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SA DX & TX I > Final Exam - Tumors of the Skeletal System > Flashcards

Final Exam - Tumors of the Skeletal System Flashcards

1
Q

what is the most common primary bone tumor?

A

osteosarcoma

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2
Q

what is important about the biphasic distribution with osteosarcoma?

A

effects young dogs & older dogs

18-24 months & then older than 7 years

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3
Q

what dogs are typically affected by osteosarcoma?

A

large & giant breed dogs

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4
Q

what breeds have shown predisposition to developing osteosarcomas?

A

great danes, dobermans, rottweilers, scottish deer hounds, & greyhounds

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5
Q

T/F: dogs weighing > 40kg account for 30% of osteosarcoma with only 5% occurring in the axial skeleton

A

true - dogs under 15kg account for about 5% of cases with 59% occurring in the axial skeleton

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6
Q

compared to large/giant breed dogs, appendicular osteosarcomas in small dogs have what differences?

A

histological grade & mitotic index are significantly lower when compared to large breed dogs

median survival time following amputation alone without chemo is longer

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7
Q

what anatomical locations are osteosarcomas most common?

A

75% occur in the appendicular skeleton particularly in the metaphyseal region of long bones with front limbs more commonly affected than hind limbs

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8
Q

what saying can help you remember the predilection sites for osteosarcomas?

A

toward the knee & away from the elbow

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9
Q

where are the most common sites for osteosarcomas in the axial skeleton?

A

mandible 27%, maxilla 22%, spine, cranium

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10
Q

T/F: local & distant metastasis is less common for axial osteosarcoma when compared to appendicular osteosarcoma

A

true - 40 to 60% for axial vs > 90% for appendicular

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11
Q

when is local recurrence most common for axial osteosarcoma?

A

greatest for maxillary ~60%

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12
Q

what is the most common extraskeletal primary site for osteosarcoma? what are some other locations?

A

spleen

mammary tissue, subcutaneous tissue, gi tract, kidney

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13
Q

what are extraskeletal osteosarcomas characterized by?

A

formation of osteoid in absence of bone involvement

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14
Q

what is the median survival time for extraskeletal osteosarcoma?

A

wide or radical excision - 90 days

marginal excision - 13 days

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15
Q

why must histology of small biopsy samples of osteosarcomas be interpreted with caution?

A

histological pattern may vary within the tumor

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16
Q

what is the basis of histological diagnosis for osteosarcomas?

A

tumor osteoid

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17
Q

what is the pathology of osteosarcoma?

A

malignant mesenchymal tumor with cells producing an extracellular matrix of osteoid

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18
Q

what are the histological subclassifications based on for osteosarcomas?

A

type & amount of matrix & the characteristics of cells - but no significant difference in subtype & clinical outcome

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19
Q

what are some examples of histological subclassifications for osteosarcoma?

A

osteoblastic, chondroblastic, fibroblastic, giant cell, poorly differentiated

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20
Q

what factors are associated with pathological fractures from osteosarcomas?

A

femur is the most common location to fracture with humerus being 2nd

radius is least likely to fracture

lytic lesions more likely to fracture

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21
Q

how does osteosarcoma spread?

A

hematogenously

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22
Q

T/F: metastatic disease is very common for osteosarcoma

A

true - 85-90% will die from metastatic disease

23
Q

where is the most common metastasis site for osteosarcoma?

A

lung

others include other bones, lymph nodes, subcutaneous tissue, eyes, liver, & adrenal glands

24
Q

what should be included in your workup prior to determining most suitable treatment for osteosarcoma?

A

CBC/chem/UA, thoracic rads/ct scan, abdominal ultrasound, & bone scan

25
Q

what is step one when working on an osteosarcoma patient?

A

triage the patient, address pain/discomfort before starting workup

26
Q

what may be seen on radiographs that is supportive of an osteosarcoma?

A

cortical lysis causing a pathological fracture, soft tissue extension, sunburst/pallisading pattern, & codman’s triad (periosteum is elevated & new bone is laid down resulting in deposition of dense new bone on the cortex)

27
Q

what is the sensitivity & specificity of doing an ultrasound guided FNA for diagnosing osteosarcoma?

A

97% sensitive & 100% specific

28
Q

T/F: results for any tissue biopsy of a suspected osteosarcoma should be interpreted cautiously because until the whole tumor is evaluated with histopathology a final diagnosis can’t be made

A

true

29
Q

what percentage of animals have lung mets at the time of presentation?

