ANAL CARCINOMA IS RELATIVELY rare in the general population, although the incidence of anal cancer is increasing among men, particularly among HIV-infected men who have sex with men (MSM).1 Recent studies have shown a rising incidence of anal cancer among HIV-infected men and women despite the widespread use of highly active antiretroviral therapy (HAART).2,3 The current estimated incidence of anal cancer is 37 per 100,000 among men with a history of receptive anal intercourse and is estimated to be approximately twice as high among the same group of men who have HIV.4–6 One cohort study has shown that as many as 49% of HIV-infected homosexual and bisexual men developed high-grade anal dysplasia over the course of a 4-year period compared to 17% of HIV-uninfected homosexual and bisexual men.7 As patients are living longer with HIV, it is likely that the incidence and complications from anal cancer will continue to increase in HIV-infected patients.
Anal carcinoma shares many similarities with cervical cancer in anatomy and histology as well as its association with human papillomavirus (HPV) infection.8–10 HIV-associated immunosuppression increases the risk of anal HPV detection.8,11,12 Several studies have demonstrated the association of HPV infection with increased risk of development of anal high-grade squamous intraepithelial lesions (HSIL) and low-grade intraepithelial lesions (LSIL).7,13–15 Similar to cervical cancer, these lesions are thought to be precursor lesions that can progress to invasive carcinoma among HIV-infected women.10,13
Routine cervical Papanicolaou smear screening has been associated with a significant decrease in the incidence of cervical cancer from 40–50 per 100,000 to approximately 10 per 100,000.16 Based on the success of the cervical cancer screening program, many experts have suggested that routine anal cytology screening should be performed on high-risk individuals to detect and remove precancerous anal lesions.17–19 It has been shown to be a cost-effective procedure for homosexual and bisexual men with benefit comparable to that of other preventative medical protocols used in HIV care.20,21
Although most available data on anal carcinoma are derived from homosexual and bisexual men, there is also an increased incidence of anal carcinoma among other groups.14,22 Cross-sectional studies identified 26% of HIV-infected women and 34% of HIV-infected men without a history of anal intercourse with anal dysplasia.14,23 As the majority of evidence for anal cancer screening programs is from HIV-infected MSM, there are no substantial data on anal dysplasia and anal cancer screening in a diverse population of HIV-infected patients seen in an urban HIV clinic. We started an anal cancer-screening program in response to concerns from many providers who noted an increased number of anal cancer cases. When we implemented the program, we felt that it would be important to re-examine the program in 1–2 years to determine its feasibility and barriers to implementation. Our goals are to describe our experience with a routine anal cytology screening program in an urban HIV-infected population to determine if anal disease on examination is predictive of abnormal anal cytology findings and if there is an association among abnormal cytology, abnormal histology, and abnormal anoscopy.
Materials and Methods
This study was conducted with the approval of the Institutional Review Board, Hospital of Saint Raphael (HSR) and the Human Investigations Committee, Yale School of Medicine. In November 2002, we implemented an anal cancer-screening program, using anal cytology, into our HIV clinical care. Six providers received in-service training on the anal cytology procedure and all HIV-infected patients seen at the HIV clinic at the HSR were offered anal cytology as part of routine clinical care. All samples were read by 1 pathologist at the HSR who was trained in interpreting anal cytology. Anal cytology results were reported as negative for dysplasia, atypical cells of undetermined significance (ASCUS), anal intraepithelial neoplasia (AIN) I, AIN II, or AIN III. The cytology reports interpreted as AIN were recoded as LSIL for AIN I and HSIL for AIN II and AIN III. Patients with abnormal anal cytology findings, classified as ASCUS or greater, were referred for surgical evaluation and anoscopy. We used the anal cancer screening protocol suggested by Drs. Chin-Hong and Palefsky.24 At the discretion of the surgeon, some patients received another screening anal cytology before anoscopy. Anoscopy was preformed using a high-resolution anoscope with biopsy of any obvious lesions seen with addition of 3% acetic acid. Biopsy results were reported as AIN I, AIN II, AIN III, or squamous cell carcinoma in situ (SCCIS).
Outpatient charts were reviewed for all patients seen between November 2002 and November 2004 who had an anal cytology examination. The following data were extracted: demographics [age, race, HIV risk factor(s)], CD4+ T-cell count at the time of anal cytology, CD4+ T-cell count nadir, HIV viral load at the time of anal cytology, current use and history of antiretroviral therapy (ART), history of provider diagnosed herpes simplex virus infection, and/or genital warts, anal disease on perianal visual inspection (anal disease was defined as wartlike lesions, ulcerations, and/or fissures), history and stage of cervical dysplasia for women, history of any other provider diagnosed genital-urinary disease, results of anal cytology, and results of high-resolution anoscopy findings. For patients with more than 1 anal cytology, the reason for additional anal cytology was recorded. Data for all patients with anal cytology were coded and entered into a computerized spreadsheet. Data collection was verified by nonprimary data collector on 10% of randomly selected charts. Less than 5% variation was found between the 2 data collectors.
