other illness such as hypothyroidism, renal disease, osteoarthritis, mild or moderate pyoderma or other such minor illnesses.
Antech labs offers a test called the CADET-BRAF to detect the presence of Transitional Cell Carcinoma in the urinary tract using urine samples.
Idexx labs announced new testing will soon be available to help diagnose and manage cancer, including:
- A liquid biopsy test that utilizes next-generation DNA sequencing technology to aid in diagnosing the most common canine cancers: lymphoma, hemangiosarcoma, and osteosarcoma.
- A diagnostic panel for biopsy tissues that is used to identify genetic mutations in canines, assisting in therapy selection and personalized treatment options.
- Newly designed diagnostic profiles to support cancer therapy management and monitoring.
Any lumps or masses should be evaluated as soon as possible if they are greater than one centimeter in size or have been present for more than one month. Masses felt on or under the skin can be aspirated; cells from the aspirate can be examined under the microscope to determine if they may be cancerous.
Impression smears using a microscope slide can be obtained from masses that are open or ulcerated.
Any mass that appears to be malignant should be biopsied, with full removal including clean margins, as soon as possible. Many times, surgical removal of a malignant mass will be fully curative.
Imaging to find internal masses may include radiographs, ultrasound, CT scan, or MRI.
How is cancer treated in pets?
There are many options for therapy, including chemotherapy, immunotherapy, radiation, and surgery, along with holistic or alternative therapies. Conventional treatment may be instituted if the pet is likely to live longer with treatment than without, however, financial constraints and difficulty accessing specialist oncology treatment centers may limit the options available.
Side effects from radiation and chemotherapy are variable. Both chemotherapy and radiation may predispose the pet to developing secondary cancers from treatment. For instance, cyclophosphamide is a proven bladder carcinogen and is associated with a 4.5 fold increased risk of development of kidney tumors.
The goal of any therapy is a high quality of life, not necessarily a longer life where the pet's health has deteriorated into a poor condition.
Holistic options may include:
Cancer cells have different metabolic needs than that of healthy tissues. Most cancer cells have an altered metabolism that allows them to break down sugar (glucose) to make energy. Tumor cells typically rely on significant amounts of sugar (glucose) to fuel their high-demand energy needs. Glucose is the primary source of energy for many types of cancers.
- Nutritional therapy with diets designed to slow cancer growth and spread. These may include "keto" diets which are high-fat, moderate-protein, and low-carbohydrate diets. Limiting starches that break down to sugars is paramount in starving cancer cells. Do not feed dry kibble, potatoes, peas, or corn. Foods high in anti-oxidants and cancer-fighting chemicals that can be added to the diet include blueberries, blackberries, raspberries, parsley, basil, dark leafy greens, and oregano.
Garlic can be beneficial for both dogs and cats in appropriate doses. I use fresh crushed cloves. For cats: 1/4 clove (crushed) daily, 3-4 days per week.
For dogs: 1/2 clove (crushed) per 20 pounds of body weight daily, with a maximum of 3 cloves. Best to take at least 1 day per week off. Fresh garlic is far superior to garlic capsules, dried garlic, or jarred garlic. Animal studies have shown that possible cancer-preventive mechanisms include: inhibiting enzymes that activate carcinogens (potentially cancer-causing compounds), boosting enzymes that deactivate carcinogens, reducing inflammation that could support cancer development, supporting DNA repair, slowing growth and stimulating self-destruction of cancer cells without disturbing normal cells, and limiting cancer’s ability to spread by decreasing a tumor’s ability to grow new blood vessels.
- Digestive enzymes will help your pet absorb and utilize the nutrients in their food.
- If they are showing signs of muscle wasting, the Chinese herb Abundant Qi can help slow muscle loss.
- Acupuncture can be used to stimulate the immune system to attack cancer cells and decrease inflammation in the body.
- Mega-nutrients including vitamin, mineral, and nutritional supplementation may help. Arginine, green tea extract, broccoli, selenium, and turmeric are commonly used. Antioxidants such as vitamin C have been used effectively for cancer therapy.
- Fish oil has anti-inflammatory effects. Dosing ranges from 1,000 to 12,000 mg per day of fish oil. Minimum EPA and DHA concentration together should be 300 mg per 1,000 mg fish oil.
- Medicinal mushrooms are extremely beneficial. These can include Reishi mushrooms, which is know as the mushroom of immortality because it helps modulate the immune system, supports adrenal glands to manage stress, and helps regulate the digestive system. Lion's Mane mushrooms are known for their neuroprotective effects. Chaga mushrooms have strong antioxidant function to protect DNA from oxidative damage, support the immune system, promote muscle strength, and help regulate blood sugar. Tremella mushrooms are supportive for animals undergoing chemotherapy, are an immune system tonic, and help protect the heart. Turkey Tail mushroom has the highest beta-glucan content of any medical mushroom, making it the most-used cancer-fighting mushroom. Turkey Tail boosts the production of the cells the body relies on to kill abnormal cells that can form tumors; it helps support a healthy immune system.
- Behavior modification can be used to reduce anxiety and stress for the pet and the pet parent. This may include incorporating flower essences, music therapy, essential oils, CBD, homeopathy, Emotion Code, and counseling.
- Toys that provide mental stimulation for both dogs and cats can help alleviate stress. Be sure to use treats that are meat or organ-based, not high-carbohydrate treats.
- Herbal therapies including Essiac Tea, Chinese herbs, Western herbs, and Ayurveda. Yunnan BaiYao is used in most cases of hemangiosarcoma and other bleeding tumors.
- Neoplasene is an herbal formula that can be used topically or administered orally. The herbal formula destroys cancer cells while preserving healthy cells. Neoplasene should only be used under the supervision of your veterinarian. When used topically on open tumors, the tumor will usually fall off in about ten to fourteen days.
