A review article published in The Lancet Gastroenterology & Hepatology urged for the increased implementation of anal cancer screening in routine clinical practice. Currently, there are no national recommendations guiding anal cancer screening in any country, though several medical groups recognize its importance in high-risk groups. In a review of the existing literature, authors detailed various methods of anal cancer screening and provided recommendations for clinicians.
While anal cancer is relatively uncommon in the general population, its incidence is substantially elevated in certain groups, including patients with human immunodeficiency virus (HIV), men who have sex with men (MSM), recipients of solid organ transplants, women with genital neoplasia, and patients with certain autoimmune conditions. There exists no established screening guidelines for the detection of pre-cancerous anal lesions, and data examining the relative efficacies of certain screening procedures are scarce.
In addition to sparseness of data, no universal classification system for anal precancerous lesions has been established. One 2-tiered system describes precancerous neoplasia as either low-grade squamous intraepithelial lesions (LSILs) or high-grade squamous intraepithelial lesions (HSILs). Studies that have employed this classification system have found that the prevalence of HSILs is substantially elevated in HIV-positive MSM compared with HIV-negative MSM, emphasizing the increased cancer risk in HIV-positive men. In light of increased risk among these certain groups, authors propose that anal cancer screening could “follow a…similar process to that for cervical cancer screening, but with an exclusive focus on high-risk groups.”
Possible screening methods for anal cancer include anal cytology, high-resolution anoscopy, and digital anorectal examination. Anal cytology is an effective first-line screening method that should not be the basis for a final diagnosis, authors wrote. Instead, abnormal cytology results may be effectively followed-up with high-resolution anoscopy, which allows for HSIL recognition and biopsy. Anoscopy can be done without sedation and in prior studies has displayed high acceptability with patients.
Digital anorectal examination is another option for detecting early-stage cancer, though it cannot recognize precancerous lesions. Guidelines in the United States recommend that HIV-positive MSM receive digital anorectal examinations every 1-3 years.
In addition to established anal cancer screening methods, “retroflexion” during gastrointestinal endoscopy can be used to detect lesions at the squamocolumnar junction. The British Society of Gastroenterology recommends that retroflexion should be attempted in all patients during colonoscopy to detect “unsuspected lesions.” A similar proposal has been made by the European Society of Gastrointestinal Endoscopy.
Beyond screening, there is also a dearth of high-quality data regarding the treatment of anal HSILs. The relative benefits of HSIL treatment compared with close surveillance remain unclear. HSIL treatment options include surgical excision, topical therapies, argon plasma coagulation, radiofrequency ablation, and endoscopic submucosal dissection. However, anal HSILs have high recurrence rates, particularly in patients with HPV or HIV.
Additionally, certain treatment methods—such as excision—can cause complications, including fecal incontinence, anal stenosis, and compromised sphincter function. As such, clinicians should carefully weigh the risks and benefits of HSIL removal prior to implementing any treatment procedure.
Based on existing information, authors urged gastroenterologists to engage more often in anal cancer screening procedures, particularly with high-risk patients. Investigators also emphasized the need for further research into the detection and treatment of anal precancerous lesions.
“Gastroenterologists can provide a valuable contribution to patient care through the following actions: identifying (I) population groups with an increased incidence of anal squamous cell carcinoma; doing a careful digital anorectal examination to notice any masses (M); and always performing (P) a retroflexion (R) with observation (O) and visualisation (V) of the squamocolumnar junction during endoscopy (E),” investigators wrote. “These actions can constitute a call to IMPROVE detection.”
Albuquerque A, Nathan M, Cappello C, Dinis-Ribeiro M. Anal cancer and precancerous lesions: a call for improvement. Lancet Gastroenterol Hepatol. 2021;6(4):327-334.