Table of Contents Purpose of This PDQ Summary Summary of Evidence
Significance Evidence of Benefit Get More Information From NCI Changes To This Summary (02/26/2009) Questions or Comments About This Summary More Information
Purpose of This PDQ Summary
This PDQ cancer information summary for health professionals provides comprehensive, peer-reviewed, evidence-based information about cervical cancer prevention. This summary is reviewed regularly and updated as necessary by the PDQ Screening and Prevention Editorial Board.
Information about the following is included in this summary:
- Cervical cancer incidence and mortality statistics and information about cervical cancer risk factors.
- Interventions for cervical cancer prevention.
This summary is intended as a resource to inform clinicians and other health professionals about the currently available information on cervical cancer prevention. The PDQ Screening and Prevention Editorial Board uses a formal evidence ranking system in reporting the evidence of benefit and potential harms associated with specific interventions. It does not provide formal guidelines or recommendations for making health care decisions. Information in this summary should not be used as a basis for reimbursement determinations.
This summary is also available in a patient version, which is written in less technical language.
Back to Top Summary of Evidence
Note: Separate PDQ summaries on Cervical Cancer Screening and Cervical
Cancer Treatment are also available.
Avoidance of Human Papillomavirus Infection
Based on solid evidence, the following measures are effective to avoid human papillomavirus (HPV) infection, and thus cervical cancer:
Abstinence from sexual activity
Description of the Evidence
-
Study Design: Evidence obtained from cohort and case-control studies.
-
Internal Validity: Good.
-
Consistency: Good.
-
Magnitude of Effects on Health Outcomes: Abstinence prevents HPV infection.
-
External Validity: Good.
Barrier protection and/or spermicidal gel during sexual intercourse
Description of the Evidence
-
Study Design: Evidence obtained from cohort and case-control studies.
-
Internal Validity: Good.
-
Consistency: Good.
-
Magnitude of Effects on Health Outcomes: Total use of barrier protection decreases cancer incidence, relative risk of 0.4 (95% confidence interval [CI], 0.2–0.9).
Based on fair evidence, vaccination against HPV-16/HPV-18 is effective to avoid HPV infection, and thus cervical cancer.
Description of the Evidence
-
Study Design: Evidence obtained from randomized controlled trials.
-
Internal Validity: Good.
-
Consistency: Not applicable.
-
Magnitude of Effects on Health Outcomes: Vaccination against HPV-16 and HPV-18 reduces incident and persistent infections with efficacy of 91.6% (95% CI, 64.5–98.0) and 100% (95% CI, 45–100), respectively. Duration of efficacy is not yet known.
-
External Validity: Good.
Screening via Gynecologic Examinations and Cytologic Screening
Based on solid evidence, screening via regular gynecologic examinations and cytologic test (Papanicolaou smear) with treatment of precancerous abnormalities decreases the incidence and mortality of cervical cancer.
Description of the Evidence
-
Study Design: Evidence obtained from cohort or case-control studies.
-
Internal Validity: Good.
-
Consistency: Good.
-
Magnitude of Effects on Health Outcomes: Estimates from population studies suggest that screening may decrease cancer incidence and mortality by more than 80%.
-
External Validity: Good.
Cigarette Smoke
Based on solid evidence, cigarette smoking, both active and passive, increases the risk of cervical cancer.
Description of the Evidence
-
Study Design: Evidence obtained from cohort or case-control studies.
-
Internal Validity: Good.
-
Consistency: Good.
-
Magnitude of Effects on Health Outcomes: Among HPV-infected women, current and former smokers have approximately two to three times the incidence of high-grade cervical intraepithelial neoplasia or invasive cancer. Passive smoking is also associated with increased risk, but to a lesser extent.
-
External Validity: Good.
Reproductive Behavior
High parity
Based on solid evidence, high parity is associated with increased risk of cervical cancer.
Description of the Evidence
-
Study Design: Evidence obtained from cohort or case-control studies.
-
Internal Validity: Good.
-
Consistency: Good.
-
Magnitude of Effects on Health Outcomes: Among HPV-infected women, women who have had seven or more full-term pregnancies have approximately four times the risk of squamous cell cancer compared with nulliparous women and two to three times the risk of women who have had one or two full-term pregnancies.[1]
-
External Validity: Good.
