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不可逆电穿孔（Irreversible Electroporation，IRE）是一种具有超短脉冲持续时间和高电场强度治疗肿瘤的新技术[1-2]。肿瘤物理治疗主要有放射治疗、射频消融[3]、微波消融[4]、光热疗法[5]、激光消融[6]、冷冻治疗[7]等，IRE为除上述之外的另一种癌症物理治疗方法[8]，其可使治疗区域内细胞形成IRE，有效破坏癌细胞[9]。在肿瘤物理消融治疗中，血管和胆道内皮细胞等细胞成分也将受到不同程度的不可逆损伤。然而，构成这些血管和胆管结构的细胞外基质可以保存其结构和功能的完整性，有助于组织的快速再生[10]。这使得IRE在理论上成为了一种安全的治疗选择，治疗胆管和内脏血管附近的肿瘤。本研究回顾了现有的临床数据，描述IRE的一般应用，分别讨论IRE在肝癌、胰腺癌和前列腺癌治疗中的应用。

1 不可逆电穿孔

1.1 工作原理

电脉冲通过在细胞膜中形成新生孔洞，以可逆或不可逆的方式渗透组织[11]。其中可逆电穿孔是在脉冲电场作用下在细胞膜上形成的一种瞬态亲水孔[12]。电脉冲引起了膜渗透性的变化的现象首先由Neumann等[13]发现。电穿孔的电脉冲剂量较小，只能导致细胞膜发生暂时的可逆性电击穿，撤销电场后，细胞膜逐渐恢复原来的形态，细胞仍然存活。例如，在一种新的癌症治疗方法中局部施加的脉冲电场可增强细胞膜的通透性，从而使化疗药物在细胞内更多的积累，从而导致局部进行性坏死[14-16]。此外，脉冲电场可以通过诱导电穿孔来破坏血脑屏障，从而增加细胞外通道的通透性[17-18]。

IRE是指在高压脉冲电场作用下，细胞膜产生了不可逆的孔洞的现象[19]。IRE是随着电脉冲剂量增加，细胞膜出现不可恢复的破裂导致细胞死亡[20-21]。这些电流的爆发可以通过破坏细胞壁的电势而穿透细胞膜，或者“穿孔”，如果稍微延长使用时间，就会导致目标肿瘤细胞不可逆的电穿孔[22-23]。

1.2 临床使用技术

在手术之前，评估肿瘤的确切大小和几何形状，以确定探针的数量和配置。尽管创建消融区域至少需要2个探针，但通常需要多个探针来彻底消融肿瘤，包括在所有方向上至少5 mm的无瘤边缘。IRE需要在全身麻醉下进行。完全肌肉放松是强制性的，以抵消由于电脉冲的传递而对骨骼肌的刺激，并防止肌肉收缩后电极针的移动。在脉冲输送之前，应通过确认完全肌肉松弛。建议将患者连接到外部除颤器，以便在发生室性心律失常时进行快速干预。可以在开腹手术中使用术中超声或经皮使用对比增强计算机断层扫描或超声引导进行内镜检查。对于计算机断层扫描引导的方法，建议进行计算机断层透视检查，以便了解针电极、目标病变及其周围结构。探针应相互平行插入，以促进均匀的能量输送。

1.3 IRE优势

可逆电穿孔技术是一种非热破坏细胞的技术[19,24-25]，可在诱导细胞死亡的同时将有害的热效应降至最低。相比于其他消融手段，IRE消融技术的优势是可应用于敏感结构附近，例如应用于邻近大血管的肿瘤治疗[26]，也可使有胆管和肝血管的肝门得以保留[27-29]。对于癌症的理想局部治疗方法是只破坏癌细胞，但同时保留或至少限制对周围重要结构的损伤。

2 肝癌治疗

中心位置的肝病变由于靠近主胆管和门静脉，不适合切除或热消融。由于IRE能够保存这些结构，其被认为是一种合适的消融手段[30]。

一项对129名患者（227 个肿瘤）的肝IRE安全性的系统评估中显示，总体并发症发生率为16%[25]。目前尚未有与肝癌IRE治疗相关的死亡的报道。穿刺相关并发症（如气胸和出血）很少遇到。施加的电场可能导致心律失常，但心脏门控大大降低了这种风险。Deodhar等[31]的研究发现，即使将针电极放置在心肌内，当电脉冲与R波同步传递时，也没有看到持久的心律失常。很少发生血管相关的并发症（如门静脉血栓形成）。也有研究表明，在电穿孔过程中，产生的热量是不可忽略的[32]，尤其是在电极针周围[33]。有研究显示，肝IRE后的胆管发生损伤，可能是由于与其中一根针电极直接接触而引起胆管热凝固所致[34]。因此，为避免损伤热敏结构，建议针电极放置在距离胆管或大血管至少5mm处[33]。

