The objective of this study was to estimate the risk of developing second malignancies to partially in-field organs from volumetric modulated arc therapy (VMAT) of cervical cancer and to compare the above risks with those from the conventional three-dimensional conformal radiotherapy (3D-CRT). Seventeen consecutive patients with uterine cervix carcinoma were selected. VMAT and 3D-CRT plans were generated with 6 and 10 MV photons, respectively. The prescribed tumor dose was 45 Gy given in 25 fractions. Differential dose-volume histogram data from the treatment plans were obtained for the partially in-field organs such as bladder and rectum. These data were used to estimate the patient-specific lifetime attributable risk (LAR) for bladder and rectal cancer induction with a non-linear model based on a mixture of plateau and bell-shaped dose–response relationships. The estimated risks per 10000 people were compared with the baseline risks for unexposed population. The patient-specific rectal cancer risk estimates from VMAT were significantly lower than those from 3D-CRT (P = 0.0144). The LARs for developing bladder malignancies from VMAT were significantly high compared to those from conventional irradiation (P = 0.0003). The mean difference between the patient-specific LARs for radiation-induced bladder and rectal malignancies as derived from 3D-CRT and VMAT plans was 6.6% and 2.0%, respectively. The average LAR for developing bladder and rectal malignant diseases due to VMAT was 9.2 × 10^-4 and 43.7 × 10^-4, respectively. The corresponding risks following 3D-CRT were 8.6 × 10^-4 and 44.6 × 10^-4. These average risks showed that pelvic irradiation increases the baseline probability for cancer induction by 12.6-19.1%. The differences in the second cancer risks associated with the VMAT and 3D-CRT for cervical cancer were found to be small. Both treatment techniques resulted in considerable increased probabilities for developing bladder and rectal malignancies relative to those of unirradiated population.

中文翻译：

---

宫颈癌放疗引起第二次膀胱和直肠恶性肿瘤的风险

本研究的目的是评估宫颈癌体积调制弧光疗法 (VMAT) 对部分野内器官发生第二恶性肿瘤的风险，并将上述风险与传统三维适形放疗 (3D-显像管）。连续选择了 17 名子宫颈癌患者。VMAT 和 3D-CRT 计划分别用 6 和 10 MV 光子生成。规定的肿瘤剂量为 45 Gy，分 25 次给药。从治疗计划中获得差异剂量体积直方图数据，用于部分在场的器官，如膀胱和直肠。这些数据用于通过基于平台和钟形剂量-反应关系混合的非线性模型估计膀胱癌和直肠癌诱发的患者特定终生归因风险 (LAR)。将每 10000 人的估计风险与未暴露人群的基线风险进行比较。VMAT 的患者特定直肠癌风险估计值显着低于 3D-CRT 的值。P  = 0.0144）。与常规照射相比，VMAT 用于发展膀胱恶性肿瘤的 LAR 显着高（P  = 0.0003）。来自 3D-CRT 和 VMAT 计划的辐射诱发膀胱和直肠恶性肿瘤的患者特异性 LAR 之间的平均差异分别为 6.6% 和 2.0%。VMAT 导致膀胱和直肠恶性疾病的平均 LAR 分别为 9.2 × 10 ^-4和 43.7 × 10 ^-4。3D-CRT 后的相应风险分别为 8.6 × 10 ^-4和 44.6 × 10 ^-4. 这些平均风险表明，盆腔照射使癌症诱发的基线概率增加了 12.6-19.1%。发现与宫颈癌 VMAT 和 3D-CRT 相关的第二种癌症风险的差异很小。与未受辐射人群相比，这两种治疗技术都显着增加了患膀胱和直肠恶性肿瘤的可能性。