Long-term use of oral contraceptives
Based on solid evidence, long-term use of oral contraceptives is associated with increased risk of cervical cancer.
Description of the Evidence
-
Study Design: Evidence obtained from cohort or case-control studies.
-
Internal Validity: Good.
-
Consistency: Good.
-
Magnitude of Effects on Health Outcomes: Among HPV-infected women, women who used oral contraceptives for 5 to 9 years have approximately three times the incidence of invasive cancer, and those who used them for 10 years or longer have approximately four times the risk.[2]
-
External Validity: Good.
References
-
Muñoz N, Franceschi S, Bosetti C, et al.: Role of parity and human papillomavirus in cervical cancer: the IARC multicentric case-control study. Lancet 359 (9312): 1093-101, 2002.
[PUBMED Abstract]
-
Moreno V, Bosch FX, Muñoz N, et al.: Effect of oral contraceptives on risk of cervical cancer in women with human papillomavirus infection: the IARC multicentric case-control study. Lancet 359 (9312): 1085-92, 2002.
[PUBMED Abstract]
Back to Top Significance
Incidence and Mortality
An estimated 11,070 new cervical cancers and 3,870 cervical cancer deaths will
occur in the United States in 2008.[1] An additional 1,250,000 women will be diagnosed with precancers annually by cytology using the Papanicolaou (Pap) smear. A continuum of pathologic changes may be diagnosed, ranging from atypical squamous cells of undetermined significance to low-grade squamous intraepithelial lesions (LSIL) to high-grade squamous intraepithelial lesions (HSIL) to invasive cancer. The precancerous conditions LSIL and HSIL are also referred to as cervical intraepithelial neoplasia (CIN) 1, 2, and 3. Lesions can regress, persist, or progress to an invasive malignancy, with LSIL (CIN 1) more likely to regress spontaneously and HSIL (CIN 2/CIN 3) more likely to persist or progress. The average time for progression of CIN 3 to invasive cancer is estimated to be 10 to 15 years.[2]
The incidence of cervical cancer has decreased dramatically with the advent and widespread adoption of screening via gynecological examinations and Pap smears (refer to the PDQ summary on Cervical Cancer Screening for more information). Regular screening, however, is associated with large numbers of diagnostic procedures to evaluate abnormal tests, and the treatment of low-grade lesions may adversely affect subsequent fertility and pregnancy. Prevention of cancer may be more efficient, with fewer adverse consequences.
Nearly all cases of cervical cancer are associated with human papillomavirus (HPV) infection,[3,4] which is transmitted during sexual activity. Therefore, cervical cancer is seen more frequently in women with sexual activity at an early age and with multiple partners. Barrier contraception and/or spermicidal gels may offer some protection (refer to the Human Papillomavirus section of this summary for more information).
Cigarette smoking or exposure to environmental smoke is also associated with increased risk among HPV-infected women,[5] suggesting that components of tobacco are promoters of abnormal growth of viral-infected cells.
References
-
American Cancer Society.: Cancer Facts and Figures 2008. Atlanta, Ga: American Cancer Society, 2008. Also available online. Last accessed October 1, 2008.
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Holowaty P, Miller AB, Rohan T, et al.: Natural history of dysplasia of the uterine cervix. J Natl Cancer Inst 91 (3): 252-8, 1999.
[PUBMED Abstract]
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zur Hausen H, de Villiers EM: Human papillomaviruses. Annu Rev Microbiol 48: 427-47, 1994.
[PUBMED Abstract]
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Schiffman MH, Bauer HM, Hoover RN, et al.: Epidemiologic evidence showing that human papillomavirus infection causes most cervical intraepithelial neoplasia. J Natl Cancer Inst 85 (12): 958-64, 1993.
[PUBMED Abstract]
-
Ho GY, Kadish AS, Burk RD, et al.: HPV 16 and cigarette smoking as risk factors for high-grade cervical intra-epithelial neoplasia. Int J Cancer 78 (3): 281-5, 1998.
