University of Toronto, Department of Radiation Oncology, Princess Margaret Hospital, Toronto, Ontario, Canada.
Radiat Oncol. 2007 Mar 15;2:13. doi: 10.1186/1748-717X-2-13.
Hodgkin's lymphoma (HL) survivors who undergo radiotherapy experience increased risks of second cancers (SC) and cardiac sequelae. To reduce such risks, extended-field radiotherapy (RT) for HL has largely been replaced by involved field radiotherapy (IFRT). While it has generally been assumed that IFRT will reduce SC risks, there are few data that quantify the reduction in dose to normal tissues associated with modern RT practice for patients with mediastinal HL, and no estimates of the expected reduction in SC risk.
Organ-specific dose-volume histograms (DVH) were generated for 41 patients receiving 35 Gy mantle RT, 35 Gy IFRT, or 20 Gy IFRT, and integrated organ mean doses were compared for the three protocols. Organ-specific SC risk estimates were estimated using a dosimetric risk-modeling approach, analyzing DVH data with quantitative, mechanistic models of radiation-induced cancer.
Dose reductions resulted in corresponding reductions in predicted excess relative risks (ERR) for SC induction. Moving from 35 Gy mantle RT to 35 Gy IFRT reduces predicted ERR for female breast and lung cancer by approximately 65%, and for male lung cancer by approximately 35%; moving from 35 Gy IFRT to 20 Gy IFRT reduces predicted ERRs approximately 40% more. The median reduction in integral dose to the whole heart with the transition to 35 Gy IFRT was 35%, with a smaller (2%) reduction in dose to proximal coronary arteries. There was no significant reduction in thyroid dose.
The significant decreases estimated for radiation-induced SC risks associated with modern IFRT provide strong support for the use of IFRT to reduce the late effects of treatment. The approach employed here can provide new insight into the risks associated with contemporary IFRT for HL, and may facilitate the counseling of patients regarding the risks associated with this treatment.
霍奇金淋巴瘤（HL）幸存者接受放疗会增加第二癌症（SC）和心脏后遗症的风险。为了降低这些风险，HL 的扩展野放疗（RT）已在很大程度上被累及野放疗（IFRT）所取代。虽然人们普遍认为 IFRT 将降低 SC 风险，但很少有数据量化与纵隔 HL 患者现代 RT 实践相关的正常组织剂量减少，也没有对 SC 风险降低的预期估计。
为 41 名接受 35Gy 斗篷 RT、35Gy IFRT 或 20Gy IFRT 的患者生成了器官特异性剂量体积直方图（DVH），并比较了三种方案的器官平均剂量。使用剂量学风险建模方法，通过分析辐射诱导癌症的定量、机械模型的 DVH 数据，估计器官特异性 SC 风险估计。
剂量减少导致预测的 SC 诱导超额相对风险（ERR）相应降低。从 35Gy 斗篷 RT 转移到 35Gy IFRT 可使女性乳腺癌和肺癌的预测 ERR 降低约 65%，男性肺癌的预测 ERR 降低约 35%；从 35Gy IFRT 转移到 20Gy IFRT 可使预测 ERR 降低约 40%。向 35Gy IFRT 过渡时，整个心脏的积分剂量中位数降低了 35%，而近端冠状动脉的剂量降低了 2%。甲状腺剂量没有显著降低。
与现代 IFRT 相关的辐射诱导 SC 风险的显著降低为使用 IFRT 降低治疗的晚期影响提供了有力支持。这里采用的方法可以为 HL 现代 IFRT 相关风险提供新的见解，并可能有助于患者就该治疗的相关风险进行咨询。
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