Bone Cancer

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Article Written by Dr. Daniel A. Degner, Board-certified Veterinary Surgeon (DACVS)

Key Points

Osteosarcoma, which is the most common tumor type, is highly malignant

Amputation for a highly malignant cancer such as osteosarcoma is the treatment of choice for most cases, but is largely palliative

Chemotherapy is needed to extend life of the patient in many cases

One study that evaluated owner satisfaction showed that nearly all owners were very pleased with their pet's quality of life following limb amputation


multiple myelomaIntroduction

  • Bone cancer is common in dogs. Like humans, many types of bone cancer exist in dogs and cats. In fact, 10,000 new cases of bone cancer are diagnosed in dogs each year
  • There are two basic groups: primary, which originate from the bone and metastatic which originate from a cancer located in another part of the body, but have migrated to the bone.
  • Metastatic bone tumors may not be treated if extensive tumor involvement is present elsewhere in the body (see photo right - this is a case of multiple myeloma)
  • Primary bone tumors in dogs and cats usually comprise of osteosarcoma, chondrosarcoma, and fibrosarcoma. The different tumor types behave differently and the behavior may be dependant on the grade of tumor.
    • Osteosarcoma, which is the most common tumor type is highly malignant and about 95% of the dogs have metastatic disease (spread of this tumor) at the time of diagnosis. Most dogs that have Osteosarcoma will die from the metastasis of tumor to the lungs or other bones. Amputation of the limb will ameliorate the pain, but does not extend the life of the patient unless chemotherapy is also given. Osteosarcoma in the cat can potentially be cured with amputation of the limb alone, as the metastatic potential of the tumor in this species is much lower.
    • Chondrosarcomas generally have a less aggressive tendency to spread than osteosarcomas.
    • Fibrosarcomas generally are locally invasive and have a low tendency to spread unless the tumor is high grade.
    • Another type of tumor which causes bone destruction is the synovial cell carcinoma. Grade 1 and 2 synovial cell sarcomas have a good prognosis and are potentially curable, however grade 3 synovial cell sarcomas usually result in death of the patient within a couple of months.  Right is an example of a hock joint that has been destroyed by a synovial cell sarcoma.

 

 

 

Signs of bone cancer

  • The first clinical sign of a bone tumor is usually lameness of the affected limb. Initially the lameness may be subtle, but then becomes progressively worse. Anti-inflammatory medication generally does not resolve the lameness. Some dogs develop acute nonweight-bearing lameness which is caused by bone fracture due to weakening of the bone structure by the tumor.
  • A swelling may also be noticed over the bone, but this is not always a consistent finding in the early stages.
  • As time passes on the dog may develop loss of appetite and significant weight-loss. These findings may be due to factors released by the tumor or due to pain caused by the tumor.
  • Bone cancer is very painful….just ask a human who has had it. Because this is a very painful tumor in dogs, surgery is usually recommended.

 

Diagnostic testing prior to surgery

  • Before bone cancer is treated a diagnostic work-up should be completed.
    • Chest x-rays are taken to ensure that there is no evidence of spread of cancer to the lungs.
    • X-rays of the affected limb are always taken. If your pet has been traveling in the southern United States there is a possibility that the abnormal appearance of the bone is not due to cancer, rather a fungal infection. In this situation the dog would be treated with medications.  Note the large expansile tumor in the mid part of the radius bone (Fig 1), which is evidence of a bone tumor; in this case it was a neurofibrosarcoma, which is a less common tumor type affecting the bone.
    • Other diagnostics run include a complete blood cell count, chemistry profile to check the function of internal organs, and sometimes a urinalysis.
    • Ultrasound of the heart is done if Adriamycin is chosen as the chemotherapeutic agent, as this medication is contraindicated for dogs that have heart muscle disease called cardiomyopathy.
    • Nuclear scintigraphy or PET scan can be used to help rule out macroscopic spread of bone cancer.
  • If the appearance of the bone is not classic for a primary bone cancer, a biopsy to confirm this is generally done. Your pet would be anesthetized for this procedure and multiple small samples of the bone are collected and submitted for analysis by a pathologist. Bone biopsy is 90% accurate at arriving at a diagnosis, therefore 10% of the time the diagnosis of cancer will be missed when it really is present.
  • If the hind limb of your pet is going to be removed and your pet has had signs of stiffness of the hind limbs in the past due to hip problems, x-rays of the pelvis are generally taken to rule out other diseases.  Arthritis that is not causing significant functional impairment of ambulation is not a contraindication to amputation.

