Imiquimod and 5% Fluorouracil Therapy for Anal and Perianal SquamousCell Carcinoma In Situ in an HIV-1–Positive Man

A 59-year-old human immunodeficiency virus-1–positive (HIV-1+)white man presented with a nonhealing area that extended extensively aroundthe perianal skin and up into the anal canal. The area had been present forgreater than 2 years with an increase in size over the past 6 months. Biopsieswere performed, and multiple biopsy specimens sampled from the cutaneous surfaceas well as within the distal anal canal showed squamous cell carcinoma insitu.

The patient's HIV-1 disease had been diagnosed approximately 15 yearsearlier, and had been well controlled during most of that time with antiviraltherapy, including protease inhibitors over the past 4 years. The patient'sCD4 cell count was more than 500/µL, and he had an unmeasurable viralload; he had been taking stavudine (40 mg twice daily), lamivudine (150 mgtwice daily), indinavir (400 mg twice daily), and nelfinavir (250 mg 3 timesper day) for approximately 1 year. Other significant medical history included5 basal cell carcinomas, both nodular and superficial types, dating from 1990,with the last tumor treated in 1996.

Physical examination revealed an area of perianal erythema with extensiveareas of ulceration around the rectum and extending into the rectum (Figure 1). Anoscopic examination showed thatthe area of visually atypical anal mucosa extended just inside the anal canal.

Multiple biopsies were performed on the involved skin, including themucosa, to better define the extent of disease.

Both radiotherapy and Mohs micrographic surgery for the area of cutaneousinvolvement followed by surgical excision of the rectum were considered aspossible therapies. However, because the patient's HIV-1 disease was wellcontrolled, he wished to try a less aggressive treatment.

After we confirmed that the results of viral studies for the herpessimplex virus and bacterial and fungal cultures for pathogens were negative,treatment was started with 5% imiquimod cream on a Monday-Wednesday-Fridayschedule. The patient applied the cream at bedtime to the external area ofinvolvement and within the anal canal, washing it off in the morning. Thepatient also applied daily 5% fluorouracil in the morning to the area of cutaneousinvolvement and within the anal canal. Although initially the patient experiencedsome increased irritation, he tolerated the treatment well and continued thetherapy for 16 weeks. Clinically and symptomatically, there was gradual improvementafter approximately 4 weeks of therapy, and at 16 weeks, there was minimalsuperficial ulceration with moderate residual erythema. At approximately 12weeks, the patient showed signs of infection, with increased greenish mucoidmaterial overlying the area of involvement. Cultures showed a mixed bacterialinfection. The patient was treated with 2% topical mupirocin ointment, 0.75%metronidazole cream, and oral levofloxacin, 500 mg, for 10 days with clearingof the infection.

The erythema and residual superficial erosions healed rapidly afterall therapy was discontinued. Approximately 3 weeks later, a biopsy was againperformed on the patient, with specimens taken from multiple sites withinthe prior area of involvement; 4 of the biopsy specimens came from the areaimmediately around the rectal opening (Figure2). In addition, the patient had a ThinPrep (Cytyc Corp, Boxborough,Mass) cytologic smear performed using both a firm spatula and a brush to samplethe anal mucosa extensively, including the areas well proximal to the areaof involvement previously defined clinically and histologically. Follow-upclinical examinations, cutaneous biopsy specimens, and mucosal cytologic examinationshowed no evidence of residual dysplasia.

The initial biopsy specimens showed multiple areas of full-thicknessepithelial dysplasia within both the overlying skin and far distal anal squamousmucosa. The cells were markedly atypical and pleomorphic, with large, hyperchromaticnuclei, many with prominent red nucleoli. In addition, there were some epithelialgiant cells and numerous mitoses, some atypical, and scattered dyskeratoticcells. In situ DNA probes (Pathgene-Enzo Diagnostics, Syosset, NY) for humanpapilloma virus (HPV) types 6/11, 16, 18, and 31 were performed using standardtechniques described by the manufacturer on the initial biopsy sections aswell as the sections used to determine the extent of the tumor. Results ofthe in situ DNA probe for HPV type 16 were positive in the keratinocytic nucleimost numerous in the areas near the periphery of the tumor (Figure 3), but focally positive throughout the tumor.

Follow-up cutaneous biopsy specimens showed mild dermal fibrosis witha moderate residual chronic inflammatory infiltrate. Flattening of the reteridge pattern was seen in all biopsy specimens. The overlying epidermis showeda bland epithelium with ordered differentiation. ThinPrep cytologic examinationshowed evidence of HPV, but no significant cytologic dysplasia. Follow-upclinical examination, including anoscopic examination, and ThinPrep cytologicexamination 3 months later showed no evidence of recurrence of carcinoma insitu.

