2007 AKC CHF ANNUAL CONFERENCE
DISPELLING MYTHS OF CANINE CANCER AND ITS TREATMENT
Dr. Douglas Thamm, Colorado State
Cancer is the leading cause of death in dogs. About half of all dogs will have some sort of tumor in their life. It seems to be more frequent now that in the past because dogs are living longer and it is being better diagnosed.
Q & A:
Did I cause it? People tend to blame themselves for exposing the dog to toxins or bad food, but based on current knowledge, lawn chemicals, food additives, pesticides, cosmic rays, etc do not significantly increase dog's chance for cancer, with a couple of fairly rare exceptions: canine lymphoma and certain herbicides or living in an urban environment; mesothelioma and asbestos; nasal tumors and second hand smoke in dolichocephalic breeds---like salukis).
Should I treat it? Usually, yes.
Can we just wait and see? Whether waiting to see if it grows, grows back, or spreads, this is a bad idea. Larger tumor size is related to worse outcome for several important cancers such as mammary carcinoma and oral melanoma. Locally recurring tumors are associated with a worse prognosis in certain cancers such as oral melanoma and mast cell tumor. For example, median survival after first time mast cell removal is 1696 days, but for a recurrent tumor is 245 days. If a tumor is incompletely removed, the time to get aggressive is now. And when waiting to see if it spreads, asking drugs to kill a big visible tumor is asking a lot more than asking them to kill microscopic tumor cells. For example, median survival time for dogs with osteosarcoma undergoing amputation but delaying chemotherapy until metastasis is about 6 months; if they get chemotherapy immediately after amputation it's 12 months.
Will performing a fine needle aspirate or a biopsy aggravate or spread it? No - getting from the primary tumor into the bloodstream is but one of many steps needed to spread it, and besides, it's probably already there. There are some exceptions, though. Aspiration or biopsy of splenic or bladder masses is inadvisable because there is a risk of local tumor dissemination or seeding of the biopsy tract. When getting an aspirate or biopsy of a cutaneous or subcutaneous mass, the biopsy tract should be included as part of the excised area in surgery to prevent recurrence along the tract.
Why bother with a biopsy or aspirate before surgery? This helps with the diagnosis and with planning the surgery.
Why pay for histopathology if it's been removed? If it's worth surgery, it's worth microscopic examination. This allows additional treatment to begin, rather than waiting and seeing if the tumor recurs. Also, don't send in a representative section. The whole tumor must be submitted so they can see the surgical margins and know if the whole thing was removed. If not, a subsequent surgery should be planned. Again, do not wait and see. A difference in clean versus dirty margins in one cancer is 54 versus 11 months.
Does chemo make dogs feel sick? Dogs get the same drugs that humans get, but at lower doses. Less than Â? of dogs have unpleasant side effects, and 5% or less have severe side effects from chemo. Reducing doses or changing or adding drugs can reduce side effects 90% of the time.
What kind of side effects? Usually gastrointestinal - mild nausea, decreased appetite, vomiting, loose stool for 3-5 days. Some dogs may have a lowered white blood cell count.
Will the dog go bald? Most breeds have little noticeable hair loss but may seem to shed more. Non-shedding breeds will often have significant hair loss, but seldom go completely bald. It grows back.
Will the dog have to be hospitalized, or treated for months on end? Most is done on an outpatient basis, usually involving simple injections (although some require longer infusions). Most protocols involve a series of treatments followed by a period of observation.
Will the dog contaminate other family members with the chemo? No, although you shold wear gloves when handling that dog's urine or feces in the 72 hours after treatment. You should also wear gloves when handling the oral chemo medications.
How old is too old for a dog to be treated? Age is not really a consideration, but overall health is.
Is treatment an "either/or" thing? Give chemo or put him to sleep? In many cases there is a range of treatments with different costs, side-effects, trips to the vet, and effectiveness.
Examples are lymphosarcoma and osteosarcoma:
For lympho, options range from prednisone alone; prednisone plus doxyrubicin; cyclophosphamide/vincristine/prednisone; or a mult-agent injectable such as the UW-Madison protocol. For osteo, amputation plus platinum based chemo may be optimal, but other options include palliative radiation therapy or amputation plus doxyrubicin.
What about radiation therapy? Radiation is very useful for certain tumors such as those with a high likelihood of local spread and low likelihood of metastasis. Each treatment session requires a brief anesthesia to keep the dog still. Some treatment may require 10-25 fractions either Monday through Friday or three days a week until completed. Others may just require 1-6 fractions. The dog may develop a sunburned-like area, or worse, on the site. He will not be radioactive. Not cheap: a full-course treatment of 19 fractions costs $4000.00-$7000.00, but a partial course can also be helpful.
