Signs A Dog is Dying of Cancer (Plus Advice for 8 Common Cancers)

The signs a dog is dying of cancer are something no dog parent wants to think about. But if your dog has cancer and is declining, you need to know what symptoms to be on the lookout for. To help provide guidance and support, integrative veterinarian Dr. Julie Buzby invited end-of-life-care veterinarian Dr. Dawnetta Woodruff to share some words of wisdom. Dr. Woodruff discusses the general signs a dog is dying of cancer and provides specific guidance about how to know if your dog is dying from eight common cancers.

When we bring a new dog into our lives, we anticipate years of love, fun and adventure! Dogs certainly bring us an abundance of joy during our time together. And we hope that our dogs will be very old before we must consider end-of-life decisions for them. Sometimes they are indeed blessed with a long and wonderful life before they get sick. However, other times, they receive a scary diagnosis like cancer at an age that feels all too young.

The American Veterinary Medical Association’s (AVMA) research on aging reports that one in four dogs will have a benign or malignant tumor at some time in their life, and that 50% of dogs over the age of 10 will develop cancer. This statistic means that most dog parents will someday hear the dreaded phrase, “Your dog has cancer.”

The word cancer itself brings up many questions and uncertainties. How will you know it is the right time to say goodbye to your dog? What signs tell you that a dog is dying of cancer?

What are the signs a dog is dying of cancer?

Although we wish for a simple answer to these questions, there are rarely “black and white” answers that apply to all cancers and all patients. Every dog’s disease will progress in a slightly different way. And every type of cancer will look and act a bit different.

Knowing what to watch for gives a measure of comfort in the middle of uncertainty. Your vet may be able to give you an average survival time based on what type of cancer your dog has. But even these estimates are somewhat of an educated guess. Some dogs will decline more rapidly than anticipated, while others may far outlive what is expected.

Typically, a canine cancer patient will show multiple signs that they are nearing the end of their life. You may notice one primary area of concern, or you may see that they are struggling with many different issues. The signs may happen gradually, or you may see many of them within a matter of days.

All of the following are signs that your dog with cancer is nearing the end of his or her life:

Not eating

A decrease in appetite may be due to pain, nausea, cancer within the GI tract, or a tumor putting pressure on your dog’s stomach. If you notice a lot of drooling and your dog keeps licking his or her lips, or if your dog is vomiting, it is important to discuss anti-nausea medications such as Cerenia for dogs with your dog’s veterinarian. You may also wish to ask about pain medications or appetite stimulants for dogs (when medically appropriate). 

These medications are good ways to keep your dog comfortable. They won’t stop the cancer from progressing. But they will help your dog feel better for the time he or she has left. However, if your dog with cancer is already on these medications and he or she is still not eating, this can be a sign that humane euthanasia is the kindest decision.

Eating but losing weight

Sometimes dogs with cancer have a good appetite and may even seem more hungry than usual. Yet, they are still losing weight and growing more and more weak.

A body trying to fight cancer burns a lot of calories. And it is difficult for your dog to eat enough to make up for their increased caloric needs. Sometimes, the calories they are taking in just can’t compensate for the calories being lost. This leads to weight loss, muscle loss and associated weakness.

Or in some types of cancer, a dog may be eating a lot, but not absorbing the nutrients. Dogs in this situation might have diarrhea in addition to weight loss.

In the case of cancer, if your dog is losing weight but eating well, it may be time to set him or her free.

Not sleeping well

Your dog may sleep well during the day, but be awake and pacing all night. Or he or she may never sleep deeply, and take short naps throughout the day and night instead. Restlessness and an inability to truly relax is often a sign of pain, anxiety, or both. 

Your dog’s vet may be able to help relieve some pain and anxiety by prescribing palliative medications. So, if your dog isn’t sleeping well, please talk to your pup’s care team to see if there are additional things that may be helpful. Eventually, though, the medication will not last long enough, or will stop helping altogether. This can be a sign that the cancer has reached its end stages. 

Panting all the time

Many dogs will pant when they are hot or when they have been more active than normal. This type of panting usually resolves quickly when the dog rests or moves inside where it is cool. However, in dogs with cancer, panting can be a sign of distress. They may be dealing with internal stress from their disease, or with anxiety or pain.

If your dog is panting even when he or she is relaxed, be sure to discuss it with your vet. He or she may recommend adding new medications or changing dosages of current medications.

