The incidence of anal cancer has increased in developed countries and it is more common among women than men in the general population.1 However, HIV-seropositive men and men who have sex with men (MSM) have a particularly high risk for developing anal cancer compared with the general population.2-5 Recent studies from developed countries have shown an increase in the incidence of anal cancer in the postantiretroviral era among HIV-seropositive men, with annual incidence rates that ranged from 75 of 100,000 to 137 of 100,000.5,6
There is strong evidence that high-grade anal intraepithelial neoplasia (HGAIN), the putative anal cancer precursor lesion and anal cancer are both linked to some human papillomavirus (HPV) infections.2,7 Anal infection with oncogenic genotypes of HPV is a key causal factor of anal intraepithelial neoplasia and anal cancer as cervical HPV infection is for cervical cancer.8 The prevalence of anal HPV is high among male populations, including heterosexual men with HIV infection and MSM, and HIV-seronegative heterosexual men.9-11 Estimates of the prevalence of anal HPV infection in HIV-seropositive men are found to be more than 90%, and the prevalence of anal infections with multiple HPV types is high as well.3,9 Likewise, a high prevalence and incidence of HGAIN among HIV-seropositive heterosexual men and MSM has been previously described.2,3,12,13
Receptive anal intercourse is an important risk factor for anal HPV infection and anal cancer.10 Other risk factors for anal HPV infection in men include younger age, younger age at first sexual activity, lack of steady sexual partner, single marital status, increased frequency of sex, larger lifetime number of female sexual partners, lack of circumcision, lack of condom use, smoking, presence of genital warts, and HIV-positive status.11,14,15
There are scarce data on anal cancer or male anal HPV infection in Brazil, where anal cancer is not officially reported as a distinct disease. Similarly, there are few data on anal HPV or HGAIN among HIV-seropositive men treated with antiretroviral therapy (ART) in Brazil, where such treatment is universally available. In addition, there is a high proportion of men who have sex with both men and women among the reported AIDS cases, and most HPV studies do not separate MSM who have sex only with men or with both men and women. Consistent anal cancer screening and proper referral for care must be priorities to ensure effective prevention and treatment. To improve public health programs, studies that characterize anal HPV infection, anal intraepithelial neoplasia, and anal cancer prevalence among HIV-seropositive men in Brazil are warranted. The purpose of this study was to assess the prevalence of anal HPV infection and associated risk factors, stratified by oncogenic and nononcogenic types, in a sample of HIV-seropositive men who were followed at public health services in Rio de Janeiro and Minas Gerais, Brazil.
PATIENTS AND METHODS
This was a multicenter cross-sectional study of HIV-seropositive male patients attending 6 public AIDS referral clinics in urban Brazil (4 in Rio de Janeiro and 2 in Belo Horizonte, Minas Gerais), from May through November 2007. Patients who participated in a similar cross-sectional study in 2003 were invited to return to participate in the currently reported study. All participants were required to have a confirmed HIV diagnosis and be 18 years of age or older at the time of the study. Participation in the study was voluntary, and confidentiality was protected for all who signed the consent forms. This project was approved by local institutional review boards, the University of California San Francisco institutional review board, and the Brazilian National Ethical Committee Board.
Interview and Questionnaire
All patients who agreed to participate were interviewed using a semistructured questionnaire administered by trained interviewers. The main variables of interest included sociodemographics (eg, age, marital status, race, education, and income); sexual behavior (eg, sexual behavior with men and women, age at first intercourse, condom use, receptive anal intercourse, and number of frequency of sexual partners), lifestyle behavior (eg, injecting drug use, current cigarette smoking or alcohol use, illicit drug, and sexual stimulants use such as sildenafil). For sexually transmitted diseases, subjects were asked about symptoms of urethral discharge; evidence of genital ulcerative lesions or anogenital warts; and past diagnosis of genital herpes, syphilis, chancroid, gonorrhea, chlamydia, lymphogranuloma, and condyloma. Clinical data were obtained from medical charts and included HIV test results, current CD4+ T-lymphocyte count, HIV viral load, ART, and clinical classification.
Anal HPV Testing
All participants were invited to provide a specimen for HPV and anal cytology testing, and had precounseling and postcounseling about the meaning of these tests and procedures. After a perianal visual inspection, a moistened Dacron swab was inserted into the anal canal using previously published methods.16 This swab was inserted into the ThinPrep sample collection kit. The DNA was prepared from each ThinPrep specimen and frozen until batch analysis was performed using previously described standard procedures.16 Five microliters of sample were used for polymerase chain reaction amplification using a standard 30-cycle protocol.16 Polymerase chain reaction products from positive samples were typed by dot-blot hybridization using 39 individual type-specific probes and a mixture of probes for 10 other uncommon HPV types. Specimens that were positive with the generic probe mix but negative with the type-specific probes were considered to be HPV positive but with an unknown HPV type or types.
