Osteosarcoma

Osteosarcoma – An Overview

  • Most common primary bone tumor in dogs
  • “Appendicular” is an adjective relating to the limbs; “axial” is an adjective relating to the head and trunk of the body
  • Osteosarcoma typically affects the appendicular skeleton of large- to giant-breed dogs; may be seen in the axial skeleton (composed of skull, spine, ribs, and sternum)
  • Cancerous (malignant) tumor, with spread to the lungs (known as “lung metastases”) in more than 90% of dogs at the time of diagnosis; lung metastases may be microscopic
  • Osteosarcoma may spread to soft tissues, such as the skin, kidney, and liver
  • Osteosarcoma accounts for up to 85% of primary bone tumors in dogs

Genetics

  • Appears to be inherited in giant breeds, such as Scottish deerhounds and Irish wolfhounds
  • Increased likelihood of developing osteosarcoma does occur in some breeds
  • Breed size and rate of maturity may be more important than breed or family line

Signalment/Description of Pet

Breed Predilections

  • large- to giant-breed dogs

Mean Age and Range

  • bimodal peak at 2 years and 7 years; reported as young as 6 months of age.

Predominant Sex

  • no strong indication that a particular sex is more likely to develop osteosarcoma than the other sex

Signs/Observed Changes in Pet

  • Depend on site
  • Signs may be subtle
  • Appendicular skeleton (limbs)—welling, lameness, and pain common
  • Axial skeleton (skull, spine, ribs, sternum)—localized swelling, detectable mass, pain
  • Other complaints—lack of appetite (inappetence) and sluggishness (lethargy)
  • A firm, painful swelling of the affected site common
  • Degree of lameness—varies from mild to non–weight-bearing
  • Buildup of fluid (known as “edema”) around affected area
  • Fractures occurring at the site of weakened bone (known as “pathologic fractures”) are rare

Causes

  • Unknown

Risk Factors

  • Dogs—large- to giant-breed dogs; metallic implants at fracture-repair sites; history of exposure to ionizing radiation
  • Early spay/neuter

Treatment

Health Care

  • Diagnostic evaluation—outpatient
  • Surgery and the first chemotherapy treatment—inpatient
  • Subsequent chemotherapy—outpatient
  • Manage pain, as needed
  • Radiation therapy will decrease pain effectively in dogs

Activity

  • Restricted after surgery, until adequate healing has occurred

Diet

  • Dietary management is not required
  • Weight lost may benefit amputees in general

Surgery

Appendicular Sites (Relating to the Limbs)

  • Amputation of affected limb—limb amputated at the forequarter (including the scapula and shoulder joint) or hip
  • Limb-sparing or salvage therapy—used for osteosarcoma of the distal radius (bone in the lower front leg); available at a limited number of referral hospitals
  • Chemotherapy—recommended after either surgical procedure

Axial Sites (Relating to the Head and Trunk of the Body)

  • Amputation of affected limb—limb amputated at the forequarter (including the scapula and shoulder joint) or hip
  • Limb-sparing or salvage therapy—used for osteosarcoma of the distal radius (bone in the lower front leg); available at a limited number of referral hospitals
  • Chemotherapy—recommended after either surgical procedure

Soft Tissue Sites (Tissues Other than Bone)

  • Amputation of affected limb—limb amputated at the forequarter (including the scapula and shoulder joint) or hip
  • Limb-sparing or salvage therapy—used for osteosarcoma of the distal radius (bone in the lower front leg); available at a limited number of referral hospitals
  • Chemotherapy—recommended after either surgical procedure

Metastasectomy (Surgical Removal of Metastasis)

  • Surgical removal of metastasis to the lungs (known as “pulmonary metastasectomy”)—has been described; indicated in dogs that: (1) had a long disease-free interval (over 300 days) after diagnosis; (2) have only 1–2 detectable lung nodules based on computed tomography scan (CT scan)
  • Inoperable cancer—radiation therapy to control signs and improve the pet’s condition, but not to cure (known as “palliative intent”)
  • Pain management with medications such as nonsteroidal anti-inflammatory drugs (NSAIDs), opiods, or bisphosphonates may improve quality of life and thus prolong survival

