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
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
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.