When an oncology referral isn’t in the cards

November 2, 2020
Michael D. Lucroy, DVM, MS, DACVIM (oncology)
Michael D. Lucroy, DVM, MS, DACVIM (oncology)

Michael D. Lucroy, DVM, MS, DACVIM (oncology), is chief medical officer at Torigen Pharmaceuticals, a startup biotechnology company focused on cancer immunotherapy for the veterinary market. Before joining Torigen, he was director of clinical studies for MedVet emergency and specialty hospitals. He also spent nearly 2 decades in academic and private specialty practice.

Volume 51, Issue 11

You’ve just made a cancer diagnosis and offered an oncology referral to the owner, but they won’t go. Now what?

It is not uncommon to diagnose cancer in a patient and refer the client to an oncologist, only to have the owner decline your recommendation, and the reasons why are numerous.

Sometimes, it’s a function of the owner’s emotional attachment to the pet; they may not consider their dog or cat a member of the family.1 In other instances, it is related to presumptions or misperceptions about recovery from treatment, along with worries about how to care for a pet that has undergone major surgery or experiences an acute effect from radiation therapy.1 And, despite reassurances and the documented potential benefit for increasing survival, many pet owners have concerns about the risk of adverse events from chemotherapy.2 Other reasons include financial matters and the logistics of getting to the referral center for multiple visits.

Regardless of their reasons for declining an oncology referral, you now have another cancer patient under your care. Oncology cases can be challenging and sometimes heartbreaking,but they can also be rewarding. Fundamentally, managing a cancer patient is divided into 3 overlapping spheres: engaging the owner, treating the cancer, and supporting the patient.

Engaging the owner

Soliciting input from the owner is an important part of designing a successful cancer treatment plan. These conversations help define what success looks like for the family, from longevity to quality of life. Understanding why the client declined the referral may provide better insight into the client’s fears and motivations, which in turn helps drive the treatment plan. Many pet owners struggle with choosing the “best” treatment for their pet,3 and they may have feelings of guilt over not visiting an oncologist.

It is important to recognize that most owners prefer forthright communication about their pet’s condition presented in an unrushed, compassionate, nonjudgmental, and positive manner from staff with whom they have a relationship.4 Giving clients the truth about their pet’s cancer diagnosis builds trust, allows for informed decision-making, offers a sense of control over the situation, and helps them maintain hope.5 Unfortunately, the recent departure from traditional face-to-face practice resulting from the coronavirus disease 2019 pandemic has created new challenges with these difficult conversations.

Clients can be a great asset for at-home patient monitoring and ongoing decision-making. Having them use assessment tools to gauge quality of life (QOL) and pain in a continuous fashion helps you better evaluate the patient’s response to treatment and recognize when medical intervention is required.6 It also reinforces to owners they are an integral part of the cancer care team. Regular, objective assessment with QOL and pain scores also helps owners with the decision for euthanasia, if that becomes appropriate.

Treating the cancer

Although declining an oncology referral leaves the owner with fewer treatment options for their pet, plenty of available modalities may be appropriate and align with an owner’s preferences. First is palliative surgery. Keep in mind that not every cancer surgery is done with curative intent. For patients with primary bone tumors, amputation provides relief from chronic pain. For soft tissue sarcomas, even modest surgical margins can provide long disease-free intervals for low- and intermediate grade tumors. Debulking oral tumors can improve food intake.7

Metronomic chemotherapy is an option many owners find more appealing than traditional maximumtolerated-dose chemotherapy. Metronomic chemotherapy consists of a daily oral low dose of an alkylating chemotherapy drug (eg, cyclophosphamide, chlorambucil) and a nonsteroidal anti-inflammatory drug (NSAID). This type of chemotherapy has a low risk of adverse effects and requires infrequent trips to the clinic for monitoring blood work. Metronomic chemotherapy helps control cancer growth by inhibiting angiogenesis, reversing the tumor’s immune tolerance by depleting regulatory T cells, disrupting cancer stem cells, and promoting tumor dormancy.8 The drugs used are typically compounded and can be sent directly to the pet owner, which simplifies compliance with regulations for practices that do not routinely handle cytotoxic drugs.