 

AmputeeSurgical treatment of bone cancer

  • Amputation for a highly malignant cancer such as osteosarcoma is the treatment of choice for most cases, but is largely palliative. That is, amputation is done to remove the pain that the pet is experiencing. In this situation it generally does not increase the length of survival of the patient. Chemotherapy is needed to extend life of the patient. Amputation for the less aggressive bone tumors should cure the patient of cancer. The dog in Fig 2 had an amputation one day prior to this photo and can already walk relatively well.
  • If your pet has bone cancer of the lower part of the radius bone, a limb sparing procedure can be done as an alternative to amputation.  The cancerous portion of bone is removed and replaced with a living bone graft.  Very good function of the limb is expected after the bone graft heals in place (2 to 3 months).
  • If you elect to not have the limb amputated and chemotherapy done, a couple of large doses of radiation can be administered to the site to decrease the pain. If no treatment is going to be administered to a pet that has bone cancer and the pet is in pain, euthanasia is recommended.

Palliative treatment of bone cancer

  • Palliative treatment is a means of making the pet more comfortable during the last phase of their life. This is utilized if the owners elect to not have surgery performed. In addition, if the patient already has spread of the cancer to other areas in the body, amputation of the limb may not be elected.
  • Palliative radiation therapy involves about 4 to 6 treatments (number of treatments may vary depending on the oncologists preference). This treatment will not eliminate the tumor rather, it reduces the pain in the bone by reducing tumor associated inflammation.
  • Bisphosphonates can reduce bone tumor-associated pain by strengthening the weakened bone. This medication inhibits the osteoclasts within the bone from dissolving the bone. Some dogs will have a dramatic improvement in clinical lameness with this treatment.
  • Analgesics such as narcotics (tramadol and codeine) and nonsteroidal anti-inflammatories (Rimadyl, Deramaxx, Piroxicam, Metacam, Previcox and others)

After care and convalescence

  • After surgery has been completed intensive care must be provided for the best chance for a successful outcome. Intravenous fluids may be continued over night to minimize dehydration.
  • Pain control after an amputation is very important in the postop period. Generally we place an epidural catheter or incisional catheter through which medication is administered to relieve pain. A pain patch can also be applied to the skin. The medication from the patch will slowly be absorbed into the body. Pain control from the patch will last about 3 days.
  • Medications at home:
    • If your pet has an incisional catheter or epidural catheter, medication will need to be administered by you for about 2 days via this port.
    • An oral nonsteroidal anti-inflammatory is prescribed for a period of 10 days to relieve inflammation related pain
    • Tramadol (narcotic) blocks pain perception at the level of the brain. Initially this medication is given four times daily for four days, then twice daily for one month.
    • Gabapentin is prescribed for one month after surgery. The gabapentin blocks amplification of pain at the level of the spinal cord
    • Occasionally a patient will experience phantom pain after amputation. For this reason, the tramadol and gabapentin are continued for one month after surgery
  • A bandage may be used to cover the incision for a day or two. The bandage should be kept clean, but should be changed if we feel that is needed.
  • Pets are usually hospitalized for 1 to 2 days following amputation and limb spare surgery
  • In general your pet will learn to walk with three limbs within a day or two. Older dogs may take a bit longer to learn to adapt to having three limbs. By 10 days after surgery these older pet also adjust to being able to walk well.