[PUBMED Abstract]
Back to Top Evidence of Benefit
Human Papillomavirus
Epidemiologic studies to evaluate risk factors for the development of squamous intraepithelial lesions (SIL) and
cervical malignancy demonstrate conclusively a sexual mode of transmission of a
carcinogen.[1] It is now widely accepted that human papillomavirus (HPV) is the primary etiologic
infectious agent.[2-4] Other sexually transmitted factors, including
herpes simplex virus 2, may play a cocausative role.[1] The finding of HPV
viral DNA integrated in most cellular genomes of invasive cervical
carcinomas supports epidemiologic data linking this agent to cervical
cancer;[5] however, direct causation has not been demonstrated. More than 80 distinct types of HPV have been identified, approximately 30 of which infect the
human genital tract. HPV types 16 and 18 are most often associated with
invasive disease. Characterization of carcinogenic risk associated with HPV
types is an important step in the process of developing a combination HPV
vaccine for the prevention of cervical neoplasia. In a population-based study
of HPV infection and cervical neoplasia in Costa Rica, 80% of high-grade
squamous intraepithelial lesions (HSIL) and invasive lesions were associated
with HPV infection by one or more of 13 cancer-associated types.[6] In this
study, the risk of about half of HSIL and invasive cervical cancer was
attributable to HPV-16. HPV-18 was associated with 15% of invasive disease
but only 5% of HSIL, suggesting that HPV-18 may have a role in more aggressive
cases of cervical malignancy.
Barrier methods of contraception are associated with a reduced
incidence of SIL presumptively secondary to protection from sexually
transmitted disease.[7,8]
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.[9] 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.[9]
Given the etiologic role of HPV in the pathogenesis of cervical neoplasia,
vaccines to immunize against HPV infection would 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 second bivalent (HPV 16, 18) vaccine is awaiting final review.
Vaccine to prevent HPV infection
Persistent infection with oncogenic types of HPV such as HPV-16 and HPV-18 is associated with the development of cervical cancer.[10] 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 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 virus-like particle (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 cervical intraepithelial neoplasia (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 versus 111 placebo-treated women.[11]
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.[12] Women received either vaccine or placebo at 0, 1, and 6 months and were assessed by cervical cytology and self-obtained cervicovaginal samples for up to 27 months. Follow-up analysis of 776 women showed that vaccinated women had stable serum antibody titers at 4.5 years and continued protection against HPV-16/HPV-18 infection. Incident infections decreased from 28 of 277 control women to 1 of 310 vaccinated women, a decline of 96.9% (confidence interval [CI], 81.3%–99.9%). Persistent infections according to 12-month definition decreased from 10 of 340 control women to 0 of 357 vaccinated women, a decline of 100% (CI, 57.0%–100%). CIN 1+ and CIN 2+ associated with HPV-16/HPV-18 were reduced from 13 of 470 control women to 0 of 481 vaccinated women. Incident infections with HPV-45 and HPV-31 were reduced by 94% and 54%, respectively. Adverse events, serious adverse events, and new-onset chronic disease were similar in vaccinated and placebo-treated women.
A quadrivalent vaccine (HPV types 6, 11, 16, and 18) was evaluated in two multinational, double-blind, randomized controlled trials of 5,455 women aged 16 to 24 years and in 12,167 women aged 15 to 26 years (FUTURE I and FUTURE II, respectively).[13,14] 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 up to 4 years. The composite endpoint for cervical disease included the incidence of HPV-16/18-related CIN 1 (FUTURE I only), CIN 2, CIN 3, adenocarcinoma in situ, or invasive carcinoma. Outcomes were reported as follows:
Vaccine Efficacy of the FUTURE I and FUTURE II HPV Vaccine Trials
Population
|
FUTURE I
|
FUTURE II
|
HPV = human papillomavirus; mo = month.
|
Negative for HPV 6/11/16/18 at enrollment and to 1 mo after 3rd injection; received all doses
(per-protocol analysis)
|
100%
(95% CI,
94%–100%)
|
98%
(95% CI,
86%–100%)
|
Negative for HPV 6/11/16/18 at enrollment
(unrestricted susceptible population analysis)
|
98%
(95% CI,
92%–100%) |
95%
(95% CI,
85%–99%)
|
All randomized subjects, including those positive for HPV 6/11/16/18 at enrollment
(intention-to-treat analysis)
|
55%
(95% CI,
40%–66%)
|
44%
(95% CI,
26%–58%)
|
|
|
|
It is important to recognize that composite endpoints were utilized as the primary endpoint in both of these trials, a substantial proportion of the cases were CIN 1 and 2 lesions, which are known to have a high likelihood of spontaneous resolution without medical intervention. This could have potentially inflated the observed vaccine efficacy. No cases of invasive cervical cancer were identified during either trial.
