miércoles, 4 de abril de 2012

Anal HPV Infections and Precancerous Lesions Are Common in Men Who Have Sex with Men || NCI Cancer Bulletin for April 3, 2012 - National Cancer Institute

NCI Cancer Bulletin for April 3, 2012 - National Cancer Institute

Anal HPV Infections and Precancerous Lesions Are Common in Men Who Have Sex with Men

A large percentage of men who have sex with men (MSM) have anal human papillomavirus (HPV) infections and anal precancerous lesions, according to a meta-analysis of data from more than 50 studies. The rate is even higher among those infected with the human immunodeficiency virus (HIV). The findings were published online March 23 in Lancet Oncology.

MSM are known to be at elevated risk for developing HPV-associated anal cancer, but because of a lack of data it has been unclear whether anal cancer screening would be beneficial in this subgroup. Dorothy A. Machalek of the University of New South Wales in Sydney, Australia, and her colleagues examined 53 studies published before November 2011 to determine the frequency of HPV infections, anal lesions, and anal cancers in HIV-negative and HIV-positive MSM.

The researchers estimated that nearly three-quarters of HIV-positive MSM are infected with high-risk HPV types, which can cause cancer. In contrast, 37 percent of HIV-negative MSM were infected with the same high-risk types.

Moderate and severe anal lesions were detected in 29.1 percent of HIV-positive and 21.5 percent of HIV-negative MSM. The overall incidence of anal cancer in these two groups was 46 per 100,000 HIV-positive MSM and 5 per 100,000 HIV-negative MSM.

Using these data, the researchers estimated that, each year, high-grade lesions progress to anal cancer in 1 of 600 HIV-positive MSM and in 1 of 4,000 HIV-negative MSM. These progression rates are much lower than those seen for high-grade cervical lesions, which progress to cervical cancer in 1 of 80 women with those lesions every year, suggesting that anal cancer screening in MSM may need to be approached differently than cervical cancer screening.

However, in an accompanying editorial, Dr. Nicolas Wentzensen of NCI’s Division of Cancer Epidemiology and Genetics pointed out that progression rates for cervical cancer and anal cancer may not be directly comparable. The researchers “were not able to differentiate between moderate and severe dysplasia,” said Dr. Wentzensen. “The progression models in the cervix are based only on severe dysplasia. If we also included moderate dysplasia in the cervix, we might find similarly lower progression rates.”

The researchers and editorialist agree that more research is needed before anal cancer screening is recommended as part of standard clinical care for MSM. “There needs to be a lot of standardization and better appreciation for how [screening] methods perform and how the treatment triggered by those findings affects men,” said Dr. Wentzensen. “That is very important data to obtain before implementing widespread screening.”

Also in the Journals: Methylation Levels in HPV DNA May Indicate Risk for Cervical Precancer A new study suggests that human papillomavirus (HPV) DNA methylation levels could be used as a biomarker to predict which cervical HPV infections are most likely to progress to cervical precancer.
Using samples from some women in the Costa Rica HPV Vaccine Trial, Dr. Lisa Mirabello of NCI’s Division of Cancer Epidemiology and Genetics and her colleagues measured methylation levels at several sites of the genome of HPV 16, the HPV type that causes the majority of cervical cancers and precancers. Women with high methylation levels were at greater risk for persistent infection and cervical precancer than women who cleared the virus within 2 years.
The authors of the study, published March 23 in the Journal of the National Cancer Institute, are conducting follow-up studies to confirm their findings.

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