Human papillomavirus-associated anal squamous intraepithelial lesions in men who have sex with men and transgender women living with and without HIV in Karachi Pakistan: implications for screening and prevention

Persistent infection with Human Papillomavirus (HPV)—predominantly high-risk HPV type 16 is the major cause of anal cancer [1] Over the past decade, the global incidence of anal squamous cell carcinoma (SCC), is rare and stable in the general population [2] however, it is 20 times more likely to occur in men who have sex with men (MSM) [3, 4] compared to heterosexual men [5]. The risk of anal cancer is highest in MSM living with HIV [4, 6‐8], other individuals living with HIV [9], immunosuppressed individuals [10], and women with history of HPV associated anogenital dysplasia [11]. The reported incidence of anal cancer in general population is 1.8 per 100,000 persons [12], in MSM it ranges between 19–35 cases per 100,000 and up to 88–131/100,000 in MSM living with HIV, i.e., more than 70 times more common than in the general population [9, 13‐15]. The increasing incidence of anal cancer can be associated with increases in the number of sexual partners and a higher prevalence of anal sex in the past few decades [16, 17].

Anal squamous intraepithelial lesions (ASIL) are the putative precursors of anal cancer, similar to cervical squamous intraepithelial lesions (CSILs) in cervical cancer [18‐22]. ASIL spans from low grade squamous intraepithelial lesions (LSIL) to high grade squamous intraepithelial lesions (HSIL) [23]. Approximately 90% of LSIL are caused by infection with low-risk HPV types 6 and 11 often clinically presenting as condyloma—genital warts—while infections with high-risk HPV types 16 and 18 are associated with HSIL [24]. However, persistent anal infection with both low-risk or high-risk HPVs and related ASILs have been associated with an increased risk for invasive anal cancer [24, 25]. Both people living with HIV and MSM generally have a higher prevalence and incidence of anal canal and perianal HSIL [21, 26]. The impact of antiretroviral therapy (ART) for HIV appears to be very limited in terms of reducing the risk of HSIL or squamous cell cancer of the anal canal and perianal region [27, 28].

Although there is a dearth of evidence-based uniform screening recommendations as well as benefits verses harm appraisals [29], however, recent research suggests that anal Papanicolaou (Pap) screening may have utility in preventing anal cancer [30‐32], and is cost-effective screening method for anal cancer prevention among MSM [30, 33] Anal cytology can be used as a standard screening tool for individuals at risk for anal cancer to detect early stage ASIL as screening tests used for cervical cytology [24, 34, 35]. High levels of abnormal cytology have consistently been reported among previously unscreened MSM both without (12–32%) and with (34–58%) HIV [36‐38] in various settings.

Anal cytology screening and preventive treatment programs for MSM have not yet been routinely adopted by Pakistan for multiple reasons, including an absence of local prevalence estimates, sufficient clinical expertise and infrastructure and updated guidelines for the management of sexually transmitted infections (STI). To contribute evidence for future policy, prevention, screening and management of the anal cancer burden in Pakistan, we studied HPV, ASIL, STIs and associated socio-demographic, behavioral and clinical factors among MSM and transgender women with and without HIV infection in Karachi, Pakistan.

This study included a total of 118 participants living with HIV and 153 without HIV in the final cytological and statistical analyses. Those living with HIV were significantly older than HIV negative participants (30.9 versus 27.2; p ≤ 0.001), among PLWH 89.3% were on combination ART, 74.8% had recent CD4 count of more than 350 cells/μl) and nearly two-thirds (76.3%) had undetectable HIV viral load at their last assessment. There were also significant differences in the duration of sex work, number of sexual partners, receptive anal intercourse, and inconsistent condom use at anal intercourse in the last 6 months between study participants living with versus without HIV (Table 1).

HIV status (53.8% vs 38.1%; p = 0.014), age at sex work initiation (15.6 vs 17.0 years p = 0.02), inconsistent condom use (74.7% vs 52.3% p = 0.001) and receptive anal sex (95.8% vs 86.4% p = 0.01) were associated with greater prevalence of ASIL detection (Table 2).

