Quality assurance in cervical cancer screening: the Icelandic experience 1964-1993

Is a liquid-based cytology more sensitive than a conventional Pap smear?

BACKGROUND

The comparative sensitivity of liquid-based cytology (LBC) test and conventional Papanicolaou (Pap) smears is controversial.

MATERIAL AND METHODS

This study analyses the distribution of cytology, histology, colposcopy and large loop excision of the transformation zone among women screened in Iceland with LBC at the Cancer Detection Clinic in Reykjavik and with a conventional Pap smear outside the Detection Clinic in 2007-2011. The study material included 42 654 LBC tests from 20 439 women and 103 909 Pap smears from 61 574 women. The period 2000-2004 is used to correct for potential bias as a result of unequal distribution of the studied parameters between the study sites before the introduction of LBC.

RESULTS

The observed results indicated that women screened with an LBC sample had significantly decreased detection rates of inadequate smears, increased detection of low-grade squamous intraepithelial lesion (LSIL)/atypical cytology and referrals to colposcopy, and an increased detection rate of cervical intraepithelial neoplasia grade 2 or worse (CIN2+) irrespective of age. LBC increased significantly the detection rates of high-grade squamous intraepithelial lesion or worse (HSIL+) cytology and CIN3+ histology only in women under 40 years of age. Taking into consideration the unequal prevalence of the studied parameters between the study sites in 2000-2004 indicated, however, that LBC only affected the rate of inadequate and low-grade cytology tests under the age of 40 years. Positive predictive values for CIN2+ were not significantly different between the tests.

CONCLUSIONS

The study results support the view that LBC is no more sensitive than Pap smears for the detection of HSIL+ and CIN2+ irrespective of age. LBC decreased the rate of inadequate smears, but increased the rate of low-grade cytology under the age of 40 years and decreased the total rate of abnormal smears over the age of 40 years.

Benchmarking epidemiological characteristics of cervical cancer in advance of change in screening practice and commencement of vaccination

OBJECTIVES

To investigate trends in cervical cancer incidence, mortality and survival by histology for benchmarking purposes ahead of practice change and the introduction of Human Papilloma Virus (HPV) vaccine.

METHODS

Using data from the South Australian Cancer Registry, age-standardised rates are presented for four-year periods from 1977 to 2004. Socio-demographic and secular predictors of glandular as opposed to squamous cancers are investigated, using multivariable logistic regression. Disease-specific survivals are analysed using Kaplan-Meier product-limit estimates and Cox proportional hazards regression.

RESULTS

Incidence and mortality rates reduced by 55.1% and 59.3% respectively between 1977-80 and 2001-04, with larger reductions for squamous than glandular cancers. The ratio of squamous to glandular cancer incidence reduced from 5.4:1 in 1977-88 to 2.8:1 in 1993-2004, with a corresponding reduction from 5.2:1 to 3.0:1 for mortality. Compared with squamous cancers, glandular lesions were more common in patients from higher socio-economic areas, but less common in those over 70 years of age, Aboriginal patients, and those born in Southern Europe.

CONCLUSION

The proportion of cancers comprising glandular lesions has increased, possibly reflecting prevention of squamous cancers through treatment of screen-detected preinvasive lesions. Additional mortality reductions from screening may be limited where the proportion of glandular lesions is high, with vaccination offering the best prospects for gains in the long term. Priority should be given to Aboriginal and Torres Strait Islander women in vaccination programs in view of their high death rate from cervical cancer.

