FACTORS INFLUENCING PROTOCOL SELECTION FOR INITIAL TREATMENT

A variety of chemotherapy treatment protocols have been developed for the treatment of cats with lymphoma. When reviewing potential treatment protocols for use in their practices, veterinarians should familiarize themselves with the anticipated remission rate and duration, survival time, and the frequency of toxicity. This information will be essential in communicating with the cat owner during the decision-making process about lymphoma treatment. Table 63-1 contains some of this information for commonly used chemotherapy protocols.

If a single-agent treatment protocol was optimal for the treatment of all cats with lymphoma, veterinary oncologists would not continue investigations to identify better treatments. Most studies of treatment protocols for feline lymphoma are retrospective, making comparisons between published data difficult because of the variations in the cat population studied. For example, the COP (cyclophosphamide, Oncovin, prednisone) protocol was used to treat cats in the United States and The Netherlands.^9,10 In these studies, the median remission duration was 8 months in the Dutch study and 5 months in the American study. These data suggest that the COP protocol works better in 2002 than it did in 1983; however, a critical review of the publications suggests that the study populations were very different between the two countries. The feline leukemia virus (FeLV) status differed tenfold between the two countries, with 7 per cent of Dutch cats and 70 per cent of the American cats testing positive for the virus. Both studies reported approximately 30 per cent of cats with the mediastinal form of lymphoma; however, the Dutch study had a large proportion of young, FeLV-negative Siamese cats with mediastinal lymphoma. These cats had among the highest percentages of remission and longest survival rates ever reported for cats with lymphoma. No young, FeLV-negative Siamese cats were reported in the American study. Veterinarians should avoid comparing the success of retrospectively evaluated treatment protocols without considering the differences in cat population included in the studies. These examples highlight the critical need for veterinarians to review the reported data carefully and to determine how the data apply to the cats in their practices before selecting a treatment protocol for feline lymphoma.

FACTORS INFLUENCING PROTOCOL SELECTION WHEN LYMPHOMA PROGRESSES OR RELAPSES

Progression of the tumor during treatment or relapse of the tumor after discontinuation of therapy are poor prognostic indicators. Suggested guidelines for selection of a rescue protocol are included in Table 63-2. Little has been written on the success of additional chemotherapy treatment for feline lymphoma once progression or relapse occurs. Response to treatment was reported in 10 cats who relapsed after receiving a multi-agent chemotherapy protocol that did not contain doxorubicin.³ In nine of these cats, the original treatment protocol was continued at more frequent, weekly intervals and achieved a response rate of 66 per cent. The tenth cat received doxorubicin followed by mitoxantrone for a second complete response of 40 weeks. A phase I clinical trial of CCNU (Lomustine) in cats with a variety of refractory tumors reported the response of 13 cats with lymphoma.¹¹ Five of 13 cats had a partial response to treatment with CCNU. The use of Mustargen (nitrogen mustard), Oncovin, procarbazine, and prednisone (MOPP) has been reported for the treatment of cats with relapsed lymphoma.¹² Fifty-six per cent of cats treated with MOPP had a measurable response and a median MOPP survival time of 65 days. The median survival time in cats after relapse of lymphoma is similar to that in dogs, approximately 2 months, regardless of the protocol chosen.^13,14

Table 63-2 Guidelines for Selection of a Rescue Protocol

CAT OWNER AND VETERINARIAN COMMUNICATION

The diagnosis of lymphoma is devastating to cat owners. Because of cats’ innate ability to hide the seriousness of their illnesses, owners may not be expecting a terminal diagnosis. Veterinarians need to anticipate the cat owner’s need for sympathy, crying, and some handholding. Each cat owner will react somewhat differently to the news, and the veterinarian will need to respond a little differently in each situation. The cat owner also may need some time to digest the information and will need to schedule time in the future to discuss the implications of the diagnosis of lymphoma. Others will have many questions immediately about treatment and prognosis.

Client expectations of their relationship with their veterinarian have been studied, and several points are applicable to the owner of a cat with lymphoma¹⁵ (Box 63-1). Cat owners take their cats to the veterinarian less frequently than dog owners take their dogs to the veterinarian; however, pet owners seeking high-level medical care have a stronger bond with their pet and take their pet to the veterinarian 40 per cent more often.¹⁶ Strongly bonded cat owners are those who typically pursue chemotherapy for lymphoma.

Communication regarding expectations for cats on chemotherapy is critical because there is a perception by the pet-owning public that treatment with chemotherapy causes pain and suffering in companion animals.¹⁷ In a survey of cat owners who treated their cats for lymphoma, 78 per cent expressed apprehension about embarking on a course of chemotherapy for their cat.¹⁸ Cat owners are more highly educated than dog owners and should be excellent candidates to understand the medical needs of their cat with lymphoma, if the veterinarian allows adequate time to discuss treatment.¹⁶ Adequate time may require one long session with the owners to answer their questions or multiple short phone calls and e-mails to answer short questions.

