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.

中文翻译：

---

带或不带滤光片的强度调节放疗后局部前列腺癌患者继发恶性肿瘤的风险

通过放射疗法治疗局部前列腺癌的男性的剩余寿命通常为10年以上。因此，应考虑继发性恶性肿瘤的风险。评估了在Onentra®治疗计划系统上执行的针对10位患者的计划，该计划用于带有Elity头的Elekta Synergy™直线加速器的治疗。研究的技术涉及带有和不带有平坦滤波器的IMRT和VMTA。将不同的剂量反应模型应用于治疗区域和周边地区的继发性癌和肉瘤风险。作为有风险的器官，我们考虑了有癌风险的膀胱，直肠，结肠，食道，甲状腺以及有肉瘤的骨骼和软组织。在两种技术（IMRT和VMAT）以及带或不带扁平滤波器的治疗区域中，发现绝对风险（EAR）都非常相似。继发肉瘤的风险比继发癌的风险小约一个数量级。通过应用无展平过滤器模式将展平过滤器作为分散剂量的主要来源，降低了对外周器官的EAR的统计显着性。因此，无滤波器平坦化模式的应用可以支持降低局部前列腺癌患者的第二次恶性肿瘤风险。通过应用无展平过滤器模式将展平过滤器作为分散剂量的主要来源，降低了对外周器官的EAR的统计显着性。因此，无滤波器平坦化模式的应用可以支持降低局部前列腺癌患者的第二次恶性肿瘤风险。通过应用无展平过滤器模式将展平过滤器作为分散剂量的主要来源，降低了对外周器官的EAR的统计显着性。因此，无滤波器平坦化模式的应用可以支持降低局部前列腺癌患者的第二次恶性肿瘤风险。