Conclusion of increased risk of cataracts associated with CT studies of the head may not be justified.
Conclusion of increased risk of cataracts associated with CT studies of the head may not be justified.
复制标题
头部 CT 研究导致白内障风险增加的结论可能并不合理。
DOI：
--
复制
发表时间：
2014
期刊：
影响因子：
--
通讯作者：
M. Doss
中科院分区：
文献类型：
--
作者：
M. Doss
AJR 2014; 202：W 413 0361- 803 X/14/2024-W 413 ©美国X射线学会关于头部CT检查相关白内障风险增加的结论可能不合理本函参考Yuan等人[1]最近的文章，“重复头部和颈部CT检查相关白内障风险：一项全国性的基于人口的研究，“其中作者得出结论，头部和颈部的重复CT研究与白内障风险增加有关，他们的数据提供了CT辐射对眼睛危害的证据。透镜。这封信的目的是指出为什么这样的结论可能是不合理的几个原因。作者比较了接受头颈部CT检查的头颈部癌症患者与未接受任何CT检查的对照组的白内障发生率。癌症治疗的众所周知的副作用之一是白内障。例如，已知化疗和类固醇治疗会引起后囊下白内障[2，3]，这与高剂量辐射引起的白内障相似。由于许多头颈癌患者可能接受了这些癌症治疗，并且作者没有考虑CT组中此类治疗的白内障发生效应，因此CT研究中计算的白内障风险比可能被大大高估。作者也没有考虑接受放射治疗的头颈部癌症患者的眼透镜辐射剂量。尽管现代技术，例如调强放射治疗（IMRT），已经降低了对非靶体积的辐射剂量，从而减少了治疗副作用，但是来自这种治疗的对眼睛透镜的剂量仍然是相当大的。据估计，头颈部癌症IMRT对眼透镜的辐射剂量在肿瘤处方剂量的2-61%范围内[4]。使用该估计的最小百分比值并使用20戈伊的低端处方剂量，眼晶状体将从放射治疗中接收约40 c戈伊的最小剂量，鉴于单次CT研究中估计的5-c戈伊透镜剂量，该剂量远高于CT研究中可能的累积剂量[1]。因此，由于CT研究的辐射剂量对眼透镜的任何生物效应将被由于放射治疗的辐射剂量的生物效应所压倒，使得无法根据此类患者的数据可靠地估计CT研究的白内障发生效应。Yuan等人[1]提供的数据中有证据表明，癌症治疗的影响被忽视，从而混淆了报告的结果。作者在其研究的表3中列出了接受和未接受放射治疗的患者的调整后CT白内障风险比分别为1.38和2.2。这似乎意味着放射治疗患者中白内障的危害降低，这些患者可能因治疗而对眼睛透镜产生额外的辐射剂量。没有接受放射治疗的头颈癌患者可能更有可能接受化疗或其他可能增加白内障风险的治疗，从而为结果的这一特征提供了可能的解释。总之，不可能从头颈部癌症患者的数据分析中分离出来自CT研究的辐射剂量的推定白内障发生效应，因为此类患者接受的放射治疗的生物学效应可能会超过CT研究对眼透镜的生物学效应，并且其他癌症治疗的白内障发生效应会混淆结果。Mohan Doss Fox Chase癌症中心，宾夕法尼亚州费城
AJR 2014; 202:W413 0361–803X/14/2024–W413 © American Roentgen Ray Society Conclusion of Increased Risk of Cataracts Associated With CT Studies of the Head May Not Be Justified This letter is with reference to the recent article by Yuan et al. [1], “The Risk of Cataract Associated With Repeated Head and Neck CT Studies: A Nationwide PopulationBased Study,” in which the authors concluded that repeated CT studies of the head and neck are associated with increased risk of cataracts and that their data provide evidence of the hazards of the radiation from CT to the eye lens. The purpose of this letter is to point out a few reasons why such a conclusion may not be justified. The authors compared the cataract rates in head and neck cancer patients who underwent CT of the head and neck region to a control group who had not undergone any CT. One of the well-known side effects of cancer treatment is cataracts. For example, chemotherapy and steroid treatment are known to cause posterior subcapsular cataracts [2, 3], which are similar to those from high-dose radiation. Because many patients with head and neck cancer likely underwent these cancer treatments and the authors did not account for the cataractogenic effects of such treatments in the CT group, the calculated hazard ratios for cataracts from CT studies are likely to be considerably overestimated. The authors also did not account for the eye lens radiation dose for the head and neck cancer patients undergoing radiation therapy. Although modern technologies, such as intensity-modulated radiation therapy (IMRT), have decreased the radiation doses to untargeted volumes thereby reducing treatment side effects, the dose to eye lens from such treatments can still be substantial. Radiation dose to the eye lens from IMRT for head and neck cancers has been estimated to be in the range of 2–61% of the prescribed dose for tumors [4]. Using the minimum percentage value from this estimate and using the low-end prescription dose of 20 Gy, the eye lens would receive a minimum dose of approximately 40 cGy from the radiation therapy, which, in view of the estimated 5-cGy lens dose from a single CT study, is much higher than the likely cumulative dose from the CT studies [1]. Thus, any biologic effects in eye lens due to the radiation dose from CT studies would be overwhelmed by the biologic effects from the radiation dose due to radiation therapy, making it infeasible to reliably estimate the cataractogenic effects of CT studies from data in such patients. There is evidence in the data presented by Yuan et al. [1] for confounding of the reported results by the neglected effects of the cancer treatments. The authors have presented the adjusted CT cataract hazard ratios in patients with and without radiation therapy to be 1.38 and 2.2, respectively, in Table 3 of their study. This seems to imply a reduced hazard for cataracts in the radiotherapy patients who likely had the additional radiation dose to the eye lens from the therapy. The head and neck cancer patients who did not undergo radiation therapy were probably more likely to have undergone chemotherapy or other therapies that may have increased their risk of cataracts, thereby providing a possible explanation for this feature of the results. In summary, it may not be possible to isolate the presumed cataractogenic effects of the radiation dose from CT studies from the analysis of data in head and neck cancer patients because the biologic effects of radiation therapies such patients underwent would likely overwhelm the biologic effects of CT studies in the eye lens and the cataractogenic effects of other cancer therapies would have confounded the results. Mohan Doss Fox Chase Cancer Center, Philadelphia, PA