For those patients with more than 1 anal cytology, the highest-grade cytologic abnormality was used in the analysis. Patients with insufficient cells on cytology slide or missing cytology results were excluded. Univariate analysis was done using χ2 for comparison of proportions and t tests for continuous variables using SPSS version 14.0 (Chicago, IL). Multivariate analysis was conducted using logistic regression controlling for age, race, sex, CD4+ T-cell nadir, and HIV risk factor. These variables were chosen to control for established risk factors. Comparisons were considered significant at P <0.05 (2-tailed).
Table 1 describes the study population of the 265 patients who received an anal cytology. The demographics of the patients receiving an anal cytology are reflective of the demographics of the entire clinic population. During the 2-year study period, 560 patients came for at least 1 routine clinical visit (Fig. 1). Two hundred seventy-six patients (49%) received at least 1 screening anal cytology during this time. Eleven patients were excluded from analysis: 10 for insufficient cells on the cytology slide and 1 for missing data. Ninety-two patients had more than 1 anal cytology done during the study period. Of these 92 patients, 72 patients had 2 anal cytologies, 19 had 3 anal cytologies, and 1 patient had 4 anal cytologies. Fifty-one patients had only normal repeat anal cytologies as part of annual screening. Four patients had a repeat anal cytology after an initial anal cytology showed insufficient sample. Thirty-four patients had a repeat anal cytology to follow-up on an original abnormal anal cytology. Three patients had a repeat anal cytology for an undocumented reason.
Normal Versus Abnormal Anal Cytology Comparison
Seventy-four of 265 (27.9%) subjects had at least 1 abnormal anal cytology (Fig. 1). Twenty-four (32%) had ASCUS, 45 (61%) had LSIL, and 5 (7%) had HSIL. The subjects with an abnormal anal cytology were significantly more likely to be caucasian, report MSM as their HIV risk factor, have a lower CD4+ T-cell nadir and lower CD4+ T-cell count at the time of anal cytology, and be on ART at the time of the anal cytology (Table 2). Patients with abnormal anal cytologies were also more likely have anal disease on perianal visual inspection and to have a history of herpes simplex virus or genital warts. There was no significant difference in history of cervical dysplasia between those with abnormal anal cytologies and those with normal anal cytologies among the 84 women. In the multivariate analysis, anal disease on perianal visual inspection and CD4+ T-cell count at the time of the anal cytology were significantly associated with abnormal anal cytology, with odds ratios of 2.8 (95% CI = 1.3–6.1) and 2.6 (95% CI = 1.2–5.6) respectively (Table 3).
Follow-Up of Abnormal Anal Cytology
Fifty of 74 patients (66%) with an abnormal anal cytology were referred for surgical evaluation (Fig. 2). Of the 24 patients without a surgical referral, 3 patients were diagnosed with another malignancy, 2 patients relocated out of city/state, and 1 patient was admitted to an extended care facility. Referral and follow-up data were lacking for the other 18 patients. Of the 50 patients with a referral, 7 patients did not report for their surgical evaluation. Sixteen of these patients did not receive anoscopy; 2 were unable to tolerate the anoscopy and, at the discretion of the surgeon, the remaining 14 had either an anal exam or a repeat anal cytology. Of the 27 patients who received anoscopy, 15 patients had no abnormalities seen on anoscopy and 3 patients had lesions but no biopsy was taken (1 patient was pregnant and 2 for an undocumented reason). Nine patients had lesions seen on anoscopy and histology proven anal dysplasia (Table 4). Two patients were identified with AIN I, 2 with AIN II, 3 with AIN III, and 2 patients with SCCIS.
Association Between Anal Cytology and Histology
There was no apparent association between cytology and histology findings (Table 4).
We have demonstrated an ability to institute an anal cancer screening program as part of routine HIV care in an ethnically diverse inner city setting. During the study period we screened approximately half (49%) of the clinic population that was seen for HIV care. This included screening a substantial number (32%) of women. Although current recommendations for anal cancer screening are specifically targeted toward MSM, high-grade anal dysplasia has been demonstrated in 36% of intravenous drug users who have no history of receptive anal intercourse.15 In our study we found that 22% of patients with intravenous drug use and 35% of patients with heterosexual sex as their only recorded HIV risk factor had abnormal anal cytology. This increased rate among heterosexual men and women is consistent with other published studies.14,25–27 The proportion of abnormal anal cytologies we found in men reporting having MSM as their HIV risk factor (39%) was lower than reported in other studies, which were concentrated in high-risk MSM communities.28 However, the risk factors in our study were collected retrospectively and were based on coding by providers in clinic charts. Thus, we may have underestimated the number of patients who have receptive anal intercourse. Nevertheless, our experience is more typical of a “real-world setting” in which providers often do not routinely collect an in-depth sexual history.29,30
We found that patients with an abnormal anal cytology were more likely to have anal disease on perianal visual inspection compared to those with a normal anal cytology. In the multivariate analysis, anal disease was associated with increased odds of having an abnormal anal cytology. However, only 30% of those with an abnormal anal cytology had anal disease on physical exam. The majority (70%) of patients with abnormal anal cytology findings did not have anal disease at the time of their anal cytology. In addition, 17 (9%) patients with a normal anal cytology had anal disease. One explanation for this finding is that only the perianal area is visible on examination, whereas the anal cytology samples were from within the anal canal, where anal dysplasia may occur.