From the owner’s viewpoint, an important factor in their compliance with veterinarian-recommended protocols is the level of communication from the veterinarian about the importance of the recommended treatment.^16,19 Communication skills play a critical role in the veterinarian’s ability to develop a strong relationship with the pet owner. Pet owners who feel their veterinarian provides them with adequate information on pet care, communicates well, and recommends only what their pet needs have favorable opinions about their veterinarian, resulting in a strong client-veterinarian bond. Eighty-four per cent of clients with a strong bond to their veterinarian follow their veterinarian’s recommendations, whereas only 48 per cent of those with a weak relationship follow their veterinarian’s recommendations.¹⁶ Finally, an important determinant in compliance with the administration of recommended drugs is if the owner feels the veterinarian spent adequate time during the examination explaining the need for drug administration.²⁰

Pet owners expect informational material on diagnosis and treatment to be available in various forms. This is because adults vary significantly in their optimal learning style. Some learn by hearing or asking questions and others by visual means. Veterinarians need to provide information about lymphoma treatment in formats other than a conversation such as handouts, fact sheets, websites, or pamphlets.¹⁹ Repetition of the message to the client by a veterinary practice team member other than the primary veterinarian improves compliance with recommended treatment.¹⁹ Some cat owners may require time to consider the information and ask more questions, whereas others will make a decision immediately.

Pet owners expect treatment options to be discussed at the time of diagnosis.¹⁵ Options for treatment of a cat with lymphoma include no treatment, euthanasia, or treatment. For some cat owners, treatment of any sort is not an option because of time, finances, or personal preference. A variety of options exist for owners electing treatment. Prednisone alone, a chemotherapy protocol administered by the family veterinarian, or referral to a veterinary oncologist for discussion of chemotherapy protocols, adjuvant radiation therapy, or investigational therapy all should be presented as options for the cat with lymphoma.

Pet owners have varying degrees of health care literacy. When receiving information about potential treatments for lymphoma, the owner expects the veterinarian to tailor the discussion to their individual ability to understand medical information. Veterinarians should never use medical terms or jargon when discussing treatment with owners. The veterinarian should attempt to understand the owner’s goals for chemotherapy in their cat and help them to set realistic expectations regarding their cat’s cancer therapy (Box 63-2). Open-ended questions (How do you feel about treating your cat with chemotherapy? What will be the problems you anticipate with the treatment protocol I have described?) should be asked to determine if the owner comprehends the discussion.²¹ By asking questions frequently (Have I given you enough information about the potential chemotherapy side effects?) the veterinarian can clarify the client’s level of understanding.

Sixty-eight per cent of people making decisions about their own health care prefer the decision making to be a shared process between themselves and their physician.²¹ Similar studies in veterinary medicine have not been performed; however, owners have expressed a strong preference for the care of their pet to be a partnership between themselves and the veterinarian and for having multiple treatment options discussed, irrespective of the cost.^15,19 Pet owners can be confused by the presentation of multiple options when the “best” option is not identified.^15,19 There is no “best” option for the treatment of lymphoma because the disease is controllable but not curable by any currently available treatment. The benefits and risks of the available treatment options for each individual cat should be discussed, and the owner should be helped to choose the best treatment protocol for their cat and their family. Once a treatment decision is made, pet owners expect veterinarians to respect their decision.¹⁵

The various chemotherapy treatment protocols utilize different treatment schedules. A survey of Australian cat owners whose cats were undergoing therapy for lymphoma considered chemotherapy a substantial time commitment.¹⁸ As part of the decision-making process, veterinarians must outline the anticipated frequency of visits to allow the client to determine if they can comply with the recommended schedule.

Most cats treated for lymphoma will receive medications administered by their owners. Owner noncompliance with the recommended treatment schedule is a barrier to therapeutic success. Market research suggests that veterinarians are considered by pet owners to be the main source for information on oral medication administration.²² Despite this, veterinarians typically wait until the client expresses difficulty in administering oral medications to discuss interventions to make it more successful. Therefore, during selection of a lymphoma treatment protocol, a veterinarian or technician should enlist the owner as a partner in the treatment of their cat and discuss the importance and techniques of oral medication administration. In addition to spending time with the owner explaining the importance of the prescribed medication, there are other interventions to facilitate drug administration. These include the use of “pill pockets,” compounded formulations of medication with flavorings to improve palatability, or transdermal administration. Because of the risk of human exposure to chemotherapy drugs, there are limited options for compounded formulations of these drugs. (See Chapter 18 in the fifth volume of this series for a discussion on the use of transdermal medications.)