Department of Radiation Oncology, Erasmus MC-Daniel den Hoed Cancer Center, Rotterdam, The Netherlands.
Radiother Oncol. 2010 Jul;96(1):55-60. doi: 10.1016/j.radonc.2010.04.009. Epub 2010 Apr 27.
To provide a prescription dose for Monte Carlo (MC) treatment planning in patients with non-small-cell lung cancer according to tumor size and location.
Fifty-three stereotactic radiotherapy plans designed using the equivalent path-length (EPL) algorithm were re-calculated using MC. Plans were compared by the minimum dose to 95% of the PTV (D95), the heterogeneity index (HI) and the mean dose to organs at risk (OARs). Based on changes in D95, the prescription dose was converted from EPL to MC. Based on changes in HI, we examined the feasibility of MC prescription to plans re-calculated but not re-optimized with MC.
The MC fraction dose for peripheral tumors is 16-18 Gy depending on tumor size. For central tumors the MC dose was reduced less than for peripheral tumors. The HI decreased on average by 4-9% in peripheral tumors and 3-5% in central tumors. The mean dose to OARs was lower for MC than EPL, and correlated strongly (R(2)=0.98-0.99).
For the conversion from EPL to MC we recommend a separate prescription dose according to tumor size. MC optimization is not required if a HI > or = 70% is accepted. Dose constraints to OARs can be easily converted due to the high EPL-MC correlation.
根据肿瘤大小和位置，为非小细胞肺癌患者提供蒙特卡罗（MC）治疗计划的处方剂量。
对 53 例采用等效路径长度（EPL）算法设计的立体定向放疗计划进行了重新计算，使用 MC 进行了重新计算。通过 PTV（D95）的最小剂量、不均匀性指数（HI）和危及器官（OAR）的平均剂量对计划进行了比较。基于 D95 的变化，将处方剂量从 EPL 转换为 MC。基于 HI 的变化，我们研究了对没有用 MC 重新优化的计划进行 MC 处方的可行性。
对于外周肿瘤，MC 分次剂量取决于肿瘤大小，为 16-18 Gy。对于中央肿瘤，MC 剂量的减少低于外周肿瘤。HI 在平均外周肿瘤中降低了 4-9%，在中央肿瘤中降低了 3-5%。OAR 的平均剂量 MC 比 EPL 低，且相关性很强（R²=0.98-0.99）。
对于从 EPL 到 MC 的转换，我们建议根据肿瘤大小单独制定处方剂量。如果接受 HI>或=70%，则不需要 MC 优化。由于 EPL-MC 相关性很高，因此可以轻松转换对 OAR 的剂量限制。
