If no treatment is rendered, the animal usually succumbs to the disease within 1-2 months from the time of diagnosis. Surgical resection of the tumor and/or limb amputation are key to treatment of osteosarcoma. Though many owners are at first hesitant about surgery, they frequently observe that their dogs improve dramatically after this treatment. This is by and large because a source of constant pain has been removed. Patients generally make a dramatic recovery with 10-14 days of surgery. It is important to note, however, that surgical resection alone does little to prolong the dog's survival time.

What about Chemotherapy?
Osteosarcoma is always considered to have spread microscopically in the dog's body by the time the diagnosis is made. This is the reason that surgery alone fails to control the disease. To attack the cancer cells both locally and systemically, chemotherapeutic agents can be used. The goals of therapy are to preserve a good to excellent quality of life for the dog, eliminate pain, and provide as long a remission time as is possible. Cure is not a reasonable goal at this time, and this fact must be realized by the owner prior to initiating therapy. The two most common chemotherapy agents used for osteosarcoma are doxorubicin (Adriamycin©), and platinum compounds such as carboplatin or cisplatin. Doxorubicin and the platinum compounds act synergistically against this type of cancer and they are used together for this purpose.

Currently, the best results have been obtained by combining doxorubicin and cisplatin. Because cisplatin can have adverse effects on the patientÕs kidney function, it is given intravenously after a six hour IV fluid (saline) infusion. This helps protect the kidneys from the drug and makes the treatment easier for the patient.

We schedule a total of 3-4 combined treatment sessions (each lasting 8 hours) at approximately 3 week intervals. The first treatment ideally begins about the time the surgical site sutures are removed. Although this protocol is technically vigorous, most patients accept it well.

Expected Results:

• 55% of patients survive 1 year
• 25-30% of patients survive 2 years
• 10-16% of patients survive 3 years

The patientÕs quality of life is generally good to excellent as well as pain free.

Other Medications
After chemotherapy we generally recommend using a daily anti-inflammatory drug such as piroxicam or metacam, along with a low dose of antibiotic doxycycline. Together, these agents have been shown to reduce the growth rate of metastatic tumors. Side effects are uncommon with this combination, but if you detect that your dog has a decreased appetite, an increase in vomiting, or has dark, tar-like stools then stop the medications and alert us.

Side Effects of Therapy
Healing from surgery is usually rapid and complete. The results in terms of cosmetics, function, and owner acceptance is excellent in most cases. All chemotherapeutic agents have potential side effects, which should be understood by the owner so that proper intervention can occur if the need arises.

Post-Therapy
After therapy sessions are completed, your dog should be monitored by us or your local veterinarian about every three months. Chest radiographs (x-rays) are generally done at this time to detect possible disease metastasis. More importantly, we love to see how our K-9 and feline survivors are enjoying life.

What is Life Like for Chemotherapy Patients?
Chances are that you, or someone you know, have experienced chemotherapy for the treatment of cancer. Veterinarians who treat animals for cancer use many of the same chemotherapy agents that human oncologists use. Yet, in many ways the experience for pets seems very different. Why? For one thing, dosages of chemotherapy agents used in animals tend to be much lower than those used in people. Humans are given the highest doses possible, the consequences of which may require bone marrow transplantation, extended hospitalization, and numerous costly medications-all with good cause. However, for veterinary patients, this process would be unacceptable and cost prohibitive for most owners. The general quality of life for many veterinary cancer treatment patients can be surprisingly good and very close to normal. Most of the time they can maintain their normal activities, travel, and have fun with the families that love and care for them.

Most currently used anti-cancer agents do not specifically target cancer cells. Rather, they target and damage or kill rapidly growing cells. For the patient, this means cells lining the stomach and intestine (high turnover rate), cells of the bone marrow that make up the immune system (white blood cells, in particular), and cancer cells. It then is little surprise that the most common side effects of chemotherapy agents include mild to moderate nausea, vomiting, diarrhea, and increased risk of infection. Hair loss, in contrast to humans, is uncommon in dogs and cats on chemotherapy. In most animals, hair does not grow continually throughout their lives like it does in people. Some breeds, however, are susceptible to at least some hair loss (especially poodles, sheepdogs, Scotties and schnauzers). If your pet requires a groomer to trim its hair coat Ð then some hair loss can be anticipated. Pets, however, are not bothered much by this Ð and they seem to enjoy stylish polar-tec jackets as gifts. The good news is that the normal cell lines can almost always regenerate themselves, while the less well organized malignant cells suffer great damage. However, even at higher dosages, microscopic malignant cell clones remain alive, albeit dormant in the body. Eventually these give rise to drug-resistant cell lines. This is the biological basis of recurrent or metastatic cancers.

It is not a "given" that untoward side-effects will occur in any one patient. In fact, the majority of our patients complete their therapies without major complications. If they do occur, however, you should be prepared to recognize them and take appropriate action. Over time, the tendency is to have less frequent side effects, as the individual animalÕs sensitivity to the drug agents become known, the treatments are less frequent, and the cancer is in remission.

POST-CHEMOTHERAPY INSTRUCTIONS

Gastrointestinal Side Effects
Nausea (and refusal to eat) can occur in veterinary patients, and seems to occur more frequently in cats than in dogs. If this happens 1-3 days post-treatment, it is usually transient and requires no specific treatment. Tempting the pet with favorite foods, and warming the foods slightly will often increase palatability. For dogs, adding cooked eggs, pasta, lean chicken, or hamburger can be helpful. If this condition persists, medication to reduce nausea and promote appetite can be used; metoclopramide is most commonly used in dogs; cyproheptadine for cats.