Autologous cancer vaccines (ACVs) represent a form of immunotherapy that can be administered in any practice setting. Because these vaccines are created from the patient’s tumor, they present the immune system with the entire spectrum of tumor associated and tumor-specific antigens, along with an adjuvant to help reverse immunotolerance.9,10 ACVs are currently available to veterinarians as an experimental therapy under US Department of Agriculture regulations.11 A recently published study showed that 3 weekly subcutaneous injections of an adjuvanted ACV were well tolerated by dogs.12 The anticancer effect of that particular vaccine has been demonstrated in rodent models,13,14 and veterinary clinical studies are underway.

Supporting the patient

Pets diagnosed with cancer are often older and may have comorbidities that affect their overall QOL. The requirements for supportive care can also vary among patients. Pain and nutrition are areas that commonly require intervention in these patients.

Pain management

Clients often worry that their pets are in pain. Although many tumors are not painful upon palpation, the presence of many types of cancers can lead to chronic pain. A conservative estimate is that 30% of cancers in dogs and cats are responsible for pain at the time of diagnosis. Thought to be the most painful are tumors involving the oral cavity, bone, urogenital tract, eyes, nose, nerve roots, gastrointestinal (GI) tract, and skin.

Remember that patients with cancer may experience several forms of pain over time, and multiple types of pain may be present simultaneously. Acute pain may be associated with a biopsy procedure or the postoperative period, whereas chronic pain may be tumor-related (primary tumor or metastatic sites) or due to concurrent diseases like osteoarthritis.

As uncontrolled pain intensifies, physiologic changes in the central nervous system (CNS) lead to chronic pain. Various biochemical changes eventually result in the development of opioid-independent pain and a rewiring of the CNS, leading to central sensitization, allodynia, hyperalgesia, and wind-up pain.15

Identifying pain in dogs and cats, particularly chronic pain, is difficult. The use of a pain scale is helpful for both owners and veterinary staff. Colorado State University published several pain scales, including the 4-point scales for dogs and cats.16,17 Not only can most pet owners use these scales easily, but changes in pain score over time also help determine the efficacy of ongoing pain management strategies.

Cancer patients suffering from chronic pain often benefit from a combination of an NSAID, opioid, N-methyl-D-aspartate antagonist, and other adjuvants such as amantadine. Maropitant (Cerenia; Zoetis) may help alleviate cancer pain because of its action on the neurokinin-1 (NK-1) pathway.18 It may also help manage opioid-related GI issues. Bisphosphonate drugs such as zoledronate are useful for managing pain associated with primary and metastatic bone tumors.

When managing chronic pain, it is important to strike a balance between the adverse effects of these drugs that owners find problematic (eg, sedation, constipation, diarrhea) and the positive effect of pain control. In addition to owners monitoring pain scores, it is important for them to report any adverse events quickly so the drug protocol can be adjusted as needed. Owners must also understand the importance of administering pain medication on time and keeping their veterinary team informed about all medications and supplements they give to their pet.

Nutritional support Maintaining adequate nutrition can be difficult in cancer patients, particularly cats. Cancer pain can activate the NK-1 pathway, causing nausea and vomiting, and concurrent medications may diminish a patient’s appetite. Tumors affecting the oral cavity and GI tract can also create obstacles for food intake, and histamine release from mast cell tumors can lead to gastric erosions and ulceration that also affect appetite. Medically, various strategies can be put in place to increase food intake, including managing pain adequately, controlling nausea and vomiting with drugs like maropitant, and using specific appetite stimulants such as capromorelin (Entyce; Elanco). Glucocorticoids can boost appetite but do not provide any analgesia, and carefully weighing the potential positive impact on appetite against removing NSAIDs from the pain management regimen is important

Enteral nutrition can be a useful tool to help maintain a patient that is not eating well. Although nasogastric tubes are easy to place, their small diameter limits the number of calories delivered per day. Gastrostomy tubes can easily accommodate a large volume of a liquified diet, but they are more invasive, requiring endoscopic or surgical placement. Esophagostomy tubes may represent the best option because placement is straightforward, the tube diameter is large enough to provide ample calories, and they are well tolerated by most patients and easy for owners to manage.

Summary

Even if your client declines the offer of an oncology referral, engaging the owner, offering an innovative treatment approach, and supporting the pet through the course of its cancer can be rewarding for all parties involved. Caring for cancer patients helps build trust and strengthen the relationship with the owner.

Michael D. Lucroy, DVM, MS, DACVIM (oncology), is chief medical officer at Torigen Pharmaceuticals, a startup biotechnology company focused on cancer immunotherapy for the veterinary market. Before joining Torigen, he was director of clinical studies for MedVet emergency and specialty hospitals. He also spent nearly 2 decades in academic and private specialty practice.

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