Description

Anal cancer is a rare disease in the general population, but its incidence is higher in certain at-risk groups, such as immunosuppressed individuals, including those with HIV infections and post-organ transplantation patients, men who have sex with men, and women with HPV-related lower genital tract dysplasia or cancer.

A squamous intraepithelial anal lesion is the dysplastic growth of squamous epithelial cells in the transition zone of the anal canal. This lesion is pre-malignant and can progress to anal squamous cell carcinoma if left untreated.

Human papillomavirus (HPV) infection has been implicated as the necessary cause for the development of the majority of anogenital malignancies accounting for approximately 95% of anal cancers. Persistent infection with HR-HPV promotes progression from high-grade squamous intraepithelial lesions (H-SIL) to invasive anal cancers. In the anal canal, low-grade intraepithelial lesion LSIL correlates with anal intraepithelial neoplasia (AIN)-1 or anal condyloma, while high grade squamous intraepithelial lesion HSIL correlates with AIN-2 and AIN-3.

Prevalence of H-SIL is around 40 to 50%. Progression from H-SIL to anal cancer is about 1/250 per year in HIV-positive MSM and 1/5000 per year in HIV-negative MSM, respectively.

The diagnosis of AIN is made from cytology or biopsy during routine examinations.

Up to date, different guidelines for anal cancer screening have been proposed but are not uniform. These include 1) digital ano-rectal examination, useful in unrecognized but symptomatic subjects, and 2) anal cytology, useful in asymptomatic subjects, only if high-resolution anoscopy is available.

These observations support the need to implement screening to prevent anal precancers and cancers.

At this moment, no HPV assay has been validated for anal specimens, and none is available in the molecular diagnostics market.

Validation of HPV typing methods on anal specimens could implement anal cancer screening without an invasive procedure and with an easy approach for the patient.

The BD Onclarity™ HPV Assay (BD Diagnostics, Sparks, USA) is a real-time polymerase chain reaction PCR assay that detects type-specific genomic DNA. The target of the assay is the E6 and E7 HPV genes. It simultaneously detects all 14 high-risk HPV types and can provide an "extended" genotype information on six individual genotypes (HPV 16, 18, 31, 45, 51 and 52), and in three distinct groups (33 and 58; 56, 59 and 66; and 35,39 and 68). Briefly, the DNA was extracted using BD FOX™ magnetic particles and the eluate-containing DNA was used to set up three PCR genotyping reactions: G1 detects HPV 16, HPV 18 and HPV 45 plus the internal beta globin control; G2 detects HPV 31, HPV 33_58 and HPV 56_59_66 plus the internal beta globin.