Medications

Medications presented in this section are intended to provide general information about possible treatment. The treatment for a particular condition may evolve as medical advances are made; therefore, the medications should not be considered as all inclusive

  • Post-surgical chemotherapy with either platinum-based protocol (cisplatin, carboplatin), or doxorubicin is the current standard of care
  • Palliative medication is intended to improve the pet’s condition and quality of life, it is not a cure for the cancer; these drugs are used to control pain and/or decrease inflammation; options include: aspirin, piroxicam, or other nonsteroidal anti-inflammatory drugs; acetaminophen with or without codeine, tramadol or a fentanyl patch—not all of these drugs can be used in combination; always consult your pet’s veterinarian for the most appropriate pain management for your pet

Follow-Up Care

Patient Monitoring

  • Monitor for reduction of bone-marrow activity (known as “myelosuppression”), resulting in low number of red blood cells, white blood cells, and/or platelets; should have a complete blood count (CBC) performed 7–10 days after chemotherapy
  • Take chest x-rays (radiographs) every 2–3 months after surgery
  • Take x-rays (radiographs) of graft site for cases with limb-sparing or salvage therapy every 2–3 months after surgery, because local recurrence is possible after limb salvage

Possible Complications

  • Spread of cancer (metastasis) to lungs, bone, and soft tissue sites
  • Hypertrophic osteopathy (a bone disorder that causes painful swelling of bone and lameness) with spread of cancer to lungs (lung metastases)
  • Pets that undergo limb-sparing or limb-salvage procedures may develop infections, local recurrence of the cancer, or failure of the surgical implants
  • Amputees rarely show complications secondary to arthritis in the other legs

Expected Course and Prognosis

  • Prognosis is poor; achievable goals should be to relieve discomfort and prolong life
  • Median survival without treatment, with amputation alone, or with palliative radiation therapy alone—approximately 4 months
  • Median survival with surgery and chemotherapy—10 months
  • Osteosarcoma of the lower jaw (known as “mandibular osteosarcoma”)—less aggressive than other sites; 1-year median survival time with surgery alone—71% reported in one study

Key Points

  • The most common primary bone tumor in dogs
  • This disease has an aggressive biologic behavior; therapy should be directed at the painful bone tumor (using either surgery or radiation therapy) as well as at metastatic disease (using chemotherapy)
  • Prognosis is poor; achievable goals should be to relieve discomfort and prolong life
  • Cure is unlikely

Transitional Cell Carcinoma of the Urinary Tract

Transitional Cell Carcinoma of the Urinary Tract – An Overview

  • The urinary tract consists of the kidneys, the ureters (the tubes running from the kidneys to the bladder), the urinary bladder (that collects urine and stores it until the pet urinates), and the urethra (the tube from the bladder to the outside, through which urine flows out of the body)
  • Transitional cell carcinoma is a cancer arising from the transitional epithelium within the kidney, ureters, urinary bladder, urethra, prostate, or vagina; the transitional epithelium is a specialized type of lining in the urinary tract that contracts or stretches in response to the size of the bladder and other organs

Signalment/Description of Pet

Breed Predilections

  • Scottish terriers, West Highland white terriers, Shetland sheepdogs, American Eskimo dogs, and dachshunds; may occur in any breed

Mean Age and Range

  • Dogs—8 years; range, 1–15+ years of age
  • Middle-aged to old, spayed, female small-breed dogs most commonly reported

