Topical treatment for pre-cancerous anal cell changes safe and moderately effective

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A course of treatment with topical trichloroacetic acid appears to provide a safe and effective treatment for pre-cancerous cell changes in the anus, US investigators report in a study published in the online edition of the Journal of Acquired Immune Deficiency Syndromes. The treatment was equally effective in HIV-positive and HIV-negative men.

“Given its ease of use, low cost, and good safety profile, trichloroacetic acid represents a reasonable first-line therapy with carefully selected patients”, comment the investigators.

Higher rates of anal cancer are seen in gay men, especially those with HIV, than in the general population. Anal intraepithelial neoplasia (AIN) is the name given to pre-cancerous changes in the anus. AIN is graded AIN I, AIN II, and AIN III according to its severity.


anal intraepithelial neoplasia (AIN)

An abnormal growth on the surface of the rectum or anal canal which, when observed with a microscope, suggests that the cells could be malignant (cancerous).


Small scrapes, sores or tears in tissue. Lesions in the vagina or rectum can be cellular entry points for HIV.

first-line therapy

The regimen used when starting treatment for the first time.

retrospective study

A type of longitudinal study in which information is collected on what has previously happened to people - for example, by reviewing their medical notes or by interviewing them about past events. 


Applied directly to the affected area, as opposed to systemic. For example, a cream or lotion, applied to body surfaces such as the skin or mucous membranes inside the vagina or rectum.


Topical 85% trichloroacetic acid is a recommended first-line treatment for genital warts. Investigators from the University of California San Francisco Anal Neoplasia Clinic performed a retrospective study to determine the safety and effectiveness of treatment with this product for AIN.

Their study involved 54 men, 35 (64%) of whom were HIV-positive.

They were provided with four treatments with 85% trichloroacetic acid at intervals of one to two weeks. The treatment was administered in the clinic by healthcare staff. Treatment was considered successful if AIN II/III resolved or regressed to AIN I. It was also considered a success if AIN I resolved. Patients were followed for at regular intervals for a year after completing their treatment and were monitored for the recurrence of lesions.

Of the 28 patients with confirmed AIN II/III, 32% experienced a complete resolution of their lesions, and 29% a regression of their lesions to AIN I. This provided an overall treatment response of 61%.

Treatment with trichloroacetic acid led to a resolution of lesions in 73% of individuals with AIN I at baseline.

Complete clearance of lesions was observed in 34% of patients with HIV and 47% of HIV-negative men, a non-significant difference. However, on a per lesion basis, the average rate of clearance was 64%. When treatment response was defined as clearance of AIN II/III or the reversion of lesions to AIN I, the response rate was 71%.

Patients who cleared their lesions required a mean of two applications of the treatment.

Only 5% of patients reported side-effects, the most common being pain and discomfort in the site of the treatment.

HIV-positive patients with one or two lesions were significantly more likely to have a successful response to treatment than those with three or four lesions (p = 0.01). A higher CD4 cell count was also associated with a greater chance of clearance, but this did not achieve statistical significance.

However, the lesions recurred in 72% of HIV-positive patients and 67% of HIV-negative men. The investigators suggest that in many cases these lesions are likely to have been new rather than the reappearance of the treated AIN.

The investigators are encouraged by these results and suggest that the treatment could provide a useful first-line treatment for patients with AIN. They conclude, “larger, prospective, randomized studies are needed to determine efficacy of trichloroacetic acid for treatment of AIN in comparison with other treatment modalities and ultimately to reduce the risk of progression of AIN to invasive cancer.”


Singh JC et al. Efficacy of trichloroacetic acid in the treatment of anal intraepithelial neoplasia in HIV-positive and HIV-negative men who have sex with men. J Acquir Immune Defic Syndr (online edition), 2009.