We aimed to estimate the risk of secondary cancer after radiotherapy (RT) in high‐risk prostate cancer (HRPC) patients with pelvic irradiation. Computed tomography data of five biopsy‐proven HRPC patients were selected for this study. Two different planning target volumes (PTV₁ and PTV₂) were contoured for each patient. The PTV₁ included the prostate, seminal vesicles, and pelvic lymphatics, while the PTV₂ included only the prostate and seminal vesicles. The prescribed dose was 54 Gy for the PTV₁ with a sequential boost (24 Gy for the PTV₂). Intensity‐modulated RT (IMRT) and volumetric modulated arc therapy (VMAT) techniques were used to generate treatment plans with 6 and 10 MV photon energies with the flattening filter (FF) or flattening filter‐free (FFF) irradiation mode. The excess absolute risks (EARs) were calculated and compared for the bladder, rectum, pelvic bone, and soft tissue based on the linear‐exponential, plateau, full mechanistic, and specific mechanistic sarcoma dose‐response model. According to the models, all treatment plans resulted in similar risks of secondary bladder or rectal cancer and pelvic bone or soft tissue sarcoma except for the estimated risk of the bladder according to the full mechanistic model using IMRT_(6MV;FF) technique compared with VMAT techniques with FFF options. The overall estimation of EAR indicated that the radiation‐induced cancer risk due to RT in HRPC was lower for bladder than the rectum. EAR values ranged from 1.47 to 5.82 for bladder and 6.36 to 7.94 for rectum, depending on the dose–response models used. The absolute risks of the secondary pelvic bone and soft tissue sarcoma were small for the plans examined. We theoretically predicted the radiation‐induced secondary cancer risk in HRPC patients with pelvic irradiation. Nevertheless, prospective clinical trials, with larger patient cohorts with a long‐term follow‐up, are needed to validate these model predictions.

中文翻译：

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骨盆照射高危前列腺癌患者放疗后继发癌症风险的估计。

我们旨在评估高危前列腺癌（HRPC）盆腔照射患者放疗（RT）后继发癌症的风险。本研究选择了5例经活检证实的HRPC患者的计算机断层扫描数据。为每个患者绘制了两个不同的计划目标体积（PTV ₁和PTV ₂）。PTV ₁包括前列腺，精囊和骨盆淋巴管，而PTV ₂仅包括前列腺和精囊。PTV ₁的处方剂量为54 Gy，并依次增强（PTV _2的剂量为24 Gy）。调强RT（IMRT）和容积调制弧光疗法（VMAT）技术被用于使用平坦滤光片（FF）或无平坦滤光片（FFF）照射模式生成具有6和10 MV光子能量的治疗计划。基于线性指数，高原，完全机械性和特定机械性肉瘤剂量反应模型，计算并比较了膀胱，直肠，骨盆骨和软组织的绝对绝对风险（EARs）。根据模型，所有治疗方案均导致类似的继发性膀胱癌或直肠癌，骨盆骨或软组织肉瘤的风险，但根据使用IMRT _{（6MV; FF）}的完整机制模型估算的膀胱癌风险除外与具有FFF选项的VMAT技术相比。EAR的总体估计表明，HRPC的放疗所致的放疗所致癌症的风险低于膀胱。取决于所使用的剂量反应模型，膀胱的EAR值范围为1.47至5.82，直肠的EAR值范围为6.36至7.94。对于所检查的计划，继发性骨盆​​骨和软组织肉瘤的绝对风险很小。从理论上讲，我们预测了骨盆照射的HRPC患者中由辐射诱发的继发性癌症风险。但是，需要进行前瞻性临床试验，对更多的患者进行长期随访，以验证这些模型预测。