Lecture 21 4/7/25 Flashcards
What are the general characteristics of osteosarcoma?
-most common primary bone tumor
-much more common in dogs than cats
-seen as metaphyseal lesions of appendicular skeleton of large and giant breeds
-uncommonly seen in axial skeleton of small breeds
-highly metastatic to lungs and other bones
-very painful
What are the characteristics of osteosarcoma etiology?
-not fully understood
-possibly associated with microtrauma from fast growth or previous surgery
-genetic link
-ionizing radiation link
What are the risk factors for developing osteosarcoma?
-height and weight
-tall, heavy, large breed
What are the history and PE findings in patients with osteosarcoma?
-possible history of mild trauma resulting in pathologic fracture
-lameness
-pain
-similar signs to arthritis
-palpable mass
-cough if pulmonary metastasis is present
What are the characteristics of osteosarcoma within the appendicular skeleton?
-forelimbs more commonly affected than hind limbs
-typically seen away from the elbow, towards the knee, and at the distal tibia
-single bone is typically affected
-does not typically cross the joint
What are the characteristics of osteosarcoma within the axial skeleton?
-firm, painful swellings
-clinical signs reflecting location
What are the findings on rads that suggest osteosarcoma?
-aggressive bone lesions that are lytic/proliferative
-periosteal reaction/sunburst
-Codman’s triangle/elevation of periosteum
-possible pathologic fracture
What are differential diagnoses for osteosarcoma based on rad. findings?
-fungal or bacterial osteomyelitis
-other primary bone tumors
-metastatic bone tumors
What are the characteristics of ultrasound-guided FNA as an osteosarcoma diagnostic?
-want to sample areas of cortical lysis
-want to avoid the periphery and reactive bone
-cytologic dx of sarcoma or neoplasia is sufficient; just want to rule out infection
What are the characteristics of biopsy as an osteosarcoma diagnostic?
-done with jamshidi or trephine needle
-will provide definitive diagnosis
-requires general anesthesia
-carries risk of pathologic fracture
What are the tools used for staging of osteosarcoma?
-minimum database
-thoracic rads; 3 views
-possible nuclear scintigraphy
-possible abdominal ultrasound
Why are thoracic rads important for staging of osteosarcoma?
pulmonary metastasis is seen on presentation in less than 10% of patients, but more than 90% of patients have pulmonary metastasis after amputation
What are the two main goals of osteosarcoma treatment?
-eliminate pain
-slow down metastatic disease
What are the characteristics of limb amputation as an osteosarcoma treatment?
-main goal; will provide patient with best outcome
-permanent pain control
-improves QOL
-fast post-op recovery
-most dogs do great on 3 legs
What are contraindications of limb amputation?
-severe arthritis
-severe neurologic conditions
-significant metastatic burden
What are the characteristics of limb-sparing surgery as an osteosarcoma treatment?
-only done at select institutions
-very strict patient selection criteria
-multiple techniques
-high rate of complications
-no benefit on survival
-very expensive
What are the characteristics of chemo as an osteosarcoma treatment?
-used to slow down metastatic dz
-doubles survival rate
-should be started as soon as amputation site heals; 10 to 14 days
-carboplatin and adriamycin/doxorubicin have proven efficacy
What are the characteristics of carboplatin use in osteosarcoma?
-given every 3 weeks for a total of 4 to 6 treatments
-no hard evidence that 6 treatments is better than 4
What are the characteristics of adriamycin/doxorubicin use in osteosarcoma?
-given once every 2 weeks for 5 treatments
-more potential for cariotoxicity
What are the options for palliative treatment of osteosarcoma?
one or multiple of the following:
-palliative radiation (best outcomes)
-bisphosphonates
-oral pain medication
What are the characteristics of palliative radiation for osteosarcoma?
-2 to 4 fractions
-response rates are high
-duration of response around 3 to 4 months
-pain control begins about a week after first treatment
-fairly expensive
-requires special facilities
What are the characteristics of bisphosphonates for osteosarcoma?
-variety of mechanisms, including osteoclast inhibition
-used for therapy of hypercalcemia and malignant bone pain
-available orally and IV, but oral forms are considered poorly absorbed
What is the multimodal approach to pain control in osteosarcoma patients?
-NSAIDs
-tramadol or tylenol
-gabapentin
-amantadine
What should be discussed with owners when starting osteosarcoma patients on pain control?
-increased use of the limb with less pain can result in pathologic fracture
-poor prognosis if only doing pain control
