Hypothesis Photodynamic therapy (PDT) for carcinoma in situ of the anus is an alternative to surgical excision in patients who are seropositive for human immunodeficiency virus (HIV).
Design Before-after trial.
Settings Tertiary referral center.
Patients Twelve HIV-seropositive patients who were actively being treated for AIDS with high-grade dysplasia on anal Papanicolaou test results had site-directed biopsies of acetowhitening foci immediately after application of dilute acetic acid. Biopsy results showed that 5 patients had anal carcinoma in situ. These patients were given the photosensitizer 
-aminolevulinic acid orally. Four to 4.25 hours later, the entire anal circumference was treated with PDT. All 5 patients, after being treated with PDT, had repeated Papanicolaou tests at monthly intervals. If acetowhitening occurred at the fifth month, site-directed biopsy was done.
Main Outcome Measures Anal cytologic examination by Papanicolaou test and site-directed biopsy if acetowhitening was found at 5 months in order to determine effectiveness of PDT in downstaging cytologic findings.
Results All patients had a consistent downgrading of cytologic findings during the 5 months of follow-up. Papanicolaou test results showed 2 patients had no dysplasia, 2 had mild dysplasia, and 1 had moderate dysplasia. Moderate dysplasia was confirmed by site-directed biopsy results. No complications of PDT occurred, but all 5 patients developed various abnormalities in liver function test results that returned to baseline values within 2 weeks; this also has been noted in patients ingesting -aminolevulinic acid who are presumably HIV seronegative.
Conclusion In a group of patients who are at high risk for recurrence irrespective of initial treatment, PDT can be used as a successful alternative to surgical excision for anal carcinoma in situ.
