15. Women experienced early sexual activity or victims of abuse

Human papillomavirus (HPV) infection often occurs shortly after first sexual activity.[1] HPV infections are more likely to occur in adolescent women than in older women, as the process of squamous metaplasia of the transformation zone of the cervix is more active during adolescence and represents a vulnerability to the establishment of HPV infections.[2] There is also evidence that individuals who have been victims of sexual abuse as children have higher rates of anogenital HPV detection than individuals with no such history.[3]

Women who experience first sexual activity at an early age and are subsequently infected with oncogenic HPV may have a higher risk of carcinogenesis over time if these infections are persistent, since persistent infections are associated with an increased risk of cervical cancer.[4] Most HPV infections are transient and are cleared in adolescents and young women without the detection of cervical intraepithelial neoplasia (CIN) within 36 months.[5]

The incidence of cervical cancer in women younger than 25 years of age is very low. Since the introduction of the National Cervical Screening Program (NCSP), age-specific incidence rates in this group of women have remained relatively stable over the past two decades.[6] The introduction of the National HPV Vaccination Program, which offers the HPV vaccine to girls at age 12–13 years, provides an additional level of protection for young women. Furthermore, there is some evidence that vaccination of women after first sexual intercourse may prevent reinfection or reactivation of the disease with vaccine included HPV types.[7]

The prevalence of vaccine-included HPV types 16/18/6/11 is now very low in young women, and has reduced by 35% since 2005–2007 in unvaccinated women, as well as in vaccinated women.[8] HPV 16 is the dominant contributor to cervical cancer and precancer in young women; prior to HPV vaccination, HPV 16 was detected in 70% of CIN grade 3 (CIN3) in women aged 16–25 years.[9]

Since the introduction of the National HPV Vaccination Program, there has been a steady decline in the detection of high-grade abnormalities in women under 20 years of age[6] and a reduction in the risk of high-grade cervical abnormalities in women who completed the vaccine series at the ages of 12–26 and who had not started screening before the implementation of the vaccination program.[10]

Anogenital HPV infections are transmitted mainly by skin-to-skin or mucosa-to-mucosa contact. Penetrative sexual intercourse is not strictly necessary for transmission and HPV can be transferred to the cervix from original infection at the introitus. Therefore, genital skin-to-skin contact, vaginal sex, oral sex, and anal sex represent types of sexual activity that may facilitate the person-to-person transmission of anogenital types of HPV.

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Systematic review evidence

No randomised or pseudorandomised controlled trials were found that evaluated the safety and effectiveness of alternative screening strategies in women with a history of early sexual intercourse or sexual abuse in comparison to other women.

General literature review evidence

In the absence of any direct evidence from the systematic review, a general review of the literature was performed to ascertain the effectiveness of cervical screening in:

• women who have had first sexual intercourse at the age of 14 years or younger
• women who have experienced childhood sexual abuse

Sixteen studies were identified. No studies directly addressed the clinical question. However, one study provided indirect evidence based on the re-analysis of individual data from studies on cervical cancer risk conducted worldwide.[11] In this study, the relative risk for invasive cervical carcinoma in women who first had intercourse at the age of 14 years or younger was similar to the risk in women who first had intercourse at 16–18 years of age. In Australia, the median age at first sexual intercourse has been estimated to be 16–17 years of age.[12][13]

Although a number of studies were identified by the search, no other recent studies reported relevant outcome data by age of sexual debut. Studies found that regression of cervical abnormalities was common in young women[5][14][15][16] and that CIN3+ was rare.[17][18][19][20][16]

There is a lack of evidence that women who have experienced early sexual intercourse will benefit from commencing cervical screening before age 25 years.

The minimal benefits of cervical screening in young women should be weighed against the increased risk of harm that unnecessary excisional procedures could have for future obstetric outcomes (see Chapter 14. Screening in Pregnancy) and psychosocial well-being (see Chapter 19. Pyschosocial care).

Positive oncogenic HPV test results and mild cytological abnormalities are frequently encountered in women younger than 25 years. However, high rates of regression of low and high-grade CIN lesions have been reported in the literature and the positive predictive value of cytology screening tests appears to be lower in this age group.[16][17]

Investigation and potential treatment of these lesions, that will most likely regress, may lead to unnecessary harms (psychosocial, obstetric and financial). It is considered that the harms outweigh the benefits for young women

See Chapter 5. Benefits, harms and cost-effectiveness of cervical screening in the renewed NCSP.

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Clinical practice

A single cervical screening test may be performed before 25 years of age in women for whom there is concern about early sexual activity or sexual abuse prior to age 14 years. These are considered to be special circumstances and are not applicable to the general population of women under 25 years of age. A significant proportion of women experience their first sexual intercourse at age 14–16 years.[21] It is far less common for women to have first intercourse at age 13 years and below, and this may be more often related to child sexual abuse.[21] These data support confining recommendations to women who have experienced early sexual activity or been victims of child sexual abuse prior to the age of 14 years. Recommendations regarding symptomatic women are consistent with current clinical practice.

Resourcing

This recommendation is considered unlikely to require significant resources provided that cervical screening test providers restrict the screening of women under 25 years of age to those in whom the sexual history confirms either early sexual activity or child sexual abuse (prior to 14 years of age) and on a case-by-case basis.

Barriers to implementation

Young women may choose not to disclose their age of first sexual activity or that they have a history of sexual abuse during childhood. However, as there is a lack of evidence that women with early sexual activity will benefit from commencing cervical screening earlier than 25 years of age, this is unlikely to affect safety in regard to the development of cervical cancer in these young women.

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Unresolved issues

Uncertainty remains as to whether early sexual activity increases the risk of cervical cancer in young women as there is no currently available evidence to support an increased risk. The National HPV Vaccination Program is expected to reduce the number of at-risk women although the overall impact of vaccination will depend on how many young women were HPV-naïve before being vaccinated. Substantial indications of the effect of the National HPV Vaccination Program have already been observed in women including a reduction in the risk of high-grade cervical abnormalities in women who completed the vaccine series at the ages of 12–26 and who had not started screening before the implementation of the vaccination program,[10] a decline in the detection of high-grade abnormalities in women under 25 years of age[6] and a substantial decline in the prevalence of vaccine-included HPV types in women aged 18–24 years.[8] HPV vaccination is also expected to reduce the risk of high-grade abnormalities in unvaccinated women indirectly, via a reduction in the circulation of vaccine included HPV types within the population. A recent observational study reported a reduction in the prevalence of HPV 16/18/6/11 in unvaccinated young women in Australia since the implementation of HPV vaccination, suggesting herd immunity.[8]

Nevertheless, vaccination should not be withheld from young women post sexual debut as there is some evidence of protection even in women who were exposed to HPV prior to being vaccinated,[7] in addition to protection against any vaccine included HPV types to which they have not been previously exposed.

Future research priorities

Prospective cohort studies following women from the age at first sexual activity until the age of CIN3 diagnosis, with regular interval follow-up, are required to ascertain the importance of early first sexual activity in the development of cervical pre-cancer.

Effectiveness of post-exposure HPV vaccination of young women and correlation with type of HPV in those found to have a positive oncogenic HPV test result.

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