 

Chemotherapy

  • Chemotherapy is usually started 2 weeks after surgery by an oncologist.
  • In general chemotherapy is given every 2 to 3 weeks for a total of 5 or 6 treatments.
  • Adriamycin may be used as a sole agent, or alternating cycles of adriamycin and carboplatin may be used.
  • The oncologist may elect to choose a protocol that is different from the standard one if there is a need for this.
  • During chemotherapy blood work and potentially heart ultrasounds may be done to make sure that your pet is not having any side effects of the medication.
  • Side effects of the chemotherapy may include nausea, vomiting, loss of appetite, and infrequently heart problems if Adriamycin is used. Infections due to a low white blood cell count may also be a problem. Fortunately, side effects associated with chemo are not very common and if they occur are usually transient. Loss of hair (balding) generally is not seen in dogs. Breeds of dogs that have continually growing hair (example: poodle) may have transient thinning of the hair coat.
  • X-rays of the chest will be taken by the oncologist every 3 months to check for evidence of spread of cancer.

 

Potential complications

  • As with any surgery, complications may arise. Even though rare, anesthetic death can occur. With the use of modern anesthetic protocols and extensive monitoring devices (blood pressure, EKG, pulse oximetry, inspiratory and expiratory carbon dioxide levels, and respiration rate), the risk of problems with anesthesia is minimal.
  • Infection is also an unusual complication as strict sterile technique is used during the surgery and antibiotics are administered during the surgery.
  • Seroma formation can occur as there may be an empty space between the tissues. This problem will resolve with time. Occasionally the seroma or fluid that has build up may require draining. In cases in which seroma formation is expected a drain may be placed at the time of surgery.
  • Recurrence of cancer is not common at the surgery site, but this can also occur. More commonly the cancer spreads to another site such as the lungs or other bones. Signs of recurrence of cancer may include difficulty breathing, coughing, loss of appetite, weight-loss, and pain of the bones (which may present as lameness).

 

Owner satisfaction with amputation

  • One study that evaluated owner satisfaction showed that nearly all owners were very pleased with their pet's quality of life following limb amputation.
  • Most dogs are able to run and play again.

Prognosis

  • Osteosarcoma
    • treatment with amputation alone - survival time of 3 to 5 months
    • amputation and chemotherapy - survival for about 1 year; occasionally we have seen dogs live 3 to 4 years following treatment
  • Chondrosarcoma and fibroscaroma
    • amputation can be potentially curative without chemotherapy
  • Synovial cell sarcoma
    • grade 1 and 2 tumors - frequently are cured with amputation alone
    • grade 3 tumors - regardless of treatment these patients usually die within a few months; median survival time has been reported to be 7 months

Frequently Asked Questions After Surgery

When should my dog have the first bowel movement after surgery?

  • Many dogs will not have a bowel movement for the first 4 to 5 days after surgery
  • Reasons that a dog will not have regular bowel movements after surgery include:
    • The dog has been fasted prior to surgery
    • Dogs do not eat well during the hospital stay
    • They frequently do not eat well when they go home
    • They are fed highly digestible food that produces little stool
    • Pain medication that contain narcotics (such as morphine, fentanyl patches, and tramadol) can be constipating
  • If a pet does not have a bowel movement on the 5th day of being home, a stool softener such as metamucil can be fed
    • Dose of metamucil is 1 tsp per 25 Kg mixed in with each meal (canned dog food); feed immediately after mixing, as the metamucil will gel the food and may make it less palatable

My pet had surgery and will not eat.  What can be done?

