Radiation-induced rib fracture after stereotactic body radiotherapy with a total dose of 54–56 Gy given in 9–7 fractions for patients with peripheral lung tumor: impact of maximum dose and fraction size

Abstract

BackgroundRadiation-induced rib fracture after stereotactic body radiotherapy (SBRT) for lung cancer has been recently reported. However, incidence of radiation-induced rib fracture after SBRT using moderate fraction sizes with a long-term follow-up time are not clarified. We examined incidence and risk factors of radiation-induced rib fracture after SBRT using moderate fraction sizes for the patients with peripherally located lung tumor.MethodsDuring 2003–2008, 41 patients with 42 lung tumors were treated with SBRT to 54–56 Gy in 9–7 fractions. The endpoint in the study was radiation-induced rib fracture detected by CT scan after the treatment. All ribs where the irradiated doses were more than 80% of prescribed dose were selected and contoured to build the dose-volume histograms (DVHs). Comparisons of the several factors obtained from the DVHs and the probabilities of rib fracture calculated by Kaplan-Meier method were performed in the study.ResultsMedian follow-up time was 68 months. Among 75 contoured ribs, 23 rib fractures were observed in 34% of the patients during 16–48 months after SBRT, however, no patients complained of chest wall pain. The 4-year probabilities of rib fracture for maximum dose of ribs (Dmax) more than and less than 54 Gy were 47.7% and 12.9% (p = 0.0184), and for fraction size of 6, 7 and 8 Gy were 19.5%, 31.2% and 55.7% (p = 0.0458), respectively. Other factors, such as D2cc, mean dose of ribs, V10–55, age, sex, and planning target volume were not significantly different.ConclusionsThe doses and fractionations used in this study resulted in no clinically significant rib fractures for this population, but that higher Dmax and dose per fraction treatments resulted in an increase in asymptomatic grade 1 rib fractures.

Exploratory analysis using machine learning to predict for chest wall pain in patients with stage I non‐small‐cell lung cancer treated with stereotactic body radiation therapy

“…A subset of prior studies of chest wall toxicity15, 16 have suggested that within the commonly used total dose and fractionation schemes for SBRT, dosimetric predictors do not result in significantly different rates of toxicity. However, this does not imply that rib and chest wall doses can be simply disregarded since (a) CWS can result without the clinical appearance of rib fractures and (b) increasing risk may still occur with increasing dose in a continuous fashion 18.…”

“…Other prior studies have examined factors including rib Dmax, rib dose to 0.5 cc, 2 cc, rib V30, V40, chest wall Dmax, chest wall dose to 8 cc, and chest wall V30, without clear indication of the relative superiority or inferiority of one of these dosimetric factors relative to the others 9, 13, 27, 29, 38, 39. Global Dmax and fraction size are also suggested to be important indicators of toxicity, with higher rates of radiation‐induced rib fracture of ~50% for DMax > 54 Gy and fraction size >8 Gy 16. Regarding the chest wall specifically, constraints of V30 Gy < 70 cc,12 V30 Gy < 35 cc,13 and D30 cc < 30 Gy have been recommended 15.…”

“…A commonly used constraint is chest wall dose to 30 cc < 30 Gy,15 yet there is no prospectively validated data to support this threshold. There have been efforts in recent years to identify the risk factors for rib fractures and CWS and to refine the clinical and dosimetric predictors of chest wall toxicity using dose–response models 15, 16, 17, 18…”

High-dose irradiation of bone chips preserves the <i>in vitro</i> activity of bone-conditioned medium

“…Bone irradiation causes undesirable side effects leading to unfavorable bone remodeling and repair (8)(9)(10)(11) and, in the worst case, osteoradionecrosis (16). In the present study, we exposed cortical bone chips to a gamma radiation dose up to 120 Gy and investigated the subsequent effects on the activity of TGF-β target genes.…”

“…Adverse effects include pathologic fractures, continuity defects, and abnormalities in osteosynthesis (8)(9)(10)(11). Substantial evidence indicates that irradiation disrupts bone microvasculature (12,13).…”