A cortical thickness and radiation dose mapping approach identifies early thinning of ribs after stereotactic body radiation therapy. Issue 3 (June 2016)

• Record Type: Journal Article
• Authors: Okoukoni, Catherine; Lynch, Sarah K.; McTyre, Emory R.; Randolph, David M.; Weaver, Ashley A.; Blackstock, A. William; Lally, Brian E.; Munley, Michael T; Willey, Jeffrey S.
• Is Part Of: Radiotherapy and oncology. Volume 119:Issue 3(2016:Jun.)
• Page Start: 449
• Page End: 453
• Publication Date: 2016-06
• Subjects: Rib fracture -- Stereotactic body radiation therapy (SBRT) -- Stereotactic radiation surgery (SRS) -- Bone -- Lung cancer -- Diagnostic imaging; Oncology -- Periodicals; Radiotherapy -- Periodicals; Tumors -- Periodicals; Medical Oncology -- Periodicals; Neoplasms -- radiotherapy -- Periodicals; Radiotherapy -- Periodicals; Radiothérapie -- Périodiques; Cancérologie -- Périodiques; Tumeurs -- Périodiques; Electronic journals; 616.9940642
• DOI: 10.1016/j.radonc.2016.03.023
• Languages: English
• ISSNs: 0167-8140

Abstract

Abstract: Background and Purpose: High rates of spontaneous rib fractures are associated with thoracic stereotactic body radiation therapy (SBRT). These fractures likely originate within the cortical bone and relate to the cortical thickness (Ct.Th). We report the development and application of a novel Ct.Th and radiation dose mapping technique to assess early site-specific changes of cortical bone in ribs. Materials and methods: Rib Ct.Th maps were constructed from pre-SBRT and 3 month post-SBRT CT scans for 28 patients treated for peripheral lung lesions. The Ct.Th at approximately 50, 000 homologous points within the entire rib cage was determined pre- and post-SBRT. Each rib was then divided into 30 homologous regions. The mean dose and thinning were determined per section. Results: Regions of ribs that received ⩾10 Gy exhibited significant thinning of cortical bone ( p = 0.001). The mean Ct.Th percent difference (95% CI) in regions receiving 10–20 Gy, 20–30 Gy, 30–40 Gy, and ⩾40 Gy were −7% (−4%, −11%), −14% (−18%, −11%), −15% (−19%, −11%), and −18% (−22%, −15%) respectively. Regions receiving >20 Gy experienced significantly more thinning than regions receiving lower doses. Conclusions: Substantial early cortical bone thinning was observed post-SBRT in regions of ribs that received ⩾10 Gy. The rapid thinning of ribs may predispose ribs to fracture after SBRT.