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Polish Lowland Sheepdog - pons - pon the dog





 PON von Regensdorf- Beatrice Brack, Switzerland





 Linda Aronson, DVM


Cancer, it's not a diagnosis we want to either give or hear, but all cancer is not created equal. Certainly great strides have been made in the last decade in treating canine cancer. However, before we have to deal with the issue on an emotional level, I think it's helpful to step back and look at the condition while our dogs are still healthy, and consider what we'd do in any given set of circumstances. For me the quality of an animal's life is far more important than its quantity. Keeping an animal alive, but in pain, seems selfish. They live in the here and now. They remember the past. I don't think they would choose to live in pain. Most veterinary oncologists realize this. For this reason lower relative doses of chemotherapeutic drugs are used on animals than on people, but they may still experience severe gastrointestinal upset - diarrhea, vomiting and anorexia - after each treatment. Most dogs do not lose their hair as a result of chemotherapy. On the other hand, removing an animal's limb is far less traumatic to most dogs than it would be to us. I never cease to be amazed at how well they bounce back even 24 hours after surgery.

While veterinarians cannot predict the future, the first question will be the benefit of various forms of treatment. How long can the average dog with this kind of cancer be expected to live, and what will be the effect of treatment not only on life expectancy but on the dog's quality of life? Like it or not, cost has to be considered when considering treating cancer. The introduction of generic chemotherapeutic agents has reduced this in some instances, but it is still not going to be trivial.

In order to get a prognosis, tests have to be done, and in general treatment should not be initiated until a full work up has been completed. One of the first things will be to look for evidence that the cancer has spread or metastasized. The most likely location of secondary tumors is the lungs, and so chest X-rays will be taken. If your Beardie has a mast cell tumor, however, these rarely affect the lungs, but frequently spread to the liver and spleen, so X-rays or ultrasound of the abdomen would be in order. Lymph nodes, particularly in the region of the tumor should be evaluated. In order to identify the kind of tumor, and stage it (see how it's progressing), it is necessary to perform a biopsy. For many tumors, excision with clean margins will be curative, but only with microscopic examination of the tumor will it be possible to determine whether the whole thing has gone. Unfortunately, this is rarely as simple as it sounds. Clean margins means at least 3 cms. around the visible tumor, even if the thing seems to shell out. Often the visible tumor (especially a sarcoma) is surrounded by a pseudocapsule of tumor cells, which may be left behind. Incidentally, if radiation therapy is being considered in addition to surgery, it is helpful if the surgeon places surgical staples in the site when he operates, one of the most frequent reasons radiation therapy fails is because it is no longer possible to accurately locate the original site. This is safe if megavoltage radiation is being planned - which is more common - but can intensify the effects of radiation with orthovoltage therapy, although it rarely causes problems. Blood and urine should also be evaluated. Bone marrow biopsy may also be helpful.

Multimodal therapy is frequently more effective than relying on a single treatment method, and likewise drug cocktails can be more effective, and reduce side-effects. As well as surgery, radiation, chemotherapy, immunotherapy, cryotherapy and hyperthermia may be recommended. Even if it is not possible to remove the whole tumor, debulking it makes it easier to attack with other therapies. However, disrupting the blood supply of the remaining tumor may make it less sensitive to other forms of treatment. Although it delays surgery, preoperative radiation may shrink the tumor, so that surgical excision will not need to be as extensive.

Lymphoma in dogs generally affects many if not all the lymph nodes. However, more than 80% of cases go into remission, with around a third of these living two or three years on maintenance therapy. Spayed females live longer than intact bitches. The choice of chemotherapeutic agents is very important to the outcome for this disease. Treating with corticosteroids (e.g., prednisone) prior to diagnosis can destroy cancer cells, so that the extent of the disease is not fully appreciated. More seriously, they can select for resistant cells bearing the multiple drug resistance gene which are immune to the effects of several chemically unrelated cancer drugs - doxorubicin, vincristine, actinomycin 1. All of these drugs can induce resistance, and ultimately decrease overall survival time, although improving the dog's condition in the meantime. Treating with prednisone alone, the average prognosis is two months; with COP (Cytoxan - cyclophosphamide*; Oncovin - vincristine and prednisone) this increases to 4 to 6 months. The multidrug protocol, using Adriamycin (doxorubicin) and/or L-asparagine as well as COP increases the prognosis to 12 months with the possibility of two year's remission. To maintain remission, dogs may be given cyclophosphamide and Leukeran (chlorambucil) possibly alternating with oral vincristine. Routine lymph node inspections should be performed together with blood counts to monitor bone marrow suppression. * Cyclophosphamide can cause sterile hemorrhagic cystitis days to weeks after administration. Pretreatment with mesna can decrease the frequency and severity of the cystitis.

