Why do some precancerous lesions develop into cervical cancer?

The project investigates the regression and progression of untreated precancerous lesions of the cervix.

Treatment of precancerous conditions

More than 3,000 women in Norway each year develop precancerous lesions of the cervix that require medical treatment. Detecting and treating the precancerous lesions at an early stage prevents it from developing into cervical cancer and possible death. Treatment for cervical cancer is usually a surgical procedure called conisation, in which the lower part of the cervix is removed. This can lead to side effects in later pregnancies.

One unresolved question when it comes to cervical precancerous lesions is why some precancerous lesions disappear on their own, while others develop into cancer.


All cases of cervical cell changes must be registered in the Cancer Registry, but in order to analyse the issue in this project, it is important that correct treatment information is also registered. When the project began, we faced challenges with deficiencies in the data. The project has therefore focused on quality assuring the data instead of examining the original research question.

After reviewing three different databases at the Cancer Registry, we found a total of 51,406 women diagnosed with high-grade precancerous lesions between 1998 and 2013, of whom 8% (3983 women) were not registered with treatment during the same time period. In order to check whether the women had undergone treatment in any case, we obtained information about hospital stays from the Norwegian Patient Registry and reviewed the medical history of a sample of the women.

Several reasons for lack of treatment

For a large proportion of the women, no treatment was registered because the cervical dysplasia was under active surveillance. This means that they either did not receive treatment at all or received treatment after more than one year had passed from the time of diagnosis. Active surveillance was particularly used among women under the age of 40 and among those with less severe cervical dysplasia (CIN 2). Other reasons why no treatment had been registered could be that the diagnosis was uncertain or that they had instead received treatment for cervical cancer or other gynaecological cancer.

A small proportion of treatments were never reported to the Cancer Registry of Norway

Errors in the coding at the Cancer Registry of Norway were the main reason why the treatment was not registered, but for a small group the treatment was never reported to the Cancer Registry. Missing or incorrect registration of treatment was particularly associated with public laboratories and patients aged 40–54 years.

In addition, there were relatively more missing registrations in the last years of study. However, this is probably due to a delay in registration, so that the most recent registrations had not been included when the study was conducted.

Reliable data source

Overall, the study showed that 97% of treatments for high-grade precancerous lesions of the cervix are correctly registered in the Cancer Registry. Thus, the Cancer Registry's data on cases and treatments of premalignant lesions will be a valuable and reliable source of use.

It is nevertheless desirable that active surveillance be included as a treatment option in registry data. This measure will make the Cancer Registry's data even better for use in research and statistics.


Leinonen MK, Hansen SA, Skare GB, Skaaret IB, SIlva M, Johannesen TB, Nygård M. Low proportion of unreported cervical treatments in the Cancer Registry of Norway between 1998 and 2013. Acta Oncologica. 2018, Aug 31:1-8.

Project participants

The Cancer Registry of Norway

Espen Enerly, Giske Ursin, Suzanne Campbell, Mari Nygård, Maarit Leinonen og Madleen Orumaa, Gry Baadstrand Skare, Inger Berit Skaaret, Monica Silva og Tom Børge Johannesen

Former employees at the Cancer Registry of Norway: Paul Anthony Fronteri og Svenn Alexander Hansen


Albert Einstein College of Medicine: Philip Castle

The project is financed by the Cancer Registry of Norway.