Cheng等[35]进行了6位患者的研究，得出100%的有效率。Bhutiani等[36]进行了30位患者的研究，得出97%的有效率。Niessen等[37]进行了34位患者的研究，得出74.8%的有效率。由于肝IRE的异质性，目前文献中肝IRE的疗效结果具有差异，肝癌疗效的现有数据概述，见表1。

3 胰腺癌治疗

胰腺癌是最具侵袭性的癌症之一，总体5年生存率<5%[46]。胰腺癌经IRE后经常会出现与胃肠道相关的并发症，如恶心、呕吐、腹泻、胃排空延迟、食欲不振、摄入量减少和腹痛。溃疡、穿孔或出血也有报道[47-49]。Scheffer等[50]报道，IRE后90 d内无患者死亡。总体而言，25名患者中有10名出现了23次不良事件。6名患者出现胃肠道并发症。两名患者需要临时鼻胃引流和放置鼻空肠饲管。两名患者在术后1 d淀粉酶和脂肪酶水平显著升高，内镜逆行胰胆管造影术显示壶腹区肿胀。一名患者出现胆管炎和感染的胆道瘤，需要经皮引流和经皮经肝胆管造影术引流。

Martin等[49]进行了包括200名接受IRE治疗的局部进展的胰腺癌患者的研究，进行局部控制（n=150）和切缘强化联合切除（n=50），报告中位总生存期为24.9个月。目前大多文献中患者的中位总生存期在10～15个月左右[48,51-52]。对所有报告生存结果的研究(不包括病例报告)的概述，见表2[47-48,50-54]。

4 前列腺癌治疗

IRE作为前列腺癌的非热疗法已经在临床实践中使用了许多年[55]。数据支持IRE作为一种可行的治疗所有前列腺部分的方法，在生活质量影响方面没有显著差异[56]。从形式上来说，IRE的风险和迄今为止建立的治疗局限性前列腺癌的程序之间没有根本区别[57]。Van den Bos等[58]将消融部位描述为比预期大两到三倍，并从前列腺囊扩散到神经血管束，这带来了压力性尿失禁和勃起功能障碍的相关风险。Neal等[59]进行了IRE对于前列腺癌的消融研究，轻度血尿是唯一的术后副作用。组织病理学结果显示，在消融区内没有存活的前列腺癌细胞，但发生了局部组织坏死和炎性浸润。该治疗消融了一定体积的前列腺组织，而没有损伤邻近的结构。

IRE对前列腺肿瘤的消融是有效的，因为大多数男性在消融后6个月进行活检时没有发现任何残留癌症的迹象[60]。IRE消融主要表现为腺结构纤维化、坏死和上皮脱离。消融区域界限分明，显示出活组织和非活组织之间的清晰界限[61]。一项研究对16名患前列腺癌的男性进行IRE消融[62]，组织病理学分析显示消融区内无残留肿瘤或活组织。一系列研究都表明IRE可以有效地消融目标区域内的肿瘤。

5 未来与挑战

在IRE消融研究中，除一个肿瘤的最大直径大于3.5 cm外，所有肿瘤均小于3.5 cm[36]。但如果直径3～4 cm的肿瘤用IRE消融，则完全消融率降低，复发的可能性增加[42]。数值和实验结果表明，在治疗缺血再灌注期间，肝组织的异质性影响中场分布的均匀性，导致不均匀的细胞死亡[63]。在垂直于电极的平面中，血管周围区域的电场强度增加，但在平行平面中，血管周围组织的电场强度显著降低。在肝脏中使用IRE仅限于大于3 cm的肿瘤，且手术时间有限。由于两个因素加上成本，阻止了IRE成为所有肝肿瘤消融的唯一确定模式。随着这项技术的不断发展，放射免疫疗法将日益成为大多数肝癌的消融治疗方法[64]。IRE不仅是一种很有前途的外科组织消融技术，也是一种基因治疗技术。由于IRE消融术可能会留下完整的肿瘤抗原，这些发现促进了肿瘤消融术的临床研究，使用免疫刺激质粒进行局部根除和全身免疫治疗的结合[65]。IRE-同基因NK免疫疗法的应用是一种新的、有前途的联合疗法[66]。然而，仍然需要更大的临床试验来证实这些结论。IRE会引起肌肉收缩，H-FIRE似乎是减轻与传统IRE脉冲相关的肌肉收缩的有效技术[67]。鉴于进展速度已成为治疗肝脏恶性肿瘤的可行消融技术，电穿孔可能是未来五年大多数患者首选的消融治疗方法。随着人们对IRE潜在应用的理解越来越广泛，技术越来越进步，应用也将变得越来越普遍。

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不可逆电穿孔在腹部肿瘤治疗中的应用

引言