In the preliminary analysis, variables were examined for missing and out-of-range values and for logical consistency. Descriptive categorical and continuous data analyses were conducted. The prevalences, with 95% confidence interval, of oncogenic and nononcogenic HPV types were calculated. Odds ratios with 95% confidence interval were calculated for both the univariate and multivariate analyses to evaluate the factors associated with oncogenic and nononcogenic types, compared with those who were HPV negative, in separate analyses. If at least 1 oncogenic subtype was present in samples with multiple types, these were classified as being oncogenic. Undetermined types were excluded from univariate and multivariate analyses. Multinomial logistic regression was used to assess independent predictors of HPV infection status stratified according to HPV type, that is, oncogenic and nononcogenic HPV infection groups were separately compared with the HPV-negative group. For this analysis, variables that showed association with HPV infection in each separate univariate analysis with a P value of less than 0.20 were considered for entry into the models. The sequential deletion of variables was conducted until a final model with all variables showing statistical significance (P value of less than 0.05). The statistical importance of each variable was assessed through the Wald test. Models were compared using the likelihood ratio test, and the fitness of the final model was assessed with the Hosmer-Lemeshow test. For all analysis, level of statistical significance considered was set at 0.05. The SAS System software was used for analysis.
Among 557 HIV-seropositive male patients who were invited to participate, 43 refused to participate (7.7%), 30 (5.3%) did not come for scheduled visits, 484 (87%) were interviewed, and 445 (80%) had anal swabs collected. No difference was observed in age or distribution across the study centers between participants and nonparticipants.
The present analysis included 445 HIV-seropositive men who were interviewed and had an anal swab collected. Most of them were non-white, single, were and at least 35 years old, had more than 8 years of education, and reported a monthly income of less than U$350. Regarding sexual behavior, the majority reported sexual intercourse with both men and women in their lifetime, had a stable partner at the time of the study (woman or man), had practiced receptive anal intercourse during the past 12 months, had used condoms regularly during sexual intercourse during the past 12 months, and had used condoms regularly during receptive anal intercourse during the past 12 months. The majority were using ART, self-reported adherence to their current regimen, had CD4+ T-lymphocyte count above 200 cells per cubic millimeter, and undetectable HIV viral load; more than half were diagnosed with AIDS (Table 1).
Table 2 shows the results of HPV testing. Overall, 65.6% (n = 292) were positive for HPV DNA in the anal canal. Oncogenic types were detected in 40.7% (n = 181) of the samples, and 5.8% were positive for HPV but without any type identified. The most frequent types found were HPV 16 (22.3%) and HPV 6 or HPV 11 (28.4%), among oncogenic and nononcogenic types, respectively. Overall, 44.9% of anal samples showed multiple types of HPV, with 30.8% having 3 of more different types.
Table 3 shows univariate analysis of risk factors associated with HPV infection. Risk factors significantly associated with infection with oncogenic and nononcogenic types were similar as follows: ethnicity (white); marital status (single); higher education (more than 8 years); lifetime sexual intercourse only with men or with men and women; having a stable partner; more than 1 male partner during the last 12 months; receptive anal intercourse during the last 12 months. Four variables, that is, irregular condom use in receptive anal intercourse, previous history of illicit drug use, history of sexually transmitted disease, low CD4+ T-lymphocyte count, and detectable HIV viral load showed statistical association only with oncogenic HPV infection.
Table 4 shows the final logistic regression model. Three variables were independently associated with the detection of anal HPV infection; lifetime history of sexual intercourse only with men or with men and women; receptive anal intercourse in the last 12 months; CD4+ T-lymphocyte count below 200 cells per cubic millimeter (associated with only oncogenic HPV infection).
We found an anal HPV prevalence of 65.6%, with oncogenic types detected in 40.7% of the samples. The most common oncogenic type was HPV 16, but types 58, 52, 51, and 18 were common as well. These findings are similar to previously published data. In a cross-sectional study, Palefsky et al9 found a prevalence of 93.0% HPV infection among HIV-positive men. Among these positive samples, 80% were oncogenic HPV types and HPV 16 was the most common type (38.0%). Piketty et al10 found the anal HPV prevalence to be 46% and 85% among 50 HIV-seropositive heterosexual male injection drug users with no history of anal intercourse and 67 HIV-seropositive men who had sex with men, respectively. One or more oncogenic types were present in 59% of the samples. Similar results were reported in studies from Spain17 and Italy.18
A high proportion of HIV-seropositive men (45.0%) had multiple types of HPV in our study population; 30.8% of them with 3 or more different types. Palefsky et al9 also detected multiple HPV types in a single sample of HIV-seropositive men (73.0%), and, on average, these men had 3 or more different types of HPV. Higher numbers of HPV types detected among HIV-seropositive men compared with HIV-seronegative men could reflect the more frequent reporting of receptive anal intercourse by the former. In our sample, 45.3% of men reported receptive anal intercourse during the past 12 months. Different behaviors in the different populations or HIV-related immunosuppression may explain such discrepancies. Low clearance rates and a retention time of almost 3 years for HPV 16 infection, which was previously reported by de Pokomandy et al,3 are consistent with the high prevalence of this HPV type in the anal canal.
