Murray L, Sethugavalar B, Robertshaw H, Bayman E, Thomas E, Gilson D, Prestwich R J D
Department of Clinical Oncology, St. James's Institute of Oncology, Leeds, UK; University of Leeds, Leeds, UK.
Department of Clinical Oncology, St. James's Institute of Oncology, Leeds, UK.
Clin Oncol (R Coll Radiol). 2015 Jul;27(7):401-10. doi: 10.1016/j.clon.2015.03.005. Epub 2015 Apr 1.
Recent radiotherapy guidelines for lymphoma have included involved site radiotherapy (ISRT), involved node radiotherapy (INRT) and irradiation of residual volume after full-course chemotherapy. In the absence of late toxicity data, we aim to compare organ at risk (OAR) dose-metrics and calculated second malignancy risks.
Fifteen consecutive patients who had received mediastinal radiotherapy were included. Four radiotherapy plans were generated for each patient using a parallel pair photon technique: (i) involved field radiotherapy (IFRT), (ii) ISRT, (iii) INRT, (iv) residual post-chemotherapy volume. The radiotherapy dose was 30 Gy in 15 fractions. The OARs evaluated were: breasts, lungs, thyroid, heart, oesophagus. Relative and absolute second malignancy rates were estimated using the concept of organ equivalent dose. Significance was defined as P < 0.005.
Compared with ISRT, IFRT significantly increased doses to lung, thyroid, heart and oesophagus, whereas INRT and residual volume techniques significantly reduced doses to all OARs. The relative risks of second cancers were significantly higher with IFRT compared with ISRT for lung, breast and thyroid; INRT and residual volume resulted in significantly lower relative risks compared with ISRT for lung, breast and thyroid. The median excess absolute risks of second cancers were consistently lowest for the residual technique and highest for IFRT in terms of thyroid, lung and breast cancers. The risk of oesophageal cancer was similar for all four techniques. Overall, the absolute risk of second cancers was very similar for ISRT and INRT.
Decreasing treatment volumes from IFRT to ISRT, INRT or residual volume reduces radiation exposure to OARs. Second malignancy modelling suggests that this reduction in treatment volumes will lead to a reduction in absolute excess second malignancy. Little difference was observed in second malignancy risks between ISRT and INRT, supporting the use of ISRT in the absence of a pre-chemotherapy positron emission tomography scan in the radiotherapy treatment position.
近期淋巴瘤放疗指南纳入了受累部位放疗（ISRT）、受累淋巴结放疗（INRT）以及全程化疗后残留体积的照射。在缺乏晚期毒性数据的情况下，我们旨在比较危及器官（OAR）剂量指标和计算出的二次恶性肿瘤风险。
纳入15例连续接受纵隔放疗的患者。使用平行对光子技术为每位患者生成4种放疗计划：（i）受累野放疗（IFRT），（ii）ISRT，（iii）INRT，（iv）化疗后残留体积。放疗剂量为30 Gy，分15次。评估的OAR包括：乳房、肺、甲状腺、心脏、食管。使用器官等效剂量的概念估计相对和绝对二次恶性肿瘤发生率。显著性定义为P < 0.005。
与ISRT相比，IFRT显著增加了肺、甲状腺、心脏和食管的剂量，而INRT和残留体积技术显著降低了所有OAR的剂量。与ISRT相比，IFRT导致肺、乳房和甲状腺的二次癌症相对风险显著更高；与ISRT相比，INRT和残留体积导致肺、乳房和甲状腺的相对风险显著更低。就甲状腺癌、肺癌和乳腺癌而言，残留技术的二次癌症中位超额绝对风险始终最低，IFRT最高。所有4种技术的食管癌风险相似。总体而言，ISRT和INRT的二次癌症绝对风险非常相似。
从IFRT减少至ISRT、INRT或残留体积可降低对OAR的辐射暴露。二次恶性肿瘤建模表明，治疗体积的这种减少将导致绝对超额二次恶性肿瘤的减少。在ISRT和INRT之间观察到的二次恶性肿瘤风险差异很小，支持在放疗治疗位置缺乏化疗前正电子发射断层扫描的情况下使用ISRT。
