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Chest Wall Volume Receiving More than 30 Gy Predicts Risk of Severe Pain and/or Rib Fracture Following Lung SBRT

2008; Elsevier BV; Volume: 72; Issue: 1 Linguagem: Inglês

10.1016/j.ijrobp.2008.06.846

1879-355X

Neal Dunlap, Gregory Biedermann, Wensha Yang, Jing Cai, Stanley Benedict, Ke Sheng, Brian D. Kavanagh, James M. Larner,

Medical Imaging Techniques and Applications

To identify dose-volume parameters which predict the risk of chest wall pain and/or rib fracture following lung stereotactic body radiation therapy (SBRT). From a combined larger multi-institution experience, consecutive patients treated with 3 to 5-fraction SBRT for primary or metastatic peripheral lung lesions between March, 2005 and October, 2007 were reviewed. Peripheral lung lesions were defined as located within 1.5 cm of the chest wall (CW). To be included patients must have received a minimum point dose of 20 Gy to the CW. The CW was defined as the difference between a 3 cm three-dimensional expansion of the lung contour and the lung volume. Both soft tissue and bone were included in the CW volume. The mediastinal soft tissue and anterior vertebral body were excluded. The absolute volume of CW receiving 20, 30, 40, and 50 Gy was determined and then related to the risk of CW toxicity. Thirty-one patients with peripheral lesions were identified for analysis. Thirteen patients experienced severe CW pain, defined as requiring narcotic analgesics or having a radiographically evident rib fracture. The median time to onset of severe pain and/or fracture was 7.3 months (range 1.9 to 31.8). Among the dosimetric parameters analyzed, the volume of chest wall receiving ≥30 Gy predicted the risk of severe CW pain and/or rib fracture. The risks of severe CW pain and/or fracture for the volume of CW receiving ≥30Gy in the range of ≤10cc, 10.1-40cc, 40.1-120cc, and >120cc were observed to be 0% (0/4), 33% (2/6), 46% (6/13), and 63% (5/8), respectively. The absolute volume of CW receiving ≥30 Gy correlated with the risk of severe CW pain and/or rib fracture following SBRT. Adequate tumor dose coverage is essential, however, when planning lung SBRT for peripheral tumors, our data suggest that achieving sharp dose gradients in the CW adjacent to the tumor will minimize the risk of severe CW pain and/or rib fracture. Optimally, the volume of the CW receiving 30 Gy should be limited to no more than 10cc if possible.