In general, our results indicate a similar profile of risk factors associated with infection with the oncogenic and nononcogenic HPV types, except for the immunodeficiency level. The likelihood of infection with an oncogenic type was more than 3 times greater among patients with lower CD4+ cell counts (<200 cells/mm3), compared with HPV-negative patients. This association may reflect a longer time of HIV infection and, consequently, a longer time for HPV exposure and progression of premalignant or in situ lesions to invasive cancers.19 It may also reflect higher persistence by oncogenic HPV types such as HPV 16.3
Among HIV-seropositive men, anal cancer is a growing concern. Since the second half of the 1990s, highly active antiretroviral therapy (HAART) has dramatically decreased HIV morbidity and mortality in countries where HAART is available.20 However, the immunological reconstitution derived from HAART does not seem to protect against anal cancer, as it does for many other AIDS-defining malignancies.3,4,21 The increase in sexual activity and lengthened survival can lead to an increased incidence of HGAIN and invasive anal cancer. In our study population, the majority of patients (90%) were receiving HAART and 60% had an undetectable viral load.
The use of newly available preventive measures, specifically HPV vaccines targeting types 16 and 18, may help to mitigate the impact of HIV on anal cancer in this population by reducing the future incidence of anal carcinoma and HGAIN, thus reducing the morbidity and mortality among people who would otherwise require treatment. A prophylactic HPV vaccine against HPV 16/18 has the potential to prevent more than two-thirds of invasive anal cancer and HGAIN cases in both women and men. Because the vaccines work to prevent initial HPV infection, the greatest benefit of vaccination is conferred by vaccinating individuals before sexual debut or as early as possible after sexual debut. Knowing the viral characterization of infections in high-risk groups could be helpful in predicting the potential of preventive vaccines after sexual debut. The value of vaccinating HIV-seropositive MSM to prevent anal HPV infection is not yet known, but the results from a phase II study in HIV-seropositive men showed high seroconversion rates and good titers with the quadrivalent HPV vaccine.22
Since the relative distribution of HPV genotypes has been reported to vary by geographical region,4 HPV prevalence studies such as this one are fundamental for planning HPV immunization programs targeted at HIV-seropositive men. The high prevalence of HPV types other than HPV 16 and HPV 18 and the frequent detection of multiple HPV types in our study should be carefully taken into account when considering immunization strategies for HIV-seropositive men in our setting. Currently, HPV type 58 is not included in the quadrivalent vaccine, and there are no available data considering cross-protection to these types in immunized subjects. HPV 58 is highly prevalent in South American women, independent of cytological classification or HIV status.23,24
Multivariate analysis also indicated that sex with men and anal receptive intercourse were significantly associated with both oncogenic and nononcogenic anal HPV infection. This is consistent with the published literature and clearly indicates that receptive anal intercourse is an important means of acquiring anal HPV infection.9,10 Most HPV studies among MSM do not distinguish MSM who have sex with men only or MSM who also have sex with women, most likely due to a small proportion of the latter. In our study, a high proportion reported having sex with both men and women in their lifetime (59.0%). This group had an overall prevalence of HPV of 72.3%. This is almost as high as the prevalence found among men who reported only having sex with men in their lifetime (87.3%) and 3 times higher than the HPV prevalence among those reporting sex with women only (23.5%). In addition, men who had sex with both men and women in their lifetime were almost at an equally high risk of having both oncogenic and nononcogenic anal HPV infection, compared with men who reported sex with men only. As shown, HPV concordance between heterosexual couples is associated with HIV infection status and HIV infection in one partner may impact HPV infection in the other.25 We note that HPV and HIV infections are unfortunate regardless of the sexual practices of those infected. More effective preventive measures to control HPV and HIV infection among MSM might yield valuable public health not only among MSM but also among the female partners of MSM. In addition, many experts recommend screening and treatment for HGAIN to reduce the risk of cancer, similar to the well-established approach of treating high-grade cervical intraepithelial neoplasia to reduce the risk of progression to cervical cancer. Despite the absence of definite data on the efficacy of screening and treatment for HGAIN to prevent anal cancer and guidelines that mandate such screening and treatment, these should be considered as an ongoing part of health care for HIV-seropositive men. The high proportion of MSM who also have sex with women and the growing HIV epidemic among women in Brazil should be of public health concern for both HPV and HIV infections.
One limitation of this study is that it included a high percentage of men who had been HIV seropositive for many years and a high proportion who were taking HAART. Our study group may not be generalizable to all HIV-seropositive MSM, particularly younger HIV-seropositive men who may have been HIV infected for fewer years. In conclusion, the high prevalence of anal HPV infection in this cross-sectional study underscores the need for studying and implementing screening programs of high-risk groups.
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Keywords:© 2011 Lippincott Williams & Wilkins, Inc.
anal HPV infection; HIV-seropositive men; urban Brazil