Does Screening by "Pap" Smears Help Prevent Cervical Cancer?

Clarke, Emily; Anderson, Terence W.

doi:10.1016/s0140-6736(79)90172-7

Cited by 216 publications

(68 citation statements)

References 4 publications

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“…Adenocarcinomas and adenosquamous carcinomas of the cervix account for about 15% of invasive cervical cancers, and both absolute and relative numbers of adenocarcinomas in screened populations have increased in recent years. This may reflect a cohort effect similar to that seen for squamous cell carcinomas and related to increased exposure to HPV infection in women born since 1960 (Madeleine et al, 2001;Sasieni and Adams, 2001), and the fact that cervical screening may be less effective in detecting adenocarcinomas than squamous cell carcinomas (Clarke and Anderson, 1979;Mitchell et al, 1995;Bergstrom et al, 1999). Their relative rarity has limited attempts to define risk factors for adenocarcinomas and adenosquamous carcinomas of the cervix (Silcocks et al, 1987;Parazzini and La Vecchia, 1990;Kjaer and Brinton, 1993), but several recent controlled studies with relatively large numbers (over 100) of adenocarcinoma cases have provided clearer evidence (Ursin et al, 1994(Ursin et al, , 1996Bjorge and Kravdal, 1996;Thomas and Ray, 1996;Lacey et al, 1999Lacey et al, , 2000Lacey et al, , 2001Madeleine et al, 2001;Munoz et al, 2002;Altekruse et al, 2003).…”

Section: Discussionmentioning

confidence: 89%

Risk factors for adenocarcinoma and squamous cell carcinoma of the cervix in women aged 20–44 years: the UK National Case–Control Study of Cervical Cancer

et al. 2003

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We report results on risk factors for invasive squamous cell and adenocarcinomas of the cervix in women aged 20 -44 years from the UK National Case -Control Study of Cervical Cancer, including 180 women with adenocarcinoma, 391 women with squamous cell carcinoma and 923 population controls. The risk of both squamous cell and adenocarcinoma was strongly related to the lifetime number of sexual partners, and, independently, to age at first intercourse. The risk of both types of cervical cancer increased with increasing duration of use of oral contraceptives, and this effect was most marked in current and recent users of oral contraceptives. The risk of squamous cell carcinoma was associated with high parity and the risk of both squamous cell and adenocarcinoma increased with early age at first birth. Long duration smoking (20 or more years) was associated with a two-fold increase in the risk of squamous cell carcinoma, but smoking was not associated with the risk of adenocarcinoma. Further studies are needed to confirm the suggestion from this and other studies of differences in risk related to smoking between squamous cell and adenocarcinomas of the cervix. Among cancers of the uterine cervix, adenocarcinomas are much less common than squamous cell carcinomas. As for squamous cell carcinoma, human papillomavirus (HPV) infection appears to be a major risk factor for adenocarcinoma of the cervix (Kjaer and Brinton, 1993;Walboomers et al, 1999;Santos et al, 2001;Altekruse et al, 2003), but evidence on other factors that may affect the risk of adenocarcinoma is limited and not entirely consistent (Parazzini and La Vecchia, 1990;Kjaer and Brinton, 1993;Ursin et al, 1994Ursin et al, , 1996Lacey et al, 1999Lacey et al, , 2000Lacey et al, , 2001Madeleine et al, 2001;Altekruse et al, 2003). The question of whether there are substantial differences in the risk factors for adenocarcinomas and squamous cell carcinomas remains unresolved. Few epidemiological studies have been designed specifically to provide a direct comparison between adenocarcinoma and squamous cell carcinoma of the cervix, and most studies of cervical carcinoma have had too few cases of adenocarcinoma to allow full evaluation of the possible risk factors. We present here results from the UK National Case -Control Study of Cervical Cancer, a case -control study of risk factors for invasive cervical cancer in women under 45 years old at diagnosis, with 180 cases of adenocarcinoma (including adenosquamous carcinoma), 391 cases of squamous cell carcinoma and 923 population controls. Information was available for all study subjects on sexual and reproductive factors, cervical screening, body weight, smoking and the use of barrier and hormonal contraceptives. Additional information was collected on HPV serology for a subgroup of subjects, and for this subgroup results have previously been published on the relationship between HPV positivity and risk of cervical cancer (Jha et al, 1993), and on oral contraceptive use as a risk factor for cervical cancer in relati...