Is it rational to start population-based cervical cancer screening at or soon after age 20? Analysis of time trends in preinvasive and invasive diseases

The effect of starting screening at age 20 in 1988 was assessed by analysing (a) the age-specific incidence and distribution of stage and histology of invasive diseases, and (b) the detection rates of histologic moderate to high-grade intraepithelial neoplasia (CIN 2-3/AIS), and 1st abnormal cytology and repeat low-grade cytology after follow-up observation. Cancer incidence increased significantly at age 25-34 after 1979 due to early stage squamous cell and adenocarcinoma. After an initial increased rate of preinvasive disease, CIN 3 decreased significantly at age 30-34 after 1988, at age 25-29 after 1993, and levelled out after 1998 at age 20-24. The rates of CIN 2 levelled out after 1998. The rates of repeat low-grade smears decreased after observation at age 20-24 by 80%. The study confirms an increasing rate of preinvasive and invasive disease among younger women and indicates the benefit of starting organised screening at 2-3 year intervals soon after age 20.

International variation

There were an estimated 10 million new cases, 6 million deaths and 22 million persons living with cancer in the year 2000. The most common cancers are, in terms of new cases, lung (1.2 million), breast (1.05 million), colon-rectum (945 000), stomach (876 000) and liver (564 000). The geographic distributions of some 20 types of cancer for which national estimates have been made are summarized. These patterns are examined with respect to the likely reasons in terms of variation in exposure to carcinogens (in the external environment or through lifestyle choices) or in genetic susceptibility to them. Related data from studies of migrant populations (that allow comparisons of genetically similar populations living in different environments) and from comparisons between different ethnic groups living in the same country are used to help in the interpretation of the geographic patterns. Information on the burden of disease also has a very important role in the planning and monitoring of programmes of cancer control.

Cervical adenocarcinoma and squamous cell carcinoma incidence trends among white women and black women in the United States for 1976-2000

BACKGROUND

Although cervical carcinoma incidence and mortality rates have declined in the U.S. greatly since the introduction of the Papanicolaou smear, this decline has not been uniform for all histologic subtypes. Therefore, the authors assessed the differential incidence rates of squamous cell carcinoma (SCC) and adenocarcinoma (AC) of the cervix by race and disease stage for the past 25 years.

METHODS

Data from nine population-based cancer registries participating in the U.S. Surveillance, Epidemiology, and End Results (SEER) Program were used to compute incidence rates for cervical carcinoma diagnosed during 1976-2000 by histologic subtype (SCC and AC), race (black and white), age, and disease stage (in situ, localized, regional, or distant).

RESULTS

In black women and white women, the overall incidence of invasive SCC declined over time, and the majority of tumors that are detected currently are in situ and localized carcinomas in young women. The incidence of in situ SCC increased sharply in the early 1990s. AC in situ (AIS) incidence rates increased, especially among young women. In black women, invasive AC incidence rose linearly with age.

CONCLUSIONS

Changes in screening, endocervical sampling, nomenclature, and improvements in treatment likely explain the increased in situ cervical SCC incidence in white women and black women. Increasing AIS incidence over the past 20 years in white women has not yet translated into a decrease in invasive AC incidence. Etiologic factors may explain the rising invasive cervical AC incidence in young white women; rising cervical AC incidence with age in black women may reflect either lack of effective screening or a differential disease etiology.

Assessing the evidence for organised cancer screening programmes

The aim of this study was to review the evidence in the literature for organised cancer screening programmes. A Medline search for publications related to organised cancer screening programmes and their components was done. While there is a broad descriptive literature on various cancer screening programmes, there are few published studies that evaluate the impact of organised cancer screening. Most of the evidence to date is from Scandinavian cervical and breast cancer screening programmes. There is a moderate amount of literature that evaluates specific components of cancer screening programmes (such as quality control and recruitment). There is a substantial body of literature on organised cancer screening programmes. However, the studies tend to describe organised screening programmes rather than evaluate their effectiveness relative to opportunistic screening. Furthermore, most studies focus on individual components of organised screening programmes, rather than on the programmes as a whole. More research is needed that directly compares organised with opportunistic cancer screening.

Screening for cervical disease in mature women: strategies for improvement

BACKGROUND

Cervical carcinoma remains a significant health risk for the older woman. In the current study the yield of screening of mature women in an established, opportunistic screening program was examined. Strategies for improving screening in this age group were identified through examination of recent Pap test history of women with high grade squamous intra-epithelial lesions (HSIL).

