MSK Oncology/Osteosarcoma Flashcards
1
Q
describe the signalment of animals affected by osteosarcoma
A
- most commonly older (small juvenile subset (<3years)
- more common in large breed (>40kg)(appendicular skeleton): st. bernard, great dane, irish setter, rotties, dobermans, greyhounds, german shepherds, golden retrievers
- less common in small dogs, but higher chance in the axial skeleton
2
Q
describe the anatomic locations of osteosarcoma
A
- appendicular (75%):
-most commonly metaphysial
-most commonly away from the elbow, towards the knee: proximal humerus, distal radius (MOST COMMON SITE), distal femur, proximal tibia
-forelimb 2x more common than hindlimb - axial (25%)
-ribs, mandible/maxilla, spine, skull
-more common in small breed - extraskeletal: rare
-spleen
3
Q
describe the biologic behavior of osteosarcoma
A
- malignant cell: osteoblast
- locally invasive:
-destruction of local bone: lytic
-production of new bone: proliferative - highly metastatic:
-hematogenous: primary metastatic site is lung
-85% are negative for mets at diagnosis
but 90% will develop metastases
-other metastatic sites: other bones (<10% at time of diagnosis), rarely lymph nodes, intra-abdominal organs, and subcutaneous tissue
4
Q
describe history and clinical signs of osteosarcoma (4)
A
- acute to subactute onset of lameness of varying severity
-degree of pain/lameness is variable, does not seem to line up with radiographic signs
-may be responsive to pain medications - sensitive to palpation of area of the lesion
- firm, painful swelling may be detected
- wide variation between patients!!
5
Q
describe initial and radiographic diagnosis of osteosarcoma
A
- ortho/neuro exam: to localize the pain
- 2-view radiographs of the area
-can be lytic or proliferative, usually both
-often metaphyseal
-radiographic signs: - Codman’s triangle:
- cortical lysis
- new bone proliferation
- ill-defined zone of transition
- almost never crosses the joint space!!
radiographic differential diagnoses to consider:
1. other primary bone tumor
2. metastatic neoplasia
3. bone cyst
4. osteomyelitis (especially fungal)
6
Q
describe tissue diagnosis of osteosarcoma
A
- fine needle aspirate: sedate heavily! plus analgesia, clip and clean, sterile prep
-ultrasound guidance to an area of cortical lysis can increase yield- but will HURT
-FNA of nearby soft tissue swelling may be diagnostic
-alkaline phosphatase stain: differentiates OSA from other sarcomas
-up to 85% diagnostic
-cells will be primarily mesenchymal - biopsy:
-fluoroscopy guidance can increase yield
-options: open or needle core biopsies
7
Q
describe staging of osteosarcoma
A
- minimum: thoracic evaluation (3-view chest rads)
- nuclear scintigraphy:
-Tc99 radiotracer taken up by active bone remodeling, MAY be consistent with primary bone tumor or metastasis
-can be difficult to interpret (especially DJD versus neoplasia) - full body CT scan to detect other lesions
8
Q
what are the 2 categories of treatment of osteosarcoma?
A
- definitive intent: do either
-amputation OR
-limb-sparing surgery OR
-stereotactic radiation therapy
-plus carboplatin for best outcome - quality of life/palliative intent
-medical pain management
-bisphosphonate
-palliative radiation therapy
-if pathologic fracture: palliative amputation versus euthanasia
9
Q
describe amputation as definitive treatment for osteosarcoma
A
- most common/standard of care
- myth: large to giant breed dogs do poorly after amputation; they DO! just have to pick right candidate (full ortho/neuro exam, most are already so painful they are already 3 legged lame)
- myth: forelimb amputees do worse than hindlimb amputees: just may take a little longer to adapt but do really well once figure it out
- best outcome: amputation + adjuvant chemotherapy (carboplatin)
- micrometastasis: cells have made their way through the lung most of the time by when you make diagnosis = not detectable but most will still develop osteosarcoma post-amputation
10
Q
describe limb sparing surgery as definitive treatment for osteoarthritis (big picture be aware of)
A
- options limited by:
-lesion location (disal radius, ulna)
-surgeon availability (very few offer this) - ulna = ulnectomy
- radius: surgical removal of affected bone with a margin followed by reconstruction (hardware or allograft)
- pros:
-avoid amputation
-similar long term outcome as amputation - cons:
-radius: high post-op infection rate (from hardware)
-post-op hardware failure possible
-expensive and low availability
11
Q
describe sterotactic radiation therapy as definitive treatment of osteosarcoma (big picture be aware of)
A
1, high dose highly targeted radiation
- 3 tx over 3 days
- pros:
-avoid amputation
-similar long term outcome as amputation - cons:
-post tx fracture rate can be high
-hella expensive
-multiple anesthetic episodes
12
Q
describe adjuvant chemotherapy
A
- median survival time with surgery/local control alone is 4-6 months; if supplement with chemotherapy MST is 10-12 months, delays onset of metastasis
(KNOW THESE MONTHS NUMBERS!!!) - most common adjuvant is carboplatin
13
Q
describe medical pain management
A
lots of options and can combine, but will eventually fail to control pain; the absolute minimum you should provide
- NSAIDs
- gabapentin
- tramadol, amantadine, tylenol codeine
14
Q
describe palliative radiation therapy
A
- many protocols, but most common is 1 treatment a day for 2 consecutive days
- at last 75% respond: pain reduction within 2-3 weeks
- lasts 2-4 months and can be repeated if effective
15
Q
describe bisphosphonates
A
- inhibit osteoclasts, leading to reduced bone destruction (a major source of pain)
- 30-50% response rate: improved pain management
- IV every 3-4 weeks until no longer effective
- may be synergistic with palliative radiation therapy
- nephrotoxic and decreases renal clearance, so check renal valus prior to EVERY dose!!