The patients with an abnormal anal cytology were also more likely to have a lower CD4+ T-cell nadir and lower CD4+ T-cell count at the time of the anal cytology compared to those with a normal anal cytology. Interestingly, these patients were more likely to be on ART. This may reflect the treatment of patients' more advanced HIV disease. Although there is controversy regarding anal carcinoma's responsiveness to HAART, HAART does not appear to have an impact on anal HPV infection.15,31,32 HIV has a local immunosuppressive effect in the anal mucosa that is not responsive to HAART even with increases in systemic CD4+ T-cell counts and decrease in HIV viral load.8,33,34 This continued local immune suppression may be the mechanism via which HPV leads to anal carcinoma, as the decreased immune surveillance by dendritic cells allows transformed cells to grow unchecked.35
It has been shown previously that women with a history of cervical dysplasia are at increased risk for developing anal dysplasia. We were not able to demonstrate this in our study, but this may be because cervical Papanicolaou smear or colposcopy results were not always available. Many of the women received gynecological care at another institution and records were not available for review.
Of the 74 patients who were identified with cytologic evidence of anal dysplasia, only 27 received high-resolution anoscopy. Only 9 patients with visible lesions on anoscopy had a biopsy. This highlights many of the barriers to incorporating a cancer screening program into routine clinical care including substantial physician training and resources for anoscopy-related activities.36 The anal cytology was accepted by the patients and patients did not complain of side effects from this screening test. Yet, it was much more difficult to insure adherence with surgical anoscopy and biopsy follow-up. Barriers to surgical evaluation included patient-centered difficulties such as the perceived intolerability of the anoscopy procedure, fear of a cancer diagnosis, and difficulties with maintaining clinic appointments. Furthermore, as patients were initially referred for a surgical evaluation, there was confusion about the need and type of evaluation these patients required. Some patients were receiving high-resolution anoscopy and acetowhitening with biopsy of dysplasic lesions, while others received an anal examination or repeat anal cytology. With ongoing education to our surgical residents and scheduling the anal dysplasia follow-ups to 1 clinic day a week (2 clinic attendings), we were able to overcome this barrier.18,24,37 Lastly, even though the anal cytology was well accepted by patients, only half the patients seen were actually screened. This is at least partly due to the complexity and advanced HIV disease stage of our patients. If other more urgent medical problems were apparent, these would take priority and management of their anal disease would become a secondary or unaddressed issue. Despite these barriers, during the course of the screening program, 2 patients (0.7%) were identified with SCCIS. These 2 patients have been successfully treated with local therapy. They are currently being followed and remain disease free.
Our data does not show consistency between cytology and histology findings. The 3 patients with HSIL on cytology had no lesions seen on anoscopies and the 2 patients with SCCIS on biopsy had ASCUS and LSIL on cytology. This finding is consistent with other published reports.18,38 Palefsky et al. have shown that anal cytology screening in homosexual and bisexual men has a positive predictive value of 38% and negative predictive value of 84% when ASCUS was included as abnormal, as was done in with our study.18 The positive predictive value of the examination was driven by the higher disease prevalence in this patient population. In our study, only 38% of patients self-identified as having MSM as their HIV risk factor so the positive predictive value of the anal cytology screening program would likely be lower. Given that all the patients with high-grade lesions on histology were patients with ASCUS or LSIL, this study supports the recommendation of surgical evaluation of any patient with abnormalities, including ASCUS. One limitation is that approximately 32% of the patients with abnormal cytology did not receive anoscopy with biopsy. The majority of patients who did not receive an anoscopy were those with low-grade cytologic lesions.
In summary, we were able to incorporate anal cancer screening as part of routine HIV care in an urban HIV clinic setting with diverse HIV risk factors. We found cytologic abnormalities in patients without obvious risk factors, suggesting that anal cancer screening should be performed on all HIV-infected patients regardless of HIV risk factors and gender. The follow-up for abnormal anal cytology represents the most difficult aspect of the screening program. Our experience demonstrates some of the “real world” problems with setting up any screening program. It was difficult to get some patients to schedule or arrive for anoscopy even though they were aware of their abnormal anal cytology results. It then took several months to develop a uniform surgical evaluation for follow up of this new screening test. The estimated burden of disease is ∼146,372 men and ∼18,686 women and any widespread screening program would require substantial additional physician resources and training.36 Even in a group of physicians who are motivated to do such a screening program, there are difficulties and time involved in ensuring that everyone is appropriately trained. Any future recommendation for routine anal cancer screening for HIV-infected patients will have to take into consideration these implementation difficulties.
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