  • Dogs
    • Most pets will not eat their regular dog food after surgery, especially if it is kibble.
    • Offer a cooked diet having a 1:1 ratio of a protein source and carbohydrate source.  The protein source can be any meat (example: chicken breast, turkey breast, lean hamburger) that is low in fat and should be cooked (drain off all fat after the meat has been cooked).   The carbohydrate can be pasta, potato or white rice.
    • Try canned dog food; to enhance the flavor sprinkle a very small amount of garlic powder or chicken or beef broth (Chicken-in-a- MugTM or Beef-in-a-MugTM products)
    • Try Gerber strained meats for babies such as the chicken, beef, turkey, or veal
    • Try Hill's A/D diet available at most veterinary hospitals
    • Hand feeding: place a small amount of food in the mouth so that your dog gets the flavor
    • Warm the food slightly in a microwave, as the food will be more aromatic; stir the food before feeding and test the temperature on the bottom side of your wrist; it should only be luke warm.
    • Remember that most pets will not eat the first day or two after they get home from surgery
  • Cats
    • Offer smelly foods that contain fish such as tuna or smelly cat foods
    • Try Gerber strained meats for babies such as the chicken, beef, turkey or veal
    • Hand feeding:  with your finger place a small amount of food on the roof of your cat's mouth; use a syringe to get soft food into the mouth
    • Warm the food slightly in a microwave as the food will be more aromatic; remember to stir the food before feeding and test the temperature; it should be only luke-warm
    • Some cats will only eat dry food, try kibble if your cat normally has been fed that food
    • Petting and stroking your cat frequently will help to stimulate appetite
    • Remember that most pets will not eat the first day or two after they get home from surgery
    • Appetite stimulants such as cyproheptadine may be helpful
    • If your cat refuses to eat anything for 7 days a stomach tube or nasogastric tube should be placed to provide nutrition so that a serious liver problem (hepatic lipidosis) does not develop

My pet is vomiting.  What can be done?

  • The first thing for you to discern is whether your pet is vomiting or regurgitating.  Both will result in fluid or food being brought up.  Vomiting always will have heaving or retching of the abdomen prior to expulsion of the vomitus.  Regurgitation is not associated with heaving and the pet usually just opens the mouth and fluid or food will be expelled.  Usually the regurgited material will be clear or brown colored fluid. 
  • Next is to identify the cause of the vomiting or regurgitation.
  • Causes and treatment of vomiting after surgery
    • When some pets return home after a stay in the hospital they may drink excessive amounts of water at one time and then vomit; if this appears to be the case, the water should be limited to frequent smaller amounts.
    • Medications such as antibiotics, narcotics or nonsteroidal anti-inflammatory medication commonly cause vomiting after surgery.  In order to see which medication is causing the problem, the administration of each drug should be separated 2 hours apart.  Usually the pet will vomit or appear nauseated (drooling and sick look) within 1 hour of administration of the medication that they are sensitive to.  The antibiotic in some cases may be changed to a different one, or may be discontinued. 
    • Stomach upset from anesthesia is a potential cause of vomiting and will pass within a couple of days. 
    • An uncommon cause of vomiting after surgery is internal organ failure.  Blood testing will confirm this problem. For this reason vomiting should not be ignored if it persists for more than 24 hours.
    • If your pet had surgery of the bowels or stomach, vomiting is always a concern, as it may indicate that infection of the abdominal cavity, called peritonitis, is present.  Do not ignore this sign.
    • Symptomatic treatment of vomiting involves withholding food for 12 to 24 hours, then introducing small amounts of bland food such as rice and lean cooked hamburger, if your pet does not vomit after that then gradually wean him/her back onto the regular diet after 3 days.  In order to decrease the acidity of the stomach, Pepcid AC 0.5 mg/kg can be given by mouth twice daily for 5 days.  Metoclopramide and Cerenia are good anti-vomiting medications for dogs and cats.  You should always consult a veterinary healthcare professional before administering medication.
  • Causes and treatment of regurgitation after surgery
    • The most common cause of regurgitation is reflux of acid from the stomach into the esophagus while your pet is under anesthesia.  Acidic fluid from the stomach can cause a chemical burn of the esophagus and result in a bad case of heart burn, called esophagitis.  This results in poor motility of the esophagus, therefore water and food will accumulate in this structure.  In most cases, esphagitis is self-eliminating and will resolve within two or three days. 
    • If the esophagitis is severe the esophagus may develop one or more strictures.  A stricture is a narrowing or stenosis of the esophagus and does not allow passage of food down the esophagus, in regurgitation that lasts longer than one week.  This problem should be brought to the attention of your pet's doctor within the first two weeks so that it can be treated by ballooning the stricture (minimally invasive procedure, as it is done with the aide of an endoscope).  If an esophageal stricture is chronic surgery is needed.
    • Symptomatic treatment of regurgitation caused by esophagitis includes feeding bland food, and administering a coating agent (sucralfate) and an acid blocker (omeprazole or other).  Consult a veterinary health care professional if the regurgitation continues for more than a couple of days.

