Workup/Staging

Question 1

Define the lab and radiographic studies used in the workup and staging of osteosarcoma.

Answer 1

Osteosarcoma workup: basic labs (CBC, CMP) as well as alk phos, LDH, and ESR. After plain films of the affected bone are obtained; MRI +/– CT of the primary site with contrast and chest CT are needed. PET/CT or bone scan may be used for systemic staging.

Question 2

Define 3 principles used in the Bx of a suspected bone tumor.

Answer 2

Principles used in the Bx of a suspected bone tumor:

1. Bx should be performed at the same institution where the definitive resection will take place, preferably by the same surgeon who will undertake the definitive resection.
2. Bx should be placed carefully to avoid contamination of other areas, as can happen with a hematoma formation.
3. The Bx should not increase the extent of subsequent Sg.

Question 3

What radiographic features distinguish osteosarcoma from EWS?

Answer 3

Osteosarcoma is usually sclerotic, involves the metaphysis, and has periosteal new bone formation (sunburst pattern), whereas EWS is usually lytic, located in the diaphysis, and displays an onion skin effect. (Lee B et al., Handbook of Radiation Oncology 2007)

Question 4

What is the most common site of mets from osteosarcoma?

Answer 4

The lung is the most common site of osteosarcoma mets. Hence, cross-sectional chest imaging is an important part of osteosarcoma staging.

Question 5

What are the AJCC 8th edition (2017) TNM stage categories for bone tumors? (Note: Lymphoma and multiple myeloma have separate staging systems.)

Answer 5

Appendicular Skeleton, Trunk, Skull, and Facial Bones

T1: ≤8 cm

T2: >8 cm

T3: Discontinuous tumors in primary bone site

Spine

T1: 1 or 2 adjacent vertebra

T2: 3 adjacent vertebra

T3: ≥4 vertebra, or nonadjacent vertebra

T4a: Extension into spinal canal

T4b: Gross vascular invasion or tumor thrombus in great vessels

Pelvis

T1a: ≤8 cm confined to 1 pelvic segment

T1b: >8 cm confined to 1 pelvic segment

T2a: ≤8 cm confined to 1 pelvic segment with extraosseous extension or 2 segments without extraosseous extension

T2b: >8 cm confined to 1 pelvic segment with extraosseous extension or 2 segments without extraosseous extension

T3a: ≤8 cm in 2 pelvic segments with extraosseous extension

T3b: >8 cm in 2 pelvic segments with extraosseous extension

T4a: SI joint/sacral neuroforamen

T4b: Encasement of external iliac vessels or tumor thrombus in major pelvic vessels

N1: Regional LN mets

M1a: Lung

M1b: Bone or other

Question 6

What is the AJCC stage grouping for bone tumors?

Answer 6

Appendicular Skeleton, Trunk, Skull, and Facial Bones.

Stage IA: T1, N0, Grade 1–X

Stage IB: T2–3, N0, Grade 1–X

Stage IIA: T1, N0, Grade 2–3

Stage IIB: T2, N0, Grade 2–3

Stage III: T3, N0, Grade 2–3

Stage IVA: M1a

Stage IVB: N1 or M1b

No AJCC group staging for spine and pelvis.