Predominant Sex

  • Female

Signs/Observed Changes in Pet

  • Similar to those of bacterial urinary tract infection or the presence of stones in the urinary tract (known as “urolithiasis”); for pets showing temporary or no response to appropriate antibiotics, consider transitional cell carcinomaRecurrent straining with slow, painful discharge of urine (known as “stranguria”); abnormal frequent passage of urine (known as “pollakiuria”); blood in the urine (known as “hematuria”); difficulty urinating (known as “dysuria”); inability to control urination or leaking urine (known as “urinary incontinence”); or any combination of these signs
  • Physical examination findings often normal
  • Mass—occasionally may be felt in the abdomen at the location of the urinary bladder
  • Urethral or vaginal transitional cell carcinoma—may be able to feel mass during rectal examination
  • Rarely enlarged intrapelvic or sublumbar lymph nodes—may be able to feel during rectal examination

Causes and Risk Factors

  • Scottish terrier; obesity; environmental carcinogens (substances that cause cancer); long-term (chronic) exposure to certain flea-control products (such as organophosphates or carbamates); and rarely, long-term treatment or a large bolus dose of cyclophosphamide (a chemotherapeutic drug)

Treatment

Health Care

  • Outpatient—stable pets; initial workup generally takes 1–2 days, so hospitalization may be more convenient
  • Seek advice from a veterinary oncologist prior to initiating treatment and consider current recommendations
  • Radiation therapy

Activity

  • Normal

Diet

  • Normal, unless pet also has kidney failure

Surgery

Appendicular Sites (Relating to the Limbs)

  • Surgery for transitional cell carcinoma can be challenging as the tumor easily sheds cancer cells; these cells can be spread into the abdomen during surgery
  • Surgery may result in a cure, if the mass can be removed completely
  • Wide surgical excision (that is, surgically removing the tumor and wide borders of apparently normal tissue) is necessary; up to 50% of the urinary bladder may be removed surgically with minimal loss of function
  • Placement of a catheter from the bladder and exiting through the abdominal wall to allow urine to be removed from the body (procedure known as “tube cystostomy”)—may greatly prolong survival times by bypassing blockage of the urethra (known as “urethral obstruction”)
  • Urethral stenting (placing a medical “tube” inside the urethra) may prolong survival by temporarily relieving blockage of the urethra, and thereby, allowing the pet to urinate

Medications

Medications presented in this section are intended to provide general information about possible treatment. The treatment for a particular condition may evolve as medical advances are made; therefore, the medications should not be considered as all inclusive

  • Chemotherapy—piroxicam (Feldene), cisplatin (dogs), mitoxantrone (as single agents or as combination therapy for certain drugs); piroxicam and cisplatin cannot be combined because of kidney toxicity; other agents (doxorubicin or doxorubicin/cyclophosphamide combination) may have activity
  • Antibiotics—administered as necessary for secondary urinary tract infections

Follow-Up Care

Patient Monitoring

  • X-rays (radiographs) using contrast media in the bladder (known as “contrast cystography”) or ultrasound examination—every 6–8 weeks; assess response to treatment and screen for spread of cancer into the lymph nodes (known as “lymph-node metastases”)
  • Chest x-rays(radiographs)—every 2–3 months; detect spread of cancer into the lungs (known as “pulmonary metastatic disease”)

Possible Complications

  • Blockage of the urethra (the tube from the bladder to the outside, through which urine flows out of the body) or ureters (the tubes running from the kidneys to the bladder), and kidney failure
  • Spread of cancer (metastasis) to regional lymph nodes, lungs, or bone
  • Recurrent urinary tract infection
  • Lack of control of urination or urine leakage (urinary incontinence)
  • Reduction of bone-marrow activity (known as “myelosuppression”), resulting in low number of red blood cells, white blood cells, and/or platelets or gastrointestinal toxicity secondary to chemotherapy
  • Gastrointestinal ulceration secondary to piroxicam therapy

Expected Course and Prognosis

  • Long-term prognosis grave
  • Progressive disease probable
  • Median survival—no treatment, 4–6 months; with treatment, 6–12 months

Key Points

  • Long-term prognosis is poor, but control of signs to make the pet more comfortable (known as “palliation”) is often attainable
  • The tumor usually cannot be removed surgically in dogs