Appendicular And Axial - OSA Flashcards
What is the most common primary bone tumor in dogs and cats?
Osteosarcoma
Dogs> cats
Appendicular >axial
Signalment for OSA
Large to giant breeds (size and height are prognostic)
Male neutered (esp rotties) —> 1 in 4 early gonadectomized Rotties have lifetime risk of OSA
Bimodal age distribution: 1-2yrs and 7-9yrs
Small dog OSA has predilection for axial skeleton
What are some of the proposed etiologies of OSA?
Hormonal
Genetic
Repetitive micro-trauma
Molecular factors
-MET, Trk and HER-2 —> all encode TK receptors and control growth/proliferation of cells
Aberrant/excessive insulin like GF
Aberrant signaling through mammalian target of rapamycin (mTOR) pathway
Presence of telomerase
Presenting complaint with OSA
Lameness and localized limb swelling
—> lameness caused by periosteal inflammation, microfractures, and occasionally pathologic fracture
—> swelling- extracompartmental extension of tumor into adjacent soft tissue
DDX for appendicular skeletal masses
OSA
Chondrosarcoma
Fungal — usually systemically ill
Two most common sites for OSA?
Distal radius (23%)
Proximal humerus (18%)
Favor development of metaphyseal region of bone
What re the 3 basic types of OSA?
Endosteal (most common)
Periosteal
Parosteal
—> rare = originate from the periosteal surface and rarely involve the endosteum/medullary canal
You do a CBC/chem on your OSA dog, it shows an elevated ALP… what does this indicate?
Negative prognosis
How sensitive are thoracic metastasis checks at time of diagnosis?
90% of dogs will have micrometastatsis and diagnosis but <15% of these will have clinically detectable mets at time of initial diagnosis
Localized imaging — two view radiographs of affected limb
How do OSA appear on radiographs?
Lytic and blasting lesions
Loss of cortical bone
Periosteal proliferation
Palisading cortical bone (sunburst effect)
Codmans triangle= periosteal lifting caused by sub periosteal hemorrhage
Loss of the fine trabecular pattern in metaphyseal bone
Pathological fracture with metaphyseal collapse
Does NOT cross joints
T/F: biopsy is the preferred method for diagnosis of OSA
False
FNA/cytology —>
What two tools can be used for bone biopsy? What are the benefits/ downfalls of these?
Jam shedi —> 82% accuracy of diagnoses
Michele trephine —> large samples with diagnostic rate of 94%, but higher rate of pathological fracture
What is the gold standard for local control of OSA?
Limb amputation
What will you do for local control of OSA if the lesion is at the proximal femoral head?
More aggressive sx required
—> en block acetabulectomy or subtotal hemipelvectomy
What are indications for limb salvage in OSA cases?
Severe osteoarthritis
Neurologic disease
Morbid obesity
Reluctance of owners to proceed with amputation
Contraindications of limb salvage with OSA?
Large lesions > 50% of diaphysis
Extensive soft-tissue involvement
Pathological fracture
Poorly complaint owner or patient
Advanced disease
Inappropriate location of tumor
What are OSA sites that allow for limb salvage surgery?
Distal radius — most common site of tumor
Distal ulna - ulnectomy
Digit or metacarpus/tarsus - amputation
Scapula - partial scapulectomy
When doing limb salvage procedure on the distal radius should be transacted _______cm proximal to the tumor
3-5
T/F: Distal radius OSA limb salvage are often reconstructed with endoprothesis
True
What re the complications for limb salvage surgery?
Complication rate >50%
Implant failure - 40% of cases
Local tumor recurrence 10-28% (cn be reduced with local chemo agents)
Infection occurs in more than 50% of cases and approx 2/3rd of infections are diagnosed >6months after surgery
T/F: stereotactic radiation therapy limb salvage offers greater survival time compacted to surgical treatment
False
No advantage
Complications form stereotactic radiation therapy for OSA?
Mild skin effects
Fracture of radiated bone (36%).
What is the best site for SRS based on low post radiation fracture rate?
Proximal humerus
OSA have a 90% met rate, how do you control this systemically?
Chemo recommended in all cases of OSA
**Carboplatin **
Cisplatin
Doxorubicin
All platinum-containing protocols result in similar survival times
Protocol for carboplatin treatment?
4 treatments
Monitor CBC and renal fxn
What palliative therapeutic options are available for OSA?
Synthetic analog of pyrophosphate (amino-bisphosphonates)
—> inhibit osteoclastic bone reabsorption
What is the MOA of amino-bisphosphonates ?
Exert their effect on osteoclasts via inhibition of the mevalonate pathways which disrupts intracellular signaling and induction of apoptosis
- inhibit proliferation, angiogenesis, MMP
- immunomodulatory
- effect on cytokine and growth factors
How effect does palliative radiation therapy have >
Reduced local inflammation, minimizes pain, slows progression of metastatic lesions and improves QOL
What is the median duration of response to palliative radiation therapy?
73-130days
Better when there is less than 50% of bone involved and located in proximal humerus
What analgesic options can you give if managing OSA palliatively?
NSAIS
Opioids
NMDA antagonsit
Anticonvulsant
What re the indications for pulmonary metastatectomy?
Development >300days after initial diagnosis
< than 3 radiographically evident met lesions
No doubling of size of lesions or development of new lesions in a 4 week period
Palliative relief for hypertrophic osteopathy
What is the prognosis of OSA
Palliative
- analgesia MST 1-3months
- RT MST 4-10monts
Surgery alone MST 4-6months
Chemo alone - limited data
Surgery with chemo MST 8-12months
What are prognostic factors for OSA?
Body weight: worse prog if >40 kg
Age: worse if <7 or >10yrs
Tumor site: worse if proximal humerus (usually larger in size before diagnosis)
Tumor volume: worse when large
Histologic grade: grade 1 OSA (4%), grade II (21%), grade III(75%)
ALP —> for every 100 U/L increase in total ALO increased risk of tumor related death by 25%
T/F: Feline OSA is more common in the diaphysis than the metaphysis
True
Feline OSA are most commonly located where?
Pelvic limb > thoracic
Diaphysis
Often less aggressive and lower met rate than dog
MST in cat with OSA
Amputation alone may be curative in cats with OSA
MST 29-49months
