鳞状细胞癌

尽管尚未发现食管鳞状细胞癌的重要癌前病变,但已发现多个与食管鳞状细胞癌发病率增加相关的因素,包括:长期暴露于烟草或酒精[1]、贲门失弛缓症[2]、长期酒精和(或)烟草暴露引起的头颈部鳞状细胞癌[3]、胼胝症[4][5]、碱液摄入史[6]、乳糜泻[7]与好发于南美及中国的热饮摄入史[8]。此外,人乳头瘤病毒感染对鳞状细胞癌发生的作用仍在研究之中[9][10]

食管鳞状细胞癌的早期筛查工作主要集中于针对高发病率国家目标人群的细胞学或内镜筛查。尽管这些检查可以在无症状阶段发现早期食管癌,但目前尚无有疗效相关数据(如死亡率下降)发表。多个国家相继发表了食管癌细胞学筛查相关研究数据,包括中国[11][12]、伊朗[13]、 南非[14][15]、意大利[16]和日本[17]。在美国,类似的研究工作主要集中于食管鳞癌发生风险较高的个体[18][19]。此外,法国[20] 和日本[21]则发表了初步内镜筛查的相关研究结果。

中国和美国的筛查研究均发现,细胞学联合组织学检查确诊肿瘤的敏感性较低(14%-36%),特异性为90-99%,而其阳性预测值则从23%到94%不等[22]。因此,统一且准确的食管病灶细胞学诊断标准,需要正式的细胞学-组织学相关性研究。随着内镜筛查在高危人群中的普及率逐步提升,上述研究将变得更为可行。

对于患胼胝症或长期贲门失迟缓症的高危人群,进行细胞学或内镜检测的有效性尚不明确。

食管腺癌

对于Barrett食管患者患癌风险是否增加尚存在争议。一些已发表的前瞻性研究发现Barrett食管患者的食管腺癌年发病率波动在0.2%到1.9%之间[23]。考虑到文献偏倚的存在,部分学者认为真实的发病率可能会低于文献数据[24]。目前普遍认为在Barrett食管患者中,0.5%的食管腺癌年发病率可能是较为合理的估计值[25]

Barrett食管与胃食管反流病有显著相关性,约10%的GERD患者有Barrett食管相关改变。但GERD本身非常常见,研究发现约20%的成年美国人出现过烧心等GERD症状,且每周至少一次[26]。内镜下发现Barrett食管相关改变的发生率与胃食管反流症状的持续时间相关。一项纳入701例参与者的研究发现,GERD症状持续不足1年的患者中仅有4%经内镜检查发现了Barrett食管相关改变;而在GERD症状持续超过10年的患者中,这一比例高达21%。研究者估测医生仅诊断或发现了约5%的Barrett食管患者[27]。尚未有足够证据提示针对Barrett食管的人群筛查可以降低腺癌的死亡率[28][29]

Barrett食管的监测包括通过检查方法在确诊Barrett食管的患者中识别出癌前病变或可治愈的肿瘤。 监测的有效实施必须满足多个必要因素,包括监测方法的低危害性、对不典型增生的正确组织学诊断、证明高级别不典型增生的手术切除能降低患癌风险,和肿瘤的成功切除。内镜随访的时间间隔取决于组织学结果,以胃肠道疾病协会发表的指南为准则[30]。为了减少GERD本身的炎症反应对活检结果判读的干扰,应在实施内镜检测前治疗GERD。部分临床医生推荐采用随机四象限活检术用于组织学评估,该技术将食管柱状上皮取材区域分为四个象限,分别取材一次,各取材点间隔2cm。对于不存在不典型增生的患者,推荐每隔2到3年复查一次内镜[30]。而对于存在低级别不典型增生的患者,指南建议自诊断起第一年内每隔6个月复查一次内镜,如果不典型增生的严重程度没有进展,自第二年起可延长至每年一次复查内镜。对于存在高级别不典型增生的患者,指南建议两个选择:直接手术切除或者重复内镜评估直至诊断为黏膜内癌。尽管上述指南建议在临床实践中被广泛采用,仍需注意上述建议主要是基于非对照病例系列研究及胃肠道疾病的内镜专科医师和病理学家的意见。

其他可能识别不典型增生上皮并取标本的方法包括染色内镜[31] 以及激光诱导荧光光谱分析法[29][32]

危害证据

采用非内镜引导球囊细胞学盲法取样筛查食管鳞癌几乎不引起不舒适或不方便。食管腺癌的内镜筛查较为昂贵、不方便且常需镇静。

内镜检查可能出现穿孔或出血等并发症。穿孔、呼吸暂停及心肌梗死三大并发症的发生率在每1万次操作中约有0到13例,相关死亡率在每1万次操作中约有0-0.8例[33][34]

尽管Barrett食管的患癌风险较低,诊断为Barrett食管的患者仍会误以为自己病情较重。

参考文献

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