This is the first study to report on the prevalence and risk factors of any anal abnormal cytology among MSM and transgender women in Pakistan. Not unexpectedly, we found a strong association between concurrent high-risk HPV, HIV infection and ASIL. The overall proportion of MSM and transgender women with ASIL was 35%, and those living with HIV were almost twice as likely to have an abnormal cytology compared with HIV negative participants (42.4% versus 28.1%). Moreover, and as expected, the prevalence and number of high-risk HPV types was higher among those with an HIV infection, including HPV16—the primary causal agent for anal cancer. The prevalence of estimates for ASIL in Pakistan are consistent with previous studies from the Asian region [40‐42] and elsewhere [27, 34, 43‐46]. However, the ASIL rates that we found among in MSM in Pakistan are slightly higher than what has been reported from India (27.7%) [47], naturally influenced by study population and sampling. To date, no South Asian studies among MSM (including ours) have used high resolution anoscopy for histologic confirmation of the ASIL diagnosis, which is considered to be the gold standard method [34]. Given that previous studies have shown that anal cytology is less sensitive when diagnosing ASIL compared to the gold standard anal biopsy with the histopathological results [34], the true prevalence of ASIL is likely to be higher than found in our study. Furthermore, and as a matter of concern, we found unexpectedly high proportions of anal cancer precursor lesions, i.e., ASC-US + (35.8%) among young HIV negative MSM. This suggests that a high proportion of MSM and transgender women in Pakistan are at substantial risk for developing anal cancer, in particular those with a concurrent HIV infection. Of note, we found no HSIL cases among HIV-negative participants, possibly partly because they were relatively younger than MSM living with HIV among our participants, but similar to previous findings in an older HIV negative cohort with a mean age of 45 [21]. Although only HSIL is considered to be a precursor of anal cancer, previous studies have shown that about 40% of HIV negative homo- or bisexual men with LSIL at baseline progress to HSIL within only 2–4 years [21, 48]. Moreover, lesions diagnosed as ASC-US may also hide squamous intraepithelial lesions [34, 49], and it is recommended that all individuals with ASC-US or worse on cytology undergo an accurate diagnostic evaluation through HRA guided biopsy as it has high predictive value for Anal Intraepithelial Neoplasia (AIN) [34, 48, 50]. Moreover, one third of ASC-US and LSIL reports are associated with biopsy-diagnosed high-grade AIN [50]. Furthermore, it has been reported that AIN 2 and AIN 3 occurs in about 20% of patients with a negative cytology at baseline after an average of 2 years follow-up [34, 51‐53].

Concurrent infection with more than one high-risk HPV type has been associated with the presence of [28, 54, 55] or progression to AIN [24, 56]. The earlier work of Palefsky et al. has linked having more than one HPV type to a higher risk of progression [48] or incidence [57] of anal squamous intraepithelial lesions. Similarly, a previous study on MSM living with HIV reported a double risk of ASIL when three or more HPV types were present compared to infection with only one type of HPV [58].

MSM living with HIV had a significantly higher prevalence of high-risk HPV as well as multiple HPV types, both low-and high-risk, compared to the HIV negative participants. A possible explanation is HIV-induced immunosuppression that results in a loss of HPV specific immunity, and reactivation or upregulation of a preexisting HPV infection [58, 59]. A larger number of HPV high-risk types among men living with HIV may also indicate an inability to clear HPV infection [60]. A higher risk of reinfection may also be a factor [61], as seen in our study where MSM living with HIV reported both more unprotected anal intercourse and receptive anal sex preference compared to their counterparts who were HIV negative.

Since infection with any HR-HPV type was associated with threefold increase in risk of having any abnormal anal cytology, it would be important to prospectively monitor MSM and transgender women with high-risk HPV infections and/or HPV/HIV coinfection to prevent invasive lesions and intervene on time to prevent anal cancer, but also to learn more about the factors that influence disease progression. We do know that infection with HPV16 or HPV18 significantly increases the risk of progression to high-grade lesions [55, 56], and that concurrent STIs such as gonorrhea and trichomonas also significantly increase the risk of ASIL [60, 62, 63].

Other studies have indicated receptive anal intercourse as a risk factor for anal lesions [62, 64, 65], but anal HPV infection is not limited to men who have receptive sex [66‐68]; it can also be acquired during non-receptive sexual activity. In the current study, abnormal anal cytology was equally prevalent among MSM regardless of anal sex practice, receptive or non-receptive.

This study has some limitations. Firstly, due to lack of equipment and clinicians trained in performing HRA in Pakistan, our analysis of ASIL was based on anal cytology and not on high-resolution anoscopy-driven biopsies, the gold standard for determining disease severity. Awaiting the dispersion of affordable advanced technology, liquid-based cytology, though less sensitive, can be used as a screening tool in high-risk populations in resource-constrained settings as it is convenient, less invasive, cheaper, less time-consuming and requires less expertise than HRA [69]. The fact of the matter is that, recent development in the field of anal cancer screening research has highlighted the potential role for anal Pap testing in providing long-term risk stratification for anal precursors in HIV positive MSM [70]^. The sensitivity of anal cytology may also be improved by targeted repeated testing every 12 months among MSM who are HIV-positive but do not yet have signs of anal squamous intraepithelial lesions, or every 2–3 years for HIV-negative MSM [34, 71‐73].

A second study limitation is the cross-sectional design, undermining the evaluation of a causal relationship between HPV and abnormal anal cytology, as well as the impact of, i.e., concurrent STI. Thirdly, selection bias may have been introduced by the recruitment of people living with HIV from an ART center while the others came from a community-based organization working for MSM. However, the ART center is the only large center located in Karachi and it represents all ethnic groups in Pakistan. Moreover, given the cultural and religious barriers related to homosexuality and transgender in Pakistan, recruiting our study subjects from an CBO was the only feasible option.

To the best of our knowledge this is the first study from Pakistan reporting anal HPV associated anal dysplasia in at-risk MSM and transgender women. One third had abnormal anal cytology, and more than half were infected with high-risk HPV. Our study findings indicate the pressing need for further large-scale studies to document the efficacy of anal screening and to develop national guidelines for management of MSM in general and MSM living with HIV in particular. In the absence of the proper infrastructure required for HRA, regular screening with anal cytology of MSM and transgender women may be considered as an initial step in national HIV care and treatment program. Moreover, the benefit and harm analysis of such an approach can only be explored through further screening trials.