Anal intraepithelial neoplasia: diagnosis, screening, and treatment

Abstract

Anal intraepithelial neoplasia (AIN) is a premalignant lesion for anal cancer. It is more commonly found in high-risk patients (e.g., human papilloma virus (HPV)/human immunodeficiency virus infections, post-organ transplantation patients, and men who have sex with men) and development is driven by HPV infection. The incidence of AIN is difficult to estimate, but is heavily skewed by preexisting conditions, particularly in high-risk populations. The diagnosis is made from cytology or biopsy during routine examinations, and can be performed at a primary care provider’s office. A pathologist can then review and classify cells, based on nucleus-to-cytoplasm ratios. The classification of low or high grade can better predict progression from AIN to anal cancer. There is little debate that AIN can develop into anal cancer, and the main rationale for treatment is to delay the progression. Significant controversy remains regarding screening, surveillance, and treatment for AIN. Management options are separated into surveillance (watchful waiting) and interventional strategies. Emerging data suggest that close patient follow up with a combination of ablative and topical treatments may offer the greatest benefit. HPV vaccination offers a unique treatment prior to HPV infection and the subsequent development of AIN, but its use after the development of AIN is limited. Ablative treatment includes excision, fulguration, and laser therapy.

HPV genotyping and risk factors for anal high-risk HPV infection in men who have sex with men from Toronto, Canada

“…The incidence of anal cancer has been increasing in high-income countries 8 , with particularly rapid increases in men who have sex with men (MSM) where the incidence is 40/100,000 in HIV-negative MSM and over 100/100,000 in HIV-positive MSM 9 , in comparison to a background rate of 2/100,000 in the general population 10 . Current treatment options for anal dysplasia include mechanical or chemical ablative techniques, but there are high recurrence rates regardless of clinical approach and it has not been formally demonstrated that any of these approaches prevents the subsequent development of cancer 11 , 12 . Moreover, recent evidence shows that the clearance of anal dysplasia in the absence of any intervention occurs at a fairly high rate of 22/100 person-years, further adding to the complexity of this clinical issue 13 .…”

Risk factors for ≥high-grade anal intraepithelial lesions in MSM living with HIV and the response to topical and surgical treatments

“…The surgical option was also effective in a large proportion of our patients, although some needed retreatment due to recurrence or incomplete excision. No cases of permanent stenosis or fecal incontinence were observed in the surgical group; however, surgery is not currently recommended due to its adverse effects, especially in patients with large lesions [ 30 ].…”

“…It remains controversial whether the treatment of high-grade anal intraepithelial lesions (HSILs) prevents the subsequent development of ASCC [ 9 ], and no standard approach has been established, so that treatments vary among centers according to their resources and experience. Therapeutic options include local topical treatments with trichloroacetic acid, imiquimod, or 5-fluoruracil and more invasive treatments such as excision, fulguration, or laser therapy [ 9 ]. Surgical excision used to be a treatment of choice but is associated with adverse effects, including anal stenosis, and with recurrences and incomplete resection, especially when the anal disease is extensive [ 10 ].…”

“…In regard to infrared or laser coagulation, it can be applied in the consulting room and is well tolerated, but a recurrence rate of 61% at one year has been described in HIV+ patients [ 12 ]. Finally, topical therapies offer a non-invasive option with a good safety profile and few adverse effects [ 9 ]. In particular, imiquimod offers the advantage of self-administration, a low recurrence rate, and a high response rate in HIV+ patients, which was reported to be 61% in a clinical trial [ 13 ].…”

Definitive Radiotherapy for Patients With Anal Squamous Cell Carcinoma: A Retrospective Cohort Study

“…Among these, HPV 16 is the most frequent type and is considered a crucial factor for the development of squamous cell carcinoma [ 5 ]. Anal intraepithelial neoplasia and anal squamous intraepithelial lesions are considered premalignant signs of anal squamous cell carcinoma, which is driven by HPV infection [ 6 ]. Another risk factor is immunosuppression caused by acquired immune deficiency syndrome caused by human immunodeficiency virus (HIV) infection [ 7 ].…”