Learning Objective

To develop a framework for instituting a palliative care plan including pain relief and nutritional support in dogs and cats with cancer, and determining when surgery and radiation therapy can be applied with a palliative goal.

Definition and General Approach to Palliative Care

Palliative care is aimed at improving quality of life and relief of suffering rather than specifically treating the underlying disease.

In the case of animals with cancer, offering palliative care only as an option is appropriate in cases where the condition is likely to be terminal and owners elect not to pursue treatment, or treatment is not successful. In human studies, early palliative care is associated with not only improved quality of life at the end of life, but actually with improved survival time. Early discussion of palliative care also allows carers to prepare, resulting in reduced episodes of prolonged grieving and major depression following the death of the patient.

Many factors go into owners’ decisions when choosing treatment for pets with cancer. These include treatment-related factors (cost, side effects, time commitment); disease-related factors (prognosis with different treatments); and patient factors (comorbidities, amenability to different levels of treatment, age). Age is commonly cited as a factor in owners’ decisions, though it may not directly affect the suitability of treatment options otherwise.

Suggested Steps in Developing a Palliative Care Plan

• Client education—discussion of all of the options for diagnostic testing or treatment, and prognosis. Consideration of the bigger picture is necessary; for example, if the owners are not going to pursue specific treatment for a dog with osteosarcoma, will taking chest radiographs change the plan?
• Determination of the owner’s goals and beliefs. If the owner’s goals are unrealistic, this should be addressed clearly and honestly, with empathy. Determining the owner’s beliefs about euthanasia may be appropriate at this time.
• Developing a personalised treatment plan—patient assessment with regard to hydration, nutrition, pain, mobility, mood, and engagement to determine which need to be addressed; client assessment with regard to their willingness and ability to provide care. The plan should be agreed upon by vet and owner. Treatment protocols should be simplified as much as possible, and instructions should be clear. Owners should feel able to express concerns about their ability to deliver the recommended care.
• Implementation and reassessment. Once a plan has commenced, frequent reassessment is required to ensure that goals of the owner and needs of the patient are being met, and that quality of life is maintained as much as possible. Tumour progression alone does not mean that palliation is not successful, as long as quality of life is maintained. Use of the animal hospice care pyramid and/or the HHHHHMM quality-of-life scale may assist in assessing for changes in quality of life over time. At the beginning of the process, having owners make a list of the things that most impact quality of life for their pet (positive and negative) and then having them assess their pet regularly for these key behaviours may allow detection of changes in quality of life over time.

Pain Management in Cancer Patients

Pain is a major concern of human cancer patients and of owners of pets with cancer. Instituting analgesia early in animals with tumours likely to be painful is an important part of palliative care and of cancer treatment in general. Owners may not always recognise pain in their animals, and careful questioning and client education are important. In some cases, an analgesic treatment trial may help an owner to recognise that their pet was painful.

Drug therapy is the mainstay of pain management in veterinary oncology, and the WHO cancer pain ladder is a reasonable approach. For mild pain, an NSAID is recommended +/- adjuvant (e.g., gabapentin). For more severe pain, addition of opioids is recommended.

Multimodal management is recommended, with combinations of drugs and of modalities (i.e., massage or other physical therapy along with drugs). Using multiple drugs improves pain control and allows lower doses to be used of individual drugs. Adjuvant drugs are generally weak analgesics alone, but when used in combination with other drugs can be beneficial. Simplifying timing and frequency of dosing will improve compliance when prescribing multiple medications.

For tumours that are affecting quality of life due to local effects, surgical removal or radiation therapy may improve quality of life even in cases with metastatic disease. For example, in appendicular osteosarcoma cases, improvement in quality of life can be achieved with amputation or palliative radiation therapy due to relief of local pain, even though these modalities may not improve overall survival. Intranasal tumours are likely painful due to their invasive nature and will often respond very well to palliative radiation therapy, which has a low risk of acute side effects. When removing tumours for purely palliative purposes, aggressive resection to achieve margins should not be a major factor in the approach; but if margins are achievable without increasing morbidity, this may be reasonable.