METHODS

From the population based registry of the Ontario Cervical Screening Program, the Pap test cytodiagnoses for almost 700,000 women screened during the first six months of 2000 were classified by age quintile. Screening yields for younger women (< 50 years of age) and mature women (>/= 50 years of age) were compared using the detection ratio (abnormalities per 1000 women tested). Any pap test results during the three years preceding a diagnosis of HSIL in mature women were identified (excluding any Pap test in the six months immediately prior to the HSIL cytodiagnosis) and classified into one of three categories: no prior test known, prior negative Pap test known, and prior abnormal Pap test known.

RESULTS

Twenty four percent of all Pap tests in the six month period were from mature women. Approximately 11% of all cytodiagnoses of HSIL and carcinoma (HSIL+), and 13% of all low grade squamous intra-epithelial lesions (LSIL), HSIL, carcinoma, and atypical glandular cells of uncertain significance (AGUS); [LSIL+ and AGUS] cytodiagnoses, were from mature women. The yield of Pap testing in mature women (1.7 HSIL+ per 1000 women tested) was slightly more than 40% of that for younger women (4.2 HSIL+ per 1000 women tested). Mature women with HSIL were more likely to have had a history of no prior screening (61.1%) than younger women (49.5%). The majority (62.9%) of mature women with HSIL and a prior known Pap test had a prior registered abnormal Pap test.

CONCLUSIONS

Pap testing of mature women yields a significant number of abnormalities, but is less efficient than Pap testing of younger women. Screening yield could be increased by recruiting mature women who are currently inadequately screened and by revising guidelines for cessation of screening. Proper followup of mature women with Pap test abnormalities would improve clinical outcome but could adversely affect the yield of Pap testing, since current inappropriate repeat testing of women would decrease.

Presentation and screening history of indigent women with cervical cancer: implications for prevention

OBJECTIVE

To identify missed opportunities for screening and early diagnosis of indigent patients with cervical cancer.

MATERIALS AND METHODS

The authors conducted a retrospective review of charts and databases for demographic information, presenting symptoms, staging data, prior health system contacts, and Papanicolaou smears. Women with cervical cancer were evaluated at an urban public hospital between July 1, 1994, and March 31, 1998.

RESULTS

Among 177 women with cervical cancer where record could be retrieved, 82 were in stage I, 49 were in II, 25 were in III, and 11 were in IV. Symptoms attributable to cancer were present in 153 (86%) cases, but asymptomatic women were more likely to have stage I cancers (21 of 23 versus 70 of 153, p < .0005). Only 54 (31%) women had prior visits recorded, with emergency services the most common site for visits. Only 23 (43%) of these had prior cytology recorded, four of which were false negatives. Stage I cancers were found in 18 (78%) of these women, compared to 13 (42%) of the 31 women previously seen without a recorded Papanicolaou smear (p < .02). Women with prior visits to gynecology services or clinics were more likely to have Papanicolaou smears recorded (10 of 13 versus 9 of 32 at other sites, p < .0005) but not more likely to have stage I cancer (10 of 13 versus 20 of 41, p = .08).

CONCLUSIONS

Further reductions in cervical cancer rates are likely to require outreach, screening in nontraditional sites, and refinement of public sector screening programs.

