title: Risk of radiation-induced malignancy with heterotopic ossification prophylaxis: a case-control analysis.
abstract: OBJECTIVE
  To determine the risk of radiation-induced malignancy after prophylactic treatment for heterotopic ossification (HO).
  
  
  METHODS
  A matched case-control study was conducted within a population-based cohort of 3489 patients treated either for acetabular fractures with acetabular open reduction internal fixation or who underwent total hip arthroplasty from 1990 to 2009. Record-linkage techniques identified patients who were diagnosed with a malignancy from our state health registry. Patients with a prior history of malignancy were excluded from the cohort. For each documented case of cancer, 2 controls were selected by stratified random sampling from the cohort that did not develop a malignancy. Matching factors were sex, age at time of hip treatment, and duration of follow-up.
  
  
  RESULTS
  A total of 243 patients were diagnosed with a malignancy after hip treatment. Five patients were excluded owing to inadequate follow-up time in the corresponding control cohort. A cohort of 238 cases (control, 476 patients) was included. Mean follow-up was 10 years, 12 years in the control group. In the cancer cohort, 4% of patients had radiation therapy (RT), compared with 7% in the control group. Of the 9 patients diagnosed with cancer after RT, none occurred within the field. The mean latency period was 5.9 years in the patients who received RT and 6.6 years in the patients who did not. Median (range) age at time of cancer diagnosis in patients who received RT was 62 (43-75) years, compared with 70 (32-92) years in the non-RT patients. An ad hoc analysis was subsequently performed in all 2749 patients who were not matched and found neither an increased incidence of malignancy nor a difference in distribution of type of malignancy.
  
  
  CONCLUSIONS
  We were unable to demonstrate an increased risk of malignancy in patients who were treated with RT for HO prophylaxis compared with those who were not.
authors.affiliation: Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, Iowa. Electronic address: arshin-sheybani@uiowa.edu.
authors.forename: Arshin
authors.initials: A
authors.lastname: Sheybani
authors.affiliation: Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, Iowa.
authors.forename: Mindi J
authors.initials: MJ
authors.lastname: TenNapel
authors.affiliation: Department of Orthopaedic Surgery & Rehabilitation, Loyola University Medical Center, Chicago, Illinois.
authors.forename: William D
authors.initials: WD
authors.lastname: Lack
authors.affiliation: Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, Iowa.
authors.forename: Patrick
authors.initials: P
authors.lastname: Clerkin
authors.affiliation: Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, Iowa.
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Hyer
authors.affiliation: Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, Iowa.
authors.forename: Wenqing
authors.initials: W
authors.lastname: Sun
authors.affiliation: Department of Radiation Oncology, West Virginia University, Morgantown, West Virginia.
authors.forename: Geraldine M
authors.initials: GM
authors.lastname: Jacobson
mesh_terms: D000077:Acetabulum / Q000293:injuries*; D000328:Adult; D000367:Age Factors; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D016022:Case-Control Studies; D005260:Female; D005500:Follow-Up Studies; D005593:Fracture Fixation, Internal / Q000009:adverse effects*; D050723:Fractures, Bone / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009381:Neoplasms, Radiation-Induced; D009999:Ossification, Heterotopic / Q000209:etiology / Q000517:prevention & control*; D011879:Radiotherapy Dosage; D018570:Risk Assessment