Princess Alexandra Hospital, Queensland, Australia.
Peter MacCallum Cancer Centre, Victoria, Australia.
Z Med Phys. 2021 Nov;31(4):347-354. doi: 10.1016/j.zemedi.2021.04.003. Epub 2021 Jun 12.
Dose to the contralateral breast (CLB) from radiotherapy treatment has the potential to induce secondary breast cancer. Electronic tissue compensation (eComp) for breast cancer patients is one of the alternative methods to conventional 3D-conformal radiotherapy that eliminates the use of wedges. Several studies have investigated dose to the CLB using tangential fields involving wedges, intensity-modulated radiation therapy and volumetric modulated arc radiation therapy and various other techniques via treatment planning system calculations, Monte Carlo methods and phantoms. However, there are limited data published in assessing the actual dose received by the CLB from treatment with eComp-based tangential fields. In this study, the CLB dose for patients undergoing tangential field radiotherapy with eComp and enhanced dynamic wedged (standard) tangential fields was measured and compared to assess the CLB dose between the two methods. Measurements were conducted on a randomised trial of 40 patients, 20 of them had undergone standard planning, and the remaining 20 were treated with eComp. The mean surface dose measured with TLDs at 3cm from the medial tangential border for eComp and standard techniques was 10.04±1.37% and 10.14±2.05%, respectively for a prescription dose of 2.65Gy/fraction. The estimated dose at 1cm depth in tissue, measured with the use of perspex domes placed over the TLD at the same location, was 5.12±0.87% and 6.29±2.01% for eComp and standard, respectively. The CLB dose is dependent on the proximity of the medial tangential field edge to the contralateral breast and is patient-specific. The results of this study show that at 1cm depth, eComp technique delivers significantly less dose (p<0.05) to the CLB as compared to standard tangential fields. Furthermore, the surface dose measured for both eComp and standard are comparable indicating that the eComp-based tangential field technique does not contribute any excess dose to CLB when compared to standard tangential fields. The excess relative risk (ERR) for radiation-induced cancers for eComp was found to be 0.08, compared to 0.11 for standard tangential fields.
从放射治疗中对对侧乳房（CLB）的剂量有可能诱发继发性乳腺癌。对于乳腺癌患者，电子组织补偿（eComp）是替代传统 3D 适形放射治疗的方法之一，该方法消除了楔子的使用。已经有几项研究使用涉及楔子的切线野、强度调制放射治疗和容积调强弧形放射治疗以及通过治疗计划系统计算、蒙特卡罗方法和体模的各种其他技术来研究 CLB 剂量。然而，关于使用基于 eComp 的切线野治疗的 CLB 实际接收剂量的评估数据有限。在这项研究中，对接受 eComp 切线野放射治疗的患者的 CLB 剂量进行了测量，并与标准的增强动态楔形（标准）切线野进行了比较，以评估两种方法之间的 CLB 剂量。测量是在 40 名患者的随机试验中进行的，其中 20 名患者接受了标准计划，其余 20 名患者接受了 eComp 治疗。在距内侧切线边界 3cm 处用 TLD 测量 eComp 和标准技术的表面剂量平均值分别为 10.04±1.37%和 10.14±2.05%，处方剂量为 2.65Gy/分次。使用放置在同一位置的 perspex 圆顶在组织中测量 1cm 深度处的估计剂量，eComp 和标准分别为 5.12±0.87%和 6.29±2.01%。CLB 剂量取决于内侧切线野边缘与对侧乳房的接近程度，并且是患者特异性的。本研究结果表明，在 1cm 深度处，eComp 技术与标准切线野相比，对 CLB 的剂量明显降低（p<0.05）。此外，eComp 和标准的表面剂量测量值相当，表明与标准切线野相比，基于 eComp 的切线野技术不会对 CLB 产生任何额外剂量。eComp 的辐射诱发癌症的超额相对风险（ERR）为 0.08，而标准切线野的 ERR 为 0.11。
