Women who have had pre-cancerous cells removed remain at higher than average risk of developing cervical cancer in the 20 years following treatment, says research in the British Medical Journal (BMJ).
Cervical cancer is one of the major causes of death from cancer for women worldwide. But in countries with organised screening programmes for cervical cancer, incidence rates and deaths drop significantly.
The study looked at the long-term risks of cervical and other cancers for women after treatment to remove pre-cancerous lesions, a procedure called cervical intraepithelial neoplasia (CIN). The treatment removes abnormal cells that, if left untreated over a period of time, might turn into cancer.
Researchers studied 7,564 women treated for CIN during 1974 and 2001, and followed this up through the Finnish cancer registry until 2003.
Over the period, the researchers identified 448 new cases of cancer among the women, which was 96 more than they anticipated when considering average rates among the female population.
Of those new cases, 22 had developed invasive cervical cancer and showed that women were at more than average risk in the first and second decades after their CIN treatment.
The authors say their findings are in contrast to previous studies that said the risk of cancer did not increase after eight years follow-up after CIN treatment.
There are three types of CIN – mild, moderate and severe. The authors found that the risk of cervical cancer was higher for women previously treated for the mild or moderate type of CIN, possibly because people with less serious lesions tended to have less systematic follow-up checks than those who had experienced the more severe form of CIN.
Despite this, the authors say the treatment of CIN is still effective and that an estimated 28-39% of cases without treatment would progress to invasive cancer.