Difficulty breathing and abnormal gum color

Panting can also mean that dogs aren’t getting enough oxygen. If you notice open-mouth breathing, or your dog’s gums look blue, grey, or a “muddy” red color, he or she is experiencing a medical emergency. Being unable to get enough oxygen is a condition called “air hunger.” It is distressing for pet parents to watch, and can be traumatizing for a dog to experience.

Although we always want as much time with our dogs as we can get, it is kind to choose to euthanize a dog before air hunger happens (if possible). When changes happen more gradually, we can recognize those red flags and make a decision for euthanasia before a crisis occurs. However, sometimes a dog’s condition changes rapidly, and with very little warning. In these cases, if you are seeing air hunger, it is best to make an emergency vet visit as soon as possible.

Pale gums

Some types of canine cancer are more prone to causing internal bleeding. For example, the liver and the spleen are very vascular organs, meaning they have a large blood supply. If your dog has a liver or spleen mass in dogs, or has cancer that has spread to these organs, he or she is at risk for internal bleeding.

You may notice that your dog’s belly looks bigger than normal (i.e. a pot-belled dog appearance). Or his or her gums may look pale pink or even white. Sometimes, dogs with internal bleeding can’t even stand up on their own.

If you see these symptoms, it is best to get care for your pup right away. Your vet may be able to stabilize him or her for a period of time. Or in other situations, it may be kindest to help your dog be free from his or her struggles before things get even worse.

Skin tumor turning red or purple

Many cancers happen internally, with no external evidence of their presence. But other types of cancer, such as mast cell tumors in dogs, occur on or near the skin. If a visible tumor is small, and your dog is in good health otherwise, surgery may be the best option. And it can even be curative.

But if your sweet pup has other health conditions, or if the tumor is in a place that makes surgical removal difficult, you may not be able to move forward with surgery. In this case, it is important to watch the cancerous mass for visible changes.

A dog’s cancer might begin to grow rapidly, doubling in size over a relatively short time. Or it may lose fur or begin to change colors. When one part of the tumor is losing fur and turns dark red or purple in color, the growth may soon rupture and become an open wound. This can be painful for your dog and the risk of infection is high.

If your pup seems to be showing several signs of overall decline, a color change on his or her tumor may indicate that putting your dog to sleep is the kindest option.

Lack of energy or sleeping all the time

As cancer is progressing, weakness and being a lethargic dog are very common symptoms. A simple walk outside to go potty, or going to the front door when the mail arrives, can cause your dog to be out of breath and exhausted. Your dog may still get excited, but tire out within just a few minutes.

Additionally, your dog may be sleeping most of the day and show a lack of interest in what is going on around him or her. Although there are still moments of joy, much of life is spent just existing rather than truly living. When this happens, it is likely that the bad moments are outweighing the good ones. And it is ok to set your dog free from his or her struggles before every single moment of joy is gone.

Signs a dog is dying of 8 common types of cancer

The symptoms we’ve already talked about can apply to almost any type of cancer. However, certain types of cancer have more specific signs to watch for.

Hemangiosarcoma (HSA)

Hemangiosarcoma in dogs is a highly invasive, aggressive blood cancer. It causes blood vessels to grow improperly, become leaky, and ultimately rupture. This rupture happens internally, and the consequences can vary from a small bleed to massive blood loss. HSA is very commonly found in the liver, spleen, heart, and skin.

The type of symptoms you see can vary depending on the severity of the bleeding and the location of your dog’s HSA. You will want to monitor your pup closely for pale gums, decreased energy, inability to stand, and breathing problems. These symptoms indicate that your sweet dog is in his or her final days, or even his or her final moments. When you see those symptoms, or even before you see them, it may be time to euthanize your dog with hemangiosarcoma.

Lymphoma (LSA)

Lymphoma in dogs is one of the most common types of cancer in dogs, accounting for up to 24% of canine cancer cases. It occurs when lymphocytes, a type of white blood cell within a dog’s immune system, start to multiply out of control.

This cancer can present in many different ways. It could show up as swollen dog lymph nodes inside the body, as well as externally. The external lymph nodes will be visually swollen under the chin or neck, in the armpits, in the inguinal area, and on the back of the legs. However, lymphoma may also present as a mass within the body, or as cancerous cells that are spread throughout the GI tract. 

Dogs with enlarged and painful lymph nodes may have trouble swallowing, decreased appetite, or breathing issues. And those with GI lymphoma may be vomiting or having diarrhea. All kinds of lymphoma can cause weakness, lethargy, anorexia, and weight loss. Also, if an individual lymph node enlarges enough to block circulation, you may see sudden swelling of the face, chest, abdomen, or legs.

