Postradiation therapy sarcoma.

Abstract

e20523 Background: To evaluate the risk of radiation therapy induced sarcoma (RIS) in the prophylaxis of heterotopic ossification (HO) after traumatic fractures (TFs) followed by open reduction and internal fixation (ORIF). HO is the ectopic formation of bone matrix in soft tissues where it does not occur physiologically. RT and/or NSAIDs are often used prophylactically to decrease the risk of HO formation after surgical intervention for trauma or elective procedures. RT is usually given post-operatively within 72 hours of surgery or preoperatively (1-24 hours) prior to surgery. RIS is rare, late sequelae of RT which usually takes place after high doses of definitive RT (≥30 Gy). To the best of our knowledge it has never been reported previously in the context HO prophylaxis. Methods: This is a single-institution, retrospective study investigating the effect of low dose prophylactic RT on RIS after ORIF of TF. Between January 1990 and January 2008, 1,724 patients with various TFs were treated for HO prophylaxis with RT after ORIF. All the patients received RT±NSAIDs after ORIF. Seven hundred cGy was delivered in a single fraction to the soft tissues without bone shielding. Pregnant females (16 patients) didn't receive any RT or NSAIDs following their TFs-ORIF. HO occurrence was evaluated, by X-rays during follow-up visits by three independent reviewers; a radiologist, orthopedic surgeon, and radiation oncologist. Results: Of the 1,724 patients who had TFs and ORIF, We identified only one case of RIS, incidence rate 0.058), involving previously irradiated right thigh of a patient who had been treated with low dose RT, solely for HO prophylaxis −15 years prior to his RIS diagnosis. Conclusions: RIS is a very rare RT complication often seen many years after definitive RT doses following treating aggressive cancers. To the best of our knowledge there has been no prior report of RIS arising from prophylactic RT for HO. We speculate from that the RIS may occur even after low prophylactic radiation. The concept of administering prophylactic RT to young patients as a routine prophylactic measure against HO should be carefully evaluated and cautiously considered. No significant financial relationships to disclose.