Osteosarcoma

Question 1

What breeds most commonly develop osteosarcoma?

Answer 1

large and giant breeds

Question 2

Where is it most common for osteosarcomas to be found?

Answer 2

metaphyseal regions of the appendicular skeleton:

• distal radius
• proximal humerus
• distal femur
• proximal tibia

AWAY FROM THE ELBOW, TOWARD THE KNEE

Question 3

What is classically seen on radiographs when diagnosing osteosarcoma?

Answer 3

lytic and productive lesion at the metaphysis of the bone

• does not cross joints into adjacent bones

Question 4

How are primary and metastatic bone neoplasia differentiated on radiographs?

Answer 4

PRIMARY = metaphyseal region

SECONDARY = diaphyseal region, most likely metastasized from a primary tumor from somewhere else

Question 5

Where should an osteosarcoma be aspirated? Why? How should this be performed?

Answer 5

center of the lesion –> periphery often looks like reactive bone

use U/S guidance to insert the needle into cracks of the cortex

Question 6

What complication is associated with bone FNA/biopsies?

Answer 6

pathologic fractures

Question 7

Other than thoracic radiographs, what else should be scanned in cases of osteosarcoma?

Answer 7

thoracic radiographs - pulmonary metastasis

• not commonly present at the time of diagnosis, but develops in the future in most cases
• if present, prognosis is poor so it should be performed prior to any treatments

Question 8

How are bone scans (nuclear scintigraphy) used when diagnosing osteosarcoma? How does it work? What is a major disadvantage to this test?

Answer 8

rule in or out suspected bone metastasis

technetium-99-hydroxymethylene diphosphonate binds to areas of active bone and is detected on imaging

poorly specific - uptake can occur with bone tumors, arthritis, fractures, or osteomyelitis

Question 9

What change in blood work makes prognosis worse in cases of osteosarcoma?

Answer 9

elevated ALP

Question 10

What is the most effective way to alleviate pain associated with bone destruction in cases of osteosarcoma?

Answer 10

amputation

• palliative –> most dogs will develop metastasis in the future

Question 11

What limb-sparing procedure is available for cases of osteosarcoma? Why is it not commonly performed?

Answer 11

surgical removal of bone tumor with replacement of a prosthetic at the ostectomy site

• high rate of complications: chronic resistant infections, tumor recurrence, failure of surgical constructs
• expensive
• limited to experienced surgeons

Question 12

How is radiation therapy used in cases of osteosarcoma? What adverse effect is related?

Answer 12

can be effective in palliating pain of bone tumors (75%) for 2-3 months

pathologic fractures - pain is well controlled and use of limb typically increases

Question 13

What chemotherapy protocol is typically used for osteosarcoma? When is it not thought to be effective?

Answer 13

platinum drug (Cisplatin, Carboplatin) +/- adriamycin (Doxorubicin)

if macroscopic disease is present

Question 14

What medication is commonly added to chemotherapy protocols in cases of osteosarcoma? When is this done?

Answer 14

bisphosphonates (Pamidronate) - osteoclast inhibitors

when surgery is not an option

Question 15

How do different treatments of osteosarcoma differ in median survival time?

Answer 15

• amputation alone = 4-6 months
• surgery + chemotherapy = 10-12 months
• presence of macroscopic metastatic disease = 1-3 months

Question 16

What are 6 common sites of axial osteosarcoma? How does it compare to appendicular osteosarcoma?

Answer 16

1. mandible
2. maxilla
3. scapula
4. ribs
5. spine
6. pelvis

less common and more prevalent in small or medium-sized dogs

Question 17

What site of axial osteosarcoma has the best prognosis?

Answer 17

mandible - 70% have a 1 year MST with surgery alone

• other sites are thought to have aggressive clinical courses similar to appendicular disease