Sarcomas are tumors of muscle, bone and connective tissue. Soft tissue sarcomas are common. Typically they are locally invasive with potential metastasis to both regional lymph nodes and distant sites. They frequently recur after surgical excision, due to the presence of neoplastic cells left in the pseudocapsule after surgery. Microscopically the cancer extends along tissue planes away from the original site. In dogs radiation therapy after surgical excision results in local control rates of 67 - 95% at one year. (In one study the four year local control rate was 86% for a condition which has historically been given a very poor prognosis.) Best success is seen if radiation therapy is started two to three weeks after surgery rather than waiting to see if the tumor recurs. Some centers use intraoperative radiation therapy with chemotherapy implant enhancement, using cisplatin or carboplatin, to attack these tumors even more aggressively. Postoperative radiation therapy may also be augmented with chemotherapy using mitoxantrone, doxorubicin or carboplatin.

Osteosarcoma is diagnosed with X-rays of the leg. It is best treated with limb amputation and postoperative chemotherapy with carboplatin . (This is more expensive but does not destroy the kidneys or produce as many gastrointestinal side-effects as cisplatin which used to be the drug of choice.) Average prognosis is 12 months. If the lesion is small and towards the end of the leg local excision (limb sparing surgery) may be attempted. However, the prognosis is generally poor, with high infection and recurrence rates.

Transitional cell carcinoma of the bladder may spread to the urethra and prostate. Diagnosis is usually delayed because the signs initially mimic cystitis, and by the time it is diagnosed the cancer has usually spread over such large areas surgery is not possible. Any case of blood in the urine should be actively pursued. Chemotherapy with mitoxantrone, Feldene (piroxicam) and Pepcid (famotidine) produces a response in 50% of cases, reducing painful and bloody urination for periods of 4 - 12 months.

Breast cancer is common in dogs. Provided it has not spread to the lungs most veterinarians prefer to conservatively remove the affected mammary gland. Some however prefer to remove the whole chain either along one or both sides. While there is evidence that this is necessary in cats it has not been proven in dogs, although in many instances the cancer will appear in other mammary glands it usually does so randomly. Mitoxantrone is the preferred chemotherapeutic agent for the treatment of mammary cancer.

Mast cells are connective tissue cells which contain histamine and heparin (an anticoagulant) which are important in the body's response to injury and infection. Mast cell tumors are potentially vicious tumors no matter what the grading particularly when located in mucous membranes, groin, mammary tissue or urogenital region. Tumors on the legs have a better prognosis than those on the body. Wide deep surgical excision that does not perturb or touch the tentacles of the tumor may be curative, but any grade II or II tumor should also be treated with postsurgical chemotherapy (prednisone and Vinblastine) and or radiation therapy. If the tumor is staged local, well differentiated and postoperative radiation therapy is also given tumor free survival rates of two to five years of up to 94% have been reported. For intermediate grade tumors the figure drops to 50 to 75%. With surgery alone, recurrence rates six months after surgery range from 25 to 76% depending on the histological grade of the tumor. Radiation therapy is useful for treating draining lymph nodes as well as the tumor site, but if more extensive lymphatic involvement has occurred chemotherapy is recommended. Poorly differentiated tumors carry a very poor prognosis with a high risk of recurrence. Radiation may be helpful to debulk the tumor and make the patient more comfortable.

Many oral tumors may be treated by removal of all or part of the upper or lower jaw followed by chemotherapy with mitoxantrone or carboplatin. Median survival for dogs after removal of the mandible (lower jaw) was 9 months for malignant melanoma; 19 - 25 months for squamous cell carcinoma; 10 - 12 months for fibrosarcoma; 5 -13 months for osteosarcoma and a complete cure for epulides. Dogs with squamous cell carcinoma of the tongue may survive for long periods if the tip, up to one third of the length, is removed. However, owners may have to hand feed some of these animals depending upon the extent of the surgery. This is often unpleasant for both owner and pet.

Nasal tumors result in high morbidity. Prognosis is improved if they are discovered early and treated aggressively with radiation therapy. Without treatment average survival is 5 - 7 months. Even when treated less than 50% survive for a year, and cataracts result from treatment.

It is difficult to write about cancer because treatments seem to change from day to day. It is not one disease, and there are multiple causes, it should therefore come as no surprise that different cancers carry different prognoses. We are fortunate in New England to have available the state-of-the-art radiation center at Tufts University School of Veterinary Medicine. When we hear the word cancer however, we run the risk of shutting down our minds and not exploring the options available. Always ask about alternatives, even if they aren't available at your veterinarian's or in your area. If side-effects are mentioned, ask about ways to avoid or at least minimize them. Be sure to make thorough enquiries as to the prognosis with all forms of treatment and the quality of life associated with each. Prognosis can only be an average though, some dogs will live longer and some shorter periods. On the whole Beardies are stoic dogs. They will tolerate a lot of pain we are probably unaware of. The best thing we can do for our pets with cancer, or any other disease, is to open ourselves to what they are telling us. If they aren't having fun, and the prognosis is for more of the same or worse, we have the ultimate gift of love which we can extend to them. We can let them go, and take away their pain.

A grateful thank you to Linda Aronson, DVM for the use of this valuable article.