title: Rib fracture after stereotactic radiotherapy for primary lung cancer: prevalence, degree of clinical symptoms, and risk factors.
abstract: BACKGROUND
  As stereotactic body radiotherapy (SBRT) is a highly dose-dense radiotherapy, adverse events of neighboring normal tissues are a major concern. This study thus aimed to clarify the frequency and degree of clinical symptoms in patients with rib fractures after SBRT for primary lung cancer and to reveal risk factors for rib fracture. Appropriate α/β ratios for discriminating between fracture and non-fracture groups were also investigated.
  
  
  METHODS
  Between November 2001 and April 2009, 177 patients who had undergone SBRT were evaluated for clinical symptoms and underwent follow-up thin-section computed tomography (CT). The time of rib fracture appearance was also assessed. Cox proportional hazard modeling was performed to identify risk factors for rib fracture, using independent variables of age, sex, maximum tumor diameter, radiotherapeutic method and tumor-chest wall distance. Dosimetric details were analyzed for 26 patients with and 22 randomly-sampled patients without rib fracture. Biologically effective dose (BED) was calculated with a range of α/β ratios (1-10 Gy). Receiver operating characteristics analysis was used to define the most appropriate α/β ratio.
  
  
  RESULTS
  Rib fracture was found on follow-up thin-section CT in 41 patients. The frequency of chest wall pain in patients with rib fracture was 34.1% (14/41), and was classified as Grade 1 or 2. Significant risk factors for rib fracture were smaller tumor-chest wall distance and female sex. Area under the curve was maximal for BED at an α/β ratio of 8 Gy.
  
  
  CONCLUSIONS
  Rib fracture is frequently seen on CT after SBRT for lung cancer. Small tumor-chest wall distance and female sex are risk factors for rib fracture. However, clinical symptoms are infrequent and generally mild. When using BED analysis, an α/β ratio of 8 Gy appears most effective for discriminating between fracture and non-fracture patients.
authors: Department of Radiology, University of Yamanashi, Chuo City, Yamanashi Prefecture, Japan. nambu-a@gray.plala.or.jp
authors: Atsushi
authors: A
authors: Nambu
authors: Hiroshi
authors: H
authors: Onishi
authors: Shinichi
authors: S
authors: Aoki
authors: Licht
authors: L
authors: Tominaga
authors: Kengo
authors: K
authors: Kuriyama
authors: Masayuki
authors: M
authors: Araya
authors: Ryoh
authors: R
authors: Saito
authors: Yoshiyasu
authors: Y
authors: Maehata
authors: Takafumi
authors: T
authors: Komiyama
authors: Kan
authors: K
authors: Marino
authors: Tsuyota
authors: T
authors: Koshiishi
authors: Eiichi
authors: E
authors: Sawada
authors: Tsutomu
authors: T
authors: Araki
mesh_terms: D000230:Adenocarcinoma / Q000601:surgery*; D000077192:Adenocarcinoma of Lung; D000368:Aged; D000369:Aged, 80 and over; D019540:Area Under Curve; D002637:Chest Pain / Q000453:epidemiology; D004487:Edema / Q000453:epidemiology; D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D053208:Kaplan-Meier Estimate; D008175:Lung Neoplasms / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D010865:Pilot Projects; D011237:Predictive Value of Tests; D015995:Prevalence; D016016:Proportional Hazards Models; D012372:ROC Curve; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000000981:diagnostic imaging / Q000453:epidemiology*; D016634:Radiosurgery / Q000009:adverse effects*; D012253:Rib Fractures / Q000000981:diagnostic imaging / Q000453:epidemiology*; D012307:Risk Factors; D012737:Sex Factors; D013997:Time Factors; D014057:Tomography, X-Ray Computed
references: Cancer. 2004 Oct 1;101(7):1623-31
references: 15378503
references: J Thorac Oncol. 2009 Aug;4(8):1035-7
references: 19633478
references: Int J Radiat Oncol Biol Phys. 2005 Dec 1;63(5):1427-31
references: 16169670
references: Int J Radiat Oncol Biol Phys. 2010 Mar 1;76(3):796-801
references: 19427740
references: Anesthesiology. 2008 Mar;108(3):473-83
references: 18292685
references: Lung Cancer. 2008 May;60(2):193-9
references: 18045732
references: Acta Oncol. 1988;27(2):117-22
references: 3390342
references: Int J Radiat Oncol Biol Phys. 2010 Jul 1;77(3):685-90
references: 20510193
references: Cancer. 2009 Feb 1;115(3):587-94
references: 19130457
references: Lung Cancer. 2006 Jan;51(1):97-103
references: 16213059
references: Radiother Oncol. 2009 Jun;91(3):360-8
references: 19410314
references: Int J Radiat Oncol Biol Phys. 2011 Dec 1;81(5):1352-8
references: 20638194