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Section: Discussionmentioning

confidence: 89%

Risk factors for adenocarcinoma and squamous cell carcinoma of the cervix in women aged 20–44 years: the UK National Case–Control Study of Cervical Cancer

et al. 2003

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“…Evidence for mortality reduction, the primary aim of cervical cancer screening, has come from studies that compared regions or individuals with different screening intensities (Clarke and Anderson, 1979;Laara et al, 1987;van der Graaf et al, 1988). One indicator of such effectiveness is the incidence of cervical cancer after a negative screen related to that in the absence of screening.…”

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confidence: 99%

Low risk of cervical cancer during a long period after negative screening in the Netherlands

2003

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A condition for effective cervical cancer screening is a low incidence of cervical cancer after negative screening compared to that in the absence of screening. This relative risk was studied for the period 1994 -1997 in the Netherlands and compared with previous studies. All cases of invasive cervical cancer diagnosed from 1994 to 1997 in the Netherlands were related to woman-years at risk, stratified by age, number of preceding negative screenings and time since the preceding negative screening. These incidence rates were compared with that before screening started in the Netherlands. The relative risk increases from 0.13 in the first year after screening to 0.24 after more than 6 years after screening for women with one previous negative screening. These figures reduce to 0.06 and 0.18, respectively, for women with two or more previous screenings. However, these estimates are less favourable when account is taken of the likely decrease in risk for cervical cancer in the period studied. Our data show a low relative risk of cervical cancer for several years following the last negative Pap smear. However, the denominator of the relative risk, that is, the incidence without screening, may have been overestimated. This applies also to the IARC multicountry study, and may have caused too optimistic expectations about the effectiveness of cervical cancer screening.

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“…As an alternative, case-control studies have been proposed (Miller 1985;Sasco et al 1986). The first case-control study of cervical screening was performed and reported by Clarke and Anderson (1979 Palli et al 1990) were performed in other centers. Although a case-control study of cervical cancer screening has been conducted in Osaka, Japan, the odds ratios (ORs) for the "ever" vs. the "never" screened group in that study were not significantly different.…”

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confidence: 99%

Evaluation of the Effectiveness of Cervical Cancer Screening: A Case-Control Study in Miyagi, Japan.

Makino¹,

Sato²,

Yajima³

et al. 1995

Tohoku J. Exp. Med.

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To estimate the effectiveness of screening for invasive cervical cancer, a case-control study was performed in Miyagi, Japan. A total of 198 cases (129 mass screen-detected and 69 outpatient-detected) of invasive cervical cancer were identified between 1984 and 1990. The results of the Papanicolaou smear of these cases were compared to those of 396 age-(±5 years) and area-matched controls. Compared with women who had no prior screening (cases 51.6%, controls 16.2%), women who were screened had an odds ratio (OR) for invasive cervical cancer of 0.14 (95% confidence interval [CI] 0.088-0.230). The OR for the 175 cases of squamous cell carcinoma was 0.13 (95% CI 0.077-0.215), while the OR for the 23 cases of screened women with adenocarcinoma was 0.40 (95% CI 0.091-1.753). The time intervals following the last negative smear were assessed and we found an OR for a one-year interval and a two-year interval of 0.09 (95% CI 0.055-0.163) and 0.17 (95% CI 0.083-0.335), respectively. In conclusion, screening for invasive cervical cancer is not only effective but also the degree of protection is high for one to two years. cervical cancer; case-control study; cervical cancer screening Miyagi is one of the first areas in Japan to be involved in mass screening for cervical cancer. From 1984From -1990, in Miyagi, a total of one million Papanicolaou (Pap) smears were taken among women over the age of 30. The cytodiagnoses of the Pap smears for these women were performed primarily at the Center for Clinical Cytology (Miyagi Cancer Society). The results of the screening program and the relationship between histological features and history of prior cervical screening have previously been reported by our group (Yajima et al. 1979;. However, the effectiveness of this form of screening for cervical cancer in Miyagi using epidemiological methods has not been described before except for a prelimi-

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Does Screening by "Pap" Smears Help Prevent Cervical Cancer?

Cited by 216 publications

References 4 publications

Risk factors for adenocarcinoma and squamous cell carcinoma of the cervix in women aged 20–44 years: the UK National Case–Control Study of Cervical Cancer

Risk factors for adenocarcinoma and squamous cell carcinoma of the cervix in women aged 20–44 years: the UK National Case–Control Study of Cervical Cancer

Low risk of cervical cancer during a long period after negative screening in the Netherlands

Evaluation of the Effectiveness of Cervical Cancer Screening: A Case-Control Study in Miyagi, Japan.

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