Imiquimod belongs to a family of imidazoquinolines that have potentantiviral and antitumor properties in animal models without any demonstrabledirect antiviral or antiproliferative actions. The immune effects of 1- to5-mg/mL imiquimod appear to be mediated, at least in part, through stimulationof innate immunity. In particular, imiquimod therapy has been associated withrelease of monocyte-macrophage–derived cytokines, such as interferonalfa (IFN-α), tumor necrosis factor α (TNF-α), interleukin1α (IL-1α), IL-6, IL-8, IL-12, and prostaglandin E₂(PGE₂), resulting in a T_H1 dominant response.^1-6

Imiquimod has recently been shown to enhance the functional maturationof Langerhans cells, as well as their migration to regional lymph nodes.^6,7 Functional maturation and migrationof Langerhans cells are necessary for antigen presentation in the developmentof adaptive immune responses.^6,7In one of these studies, imiquimod was also shown to enhance contact hypersensitivityresponses.⁶ The ability to enhance cutaneousadaptive responses, as well as innate immunologic responses, may be very importantin imiquimod's antiviral and antitumor effects.

The combined effects of T_H1 cytokine switching and increasedantigen presentation may be particularly helpful in patients with underlyingimmune deficits, especially those predisposed to a T_H2 cytokineswitching pattern, ie, those with atopic dermatitis and HIV-1 disease.^7-9 Since most effectiveantiviral and antitumor responses are mediated through the endogenous systemthe presentation of tumor or viral antigens to CD8⁺ T cells bymajor histocompatibility complex class I molecules, this potentiation maystill be effective even in patients in whom immune suppression particularlytargets CD4⁺ T cells, such as those with HIV-1 disease.^8,9

Because of the extent of disease in our patient, we decided to use combinedtherapy with both imiquimod and a chemotherapeutic medication, fluorouracil.Fluorouracil has previously been used in the therapy of carcinoma in situfor patients with Bowen disease.^10-12Fluorouracil is also the first-line therapy for gastrointestinal carcinomas,and in this context it has been combined with IFN-α, one of the principalcytokines induced by imiquimod, to improve its therapeutic index.^13-15 Interferons alfa,beta, and gamma all enhance the activity of fluorouracil both in vitro andin vivo.^16,17 One mechanism bywhich they do this is through the induction of the enzyme thymidine phosphorylase,thereby enhancing the conversion of fluorouracil to its active metabolite,5-fluorodeoxyuridine monophosphate.¹⁶ Thisleads to increased depletion of thymidine triphosphate pools and increasedDNA fragmentation.^16,17 Interferontreatments also lead to the abrogation of a fluorouracil-associated increasein the enzyme thymidylate synthase, thus increasing tumor sensitivity to fluorouracil.¹⁰ Finally, IFN augments plasma fluorouracil levels.^16,17

Our patient illustrates a complication for HIV-1+patients associatedwith prolonged survival when these patients are treated with the new, highlyeffective combined antiretroviral therapies.^15,18Infections with multiple oncogenic HPV types are very common among HIV-1+homosexualmen, and show almost a 100% association with anal squamous cell carcinoma.¹⁴ Although highly effective combined antiretroviraltherapy, with its improvement in the patient's immune status, has proven effectivein dramatically decreasing some viral infections and/or malignancies, eg,molluscum contagiosum and Kaposi sarcoma, HPV infections and their associatedmalignancies have not responded as favorably.^18-20

Both cytology and anoscopy have proven useful in predicting the developmentof these intraepithelial neoplasms long before they become as extensive asin our patient. Although this patient's oncogenetic HPV infection may havebecome latent, it was not cured, and neither was his HIV-1 infection. Thus,treatment with imiquimod alone or in combination with topical chemotherapeuticagents such as fluorouracil or antiviral agents such as cidovir may proveeffective in controlling epithelial dysplasia and/or squamous cell carcinomain this growing patient population but probably will not result in a permanentcure.^15,18

Accepted for publication August 31, 2000.

The opinions or assertions contained herein are the private views ofthe authors and are not to be construed as official or as reflecting the viewsof the Department of the Army, the Department of the Navy, or the Departmentof Defense.

Corresponding author and reprints: COL Kathleen J. Smith, MC, USA,Department of Dermatology and Pathology, National Naval Medical Center, Bethesda,MD 20889-5600 (e-mail: HSkelIII@aol.com).