Aims

The 15-year results of the EORTC 229922-10925 phase III trial showed a significant reduction in breast cancer mortality and breast cancer recurrences after internal mammary chain (IMC) and medio-supraclavicular irradiation. Unexpectedly, cardiac death was not increased, and the incidence of cardiac events did not differ between left- and right-sided cases, although target volume coverages and organ at risk doses were unknown. Therefore, a planning study was carried out comparing the past and the present, to eventually enable, thereafter, an increased therapeutic ratio of IMC irradiation.

Materials and methods

A planning study was carried out on target volume coverage and organ at risk doses for whole-breast irradiation (WBI) ± IMC comparing the results between two-dimensional radiotherapy (free-breathing), hybrid intensity-modulated radiotherapy (IMRT; breath-hold) and robust intensity-modulated proton therapy (IMPT; free-breathing) for 10 left-sided breast cancer cases. Two-dimensional radiotherapy consisted of two tangential wedged photon breast fields and mixed electron/photon beams for the IMC. Hybrid IMRT included two tangential photon breast fields (70%) complemented with IMRT (30%). IMPT plans were created using multi-field robust optimisation (5 mm set-up and 3% range uncertainties) with two (WBI) or three (WBI + IMC) beams.

Results

Target volume dose objectives were met for hybrid IMRT and IMPT. For two-dimensional radiotherapy, target coverage was 97% and 83% for breast and IMC, respectively. The mean heart dose for WBI only was <2 Gy for all techniques. For WBI + IMC, heart doses (mean heart dose, mean left anterior descending region, volume of the heart receiving 5 Gy (V5) were significantly higher for two-dimensional radiotherapy when compared with contemporary techniques. The V5 left anterior descending region reduced from 100% (two-dimensional radiotherapy) to 70% and 20% for hybrid IMRT and IMPT, respectively. Conclusion: Contemporary radiotherapy techniques result in improved target volume coverage and significantly decreased heart doses for WBI + IMC radiotherapy. Hence, nowadays an increased therapeutic ratio of elective IMC irradiation may be anticipated.

中文翻译：

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有或没有内乳链照射的左侧全乳照射的靶区覆盖率和危险器官剂量：代表过去和现在的三种技术之间的比较

目标

EORTC 229922-10925 III 期试验的 15 年结果显示，内乳链 (IMC) 和锁骨上中段照射后乳腺癌死亡率和乳腺癌复发率显着降低。出乎意料的是，心脏死亡并没有增加，心脏事件的发生率在左侧和右侧病例之间没有差异，尽管目标体积覆盖率和风险器官剂量未知。因此，进行了一项计划研究，将过去和现在进行了比较，以最终提高 IMC 照射的治疗率。

材料和方法

对全乳照射 (WBI) ± IMC 的靶区覆盖率和器官风险剂量进行了规划研究，比较了二维放疗（自由呼吸）、混合调强放疗（IMRT；屏气）的结果) 和强大的调强质子治疗 (IMPT；自由呼吸) 治疗 10 例左侧乳腺癌病例。二维放射治疗由两个切向楔形光子胸野和用于 IMC 的混合电子/光子束组成。混合 IMRT 包括两个切向光子乳腺场 (70%)，辅以 IMRT (30%)。IMPT 计划是使用具有两个 (WBI) 或三个 (WBI + IMC) 光束的多场稳健优化（5 mm 设置和 3% 范围不确定性）创建的。

结果

混合 IMRT 和 IMPT 达到了目标体积剂量目标。对于二维放射治疗，乳腺和 IMC 的靶覆盖率分别为 97% 和 83%。对于所有技术，仅 WBI 的平均心脏剂量<2 Gy。对于 WBI + IMC，与现代技术相比，二维放射治疗的心脏剂量（平均心脏剂量、平均左前降区、接受 5 Gy 的心脏体积（V5）显着更高。V5 左前降区从混合 IMRT 和IMPT分别为 100%（二维放疗）至 70% 和 20%。：现代放射治疗技术提高了靶区覆盖率，并显着降低了 WBI + IMC 放射治疗的心脏剂量。因此，现在可以预期选择性 IMC 照射的治疗率会增加。