Vomiting can also occur at any time during treatment. When it occurs 1-2 days post-treatment, and the pet is otherwise bright, active, and alert you can use Pepto Bismol¬ using the label "adult dose" for dogs over 40 lbs.; "childrenÕs dose" for dogs under 40 lbs., and 1/4 tsp. for cats (dosed up to twice daily). Remove food for 12-24 hours, and replace it with a pile of ice in a dish. This will help to maintain hydration without stimulating further vomiting. If the vomiting is repetitive (greater than 4X), contains blood, or the pet seems weak and depressed, assume your pet requires immediate veterinary attention.

Diarrhea may occur, but is often mild and transient. Several over-the-counter treatments may be given safely to pets and may reduce intestinal discomfort. Imodium A-D ¬ or "Kaopectate¬ is dosed at "adult dose" for dogs 40 lbs. and over; "childrenÕs dose" for dogs less than 40 lbs.; and 1/4 tsp. for cats up to 2-3X daily. If the diarrhea is severe, persistent, contains blood, or the animal seems weak or depressed, veterinary attention is required.

Fever/Sepsis As previously mentioned, virtually all chemotherapeutic drugs have the ability to at least temporarily suppress the bodies own immune system. The normal range of white blood cell counts in animals is about 6,000-17,000/cmm. If the white blood cell count (neutrophils or "wbcs") are below about 2,000, then the pet runs the risk of systemic infection. The pet will usually manifest fever (but not always). If the bacteria travel through the bloodstream, it is known as "sepsis." In rare cases, shock can occur (septic shock), and without rapid treatment, the risk of death is high. Though this period of susceptibility is brief, and occurs at a fairly predictable time, its consequences can be life-threatening. Below is a list of the most commonly used drugs and the expected low point in cell counts (the "nadir"), given in days post-treatment:

CHART NEEDS TO BE INSERTED

Signs of Fever or Sepsis

• Fever > 103F (temperature taken by rectal thermometer should be between 100 and 102.8 F).
• Extreme lethargy (refusal to get up off of dog bed, etc.)
• Complete disinterest in food
• Extreme weakness
• Pale and somewhat "sticky" gums
• Severe vomiting/diarrhea

WHAT DO YOU DO IF YOU SUSPECT INFECTION

• Immediate action is necessary
• Start the antibiotics you have been given; double the first dose, then continue as label directs
• Track the temperature at hourly intervals
• If pet is not significantly better in 1-2 hours, call us, your local veterinarian, or local emergency clinic immediately. DO NOT WAIT OVERNIGHT! This situation can be treated rapidly and almost always successfully. However, an extended delay before initiation of treatment may result in health complications or even death. Your local veterinarian has been given treatment protocols for this situation and in most cases this will be more convenient for you.

Drug Dosages
Chemotherapy treads a narrow path between effectiveness and toxicity. In fact, chemotherapeutic protocols are most often limited not by the ability of drugs to kill tumor cells, but by their toxicity to the patient. The goal is to destroy as many malignant cells as possible while leaving enough normal, "organized" cells to recover organ function. It is important, therefore, that we use the highest dosages that we think the patient can tolerate. The more cancer cells surviving any one time, the sooner the patient will become resistant to the beneficial effects of the drugs.

Visits and Costs
It is important to make an appointment for each chemotherapy administration. At each visit, a doctor or an oncology nurse will examine and treat your dog or cat. We work as a team to minimize the time you and your dog or cat will spend at the hospital. The team approach maximizes quality care and extends the time, which we are available to you. This may mean you might not see the same veterinarian or nurse each time you visit but rest assured that our intent is to provide the most comprehensive and compassionate care possible.

For a cancer such as lymphoma, therapy involves a significant time commitment on the part of the owner/family. Outpatient visits are generally once weekly for 4 weeks, then every 3 weeks for up to 18 months. Other types of cancer require less treatment time. However, we make every effort to accommodate the ownerÕs schedule, and most visits require 20 to 30 minutes. Many clients like to leave their pet with us temporarily while they go do errands, and you are welcome to do this. You may halt therapy at any time, but we like to have the owner commit to at least 4 weeks, so you will have the benefit of seeing how well a pet can do. Due to the new OSHA hazard laws, and the fact that the animal must make no movement during the intravenous injections, we regret that it is not feasible to have the owner present during the few minutes of chemotherapy injections. Rest assured that your pet will be gently and expertly restrained by the oncology technician and the doctor. Relative to most other treatments in veterinary medicine, chemotherapy is a costly service to provide. The costs reflect the professional time and expertise required, the high costs of chemotherapy agents (the same used by humans), the special equipment and personnel protection required, and the removal of biomedical hazard waste. Realize however, that this therapy is unique in that it can successfully prolong an animal 's life!

Is it worth it?
This is a difficult question for us to answer. Every situation and client-pet relationship is different and must be dealt with individually. If it were ever obvious that therapy was not working, or that the pet was indeed experiencing pain or discomfort, we are ethically obligated to inform you. What we can say is that most pets do indeed appear to enjoy their extended life period and do not even realize that they are "ill." However, the owner(s) must believe that they are doing the right thing for their pet and for their situation.

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Portland Veterinary Specialists
Tel: (207) 780-0271
2255 Congress Street, Portland, Maine 04102

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