A new smear test to prevent anal cancer

Scientists at the Medical Research Council (MRC) have found a new and improved technique to detect anal cancer that may cause the number of people dying from the disease to drop significantly.

The research, carried out at the MRC Cancer Cell Unit in Cambridge, explores using minichromosome maintenance proteins (MCMs) to detect pre-cancerous and cancerous cells in the anus. The study, funded by the MRC and Cancer Research UK, is published today in the American journal Cancer Epidemiology Biomarkers and Prevention.

MCMs have been used to find pre-cancerous and cancerous cells in other areas of the body more accurately and effectively but this is the first time they have been used to detect anal cancer.

Lead author of the study, Dr Nick Coleman, said: “This is welcome news for people who are at high risk of developing anal cancer. We have uncovered a more effective way to detect anal cancer in its early stages, meaning fewer people would have to undergo the rigours of radiotherapy and chemotherapy treatment.

“Anal cancer is a difficult disease to detect and many cases are identified after it becomes too late for people to undergo simple surgery to remove it. We wanted to create a test which was easier to perform and had a high rate of accuracy. This study suggests that MCM testing fits the bill very well indeed.”

The study first involved screening anal tissue samples from different patients to pick up the biological differences between normal cells and cancer cells. The scientists found that normal tissue lacked MCMs whereas anal cancer and pre-cancer had an abundance of MCMs. The power of MCM testing was then shown in an independent group study of 235 anal smears from 144 subjects.

The test successfully identified 84% of the patients with anal pre-cancer, without producing a high rate of false alarms in people without disease.

Dr Coleman said: “This is a much better overall performance than existing methods of detecting anal disease, which either miss too many cases or show up as positive when no disease is actually there. MCM tests can also be read by a computer, which would avoid the risk of human error and be a cheaper option too.”

Dr Lesley Walker, director of cancer information at Cancer Research UK, said: “MCMs are already showing promise as early markers to be used in screening for a number of cancers, so it is encouraging to see this research progressing.

“We must also continue to raise awareness of the disease, particularly among people in high risk groups such as gay and bisexual men so they can take action if they have symptoms.”

The incidence of anal cancer is estimated as high as 37 per 100,000 in gay men and about double if they are also HIV-positive.

Human rights campaigner Peter Tatchell has lobbied for anal cancer screening and treatment programmes targeted at the higher risk gay community for many years.

He said: "For gay and bisexual men who are at risk of anal cancer, these tests are an important medical breakthrough. They will help save lives. With this reliable screening test, signs of anal cancer will be detected earlier, leading to speedier, more effective treatment."

(Source: Cancer Epidemiology Biomarkers and Prevention: Medical Research Council: October 2008)