SBRT of lung cancer Dosimetric predictors of chest wall pain after lung stereotactic body radiotherapy Kimberly M. Creach a , Issam El Naqa b , Jeffrey D. Bradley a , Jeffrey R. Olsen a , Parag J. Parikh a , Robert E. Drzymala a , Charles Bloch a , Clifford G. Robinson a,⇑ a Department of Radiation Oncology, Washington University School of Medicine, St. Louis, USA; b Department of Oncology, McGill University, Montreal, Canada article info Article history: Received 29 April 2011 Received in revised form 6 January 2012 Accepted 26 January 2012 Available online 3 March 2012 Keywords: Stereotactic body radiation therapy Chest wall Pain Thoracic Lung abstract Purpose: To identify risk factors for the development of chest wall (CW) pain after thoracic stereotactic body radiotherapy (SBRT). Methods and materials: A registry of patients with lung lesions treated with lung SBRT was explored to identify patients treated with 54 Gy in three fractions or 50 Gy in five fractions. One hundred and forty-six lesions in 140 patients were identified; complete electronic treatment plans were available on 86 CWs. The CW was contoured as a 3 cm outward expansion from the involved lung. Univariate and multivariate analyses were used to correlate patient, tumor, and dosimetric factors to the develop- ment of CW toxicity. Results: CW pain occurred in 22 patients (15.7%). The Kaplan–Meier estimated risk of CW pain at 2 years was 20.1% (95% C.I., 13.2–28.8%). On univariate analysis of patient factors, elevated BMI (p = 0.026) and connective tissue disease (p = 0.036) correlated with CW pain. The percent of CW receiving 30, 35, or 40 Gy was most predictive of CW pain on multivariate analysis using logistic regression, while V40 alone was predictive using Cox regression. A V30 threshold of 0.7% and V40 threshold of 0.19% was correlated with a 15% risk of CW pain. Conclusions: We have described patient and dosimetric parameters that correlate with CW pain after lung SBRT. The risk of CW pain may be mitigated by attempting to reduce the relative proportion of CW receiving 30–40 Gy during treatment planning. Ó 2012 Elsevier Ireland Ltd. All rights reserved. Radiotherapy and Oncology 104 (2012) 23–27 Stereotactic body radiation therapy (SBRT) is an established treatment for patients with medically inoperable, early stage non-small cell lung cancer (NSCLC) [1–4], and SBRT is being increasingly utilized for the treatment of oligometastatic disease with good results [5]. While thoracic SBRT is generally well toler- ated [1,3,4], toxicities such as fatigue, pulmonary toxicity, brachial plexopathy, and chest wall toxicity have all been reported [1–4,6– 10]. Chest wall (CW) toxicity refers to a range of conditions inclusive of soft tissue fibrosis, skin ulceration, neuropathic pain, and rib fracture. The reported incidence of CW toxicity ranges from 10% to 44% [7,11–17], and frequently occurs greater than 6 months after the completion of therapy [7,9,11,18]. For the subset of pa- tients with CW pain, the severity is typically mild, though it can occasionally be severe and require narcotic analgesia [4,7,16,18]. Although there are numerous reports documenting CW toxicity after SBRT, only a handful of studies have attempted to identify risk factors for the development of CW pain. In a report from the Cleve- land Clinic comparing outcomes of differing fractionation schemes for lung SBRT, Stephans et al. reported an increased incidence of CW pain in patients with peripheral versus central tumors [18]. The same study also found a correlation with decreased CW pain in patients treated with 50 Gy in five fractions compared to 60 Gy in three fractions, and this difference remained evident even when patients with central tumors were excluded from the analy- sis [18]. Recently, MD Anderson and University of Virginia have re- ported their experiences with CW pain after SBRT. Both groups found that the absolute volume of CW (threshold, 30 cm 3 ) treated to greater than or equal to 30 Gy (V30) was strongly predictive of the development of CW pain [7,14]. A number of recent abstracts have also reported the volume of chest wall radiated (including V30) to be an important predictor of CW pain [11,13,17]. Elevated body mass index (BMI) and diabetes mellitus (DM) are the only pa- tient related risk factors for CW pain that have been identified to date [14,19]. In light of the limited literature reviewing CW pain after SBRT and the small cohorts investigated, we reviewed the Mallinck- rodt Institute of Radiology experience in an effort to identify pa- tient, tumor, and treatment factors that might predict for CW pain. 0167-8140/$ - see front matter Ó 2012 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.radonc.2012.01.014 ⇑ Corresponding author. Address: Department of Radiation Oncology and Mal- linckrodt Institute of Radiology, Washington University School of Medicine, 4921 Parkview Place, Box 8824, St. Louis, MO 63110, USA. E-mail address: crobinson@radonc.wustl.edu (C.G. Robinson). Radiotherapy and Oncology 104 (2012) 23–27 Contents lists available at SciVerse ScienceDirect Radiotherapy and Oncology journal homepage: www.thegreenjournal.com