Cervical Cancer Prevention (PDQ®) 3/4 —Health Professional Version - National Cancer Institute

Cervical Cancer Prevention (PDQ®)—Health Professional Version - National Cancer Institute

Interventions With Adequate Evidence of a Decreased Risk of Cervical Cancer

HPV vaccination

Given the etiologic role of HPV in the pathogenesis of cervical neoplasia, vaccines to immunize against HPV infection offer a primary prevention strategy for cervical cancer. A quadrivalent (HPV-6, -11, -16, and -18) vaccine using a late protein L1 construct to induce antibody-mediated immunity was approved for use by the U.S. Food and Drug Administration in 2006; a bivalent (HPV-16, -18) vaccine was approved in 2009; and a vaccine targeting nine HPV types was approved in 2014. Vaccination during pregnancy has not been associated with adverse pregnancy outcomes.[22]

Persistent infection with oncogenic types of HPV, such as HPV-16 and HPV-18, is associated with the development of cervical cancer.[23] A vaccine to prevent HPV infection with oncogenic-type viruses has the potential to reduce the incidence of cervical cancer. A vaccine against HPV-16 using empty-viral capsids called virus-like particles (VLP) was developed and tested for efficacy in preventing persistent infection with HPV-16.

A multicenter, double-blind, placebo-controlled trial enrolled 2,391 women aged 16 to 23 years and randomly assigned them to receive either 40 µg of HPV-16 L1 VLP vaccine or placebo on day 1, at 2 months, and at 6 months. Papanicolaou (Pap) tests and genital samples for HPV-16 DNA were obtained on day 1, at 7 months, and every 6 months for 48 months. Colposcopy and cervical biopsies were obtained when clinically indicated at study exit. Serum HPV-16 antibody titers were obtained at study entry, at 7 months, and then every 6 months. A total of 1,505 women (755 receiving vaccine and 750 receiving placebo) completed all three vaccinations and had follow-up after month 7. After immunization, HPV titers peaked at month 7, declined through month 18, and then stabilized in months 30 through 48. There were no cases of CIN in the vaccine-treated women, but there were 12 cases in the placebo group (six CIN 2 and six CIN 3). HPV-16 infection that persisted for at least 4 months was seen in seven vaccine-treated women compared with 111 placebo-treated women.[24]

An international, double-blind, placebo-controlled trial of a bivalent HPV-16/HPV-18 VLP vaccine was performed in 1,113 women aged 15 to 25 years with normal cervical cytology who were seronegative for HPV-16, HPV-18, and 12 other oncogenic HPV types at enrollment. Women received either vaccine or placebo at 0, 1, and 6 months and were assessed by cervical cytology and self-obtained cervicovaginal samples for at least 18 months. A masked treatment-allocation follow-up study was performed for an additional 3 years, for a combined analysis of up to 6.4 years of follow-up. The 12-month persistent infection rate of HPV-16 or HPV-18 in an according-to-protocol cohort (i.e., women who received all three doses of vaccine or placebo on the correct schedule) was 0 of 401 women in the vaccine arm compared with 20 of 372 women in the placebo arm, with a vaccine efficacy of 100% (95% CI, 81.8–100). Diagnoses of CIN 2 or higher in a total vaccinatedcohort (i.e., women who received at least one dose of vaccine or placebo) were 0 of 481 women in the vaccine arm compared with 9 of 470 women in the placebo arm, with a vaccine efficacy of 100% (95% CI, 51.3–100). Adverse events were similar in vaccinated and placebo-treated women. Neither analysis was intention-to-treat (ITT), making it difficult to know what the true vaccine efficacy for either virological or cytohistological endpoints would be in the routine clinical setting. Furthermore, cytohistological outcomes were reported only as composite endpoints (CIN 2+), making it impossible to distinguish the vaccine’s efficacy against invasive cervical cancer alone and potentially inflating the observed efficacy by including lesions with a relatively high probability (approximately 50% for CIN 2 [25]) of spontaneous regression.[26]

A quadrivalent vaccine (HPV types-6, -11, -16, and -18) was evaluated in a multinational, double-blind, randomized controlled trial of 17,622 women aged 15 to 26 years (FUTURE I and II).[27] Women received either the HPV vaccine or placebo at 0, 2, and 6 months; participants were assessed by clinical exam, Pap test, and HPV DNA testing for 4 or more years. Two analyses were reported. One group was considered to be HPV naive: negative to 14 HPV types. The second group was an ITT analysis, which approximates a sexually active population. The composite endpoint for cervical disease included the incidence of HPV-16/HPV-18–related, CIN 2, CIN 3, adenocarcinoma in situ, or invasive carcinoma. Outcomes were reported as follows:

Table 1. Vaccine Efficacy of the Quadrivalent HPV Vaccine

Population	Point Estimate and 95% CI
CI = confidence interval; CIN = cervical intraepithelial neoplasia; HPV = human papillomavirus; ITT = intention-to-treat.
HPV-naive population for HPV-CIN 3	100% (90.5%–100%) for lesions associated with HPV-6, -11, -16, or -18
ITT CIN 3	45.3% (29.8%–57.6%) for lesions associated with HPV-6, -11, -16, or -18

This study also demonstrated decreased rates of abnormal Pap tests and subsequent diagnostic procedures. No cases of invasive cervical cancer were identified during the trial.