How do you know what to do? Besides asking your own veterinarian or an internal medicine specialist or oncologist, you can call the Colorado State consult line for free at 970-297-4195, or go to www.csuanimalcancercenter.org
Cancer is the leading cause of death in dogs. About half of all dogs will have some sort of tumor in their life. It seems to be more frequent now that in the past because dogs are living longer and it is being better diagnosed.
Q & A:
Did I cause it? People tend to blame themselves for exposing the dog to toxins or bad food, but based on current knowledge, lawn chemicals, food additives, pesticides, cosmic rays, etc do not significantly increase dog's chance for cancer, with a couple of fairly rare exceptions: canine lymphoma and certain herbicides or living in an urban environment; mesothelioma and asbestos; nasal tumors and second hand smoke in dolichocephalic breeds---like salukis).
Should I treat it? Usually, yes.
Can we just wait and see? Whether waiting to see if it grows, grows back, or spreads, this is a bad idea. Larger tumor size is related to worse outcome for several important cancers such as mammary carcinoma and oral melanoma. Locally recurring tumors are associated with a worse prognosis in certain cancers such as oral melanoma and mast cell tumor. For example, median survival after first time mast cell removal is 1696 days, but for a recurrent tumor is 245 days. If a tumor is incompletely removed, the time to get aggressive is now. And when waiting to see if it spreads, asking drugs to kill a big visible tumor is asking a lot more than asking them to kill microscopic tumor cells. For example, median survival time for dogs with osteosarcoma undergoing amputation but delaying chemotherapy until metastasis is about 6 months; if they get chemotherapy immediately after amputation it's 12 months.
Will performing a fine needle aspirate or a biopsy aggravate or spread it? No - getting from the primary tumor into the bloodstream is but one of many steps needed to spread it, and besides, it's probably already there. There are some exceptions, though. Aspiration or biopsy of splenic or bladder masses is inadvisable because there is a risk of local tumor dissemination or seeding of the biopsy tract. When getting an aspirate or biopsy of a cutaneous or subcutaneous mass, the biopsy tract should be included as part of the excised area in surgery to prevent recurrence along the tract.
Why bother with a biopsy or aspirate before surgery? This helps with the diagnosis and with planning the surgery.
Why pay for histopathology if it's been removed? If it's worth surgery, it's worth microscopic examination. This allows additional treatment to begin, rather than waiting and seeing if the tumor recurs. Also, don't send in a representative section. The whole tumor must be submitted so they can see the surgical margins and know if the whole thing was removed. If not, a subsequent surgery should be planned. Again, do not wait and see. A difference in clean versus dirty margins in one cancer is 54 versus 11 months.
Does chemo make dogs feel sick? Dogs get the same drugs that humans get, but at lower doses. Less than Â? of dogs have unpleasant side effects, and 5% or less have severe side effects from chemo. Reducing doses or changing or adding drugs can reduce side effects 90% of the time.
What kind of side effects? Usually gastrointestinal - mild nausea, decreased appetite, vomiting, loose stool for 3-5 days. Some dogs may have a lowered white blood cell count.
Will the dog go bald? Most breeds have little noticeable hair loss but may seem to shed more. Non-shedding breeds will often have significant hair loss, but seldom go completely bald. It grows back.
Will the dog have to be hospitalized, or treated for months on end? Most is done on an outpatient basis, usually involving simple injections (although some require longer infusions). Most protocols involve a series of treatments followed by a period of observation.
Will the dog contaminate other family members with the chemo? No, although you shold wear gloves when handling that dog's urine or feces in the 72 hours after treatment. You should also wear gloves when handling the oral chemo medications.
How old is too old for a dog to be treated? Age is not really a consideration, but overall health is.
Is treatment an "either/or" thing? Give chemo or put him to sleep? In many cases there is a range of treatments with different costs, side-effects, trips to the vet, and effectiveness.
Examples are lymphosarcoma and osteosarcoma:
For lympho, options range from prednisone alone; prednisone plus doxyrubicin; cyclophosphamide/vincristine/prednisone; or a mult-agent injectable such as the UW-Madison protocol. For osteo, amputation plus platinum based chemo may be optimal, but other options include palliative radiation therapy or amputation plus doxyrubicin.
What about radiation therapy? Radiation is very useful for certain tumors such as those with a high likelihood of local spread and low likelihood of metastasis. Each treatment session requires a brief anesthesia to keep the dog still. Some treatment may require 10-25 fractions either Monday through Friday or three days a week until completed. Others may just require 1-6 fractions. The dog may develop a sunburned-like area, or worse, on the site. He will not be radioactive. Not cheap: a full-course treatment of 19 fractions costs $4000.00-$7000.00, but a partial course can also be helpful.
How do you know what to do? Besides asking your own veterinarian or an internal medicine specialist or oncologist, you can call the Colorado State consult line for free at 970-297-4195, or go to www.csuanimalcancercenter.org