As largely expected based upon their mechanism of action, L1/2 HPV vaccines do not appear to impact pre-existing infections. The FUTURE trials demonstrated markedly lower vaccine efficacy rates in the total randomized study populations, which included individuals positive for HPV at baseline, versus the “per-protocol” populations (44%–55% vs. 98%–100%, see table above).[13,14] 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.[15]
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.[16] 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 HPV-16 and HPV-18 types, the two most common strains, would prevent 71% of cervical cancers worldwide.[16]
Cigarette Smoking
Cigarette smoking by women is associated with an increased risk for squamous
cell carcinoma.[1,17,18] This risk increases with longer duration and
intensity of smoking and may be present with exposure to environmental tobacco
smoke, being as high as four times that of women who are nonsmokers and
are not exposed to environmental smoking.[1] Case-control studies of women infected with HPV have examined the effect of various types and levels of tobacco exposure and found similar results.[18,19]
Reproductive Behavior
High parity has long been recognized as a risk factor for cervical cancer, but the relation of parity to HPV infection was uncertain. A meta-analysis of 25 epidemiologic studies including 16,563 women with cervical cancer and 33,542 women without, showed that the number of full-term pregnancies was associated with increased risk, regardless of age at first pregnancy. This finding was also true if analyses were limited to patients with high-risk HPV infections (relative risk = 4.99 [3.49–7.13] for seven or more pregnancies versus no pregnancies; linear trend test x2 = 30.69; P < .001).[20]
Long-term use of oral contraceptives has also been known to be associated with cervical cancer, but its relation to HPV infection was also uncertain. A pooled analysis of HPV-positive women from the studies described above was undertaken. Compared with women who have never used oral contraceptives, those who have used them for fewer than 5 years did not have an increased risk of cervical cancer (odds ratio [OR] = 0.73; 95% CI, 0.52–1.03). The OR for women who used oral contraceptives for 5 to 9 years was 2.82 (1.46–5.42) and for 10 or more years the OR was 4.03 (2.09–8.02).[21] A meta-analysis of 24 epidemiological studies confirmed the increased risk associated with oral contraceptives, which is proportionate to the duration of use. Risk decreases after cessation and returns to normal risk levels in 10 years.[22]
Dietary Factors
Multiple case-control studies show an association between intake of some micronutrients and lower risk of cervical cancer, but results are conflicting and difficult to control for other risk factors. Two randomized trials of oral folate as a chemopreventive agent have shown no protective effect.
References
-
Brinton LA: Epidemiology of cervical cancer--overview. IARC Sci Publ (119): 3-23, 1992.
[PUBMED Abstract]
-
Schiffman MH, Bauer HM, Hoover RN, et al.: Epidemiologic evidence showing that human papillomavirus infection causes most cervical intraepithelial neoplasia. J Natl Cancer Inst 85 (12): 958-64, 1993.
[PUBMED Abstract]
-
Ley C, Bauer HM, Reingold A, et al.: Determinants of genital human papillomavirus infection in young women. J Natl Cancer Inst 83 (14): 997-1003, 1991.
[PUBMED Abstract]
-
Muñoz N, Bosch FX, de Sanjosé S, et al.: The causal link between human papillomavirus and invasive cervical cancer: a population-based case-control study in Colombia and Spain. Int J Cancer 52 (5): 743-9, 1992.
[PUBMED Abstract]
-
Reeves WC, Rawls WE, Brinton LA: Epidemiology of genital papillomaviruses and cervical cancer. Rev Infect Dis 11 (3): 426-39, 1989 May-Jun.
[PUBMED Abstract]
-
Herrero R, Hildesheim A, Bratti C, et al.: Population-based study of human papillomavirus infection and cervical neoplasia in rural Costa Rica. J Natl Cancer Inst 92 (6): 464-74, 2000.
[PUBMED Abstract]
-
Parazzini F, Negri E, La Vecchia C, et al.: Barrier methods of contraception and the risk of cervical neoplasia. Contraception 40 (5): 519-30, 1989.
