Epigenetic Markers May be Used to Estimate Anal Cancer Risk
Microscope image of abnormal cells within the anus. Credit: QMUL
A new genetic test could be an accurate and inexpensive way to find and treat those at highest risk of anal cancer - a disease with growing incidence in women, men who have sex with men (MSM) and people with HIV.
The early research by Queen Mary University of London (QMUL), which was funded by Cancer Research UK, finds that the test could lead to a reduction in painful procedures and minimise the over-treatment of people at low risk.
Anal cancer is mostly caused by human papillomavirus (HPV) - the same virus that causes cervical cancer. In 2014, the UK had around 1,300 new cases of anal cancer and 360 deaths. In addition to rising levels in women and MSM, anal cancer is more common in HIV-positive MSM with around 100 cases per 100,000, compared to 25 in HIV-negative MSM, and only 1.5 in men in general.
Diagnosis presents many challenges. Full biopsies are painful, and taking a small sample of cells (‘cytology’) is problematic because lesions can be hidden and clinicians give varying interpretations of results. High-resolution anoscopy, where the anal canal is examined with a high resolution magnifying instrument, is often used as the primary screening tool for high-risk populations but is uncomfortable for the patient, expensive, complex and generates subjective results.
Lead researcher Professor Attila Lorincz from QMUL's Wolfson Institute of Preventive Medicine said: “The widespread over-treatment of anal precancerous lesions is necessary today because we don’t know which ones will progress to cancer. But this creates a large burden on anoscopy clinics in the UK and the procedures can be detrimental to people’s quality of life. Many people are undergoing these procedures unnecessarily, so what we really need is precision medicine to identify those who do need treatment.”
The research, published in the journal Oncotarget, involved studying anal biopsy specimens from 148 patients in London, including 116 men (mostly MSM). The specimens were analysed to look for genetic markers that may be associated with the presence of anal cancer.
The team specifically looked at the patients’ ‘epigenetics’ - the naturally-occurring chemical ‘tags’ on genes which control whether or not they are switched on. Liver cells and kidney cells are genetically identical apart from their epigenetic marks. They found that all of the anal cancers showed the presence of specific epigenetic markers on the patients’ EPB41L3 gene (a tumour suppressor gene) and also on certain regions of their viral HPV genome.
The results suggest that epigenetic testing may be an accurate and thorough method to indicate whether a patient’s lesions are destined to progress to anal cancer. This could reduce the costs, pain and anxiety from other methods of diagnosis, and minimise over-treatment of low risk people.
Professor Lorincz added: “We believe this new set of biomarkers goes a long way to indicating which men and women are at risk of developing anal cancer. Now that we can identify those at risk, and conversely, those not at risk, we hope to see a big improvement, by making sure that anoscopies and laser or chemical surgery are only given to those who need it.”
Once developed, the test would involve taking a small sample of cells from the anal canal via a swab and then sending the sample off to a laboratory for epigenetic analysis.
While a test could be developed within five years, the researchers caution that the results first need to be confirmed in a much larger study across the UK, and repeated using swab samples rather than the biopsies which were used in the current study.
Dr Rachel Orritt, Cancer Research UK’s health information officer, said: “This study builds on what we already know about the link between changes to cell DNA and cervical cancer, and shows that similar changes to the DNA in anal cells could suggest anal cancer.
“If other studies confirm and build upon these findings, this promising research could be used to develop a less invasive method to help doctors identify people who are at a higher risk of anal cancer and avoid unnecessary procedures for those who are at a lower risk.”