How do I know that my dog is in pain following surgery?

  • Signs of pain include
    • crying
    • biting if you get near the surgical site
    • grimacing (lips are pulled back and the the dog looks anxious)
    • tragic facial expression
    • panting
    • restlessness and unable to sleep; pacing
    • if abdominal surgery was done the pet will not lie down on the incision, or will continually sit up in spite of appearing very tired
    • the worst pain will be for the first 2 to 3 days after surgery

What can I do to control my dog's pain?

  • Narcotic medications that control pain: tramadol, butorphanol, Duragesic (fentanyl patch)
  • Anti-inflammatories used to control pain: Deramaxx, Rimadyl, Previcox, or Etogesic
  • If an orthopedic surgery has been done cold packing the surgical site may be helpful
    • A cold pack may be a pack of frozen peas, crushed ice in a Ziploc bag, or a cold gel pack; place a thin barrier between the skin and the cold pack.  An alternative to a cold pack is to freeze water in a styrofoam cup; after frozen cut the bottom of the styrofoam cup out. Cool the surgical site around the incision by rubbing the exposed ice directly on the skin in a circular pattern.  Cooling the surgical site helps to numb the area.

How do I know that my cat is in pain following surgery?

  • Pain is more difficult to assess in cats versus dogs, as signs can be more subtle and they usually do not vocalize when in pain
  • Signs of pain in a cat include the following:
    • biting if you get near the surgical site
    • growling or deep cry
    • not wanting to eat
    • hiding and not wanting to be near owner (remember that this could also be caused by the cat just being upset about leaving home and coming back)

What can be done for pain at home for my cat?

  • Pain medication such as buprenorphine or a Duragesic (fentanyl) patch
  • Tylenol will kill a cat as they lack abundant glutathione enzyme in the liver
  • Anti-inflammatories can be used, but the dose is much less than dogs

Is it okay for my pet to lick the incision?

  • If a dog licks the incision, the healing process may be delayed.
  • Licking can remove stitches and cause the incision to open
  • Licking can become a severe habit that is difficult to break
  • Licking can cause infection as the mouth has many bacteria
  • Dogs will frequently lick the incision when the owner is not watching such as at night time; if the skin looks red or excoriated the most common cause is from licking.
  • To stop your pet from licking the following can be tried:
    • Elizabethan collar can be placed on the neck; this will not help stop your pet from scratching at the region
    • Cervical collar (bite not collar) is a less awkward device and can be effective at stopping a pet from licking the surgical site
    • A tee shirt can be used to cover an incision on the chest or front part of the abdomen; gather the waist of the shirt up over the dog's back and wrap an elastic band around this part of the shirt.
    • A bandage or sock can be used to cover an incision on a limb; fasten the top of the sock to the dog's limb with tape.
    • Bitter apple can be applied around the incision; many dogs will continue to lick  after application of this topical
    • Bitter Apple and Liquid HeetTM (obtain this from a drugstore...it is used for sore muscles) mixed in a 2:1 ratio can be applied around the skin incision
    • Antipsychotic medication in some cases is needed

Board-certification by the American College of Veterinary Surgeons

What does it mean?

  • Four years of advanced training in surgery beyond the Doctor of Veterinary Medicine Degree

  • Experience in the development of new surgical treatments

  • Rigorous examination by the American College of Veterinary Surgeons to ensure competency in advanced surgical techniques

  • Assurance that a veterinarian is a surgical specialist

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