In this section you’ll find several tips on how you can recognize pain/decline in your dog and keep track of the process. After all, this information can be useful to adapt the treatment plan and/or painkilling scheme.

Quality of life

When treating a pet, the veterinarian will always try to achieve the highest possible quality of life. A good quality of life is pursued by limiting the side effects of treatments, as well as pain and discomfort arising from tumor growth and/or the treatment itself.

Not all tumors are painful, but dependent on the tumor type, the location and stage they can be associated with different kinds of pain.

Prevalence of pain associated to cancer

Even if a dog does not react painfully when you touch the tumor, it still might be painful. In humans, 20-50% experience pain at the time of their cancer diagnosis, this becomes almost half of treated patients and up to 90% in advanced or terminally ill patients.

Treatments can cause discomfort as well and this discomfort can vary from treatment to treatment. Chemotherapy will possibly cause other issues than radiotherapy or surgery. Side effects of chemotherapy, such as nausea and diarrhea can be handled with appropriate agents. Appetite can be stimulated via adaptation of the diet and/or appetite inducers.

The frequency of pain in animals is hard to estimate, as well as the efficiency of the painkilling. This is why it is important to be aware of the tumor type and stage, as well as symptoms indicating pain.

Types of pain

Acute pain is the type of pain that occurs within hours to days after a painful incident (such as trauma or surgery). This type of pain has a protective, physiological function, as it warns the animal to rest and limit the use of the painful body part. Acute pain disappears when the body part has healed. Chronic pain on the other hand, is a prolonged type of pain which can evolve to maladaptive pain. Maladaptive pain has no physiological function, it is pathologic and persists even when the affected part of the body has healed and the primary cause of pain is no longer present. This type of pain leads to changes in the central nervous system and causes a change in pain perception (the pain signals are processed differently). As a result, a dog with maladaptive pain can experience a pain stimulus much longer (e.g. perceive a bruise much longer or more intensely as painful), can be oversensitive (e.g. an injection can be perceived as more painful than under normal circumstances), but can also experience pain at another location than expected (e.g. not at the tumor itself).

Treatment plan

The cancer itself, but also its treatment can cause (temporarily) pain and may require more than one type of painkiller. The choice of painkillers should take into account the type and intensity of the pain as well as the dog’s comorbidities. Extensive guidelines have been drafted to manage pain (AAHA/AAFP pain guidelines). The sooner pain is treated, the better as this will lower the risk of this pain becoming maladaptive.

Different individuals may require a different pain plan. A certain painkiller can be very effective for dogs in general, but maybe not for your dog in particular. In that case, your veterinarian will look for an alternative painkiller and also examine which combinations of painkillers will provide the best effect. This is a process in which feedback towards your veterinarian is very important. You will shape the pain plan together with your veterinarian.

For safety precautions, your veterinarian should regularly check your dog to make sure that the painkillers are not causing side effects, but also to examine whether the treatment and/or pain plan need to be adapted.

The acute pain or discomfort caused by a tumor is generally dependent on the location and pressure of the tumor on the surrounding tissues. Large tumors within organs can cause painful stretching of this organ and/or interfere with the organ’s function. For example, a tumor in the lungs can compromise the respiratory function. The feeling of not being able to breathe properly is very stressful and has a serious impact of the dog’s quality of life. Large tumors outside organs can impact through their size the organ’s function as well. Tissue breakdown within the tumor can cause a painful inflammatory response, and metastases (especially towards the bones) can ultimately cause pain as well. Several pain meds work in different ways and may have different beneficial effects on the tumor: from an anti-inflammatory and painkilling effect to even inhibiting tumor growth.

Locations

Below, tumor types most commonly associated with moderate to severe pain are listed in descending order. Other possible causes than pain for a decreased quality of life are also described in this list.

the bone is involved:

via bone invasion, microfractures, increased pressure in the bone, deformation of the bone membranes and/or inflammation pain can arise in the bone.

inflammatory mammary gland carcinoma:

this tumor type is rare, but very aggressive. It causes considerable pain and discomfort by an acute inflammation that often is not responsive to standard anti-inflammatory treatment. In these cases radiotherapy may be the best choice for these patients to control the pain. Alternatively, euthanasia needs to be considered, as the prognosis is generally poor.

mouth and throat tumors:

tumors growing on the surface seem relatively painless, while those penetrating the tissues of the upper and lower jaw or involving the bone are clearly more painful. Especially tumors in the back of the oral cavity or throat are painful.

in the nose:

pain associated to these tumors originates from the destruction of the nasal bone. Other possible causes than pain for a decreased quality of life: a tumor mass in the nose can cause nose bleeds and impact breathing.

invasive skin tumors:

especially ulcerated tumors are painful. Often secondary infection and/or inflammation contribute to the pain and discomfort, and need to be addressed by adjusting the treatment plan.