Transitional cell carcinoma (TCC)

Bladder cancer in dogs is relatively common. And the most common kind is called TCC (transitional cell carcinoma). This type of cancer may originally look like repeated urinary tract infections (UTIs in dogs). A dog may have accidents in the house, blood in the urine, and frequent urination. The vet will treat a UTI (if present) with antibiotics. And or she may recommend chemotherapy in some cases. Or the dog may take palliative medication such as an NSAID or a steroid to help decrease swelling and increase comfort.

As bladder cancer progresses, the tumor can take up most of the space within the bladder. This makes a dog feel like they constantly have to go potty. And they may leak urine frequently. Your dog may also have pain that leads to restlessness, panting, pacing, and frequent squatting.

In the very end stages of bladder cancer, the tumor can fully block the flow of urine. These dogs will have sudden severe pain, and when they squat to potty they don’t get any urine out. This is a medical emergency that requires immediate help before the bladder ruptures.

Liver cancer

There are many types of liver cancer in dogs. Some liver cancers form a solitary mass in one lobe of the liver. These cancers may respond well to surgery as a treatment option. Other types of liver cancer can occur in multiple locations, creating a more nodular cancer that is present throughout all of the liver lobes. These kinds of cancer are more likely to require chemotherapy or palliative care.

Cancer that has spread throughout the liver may decrease the liver’s overall function. Toxins can build up within the bloodstream. And your sweet dog may experience weakness, lethargy, and jaundice. A dog with jaundice will have a yellow look to the whites of their eyes, the inside of their ears, their gums, and even their skin. When a dog with liver cancer is jaundiced, they are in the very final stages of their disease.

Liver cancers are also at risk for bleeding. The tumor tissue may become friable (i.e. fragile) and can be damaged or ruptured by normal activities like playing, jumping, or even flopping down on the floor. If your dog with liver cancer suddenly collapses, or can’t get up on his or her own, it is important to evaluate your dog for signs of bleeding (as discussed in the section on hemangiosarcoma).

Prostate cancer

An enlarged prostate in dogs can be common in older male dogs. In many cases, benign prostatic hyperplasia or BPH (the condition most likely to be responsible for prostate enlargement in intact males) is hormone responsive. So it can resolve by having your dog neutered. Thankfully, prostate cancer in dogs is much less common than BPH. But it does occur, and it can be devastating if your beloved dog is the one struggling with it.

The prostate gland wraps around the urethra (i.e. the tube that carries urine from the bladder to the outside of the body). For this reason, when the prostate is enlarged, a dog will often present with urinary issues. The symptoms can look like a urinary tract infection or bladder tumor. Your dog may be squatting to urinate in multiple places, but only dribbling urine. He may also have abdominal pain, lethargy, weakness, and weight loss. It is worth noting too that pain from prostate cancer can mimic that of hind limb osteoarthritis in dogs.

If your dog with prostate cancer is dealing with a lot of pain, or the inability to urinate, it is kindest to let him go.

Bone cancer

Bone cancer is common in dogs, and unfortunately, it can happen at any age. The most common type of bone cancer is osteosarcoma in dogs (OSA). Other types include fibrosarcoma, chondrosarcoma, multiple myeloma, and metastatic tumors. These tumors may be treated differently, but they all cause similar symptoms as they progress. 

Initially, the symptoms of bone cancer may look similar to the signs of arthritis in dogs. Your dog might be limping after exercise, and the pain may respond well to pain medications. However, as the cancer progresses, the pain in the bones becomes more severe. Medications may still help, but may not alleviate all of the pain. You might see visible swelling of the affected leg, and your dog may be very sensitive to touch in this area.

Pain, fractures, and respiratory issues are common with bone cancer

As bone cancer proliferates (i.e. grows), it weakens the structure of the bone itself. A weakened bone is more likely to break under normal pressure, such as from walking. This is called a pathological fracture.

If you see that your dog’s limping has gotten more severe, the leg is swelling, and he or she does not want you to touch the leg, it is likely that your dog either has a pathologic fracture, or that one may be happening soon. A fractured leg can also cause sudden inability to use the leg, or the inability to get up. If you see these symptoms, your pup needs to see a veterinarian right away.

Bone cancers can also spread to other parts of the body, such as the lungs. If your dog with osteosarcoma begins to cough, or has difficulty breathing, it is likely that the cancer is affecting the lungs as well as the bones. You may be able to manage the coughing and shortness of breath for a while. But it means your dog’s good quality time is quickly coming to a close.

