肛门部位的癌症占所有大肠癌症的 1%-2%,所有肛门直肠癌的 4%。大部分患者 (75%-80%) 为鳞状细胞癌。[4]Beal KP, Wong D, Guillem JG, et al. Primary adenocarcinoma of the anus treated with combined modality therapy. Dis Colon Rectum. 2003;46:1320-1324.http://www.ncbi.nlm.nih.gov/pubmed/14530668?tool=bestpractice.com约 15% 的患者为腺癌或有腺癌的成分。这些癌症与直肠癌的自然病史类似,并且治疗方式相似(术前放化疗,随后进行根治性手术切除)。[4]Beal KP, Wong D, Guillem JG, et al. Primary adenocarcinoma of the anus treated with combined modality therapy. Dis Colon Rectum. 2003;46:1320-1324.http://www.ncbi.nlm.nih.gov/pubmed/14530668?tool=bestpractice.com
据估计,美国 2011 年肛门部位癌症共有 5820 例:其中男性 2140 例,女性 3680 例。[5]Siegel R, Ward E, Brawley O, et al. Cancer statistics, 2011: the impact of eliminating socioeconomic and racial disparities on premature cancer deaths. CA Cancer J Clin. 2011;61:212-236.http://onlinelibrary.wiley.com/doi/10.3322/caac.20121/fullhttp://www.ncbi.nlm.nih.gov/pubmed/21685461?tool=bestpractice.com据估计,每年会有 690 例患者因此死亡。英国年发病率约为 1/10 万,每年新增病例约 500 例。[6]Association of Coloproctology of Great Britain and Ireland. Guidelines for the management of colorectal cancer. 3rd ed. London, UK: Association of Coloproctology of Great Britain and Ireland; 2007.肛门癌虽然仍是罕见癌症,但其发病率在过去的几十年里大幅增加。原因可能是 HPV 的性传播,尤其是 HPV-16 和 HPV-18。[7]Frisch M, Fenger C, van den Brule AJ, et al. Variants of squamous cell carcinoma of the anal canal and perianal skin and their relation to human papillomaviruses. Cancer Res. 1999;59:753-757.http://cancerres.aacrjournals.org/content/59/3/753.fullhttp://www.ncbi.nlm.nih.gov/pubmed/9973228?tool=bestpractice.com
HIV 感染与肛管癌之间存在明显的相关性。但肛门癌并不是获得性免疫缺陷综合征 (AIDS) 定义性的恶性肿瘤。美国患癌症的 AIDS 患者的交叉引用数据库显示,对于男同性恋者,在 AIDS 确诊时或确诊之后,肛门癌的相对风险 (relative risk, RR) 为 84.1。对于 AIDS 确诊前最长 5 年内,肛门癌的 RR 为 13.9。[8]Melbye M, Cote T, Kessler L, et al. High incidence of anal cancer among AIDS patients. Lancet. 1994;343:636-639.http://www.ncbi.nlm.nih.gov/pubmed/7906812?tool=bestpractice.com男男性行为者罹患肛门癌的风险较高。[9]Palefsky JM, Holly EA, Efirdc J, et al. Anal intraepithelial neoplasia in the highly active antiretroviral therapy era among HIV-positive men who have sex with men. AIDS. 2005;19:1407-1414.http://www.ncbi.nlm.nih.gov/pubmed/16103772?tool=bestpractice.com
对于接受实体器官移植的患者,由于慢性免疫抑制治疗,其肛门癌的患病率增加。在接受实体器官移植的 3595 名患者系列中,肛门癌的患病率为 0.11%,相应的 RR 约为 110。[10]Aigner F, Boeckle E, Albright J, et al. Malignancies of the colorectum and anus in solid organ recipients. Transpl Int. 2007;20:497-504.http://www.ncbi.nlm.nih.gov/pubmed/17343685?tool=bestpractice.com