Opting to have check-ups to monitor abnormal cells on the cervix instead of having them immediately removed could lead to a higher long-term risk of developing cervical cancer, a study has suggested.

While Danish researchers stressed that the possibility of developing the disease remains low, their findings found a four-fold increase in risk among those having cells monitored over 20 years when compared with people who had them removed.

In England, cervical screening is offered to women every three to five years depending on their age and takes a small sample of cells to check for abnormalities.

Abnormal cells on the cervix are not cancer, but are graded by the risk they pose of developing into cancer. CNI1 is the lowest, CNI2 is considered medium, while CIN3 or CGIN are high risk.

According to the NHS, immediate treatment for CIN1 cells is not required and women will be offered follow-up tests to monitor them.

Those with CIN2 cells will be given the option of follow-up checks or treatment to remove them, while removal is recommended for CIN3 or CGIN cells.

The study, led by researchers from Godstrup Hospital, Aarhus University, Odense University Hospital and the University of Southern Denmark – as well as the National Cancer Institute in Rockville, USA, compared monitoring cells to immediate treatment to assess the risk in the long term.

The study included 27,524 women on Danish healthcare registries aged between 18 and 40 who were diagnosed with CIN2 cells between 1998 and 2020.

Of these, 45% opted for monitoring abnormal cells, while 55% had LLETZ (large loop excision of the transformation zone), a type of surgery that removes part of the cervix.

The cohort was followed from CIN2 diagnosis to when cervical cancer developed, when the patient had a hysterectomy, moved out of the country, died, or up until December 31 2020 – whichever came first.

Researchers found 104 cases of cervical cancer – 56 in the group that had cells monitored and 48 in the group who had LLETZ.

The risk of cervical cancer was similar in the two groups – 0.56% and 0.37% in the LLETZ group – during the two-year monitoring period.

However, the risk in the group that opted to have cells monitored increased over time to 2.65%, while it remained stable in the group that had treatment (0.76%).

The increased risk was mainly seen in women over the age of 30, researchers said.

The team added that one explanation of this could be down to underlying human papillomavirus (HPV) infection, which can lie dormant in the cells and reactivate when the immune system is weakened or as a person gets older.

HPV is a group of viruses which can be transmitted through sexual contact and cause no symptoms. Certain types cause the vast majority of cervical cancers.

Researchers said their findings “are important for future guidelines on management of CIN2 and clinical counselling of women with a diagnosis of CIN2”.

A spokesperson for the charity Jo’s Cervical Cancer Trust said: “The study has provided a unique look at the long-term impact of monitoring CIN2 compared with immediate treatment.

“Cervical cancer is a slow-growing disease, developing over five to 20 years.

“However, the results highlight the importance of follow-up after a diagnosis of cell changes, and we’d encourage all women and people with a cervix to attend their cervical screening, colposcopy or follow-up appointments when they’re invited.”

Earlier this month, NHS England chief executive Amanda Pritchard pledged to eradicate cervical cancer by 2040.

To make this possible, health officials have urged more women to come forward for cervical screening, as well as ramping up efforts to vaccinate people against HPV.

However, last week it emerged that the number of women being screened for cervical cancer in England is at its lowest level since 2020, with the proportion of younger women taking up appointments also falling sharply.

Figures released by NHS England showed 4.62 million women aged 25 to 64 were due to be screened and invited for a test last year, with 3.43 million attending appointments.

Of the women aged 25 to 64 eligible for cervical screening, 68.7% were tested within the recommended time frame. In those aged 25 to 49, some 65.8% were screened within 3.5 years.