in the central nervous system (brain, spinal cord):

a tumor within the nervous system isn’t often associated with pain, while this is the case for tumors causing pressure on nerves. In humans, 60-90% of cancer patients with brain tumors or metastases in the brain report headaches. A decreased quality of life can also occur due to a disturbed neurologic function (seizures (when the tumor is located in the brain), decreased control of the motoric function).

peripheral nerves:

a tumor to the brachial nerve plexus (nerve bundle located at the shoulder) can be perceived as (very) painful. It will impact the dog’s ability to walk and negatively impact his quality of life.

urinary tract:

pressure on the peri-renal capsule is clearly painful, as well as bladder tumors. Tumors in this region cause pain situated in the lower back and the anal region. They may also cause straining to urinate.

prostate:

these tumors can be very painful, especially in case of metastasis towards the bones. This manifests mostly as abdominal or lower back pain. They may also cause straining to defecate and/or urinate.

gastrointestinal system:

especially tumors of the esophagus, stomach, colon and rectum are experienced as painful, but expressed as vague symptoms (decreased appetite, weight loss, lethargy, possible difficulties defecating). More specific symptoms (esp for esophageal and gastric tumors) are nausea, regurgitation and vomiting. Chronic vomiting is always suspicious for a gastric tumor.

liver and biliary ducts:

especially tumors causing pressure on the capsule are perceived as painful. Like gastrointestinal tumors, liver tumors are often associated with unspecific signs and therefore are often only discovered in an advanced stage. They may cause nausea and pain leading to inappetence and weight loss.

invasive or large soft tissue tumors:

depending on the affected tissue this is more or less painful. Even barely invasive tumors can cause much pain by causing pressure on surrounding organs and tissues.

spread tumors in the thorax or abdomen (carcinomatosis):

the symptoms associated with this tumor type are vague. Painkilling applied in the chest or abdominal cavity have shown to improve the dog’s condition. It is presumed that -as in humans- carcinomatosis is accompanied with significant pain. The tumors’ size can impact the function of various organs. Although an abdominal tumor is usually not painful, it can cause discomfort by compromising the movement of the diaphragm and the bowels. Also the dog may feel nauseous after consumption of large meals, because of the lack of space in the stomach. Carcinomatosis generally has a poor prognosis.

lung tumors:

animals show few signs of pain, although painkilling improves the general state of the dog, indicating these tumors may be painful. On the other hand, depending on the presence of certain receptors in the tumor, painkilling medication may have a direct anti-cancer effect. Therefore, the benefit experienced via painkillers may not be exclusively through reduction of pain.

Dogs don’t always clearly show they’re experiencing discomfort. However, there are several noticeable behavioral changes that can help to identify pain.

On the outer left the dog is normal (happy, energetic, interested in his environment, comfortable when resting, minimal body tension, stands and walks normally, all limbs carry the same amount of weight, doesn’t mind being touched, no response to touch), while on the outer right the dog is very painful (apathetic, depressed, may not react to his environment, difficult to distract from the pain, seems uncomfortable when lying down, wants to move as little as possible, moderate to severe body tension, barely allows touching).

At the time of their dog’s cancer diagnosis, some dog owners make a list of the activities they know their dog likes to do. They then regularly check via this list how many of these activities their dog is still capable of doing and use it as guidance to make decisions (on the adaptation of the treatment and support or to determine when the final time has come).

The answers to the questions are

• 'yes' or 'no'
• or 'always', 'regularly', 'sometimes', 'seldom' or 'never'.

Filling in this questionnaire every 2 weeks can be a possible aid to determine the evolution of the quality of life of your dog.

Category	Questions	Score
Physical	Is the energy level of your dog normal?	always, regularly, sometimes, seldom, never
	Is your dog capable of completing normal everyday tasks (playing, working, going up stairs, etc.)?	yes or no
	Is your dog eating normal amounts of food?	yes or no
	Does your dog get up to greet you?	always, regularly, sometimes, seldom, never
	Can your dog get up easily?	yes or no
	Is your dog breathing normally?	yes or no
	Does your dog let you touch the painful area?	yes or no
Behavioral	Is your dog behaving normally?	always, regularly, sometimes, seldom, never
	Does your dog groom himself?	yes or no
	Does your dog sleep comfortably?	yes or no
	Is your dog urinating and defecating normally?	yes or no
	Does your dog ever seem depressed?	always, regularly, sometimes, seldom, never
	Is your dog ever anxious or nervous?	always, regularly, sometimes, seldom, never
	Does your dog cry out unexpectedly?	yes or no
	Is your dog ever aggressive?	always, regularly, sometimes, seldom, never
	Is your dog reacting adversely to any medication?	yes or no
	Do you think your dog is happy?	always, regularly, sometimes, seldom, never
Social	Is your dog happy to see you when you get home?	always, regularly, sometimes, seldom, never
	Does your dog interact normally with you and other people?	always, regularly, sometimes, seldom, never
	Does your dog interact normally with other animals?	always, regularly, sometimes, seldom, never
Generally	What is your dog's quality of life score?	0 = Quality of life could not be worse, 10 = could not be better