Osteosarcoma

Question 1

germline genetic abnormalities predisposing to osteosarcoma

Answer 1

p53

Rb

Question 2

what genetic abnormality is assoc with parosteal OS?

Answer 2

supernumerary ring chromosome (12q13-15)

Question 3

predisposing factors for osteosarcoma

Answer 3

ionizing radiation (median time 9-11 yrs after exposure), hereditary Rb (20-30 yrs of age)

Question 4

three most common primary sites of osteosarcoma

Answer 4

distal femur (55%)
proximal tibia (27%)
proximal humerus (11%)

Question 5

what are the two most common metastatic sites for osteo

Answer 5

lung, bone

Question 6

work up for new osteo

Answer 6

MRI of involved bone
CT chest
PET or bone scan

Question 7

prognostic factors for osteo

Answer 7

stage (localized vs mets), histologic subtype (parosteal, fibroblastic, telangiectatic - favourable), percent necrosis (>= 90% after 10 wks chemo), tumor location (extremity > axial), size

Question 8

outcome of patients with >= 90% necrosis

Answer 8

EFS 80%

Question 9

outcome of patients with < 90% necrosis after 10 wks chemo

Answer 9

EFS 60%

Question 10

pathology diagnosis based on

Answer 10

finding osteoid-producing (unmineralized bone matrix) malignant cells

Question 11

WHO classification of osteosarcoma

Answer 11

central (medullary) tumours (conventional, telangiectatic, small round cell, low grade central) vs surface tumours (parosteal, high-grade surface)

Question 12

type of conventional osteosarcoma

Answer 12

osteoblastic
chrondroblastic
fibroblastic

Question 13

how is local control achieved in osteosarcoma

Answer 13

local control cannot be achieved by RT - all tumour and mets must be surgically resected

Question 14

timing of surgery in osteo

Answer 14

usually approx after 10 weeks of neoadjuvant chemo

Question 15

chemo for osteosarcoma

Answer 15

MAP (HD mtx, doxorubicin, cisplatin)

Question 16

what form of osteo can be treated without chemo?

Answer 16

parosteal osteosarcoma