A

10%

30
Q

why is a thoracic ct better than thoracic radiographs for osteosarcoma patients?

A

nodules are more likely to be detected on CT - use to highlight the concept of stage migration

31
Q

why is an abdominal ultrasound recommended for dogs with suspected osteosarcoma?

A

risk of mets to the abdominal cavity is very low but it is usually done in older dogs to evaluate for the presence of a 2nd neoplastic disease

32
Q

why is a bone scan recommended for dogs with suspected osteosarcoma?

A

secondary bone mets are present in about ~8% of dogs at the time of diagnosis, so any osteoblastic activity will be identified including osteoarthritis, infection, & neoplasia

very sensitive but not specific

33
Q

what are 5 negative prognostic factors associated with osteosarcoma?

A
  1. age - younger dogs have a shorter survival time
  2. anatomic location - humerus, extraskeletal OSA has aggressive systemic behavior with a high met rate, & head OSA
  3. serum ALP - elevated levels pre-op & 40 days post-op develop earlier mets
  4. disease stage - stage III, measurable mets, pulmonary, bone, soft tissue, lymph nodes
  5. monocyte count - some cells counted with monocytes may be myeloid suppressor cells that suppress anti-tumor immune response
34
Q

what are some local treatment options for osteosarcoma?

A

amputation, limb spare - surgical or radiation using stereotactic radiation therapy

35
Q

what are some palliative treatment options for osteosarcoma?

A

oral analgesia, bisphosphonates, & palliative radiation

36
Q

what is an example of systemic treatment for osteosarcoma?

A

chemotherapy

37
Q

T/F: amputation without chemo for osteosarcoma is palliative

A

true - survival time is 3-4 months

38
Q

T/F: prior orthopedic surgery makes an animal a poor candidate for an amputation for osteosarcoma

A

false

39
Q

what is the criteria for surgical limb spare for osteosarcoma?

A

no evidence of mets, primary tumor affects <50% of the bone, absence of pathological fractures, less than 360 degrees of soft tissue involvement, firm definable soft tissue mass, & distal radius

40
Q

what are the major complications associated with limb sparing?

A

recurrent local disease, infection, & implant failure

41
Q

what is the prognosis for limb sparing?

A

80% experience good to excellent function

42
Q

what is the typical chemo regimen for dogs with osteosarcoma?

A

carboplatin - total of 4 treatments every 3 weeks

cisplatin & doxorubicin

43
Q

what is the approximate survival time for a dog treated for osteosarcoma with amputation & chemo?

A

12 months - 20% alive at 2 years

44
Q

when treating metastatic disease, what does it depend on?

A

timing of metastasis, location/clinical signs, & what drugs have already been used

45
Q

what drug has shown positive preliminary evidence for treating metastatic disease for osteosarcoma?

A

palladia - toceranib phosphate

46
Q

what is the MOA of tramadol?

A

centrally acting opiate-like agonist that has primarily mu-receptor activity

dosing is 2-5mg/kg PO every 6-8 hours

47
Q

what is the MOA of gabapentin? what are the disadvantages of using it?

A

unknown mechanism of action - takes 24 to 48 hours to reach therapeutic concentrations

sedation & ataxia are most common side effects

48
Q

what is the MOA of amantadine?

A

unclear but antagonizes NMDA receptor dosing is 305 mg/kg every 24 hours

49
Q

what side effects are associated with amantadine?

A

behavioral change (sedation) & acute gi upset

50
Q

what is the MOA of pamidronate/zolidonate?

A

inhibit bone resorption without inhibiting the process of bone mineralization

induction of osteoclast apoptosis

51
Q

what is the impact of pamidronate & chemo on survival times in dogs with appendicular osteosarcoma treated with palliative radiation therapy?

A

MST with RT & chemo - 307 days

MST with RT & pamidronate - 69 days

52
Q

what is the most effect treatment for osteolytic bone pain in humans?

A

radiation therapy

53
Q

what does radiation therapy do for osteosarcoma?

A

induction of cell death in malignant osteoblasts & resorbing osteoclasts, depletion of inflammatory cells, inhibition of osteoclast precursor recruitment, alleviation of bone pain, & no acute or late side effects

54
Q

T/F: amputation should be considered as palliative therapy in dogs with asymptomatic metastatic disease

A

true

SA DX & TX I (59 decks)

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