Nasal or oral cancer

Nasal tumors in dogs and dog mouth cancer can be a challenge to manage. There are many different types of cancer that may grow in these places. Carcinomas and sarcomas are common and can be very locally invasive. In other words, they cause a lot of damage in the nose, mouth, and surrounding bone. However, oral or nasal cancers may or may not spread to other parts of the body.

Because these tumors are locally invasive, you may see swelling of the face, nose, and mouth. Or the dog may have bloody saliva or dog nose bleeds. The cancerous tissue is more likely to get infected. So you may notice yellow or green discharge from the nose or smell a rotten odor (i.e. bad breath in dogs) when your dog breathes.

As the tumor progresses, you may notice your dog bleeding from the nose or mouth, making loud snoring or breathing noises, or having trouble swallowing. Plus, the dog could experience swelling that deforms the face. These changes are unpleasant for your dog. And he or she might be rubbing or pawing at the face or the nose as a symptom of discomfort. At this point, your vet may prescribe steroids, NSAIDs or other pain medications, and even antibiotics to help your dog feel better. 

However, when your dog with nasal or oral cancer is nearing the end of his or her life, you may see anorexia, lethargy, increased bleeding episodes, and uncontrolled pain. Medications can help, but it is merciful to set him or her free before a crisis.

Brain tumors

Brain tumors in dogs may originate in the brain or spread to the brain from other locations. A vet can typically diagnose brain cancer using advanced imaging such as an MRI or a CT scan. However, often due to lack of availability, financial constraints, or concurrent health issues, advanced imaging is not performed. In that case, the vet will say the dog has a suspected brain tumor.

If your sweet dog has a suspected or confirmed brain tumor, your veterinarian may recommend medication for pain, anxiety, or seizures. Many times, seizures in dogs are the main symptom of brain tumors in dogs. If they are happening frequently (typically more often than once a month), your dog may benefit from anti-seizure drugs like zonisamide for dogs.

These medications will decrease the frequency and/or the severity of the seizure episodes. However, as a brain tumor progresses, even the best medications will not be able to keep the seizures at bay. Your dog with a brain tumor may begin to have cluster seizures (many seizures in a row), or longer seizures (upwards of 3 to 5 minutes). And the phase after the seizures (called the post-ictal phase) where your dog is lethargic and disoriented may last longer. At this point, euthanasia is a kind option.

Additionally, you may even see your dog exhibiting permanent changes in attitude or behavior. If your dog with a brain tumor begins to act confused or aggressive, and these changes are not responsive to medications, it may be kindest to choose euthanasia before things worsen even further.

Work with your vet to develop a plan for your dog’s cancer

No matter what kind of cancer your dog is facing, the “what-ifs” can be scary. Your veterinarian may recommend seeing a veterinary specialist near you if you wish to pursue advanced cancer treatments like chemotherapy and radiation.

If these therapies are not a good option, or if they are no longer helping, it is good to let your vet know that you are interested in dog hospice care or palliative care. You might even want to seek out a hospice and palliative care veterinarian to guide you regarding the best medications for comfort care.

Think through when it is time to say goodbye

In these difficult times, it is important to keep in mind that your dog doesn’t think of life as “long” or “short.” What they focus on is the here and now. You will always want more time with your beloved canine. Yet, all the “bonus time” still won’t feel like enough because our hearts are never quite ready to say goodbye. So when cancer is present, it is good to have a plan for evaluating your dog’s quality of life.

You may want to use a quality of life scale for dogs. Or you could talk with your family and make a list of your dog’s favorite things. Then together you can evaluate if he or she is still able to enjoy those things. Some dog parents find it helpful to keep track of their dog’s good days and bad days on a calendar. Then they can determine if the good days still outnumber the bad. Additionally, you can factor in your dog’s overall comfort, activity level, and playfulness.

It can also be helpful to talk to supportive friends and family or join a pet loss support group. Plus, you could consider reaching out to a counselor as you work through anticipatory grief (i.e. the sorrow that comes from thinking about losing your beloved pet).

Think of setting your dog free as your final gift of love

Remember, you love your dog deeply, and your dog knows how much you love him or her! Dogs are good at knowing our intentions and they understand when we are trying to help. At the end of a cancer journey, the final act of love and the final way to help our dogs is to spoil them with their favorite things, and then set them free.

How did you know when it was time to euthanize your dog with cancer?

Please comment below.