Further information about cervical cancer, HPV infections, and screening

 
Cervical cancer is the fourth most common women’s cancer worldwide. The cancer develops slowly through precancerous conditions. Prolonged human papillomavirus infection (HPV) is the most significant single risk factor. Other risk factors include early age at first sexual intercourse, several partners, factors that cause immune deficiency, and sexually transmitted diseases such as chlamydia, and especially smoking. HPV, which mainly spreads through sexual contact, is very common: most people will contract HPV at some point in their lives and it is almost always symptomless. Usually HPV disappears on its own in a few years. However, sometimes the infection becomes prolonged, which may cause cellular changes and precancerous conditions.
In Finland, cervical cancer is currently fairly rare thanks to cervical screening. Around 170 new cases are diagnosed every year. Unlike several other cancers, cervical cancer occurs in young women as well: cervical cancer starts to become more common immediately after 30 years of age.
 
Cancer development is very slow. It takes 10 to 15 years for cancer to develop from the initial HPV infection through precancerous conditions. Precancerous conditions can be detected in screening and they can be treated in time before they develop into actual cancer. Thanks to regular screenings, tens of thousands of women have been able to stay healthy and keep their fertility. New cancer cases are most commonly diagnosed in women who have not participated in screening.

 

HPV infection

 
The HPV infection is very common: around 80% of sexually active people will contract HPV in their lifetime. According to research, around 25% of otherwise healthy 20- to 25-year-old women are likely to have HPV. Usually the infection lasts 6 to 24 months and it is normally symptomless and heals on its own. Even if a person has had HPV before, they can still contract it again. Sometimes HPV remains on the mucous membrane of the uterine orifice for a long time, even for years, without causing any cellular changes. Most mild cellular changes heal on their own thanks to the immune system, and only a fraction of them develop into a precancerous condition as years go by. Ultimately, only a portion of serious precancerous conditions develop into cancer.
 
SCREENING PROTOCOL AND BENEFITS OF SCREENING
 
All women aged 30 to 60 living in Finland receive an invitation to a free-of-charge, statutory screening every five years. Some municipalities send invitations also to 25- and 65-year-old women. Invitations are sent according to birth year in the Population Register. Thus, there is no need to sign up to receive the invitation and the invitation cannot also be declined beforehand. Participation in screening is recommended regardless of sexual activity, used contraceptive method, or sexual orientation. Screening is also recommended for people who have received the HPV vaccine. Breastfeeding or uterectomy do not prevent participating in screening. If you are pregnant, the sample can be taken as usual up until gestational week 35. The sample can be taken after recovery from childbirth, usually 1 to 2 months after delivery. It is not recommended to take the sample during menstruation.
 
At the screening appointment, both HPV sample and Pap sample are collected from women aged 30 or over. The HPV sample is positive in around 8% of the screening subjects, in which cases the Pap sample is also examined. Only the Pap sample is collected from women who are under the age of 30.
 
If the Pap test is clearly abnormal, the subject is referred to further examinations, which entail a cervical endoscopy a.k.a colposcopy. In milder abnormal results, in which the HPV test is positive and/or the Pap test shows mild benign changes, the subject will receive an invitation to a follow-up test in 1 to 2 years due to the increased risk of cancer. If no signs of HPV infection or cellular changes are detected, the screening subject will receive the next invitation in five years along with their age group.
 
Findings that require further examinations, a colposcopy, are fairly rare. Sampling and any required treatment take place in the colposcopic examination, and some cellular changes can also be treated during the colposcopy.
 
Cervical cancer is at present a rare cancer in Finland and other western countries thanks to cervical screening. In countries where the standard of living is lower and no opportunities for screening are offered for women, it is the most common gynecological cancer in women and the third most common cancer altogether. Precancerous conditions and early stages of cancer are quite common in all countries, including Finland. These changes are common also in the youngest screened age groups. Approximately one woman in ten thousand screening participants is diagnosed with cancer, and five women in a thousand are diagnosed with a precancerous condition or an early stage that requires treatment. Most detected cellular changes are due to HPV infection. Screening aims at finding cellular changes that are caused by prolonged HPV infection and require local treatment before they develop into cance