CATIE News - Placebo-controlled trial of Aldara for precancerous anal lesions
2010 Sept 8 - There are more than 100 types or strains of human papillomavirus (HPV). This microbe is a common sexually
transmitted infection. Some types of HPV can cause ano-genital warts while others can cause precancerous growths leading to cervical and anal cancer.
Since HPV is sexually transmitted, many HIV-positive people are also co-infected with HPV.
Anti-HIV therapy (commonly called ART or HAART) can greatly extend the survival of HIV-positive people. It does this by significantly
suppressing the production of HIV, allowing the immune system to begin repairing itself. Regrettably, ART does not cure HIV infection and the
immune system is only partially repaired by this therapy. Although the improved immunity is sufficient in most people to keep AIDS-related
infections at bay, the immune system's ability to control some cancers remains imperfect. Thus, despite the use of ART, HIV-positive
men-particularly gay and bisexual men-are at increased risk for anal cancer. HIV-positive women are also at increased risk for
cervical and anal cancer.
A recent international survey of leading dermatologists and surgeons about how they dealt with anal warts and anal precancers suggested
a lack of consensus and underscored the need for international guidelines in this area. In the absence of such guidelines, some individual
hospitals, clinics and research centres have established their own anal cancer screening programs (when funding is available), mostly in
large cities in North America and Western Europe.
Aldara (imiquimod) is a drug that is approved for the treatment of genital warts and for the treatment of biopsy-confirmed superficial,
small basal cell cancer on the trunk, legs and arms. Precisely how Aldara works is not clear. However, this drug seems to stimulate cells of the
immune system in the skin to release a group of chemical signals called cytokines, which help marshal the immune system to attack HPV-infected
cells. Aldara helps the immune system to destroy warts or, in some cases, prevent further growth and development of warts.
Aldara is supplied as a cream that is applied to the wart-affected skin on a regular basis for up to 16 weeks. This drug is approved
for use on the skin and not inside the body.
Researchers in the United Kingdom at London's Chelsea and Westminster Hospital have conducted a placebo-controlled trial of Aldara
to assess its impact on precancerous cells in the anal canal in HIV-positive people. The results of the study are promising and may encourage
other researchers to conduct similar studies.
Researchers recruited HIV-positive men who had biopsy-confirmed precancerous anal lesions. In the first part of the study, 28 men
received sachets containing Aldara cream and 25 men received sachets containing fake Aldara cream (placebo). Both products were used for 16
weeks. Participants applied a small amount of cream no farther than two centimetres into the anal canal three times weekly. If soreness in
the anus developed, participants refrained from using the cream until their symptoms cleared.
The men had their anuses inspected with high-resolution anoscopy at the start of the study so researchers could see any abnormal
growths. This procedure was repeated at the 20th week of the study to assess the impact of Aldara or placebo.
In the second part of the study, participants who still had precancerous cells in their anuses were offered a 16-week course of
Aldara and ongoing monitoring.
At the start of the study, the average profile of participants was as follows:
- age - 42 years
- tobacco use - 50% of participants
- CD4+ cell count - 350 cells
- duration of HIV infection - 12 years
- HIV viral load less than 50 copies/ml - 90% of participants
- length of time precancerous cells were present - 3 months
Although 64 participants were recruited, 53 completed the study (28 on Aldara and 25 on placebo). According to the study team,
"the commonest reason for withdrawal [from the study] was unhappiness with the 50% probability of receiving placebo."
Among people who received Aldara during the placebo-controlled phase, four had their precancerous lesions clear and remain that
way for an average of three years of monitoring.
After 42 months, one of these four people developed new anal warts and precancerous anal lesions. The study team suggested
that this was likely because of new HPV infection. He received another course of Aldara and his warts and precancerous growths cleared.
In eight other participants, use of Aldara caused their precancerous lesions to become less abnormal and, therefore, less likely to
become cancers. This change was maintained over nearly three years of monitoring. One of these eight men had even further improvement as his
abnormal growths completely resolved. Another one of these eight men developed new precancerous anal lesions after nearly four years of monitoring.
Despite the use of Aldara, precancerous anal lesions persisted among 16 men.
One man had his precancerous lesions resolve. But precancerous lesions persisted in the remaining 24 men.
A total of 21 participants chose to enroll in the second part of the study, 12 former placebo users and 9 former Aldara users.
Five of the 21 participants had their precancerous lesions resolve and four others had lesions that became less abnormal.
In total, 61% of men who received Aldara subsequently showed a prolonged absence of precancerous cells.
However, despite receiving Aldara, two men continued to have precancerous cells and subsequently developed anal cancer.
Different lesions, different rates of clearance
The researchers noted that among Aldara users sometimes anal warts cleared before precancerous lesions disappeared, or vice versa.
They also found that sometimes external precancerous growths cleared before internal ones. So they warned doctors to be careful about
assuming that all growths had cleared based on what happened outside (or inside) the anal canal.
A helpful trend
There was no impact of CD4+ cell counts on the response to Aldara. The present study has not proved that the use of Aldara will
prevent anal cancer. Moreover, not everyone treated with this drug showed improvement. However, when precancerous cells can be resolved,
and people are regularly screened for anal cancer, the risk for this complication appears to be greatly reduced.
-Sean R. Hosein
Fox PA, Nathan M, Francis N, et al. A double-blind, randomized controlled trial of the use of imiquimod cream for the
treatment of anal canal high-grade anal intraepithelial neoplasia in HIV-positive MSM on HAART, with long-term follow-up data including the
use of open-label imiquimod. AIDS . 2010; in press .
CATIE-News is written by Sean Hosein, with the collaboration of other members of the Canadian AIDS Treatment Information
Exchange, in Toronto.
From Canadian AIDS Treatment Information Exchange (CATIE). For more information visit CATIE's Information Network
Source: CATIE: CANADIAN AIDS TREATMENT INFORMATION EXCHANGE