Radiation Medicine Program, Princess Margaret Hospital, Toronto, ON, Canada.
Radiat Oncol. 2012 Sep 17;7:159. doi: 10.1186/1748-717X-7-159.
The purpose of this study was to identify clinical and dosimetric factors associated with radiotherapy induced bone injury (RIBI) following stereotactic lung radiotherapy.
Inoperable patients with early stage non-small cell lung cancer, treated with SBRT, who received 54 or 60 Gy in 3 fractions, and had a minimum of 6 months follow up were reviewed. Archived treatment plans were retrieved, ribs delineated individually and treatment plans re-computed using heterogeneity correction. Clinical and dosimetric factors were evaluated for their association with rib fracture using logistic regression analysis; a dose-event curve and nomogram were created.
46 consecutive patients treated between Oct 2004 and Dec 2008 with median follow-up 25 months (m) (range 6 - 51 m) were eligible. 41 fractured ribs were detected in 17 patients; median time to fracture was 21 m (range 7 - 40 m). The mean maximum point dose in non-fractured ribs (n=1054) was 10.5 Gy ± 10.2 Gy, this was higher in fractured ribs (n=41) 48.5 Gy ± 24.3 Gy (p<0.0001). On univariate analysis, age, dose to 0.5 cc of the ribs (D0.5), and the volume of the rib receiving at least 25 Gy (V25), were significantly associated with RIBI. As D0.5 and V25 were cross-correlated (Spearman correlation coefficient: 0.57, p<0.001), we selected D0.5 as a representative dose parameter. On multivariate analysis, age (odds ratio: 1.121, 95% CI: 1.04 - 1.21, p=0.003), female gender (odds ratio: 4.43, 95% CI: 1.68 - 11.68, p=0.003), and rib D0.5 (odds ratio: 1.0009, 95% CI: 1.0007 - 1.001, p<0.0001) were significantly associated with rib fracture.Using D0.5, a dose-event curve was constructed estimating risk of fracture from dose at the median follow up of 25 months after treatment. In our cohort, a 50% risk of rib fracture was associated with a D0.5 of 60 Gy.
Dosimetric and clinical factors contribute to risk of RIBI and both should be included when modeling risk of toxicity. A nomogram is presented using D0.5, age, and female gender to estimate risk of RIBI following SBRT. This requires validation.
本研究旨在确定与立体定向放疗后放射性骨损伤（RIBI）相关的临床和剂量学因素。
对 2004 年 10 月至 2008 年 12 月期间接受 SBRT 治疗的不能手术的早期非小细胞肺癌患者进行回顾性分析，这些患者接受了 54 或 60 Gy 的 3 次分割治疗，并且有至少 6 个月的随访。回顾性地获取存档的治疗计划，单独勾画肋骨，并使用不均匀性校正重新计算治疗计划。使用逻辑回归分析评估临床和剂量学因素与肋骨骨折的关系；创建剂量-事件曲线和列线图。
46 名连续患者在 2004 年 10 月至 2008 年 12 月期间接受治疗，中位随访时间为 25 个月（m）（范围 6-51 m），符合条件。17 名患者中有 41 根肋骨骨折；骨折的中位时间为 21 m（范围 7-40 m）。未骨折肋骨的最大点剂量平均值为 10.5 Gy ± 10.2 Gy，而骨折肋骨（n=41）为 48.5 Gy ± 24.3 Gy（p<0.0001）。单因素分析显示，年龄、肋骨 0.5 cc 处的剂量（D0.5）和接受至少 25 Gy 的肋骨体积（V25）与 RIBI 显著相关。由于 D0.5 和 V25 呈交叉相关（Spearman 相关系数：0.57，p<0.001），因此我们选择 D0.5 作为代表性剂量参数。多因素分析显示，年龄（优势比：1.121，95%CI：1.04-1.21，p=0.003）、女性（优势比：4.43，95%CI：1.68-11.68，p=0.003）和肋骨 D0.5（优势比：1.0009，95%CI：1.0007-1.001，p<0.0001）与肋骨骨折显著相关。使用 D0.5 构建了剂量-事件曲线，该曲线估计了治疗后中位随访 25 个月时骨折的风险。在我们的队列中，D0.5 为 60 Gy 时，发生肋骨骨折的风险为 50%。
剂量学和临床因素导致 RIBI 的风险增加，在进行毒性风险建模时应同时考虑这两个因素。使用 D0.5、年龄和女性性别提出了一种列线图，以估计 SBRT 后 RIBI 的风险。这需要验证。