Nutritional Support in Cancer Patients

Maintenance of adequate nutrition is a key factor in assessing quality of life in dogs and cats with many illnesses, including cancer. In the specific setting of palliative care in the veterinary oncology patient, both strategies to increase voluntary intake and strategies bypassing the need for voluntary intake (e.g., feeding tubes) may be used, but clear consideration of goals and quality of life is required. Anorexia or hyporexia in dogs and cats with cancer may be caused by inflammatory response to the tumour, pain or nausea, obstruction (oral or other GI tumours), or effects of chemotherapy. Even in patients where caloric intake appears adequate, disordered metabolism can cause loss of condition (cancer cachexia), though this does not seem to be as common in dogs as in people. It may be more common in cats.

The first step in developing a nutritional support plan is a baseline assessment including bodyweight, body and muscle condition score, and dietary history. Weight alone is not sufficient to fully assess nutritional status, as weight gain with significant loss of body and muscle condition may be seen due to, for example, tumour growth or ascites.

If nutritional supplementation is required, resting energy requirement (RER) must be calculated. There are several formulae for this. One approach, used at the University of Melbourne, is:

• RER in kcal/day =
  Bodyweight (kg) x 30 + 70 for dogs and cats
  70 x bodyweight (kg)^0.75 for dogs >45 kg

An alternative approach for lean/active cats <5 kg is: RER = Bodyweight (kg) x 60.

For hospitalised patients, aiming for RER is reasonable. Increased energy requirements are expected for more active animals at home or those in whom extensive tissue repair is taking place, and maintenance energy requirements can vary from approximately 1.2–1.8 RER, depending on activity level and neuter status. Regardless of which calculation or approach is taken, regular reassessment is required to assess whether current caloric intake is sufficient.

Recommended steps for increasing caloric intake in palliative care:

1.  Address pain, nausea, or other underlying causes where possible.

2.  Coaxing (e.g., hand feeding, dietary modification). Syringe feeding is usually not practical.

3.  Pharmacologic approaches¹ including:

a.  Mirtazapine—can cause behavioural changes (e.g., vocalisation or agitation). Should not be used concurrently with cyproheptadine. Is absorbed transdermally in healthy cats with effective appetite stimulation, although the appropriate dose has not been determined.²

b.  Cyproheptadine—may take a few days to be effective; may cause sedation or paradoxical hyperexcitability.

c.  Capromorelin—recently approved (in dogs), ghrelin receptor agonist. Can cause diarrhoea, vomiting, and excess salivation.³

d.  Prednisolone

4.  Feeding tubes
In my opinion, feeding tubes should be considered in palliative patients only in select circumstances (i.e., where other quality-of-life factors are considered good—e.g., pain is controlled, activity and mobility are acceptable—but inadequate caloric intake persists). Feeding tubes are not recommended where inadequate intake is due to effects of cancer that are not otherwise being addressed (e.g., in oral tumours where the animal is not eating well due to pain). Oesophagostomy and gastrostomy tubes are the most common approaches used. Oesophagostomy tubes typically last for weeks to months. Gastrostomy tubes should be considered when anticipated need is for >6–8 weeks. Placement of gastrostomy tubes is more challenging than oesophagostomy tubes and typically requires either an endoscopic or surgical approach. Naso-oesophageal or nasogastric tubes are quick and noninvasive to place, but are usually short term (days) and can only accommodate liquids. These approaches may be used in cases where a definitive diagnosis is pending or while assessing for rapid response to treatment before making longer-term decisions.

References

1.  Agnew W, Korman R. Pharmacological appetite stimulation: rational choices in the inappetent cat. J Feline Med Surg. 2014;16:749–756.

2.  Benson KK, Zajic LB, Morgan PK, Brown SR, Hansen RJ, Lunghofer PJ, Wittenburg LA, Gustafson DL, Quimby JM. Drug exposure and clinical effect of transdermal mirtazapine in healthy young cats: a pilot study. J Feline Med Surg. 2017;19:998–1006.

3.  Plumb’s Veterinary Drug Handbook iPhone application; accessed 20th April 2018.

4.  Vet Clinics of North America Small Animal Practice Palliative Medicine and Hospice Care; 2011.

5.  Lascelles BD. Management of chronic cancer pain. In: Withrow and MacEwen’s Small Animal Clinical Oncology. 5th ed. pp. 245–259.

6.  Wakshlag JJ. Nutritional management of the cancer patient. In: Withrow and MacEwen’s Small Animal Clinical Oncology. 5th ed. pp. 259–270.