Department for radiotherapy, Regensburg University Medical Center, Regensburg, Germany.
Faculty of computer science and mathematics, Ostbayerische Technische Hochschule, Regensburg, Germany.
J Appl Clin Med Phys. 2020 Dec;21(12):197-205. doi: 10.1002/acm2.13088. Epub 2020 Nov 4.
Men treated for localized prostate cancer by radiotherapy have often a remaining life span of 10 yr or more. Therefore, the risk for secondary malignancies should be taken into account. Plans for ten patients were evaluated which had been performed on an Oncentra® treatment planning system for a treatment with an Elekta Synergy™ linac with Agility™ head. The investigated techniques involved IMRT and VMTA with and without flattening filter. Different dose response models were applied for secondary carcinoma and sarcoma risk in the treated region and also in the periphery. As organs at risk we regarded for carcinoma risk urinary bladder, rectum, colon, esophagus, thyroid, and for sarcoma risk bone and soft tissue. The excess absolute risk (EAR) was found very similar in the treated region for both techniques (IMRT and VMAT) and also for both with and without flattening filter. The secondary sarcoma risk resulted about one magnitude smaller than the secondary carcinoma risk. The EAR to the peripheral organs was statistically significant reduced by application of the flattening filter free mode concerning the flattening filter as main source of scattered dose. Application of flattening filter free mode can thus support to reduce second malignancy risk for patients with localized prostate cancer.
接受放射治疗的局限性前列腺癌患者通常有 10 年或更长的剩余寿命。因此，应考虑继发性恶性肿瘤的风险。评估了在 Oncentra®治疗计划系统上为 Elekta Synergy™直线加速器和 Agility™头进行治疗的 10 名患者的计划。所研究的技术包括 IMRT 和 VMTA，有无平坦化滤波器。在治疗区域和周围区域，应用了不同的剂量反应模型来评估继发性癌和肉瘤风险。对于癌症风险，我们将膀胱、直肠、结肠、食道、甲状腺视为危险器官，对于肉瘤风险，我们将骨骼和软组织视为危险器官。对于两种技术（IMRT 和 VMAT）以及有无平坦化滤波器，治疗区域的超额绝对风险（EAR）非常相似。继发性肉瘤风险比继发性癌症风险小一个数量级。与作为散射线主要来源的平坦化滤波器相比，应用无平坦化滤波器模式可显著降低外周器官的 EAR。因此，应用无平坦化滤波器模式可支持降低局限性前列腺癌患者的第二恶性肿瘤风险。
