In the imiquimod group, four patients resolved and remained disease free after a median 33 months of follow-up. One went on to develop incident warts and HSIL after 42 months of follow-up, probably because of a new human papillomavirus (HPV) infection. This patient after imiquimod was reintroduced showed a sustained improvement to LSIL and resolution of warts. Further, a patient who showed complete resolution at completion of treatment, and also 3 months later, was classed as a treatment failure because HSIL was detected after 8 months of follow-up.
Eight patients downgraded to LSIL, of whom one subsequently resolved and remained clear 48 months later. The other seven had no further HSIL after a median 33 months of follow-up, but one developed incident HSIL after 44 months. There were 16 nonresponders in the treatment group, of whom two were lost to follow-up after 6 months and received no further treatment. Following further treatment, only eight continued to have HSIL after a median 43 months.
In the placebo group, one patient resolved and remained clear 37 months later.
Imiquimod, therefore, was significantly associated with a positive outcome, combining those who cleared and those who downgraded, χ2 = 8.78 applying Yates' correction with one degree of freedom, P = 0.003. There was no significant difference in CD4 cell count rise in patients who responded compared with those who did not. The mean CD4 cell count at the time of diagnosis of ACIN was 391 cells/μl in the responder group and at the time of response was 459 cells/μl, whereas in the nonresponders, the mean CD4 cell count at diagnosis was 380 cells/μl and at the end of follow-up it was 486 cells/μl. Virtually all subjects had HIV RNA viral loads below 50 copies throughout the period of study.
Twenty-one patients opted to use open-label imiquimod, of whom 12 were from the placebo arm. Five of these patients showed complete resolution and four downgraded to LSIL, of whom one subsequently cleared. One of the five patients who was clear at the end of open-label treatment had newly incident HSIL after 29 months. Further, a patient was apparently clear but was found to have HSIL after 12 months and was, therefore, counted as a treatment failure. Median follow-up post improvement or resolution was 36 months. Most patients who did not respond received further treatment with trichloroacetic acid (TCA) or laser and further courses of imiquimod, and another two downgraded to LSIL as a consequence.
In summary, of the 54 patients for whom there is follow-up data, two developed squamous carcinoma of the anus and another two exhibited spontaneous resolution of HSIL. Thirteen patients have cleared following treatment, of whom four had newly incident HSIL at 23, 29, 44 and 48 months. Sixteen have had a sustained downgrading to LSIL following treatment, one of whom showed incident HSIL after 29 months. The two patients who resolved apparently spontaneously may well have been stimulated to do so by the repeated biopsies. Putting aside for a moment the reasons for late reappearance of HSIL, the total number of patients who have exhibited prolonged absence of HSIL following treatment with imiquimod is 29 out of 47 patients (61%).
The common finding of all treatments for AIN has been high-recurrence rates in HIV-positive patients, a consequence of viral persistence. The only previously published study of using imiquimod for AIN focussed on the perianal region and showed a 61% end-of-study clearance after 16 weeks of treatment . These impressive results are not strictly comparable because nearly a third of the patients treated had LSIL only and few had internal disease. In fact, only four of the patients had high-grade anal intraepithelial neoplasia (HG-AIN). Three of them downgraded to LSIL, whereas the remaining patient who failed to improve was poorly adherent to the treatment regime. Overall 21% of the patients had poor adherence, and it is worth noting that a whole sachet of cream was being used per application, with a high rate of soreness recorded, in contrast to our study in which the dosage was halved. From the same study, 19 patients were followed up for a mean of 30 months . Twenty-six percent experienced recurrent HSIL after a mean time of 24 months, whereas a further 31% developed cytological evidence of LSIL in the anal canal. The virological data from the study is extremely interesting in that the majority of patients who initially responded showed a significant reduction rather than a clearance in the viral load of the detected oncogenic HPV types. These viral loads remained low throughout the extended follow-up, and most ‘recurrent’ disease was associated with the acquisition of new oncogenic HPV types. This phenomenon may also explain the late reappearance of HSIL in some of our patients who were otherwise doing well on their treatment for HIV.
Another observational cohort has also reported the long-term outcome of relentlessly treating AIN lesions with a mixture of modalities, predominantly laser, but including also imiquimod and surgical excision . Clearance was defined as being disease free for 12 months and on this basis 63% of patients were cleared after being treated for a median of 31.5 months. The median time to cure was longer for patients with HSIL (37.5 months) than with LSIL (30.4 months), but the difference was not statistically significant. The time to cure was significantly dependent on the area of abnormality and lesions took considerably longer to clear in HIV-positive patients (39 months) than in HIV-negative (25 months).
In the course of the current study, some interesting phenomena were observed. Patients treated with imiquimod for a combination of warts and HSIL sometimes cleared these different lesions at different times, and sometimes the HSIL cleared before the warts. Internal and external AIN do not necessarily clear simultaneously, and it should not be assumed that perianal treatment alone is sufficient. LSIL and HSIL commonly coexist, but just as with warts and HSIL, the two types of lesion can clear independently. This should not surprise us, as in the anus LSIL is more likely to be caused by nononcogenic than by oncogenic HPV . For this reason, the successful clearance of HSIL, leaving only LSIL, should constitute a considerable reduction in the risk of anal cancer.
This study has demonstrated that imiquimod can play a valuable role in the management of AIN, that it can be well tolerated when used in the manner described and that there is value in prolonged and repeated courses of treatments, especially when combined or perhaps alternated with other treatment modalities. Now that longer term follow-up studies have shown the efficacy of this approach, one of the barriers to advocating AIN screening for all HIV-positive patients has been removed. It is true that we cannot yet prove that these interventions will prevent anal cancer, but we at least know that precursor HG-AIN can be cured. This is certainly not going to prevent all anal cancers, but it would be a grave error to await the outcome of long-term natural history studies. Although much more research is needed, the time has come for all HIV centres to begin screening for and treating AIN.
The authors would like to thank 3M Health Care Ltd for providing matching boxes of imiquimod and placebo, and for supervising the randomization, the patients who volunteered, and Sundhiya Mandalia for her statistical assistance.
P.F., M.N., S.B. and M.B. were involved in the design of the study. P.F. and M.N. recruited the patients and collected all the samples. N.S. reported all the cellular pathology specimens from Homerton Hospital, reviewed independently by N.F. N.F. reported all the cellular pathology specimens from the Chelsea and Westminster Hospital, from where the biopsies were reviewed by J.W. and the cytology by G.D. P.F. wrote the paper, receiving contributions from M.N., S.B. and M.B.
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Keywords:© 2010 Lippincott Williams & Wilkins, Inc.
anal intraepithelial neoplasia; high-grade squamous intraepithelial lesion; imiquimod; low-grade squamous intraepithelial lesion; placebo-controlled studies