- Artemesinin is an herb that decreases the formation of new blood vessels; it also binds to the high iron content within cancer cells to help kill them. It should be given four hours before or after meals. A dose of 50 mg for small dogs and cats or 100 mg for medium to large dogs should be given twice daily for eleven days, then stopped for three days. Repeat in two-week cycles.
- Melatonin is a mild chelator and free-radical scavenger, decreasing oxidative damage to proteins and DNA. Melatonin directly eradicates various types of tumor cells by inducing apoptosis, or programmed cell death, while inhibiting tumor and cancer cell growth. Melatonin should be given at night. Dosing is 0.1 mg per pound of body weight. Do not use liquids that contain xylitol.
- Homeopathic remedies that match the patterns present in the diseased state within the ailing patient.
- Energy work including massage, Tui-Na, accupressure, Reiki, Craniosacral Therapy, Vibrational Healing, and TTouch.
- Ginger root (1/4 to 3/4 teaspoon per meal) if the pet is vomiting or refusing food. Ginger tea also works well; it can be given by dropper or syringe if the pet is not eating. Ginger has also been found to activate the immune system’s T-cells. It helps lower blood sugar to starve cancer cells. It also can reduce the size of cancer tumors, and causes apoptosis (death) of both normal cancer cells and cancer stem cells.
- CoQ10 is a strong antioxidant and has cancer-fighting properties. Researchers at the University of Miami added CoQ10 to prostate cancer cells – and found a 70 percent inhibition in growth over 48 hours. Adding CoQ10 to breast cancer cells also inhibited proliferation, without harming healthy cells. The team noted that treating a culture of melanoma cells with CoQ10 resulted in the death of all cancer cells within hours – and that applying CoQ10 topically to mice with melanoma tumors caused a 55 percent reduction in tumor mass. There was also a “profound disruption” of tumor vasculature – the structure of veins needed by tumors for oxygen and nutrition.
- S-adenosyl methionine (Sam-E) has been shown to prevent breast tumors from forming, reduce the growth of the tumors already present, and decrease the number of metastases. It also has cell-killing effects on liver cancer cells. Doses range from 90 mg once daily for small cats and dogs up to 425 mg daily for large dogs.
- IP-6 or inositol hexaphosphate offers significant protection against cancer and metastasis. It increases the production of NK (natural killer) cells in the immune system that kill cancer cells. It also binds to iron in the cancer cells which is a major source of food for the cells. It induces apoptosis (cell death) in many cancer lines and inhibits angiogenesis (new blood vessel growth for tumors). Doses for dogs range from 800 to 1600 mg twice daily for medium to large dogs and 400 mg twice daily for small dogs and cats.
- N-acetylcysteine (NAC) is a dietary supplement derived from the amino acid L-cysteine. It is used as an antidote for acetaminophen overdose. As an antioxidant, it is thought to reduce DNA damage. NAC is also marketed for its liver-protective properties and to support healthy immune functioning. In a 2017 study conducted by researchers from the Thomas Jefferson University, NAC succeeded in slowing down the growth of cancer cells in patients with breast cancer. The natural antioxidant reduced the aggressiveness of tumors by modulating the metabolism of cancer cells. NAC also depleted the cancer cells of nutrients, forcing them to starve and die. Dose is 1/4 tablet daily for cats and 1/4 tablet per 20 pounds body weight daily for dogs.
- MCT oil assists with burning fat instead of sugars for energy. Cancer cells thrive by utilizing sugar for energy. MCT oil can help the body make ketones, which the brain uses as an energy source.
- Research shows that Milk thistle is an inhibitor to cancer cell cycles, effectively blocking cancer growth. In addition to its direct anticancer effects, milk thistle silymarin compounds may also reduce damage to the heart and liver from chemotherapy drugs. In lab studies, silibinin from milk thistle worked even better against breast cancer cells when combined with curcumin from turmeric.
- The incredible mix of immune and growth factors in colostrum can inhibit the spread of cancer cells. And, if viruses are involved in either the initiation or the spread of cancer, colostrum could prove to be one of the best ways to prevent the disease in the first place. Colostrum contains cytokines that can help enhance the body’s response to cancer and are thought to inhibit the growth of cancer cells. It supports the immune system and helps fight viruses which can initiate the growth and spread of cancerous cells. In addition, Colostrum contains lactoferrin, which is an anti-inflammatory substance that fights viruses and bacteria. It has been extensively researched for its role in treating and preventing cancer.
Open wounds and broken or ulcerated tumors on the skin are likely to become infected. Natural products are available that can help kill bacteria and keep the wound from drying. My favorite products are Buck Mountain Wound Balm, Remedy Salve, and French green clay. These topical products often eliminate the need to use antibiotics.
While not specifically labelled as chemotherapy agents, many drugs are used off-label to help fight cancer and decrease inflammation. These may include cimetidine, doxycycline, and fenbendazole, among others.
Are you feeling overwhelmed?
When your pet has been diagnosed with cancer, it is easy to feel helpless. It is important to educate yourself about your pet's cancer and how to care for your animal with cancer. Cancer treatment for animals focuses on alleviating pain and suffering, along with extending life, as long as their quality of life can be preserved. Treatment is typically much less aggressive than in humans.
Try to stick to your normal routine as much as possible, as our pets like routine. It helps them stay active and engaged, especially if they will have to make many visits to the veterinarian for treatment. Fun activities like exercising, walks, and playtime will help to maintain a healthy mindset for both you and your pet.
Just because an animal has been diagnosed with cancer does not mean its life is immediately over. Your commitment to your pet will help them enjoy life as long as possible.