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- Represent 35% of bone sarcomas.
- Primary distribution in adolescents
- When it occurs in older patients, usually associated with pre-existing condition such as Paget's disease, prior irradiation of bones, multiple hereditary exostosis, or polyostotic fibrous dysplasia
- Hereditary risk factors:
- Distal femur/knee joint ~50%
- Proximal humerus ~25%
- Long tubular bones ~80-90%
- Hands/feet <1%
- Lab findings generally not helpful, though serum alkaline phosphatase elevated in ~50%
- Clinical presentation:
- Night pain
- Typically no effusion in the adjacent joint
- Pathologic fractures rare
- Metastatic disease:
- Approximately 15-20% at diagnosis
- Overwhelmingly in the lung
- 90% of osteosarcomas are conventional osteosarcomas; these are intramedullary high grade tumors. Subtypes include:
- 10% include osteosarcoma of the jaw, surface osteosarcomas (paraosteal and periosteal)
- Radiation-induced osteosarcomas may be a linear function of radiation dose and alkylating agents. Risk for most childhood survivors <1%, but higher with genetic predisposition (Retinoblastoma 7%, Ewings' 5%, other bone tumors 2%)
Radiologic Findings 
- Classic appearance on plain x-ray is sunburst pattern which is a mixed lytic sclerotic pattern (vs "onion skinning" in Ewing's sarcoma)
- Increased intramedullary density due to tumor bone or calcified cartilage
- Area of radiolucency due to nonossified tumor
- Cortical destruction
- Extraosseous elevation (Codman's triangle) when tumor lifts the periostium leading to a rim of subperiosteal bone.
- Biopsy should be performed by an orthopedic surgeon who will ultimately perform the resection
- Treatment is surgical resection, preferentially limb-sparing surgery (distal femur/proximal tibia, shoulder girdle/proximal humerus)
- Surgery alone historically leads to overall survival of <20%.
- Adjuvant chemotherapy plays a key role in preventing distant mets; 4-agent regimens are favored
- Randomized trial by POG showed no difference between neoadjuvant chemotherapy -> surgery -> adjuvant chemotherapy and surgery -> adjuvant chemotherapy; 5-year ERS was ~60%
- Adjuvant RT (including whole lung irradiation) does not appear to benefit survival
- Prior to advent of effective chemo, whole lung xrt was often administered b/c of high rate of pulmonary failure. Data is unclear as to whether there was any benefit to this practice
- Role for RT is mostly limited to life-threatening presentations where adequate surgical removal is unlikely, such as H&N, spine, or pelvis
- Pelvic tumors are typically unresectable, and are treated with RT and chemotherapy
- For metastatic disease, aggressive course is typically advocated, consisting of induction chemotherapy followed by maximal resection of primary and mets, followed by adjuvant chemotherapy
Primary Radiotherapy 
- Blokhin Cancer Center, Russia; 2003 PMID 12583525 "Neoadjuvant chemotherapy and local radiotherapy for high-grade osteosarcoma of the extremities," Mayo Clin Proc 2003; 78(2):147-55.
- 31 pts who refused surgery and underwent induction chemo + conventional xrt (median 60 Gy)
- Local control 56%, OS 61%
- Of pts who had local control, 86% had excellent limb function
- UC San Francisco; 1976 PMID 1064887 "The role of radiation therapy in the treatment of osteosarcoma," Radiology. 1976; 120(1):163-5.
- 70 pts w/ osteosarcoma receiving either primary xrt or surgery b/w 1950-74
- Conclusion: xrt w/o chemo did not add palliative effect or improve OS in operative pt.
Post-operative Radiation 
- Harvard; 2005 (1980-2002) PMID 15667972 "Radiotherapy for local control of osteosarcoma" DeLaney TF, Int J Radiat Oncol Biol Phys. 2005; 61(2):492-8.)
- Retrospective. 41 patients with osteosarcoma (head/face 41%, extremity 20%, spine 20%, pelvis 17%). 5 were radiation-induced. Median age 29. GTR 66%, STR 22%, biopsy 12%. If GTR, received RT for close or +margins. Median 66 Gy delivered (If gross disease >=68 Gy; if SM+ 60-68 Gy, if close SM 55-60 Gy, if radiation-induced sarcoma 10-30 Gy). Some patients pre-op 20 Gy followed by post-op RT. Chemo 85%
- Outcome: 5-year LC 68%; GTR 78% vs. STR 78% vs. biopsy 22% (SS).
- RT: No definitive dose response seen, but doses >55 Gy w/ better local control (71% vs 54%)
- Conclusion: RT can help provide local control if widely negative margins not possible
Whole Lung Irradiation 
- Peru; 1986 PMID 3522504 "Postoperative whole lung irradiation with or without adriamycin in osteogenic sarcoma," Int J Radiat Oncol Biol Phys. 1986; 12(6):907-10.
- 36 patients w/ osteosarcoma of limbs tx'd b/w 1975-78 w/ radical surgery then 20 Gy whole lung irradiation. Most pts received adriamycin.
- All pts ultimately developed lung mets, but whole lung xrt appeared to increase the time to failure.
- Mayo Clinic; 1976 PMID 824047 "Elective whole lung irradiation in the treatment of osteogenic sarcoma," Cancer. 1976 Aug;38(2):939-42.
- 53 pts w/o evidence of pulmonary mets; 2 cohorts (15 Gy prophylactic xrt to whole lung field, or no lung xrt).
- No differences in survival or interval b/w tx and development of pulmonary mets.