A 9-valent VLP vaccine was studied in another international randomized trial, which included 14,215 women. This new vaccine 9vHPV includes the four HPV types in the quadrivalent vaccine, qHPV (6, 11, 16, 18) and also 5 more oncogenic types (31, 33, 45, 52, 58). Sexually active women aged 16 to 26 years with fewer than five lifetime sexual partners received three intramuscular injections (day 1, month 2, and month 6) of either the qHPV vaccine or the 9vHPV vaccine. Women were evaluated every 6 months up to 5 years. The rate of high-grade cervical, vulvar, or vaginal disease was the same in both groups (14.0 per 1,000 person-years) because of pre-existing HPV infection, but the rate of disease related to HPV-31, -35, -45, -52, and -58 was lower in the 9vHPV vaccine group (0.1 vs. 1.6 per 1,000 person-years). Injection-site reactions were more common in the 9vHPV group.[28] Although not addressed in this study, the benefit of HPV vaccination is optimal in younger females before the onset of sexual activity.

All forms of the HPV vaccine are currently recommended by the Centers for Disease Control and Prevention (CDC) in the United States as a two-dose schedule at least 6 months apart for adolescents younger than 15 years. The current CDC recommendation for older individuals is to receive the original three-dose series. Recently, given issues of cost and adherence, there has been published data investigating whether similar vaccine efficacy could be obtainable using a reduced-dose schedule. A post hoc combined analysis of two phase III randomized controlled trials of the bivalent HPV vaccine (the Costa Rica Vaccine Trial and the PApilloma TRIal against Cancer In young Adults [PATRICIA] Trial) found that among women who were not HPV positive at enrollment for the specific virus type being studied, vaccine efficacy against either one-time incident detection of HPV 16/18 or incident infection that persisted at least 6 months was not statistically significantly different for those who received all three, two, or only one of the scheduled HPV vaccine doses (resulting from nonadherence or other factors) for up to 4 years of follow-up. Vaccine efficacy rates for persistent HPV 16/18 infection ranged from 89.1% (95% CI, 86.8%–91.0%) for three doses, to 89.7% (95% CI, 73.3%–99.8%) for two doses, to 96.6% (95% CI, 81.7%–99.8%) for one dose. To date, there are no randomized controlled trials that directly assess this clinical question.[29] A recent international study compared a two-dose schedule with a three-dose schedule in adolescents younger than 15 years who received the 9-valent HPV vaccine. The antibody response was noninferior in the two-dose schedule, supporting the current recommendation that two doses are sufficient for this age group.[30]

On the basis of their mechanism of action, L1/2 HPV vaccines do not appear to impact pre-existing infections. The FUTURE II trial demonstrated a markedly lower vaccine efficacy rate in the total randomized study population, which included individuals who were positive for HPV at baseline, compared with the per-protocol population (44% for lesions associated with HPV-16 or HPV-18, and 17% for lesions associated with any HPV type vs. 98%; refer to Table 1 above).[27] Additionally, an intermediate analysis of a randomized controlled trial primarily evaluating the efficacy of the HPV-16/18 vaccine in preventing infection found no effect on viral clearance rates in women aged 18 to 25 years who were positive at the time of study enrollment.[31]

The type-specific vaccines, if successful in preventing invasive cancer, will offer protection for only a subset of cases, the proportion of which will vary worldwide.[32] Using data from a multicenter case-control study conducted in 25 countries, it was estimated that a vaccine containing the seven most common HPV types could prevent 87% of cervical cancers worldwide. A vaccine with the two most common strains, HPV-16 and HPV-18, would prevent 71% of cervical cancers worldwide.[32]

A study of cervical HPV DNA among 202 Australian women aged 18 to 24 years who were sampled between 2005 and 2007 before implementation of a national quadrivalent prophylactic HPV vaccine program compared the results with a matched group of 1,058 women who were sampled in the postvaccination era (2010–2012). This study found an adjusted prevalence ratio among fully vaccinated women of 0.07 (95% CI, 0.04–0.14; P < .0001) for vaccine-related HPV types and a smaller but statistically significant magnitude of protection of 0.65 (95% CI, 0.43–0.96; P < .03) among unvaccinated women, suggesting herd immunity (protection of unvaccinated individuals).[33] These data strengthen previous results that suggest herd immunity in this population manifested as a reduction in genital warts among heterosexual men, a group that includes sexual partners of vaccinated women.[34] Data also suggest cross protection against carcinogenic types that are not directly targeted by the quadrivalent vaccine but are included in the new nonvalent HPV vaccine.[33]

There are data that explore the impact of national HPV vaccination programs and report on vaccine effectiveness. In England, 15,459 residual genital specimens from women aged 16 to 24 years, collected for chlamydia screening between 2010 and 2016, were utilized for national HPV surveillance.[35] In this study, vaccine effectiveness for HPV-16/HPV-18 was 82% (95% CI, 60.6%–91.8%) for women who were vaccinated before age 15 years. Within the younger age groups, the prevalence of HPV-16/HPV-18 significantly decreased within the postvaccination period between 2010 and 2011 to 2016 from 8.2% to 1.6% in 16 to 18 year olds and from 14.0% to 1.6% in 19 to 21 year olds (compared with 17.6% and 16.9% in the prevaccination era).[35]

Use of barrier method during sexual intercourse

Barrier methods of contraception are associated with a reduced incidence of SIL presumptively secondary to protection from sexually transmitted disease.[36,37] The effectiveness of condom use for the prevention of HPV infections has been evaluated in a prospective study of women aged 18 to 22 years who were virgins.[38] The number of vulvovaginal HPV infections was reduced with consistent condom use, and HPV infection rate was 37.8 infections per 100 patient-years among women whose partners used condoms 100% of the time in the 8 months before testing, compared with 89.3 infections per 100 patient-years among women whose partners used condoms less than 5% of the time (P trend = .005). No cervical SIL were detected among women reporting 100% condom use by their partner.[38]

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