[PUBMED Abstract]
-
Hildesheim A, Brinton LA, Mallin K, et al.: Barrier and spermicidal contraceptive methods and risk of invasive cervical cancer. Epidemiology 1 (4): 266-72, 1990.
[PUBMED Abstract]
-
Winer RL, Hughes JP, Feng Q, et al.: Condom use and the risk of genital human papillomavirus infection in young women. N Engl J Med 354 (25): 2645-54, 2006.
[PUBMED Abstract]
-
Wallin KL, Wiklund F, Angström T, et al.: Type-specific persistence of human papillomavirus DNA before the development of invasive cervical cancer. N Engl J Med 341 (22): 1633-8, 1999.
[PUBMED Abstract]
-
Mao C, Koutsky LA, Ault KA, et al.: Efficacy of human papillomavirus-16 vaccine to prevent cervical intraepithelial neoplasia: a randomized controlled trial. Obstet Gynecol 107 (1): 18-27, 2006.
[PUBMED Abstract]
-
Harper DM, Franco EL, Wheeler CM, et al.: Sustained efficacy up to 4.5 years of a bivalent L1 virus-like particle vaccine against human papillomavirus types 16 and 18: follow-up from a randomised control trial. Lancet 367 (9518): 1247-55, 2006.
[PUBMED Abstract]
-
Garland SM, Hernandez-Avila M, Wheeler CM, et al.: Quadrivalent vaccine against human papillomavirus to prevent anogenital diseases. N Engl J Med 356 (19): 1928-43, 2007.
[PUBMED Abstract]
-
FUTURE II Study Group.: Quadrivalent vaccine against human papillomavirus to prevent high-grade cervical lesions. N Engl J Med 356 (19): 1915-27, 2007.
[PUBMED Abstract]
-
Hildesheim A, Herrero R, Wacholder S, et al.: Effect of human papillomavirus 16/18 L1 viruslike particle vaccine among young women with preexisting infection: a randomized trial. JAMA 298 (7): 743-53, 2007.
[PUBMED Abstract]
-
Muñoz N, Bosch FX, Castellsagué X, et al.: Against which human papillomavirus types shall we vaccinate and screen? The international perspective. Int J Cancer 111 (2): 278-85, 2004.
[PUBMED Abstract]
-
Hellberg D, Nilsson S, Haley NJ, et al.: Smoking and cervical intraepithelial neoplasia: nicotine and cotinine in serum and cervical mucus in smokers and nonsmokers. Am J Obstet Gynecol 158 (4): 910-3, 1988.
[PUBMED Abstract]
-
Brock KE, MacLennan R, Brinton LA, et al.: Smoking and infectious agents and risk of in situ cervical cancer in Sydney, Australia. Cancer Res 49 (17): 4925-8, 1989.
[PUBMED Abstract]
-
Ho GY, Kadish AS, Burk RD, et al.: HPV 16 and cigarette smoking as risk factors for high-grade cervical intra-epithelial neoplasia. Int J Cancer 78 (3): 281-5, 1998.
[PUBMED Abstract]
-
International Collaboration of Epidemiological Studies of Cervical Cancer.: Cervical carcinoma and reproductive factors: collaborative reanalysis of individual data on 16,563 women with cervical carcinoma and 33,542 women without cervical carcinoma from 25 epidemiological studies. Int J Cancer 119 (5): 1108-24, 2006.
[PUBMED Abstract]
-
Moreno V, Bosch FX, Muñoz N, et al.: Effect of oral contraceptives on risk of cervical cancer in women with human papillomavirus infection: the IARC multicentric case-control study. Lancet 359 (9312): 1085-92, 2002.
[PUBMED Abstract]
-
Appleby P, Beral V, Berrington de González A, et al.: Cervical cancer and hormonal contraceptives: collaborative reanalysis of individual data for 16,573 women with cervical cancer and 35,509 women without cervical cancer from 24 epidemiological studies. Lancet 370 (9599): 1609-21, 2007.
[PUBMED Abstract]
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Back to Top Changes To This Summary (02/26/2009)
The PDQ cancer information summaries are reviewed regularly and updated as
new information becomes available. This section describes the latest
changes made to this summary as of the date above.
Evidence of Benefit
Added text about a meta-analysis of 24 epidemiological studies that confirmed the increased risk associated with oral contraceptives, which is proportionate to the duration of use (cited Appleby et al. as reference 22).
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