International trends in incidence of cervical cancer: II. Squamous-cell carcinoma

Time trends in the incidence of squamous-cell carcinomas of the cervix during the period 1973-1991 were examined using data provided by 60 population-based cancer registries from 32 defined populations in 25 countries. Three components of the incidence trend were studied: age, calendar period of diagnosis and birth cohort. Cumulative incidence rates per 1,000 person-years for 2 groups, age ranges 25-49 and 50-74 years, were calculated from the model that best described the incidence data. A significant decline in incidence was noted in the American populations (except for US Hispanic), Australia, the non-Maori women of New Zealand, northern and western Europe (except Italy and Spain, where the rates remain stable) and Asian populations (except Malay women of Singapore, who have stable rates). These trends were of similar magnitude for the whole age range studied (25-74 years). An increasing trend, mainly restricted to younger women, was found for Slovakia, Jewish women born in Israel and the United Kingdom. In Slovenia, the increasing trend was observed for all age groups. The predominant pattern shown by cancer registries in developed countries is of a reduction in the incidence of squamous cervical cancer. This could be, at least partially, attributed to the widespread practice of screening for cervical lesions. The major exception to the pattern is observed in the United Kingdom, though the increasing incidence in young women has changed to a decrease in recent years. There are only a few series covering a long period of time in developing countries, but there is little evidence for a major impact of screening.

Effect of organised screening on cervical cancer incidence and mortality in Finland, 1963-1995: recent increase in cervical cancer incidence

A nation-wide screening programme for cervical cancer started in Finland gradually from 1963 onwards. By the beginning of the 1990s, there had been a decrease of 80% both in the age-adjusted incidence of and mortality from cervical cancer. To describe the recent patterns in cervical cancer incidence and mortality and evaluate their differentials in relation with the organised screening activities, we have updated the material on the cervical cancer incidence and mortality as well as mass-screening activities up to the year 1995. Based on the files of the Finnish Cancer Registry, there is a striking increase of about 60% in the incidence of cervical cancer during the last 4 years of the study period among women below 55 years of age. The mortality rates are still decreasing. There is no overall decrease over recent years in the coverage of the programme invitations or smears taken. Incidence of invasive cancer and of moderate and severe dysplasia as detected in mass screening have increased. As to the interpretation, changes in the risk factors, such as in sexual behaviour and smoking habits, over the decades might partly explain increasing trends in cervical cancer incidence. As the change in incidence was relatively abrupt, inadequacies or changes in the effectiveness in the screening programme, particularly among young women, may also have contributed. Expanding the coverage of and attendance in the pap-screening programme among women in young target ages would still be effective. Increasing emphasis on quality assessment in screening is also needed.

Survival and prognostic factors of endometrial cancer patients in Iceland 1964-1985: can attendance at population-based Pap-smear screening affect survival?

After histological review of all cases registered during the period 1964-1985 at the Cancer Registry, 260 cases with endometrial carcinoma were eligible for analyses of survival rates and prognostic factors, as well as the association of Pap-smear screening attendance with these factors and survival. The total age-adjusted 5- and 10-year relative survival rates were 76% and 75%, respectively. The prognostic factors were tested by univariate analysis and simultaneously by a multivariate analysis using the Cox proportional hazards model. Factors that independently gave a less favorable prognosis were non-attendance at screening, older age at diagnosis, deep myometrial invasion, advancing stages and tumor grading, radiotherapy only, extra-genital symptoms and histology types of serous, clear cell and undifferentiated tumors (histologic type 3). Tested simultaneously with the Cox proportional hazards model, parameters that maintained a less favourable prognosis were grade 3, stage III-IV, deep myometrial invasion, older age, radiotherapy only and extra-genital symptoms. In addition, screening attendance showed significant interaction with age. In stages III and IV only grade 3 maintained a significantly less favorable prognosis. We conclude that our results indicate that attendance at Pap-smear screening (taking Pap smears and screening for genital symptoms) has a favorable prognostic value, especially among women under the age of 62.

Human papillomavirus (HPV) in an Icelandic population: the role of HPV DNA testing based on hybrid capture and PCR assays among women with screen-detected abnormal Pap smears

This study was based on 358 cases with abnormal smears referred for colposcopy and HPV DNA testing. We analysed: 1) the frequency of different grades of cyto- and histopathologic findings; 2) the frequency and relative amount of HPV DNA with the hybrid capture assay (HCA) in swabs, and the frequency of HPV with PCR in swabs (-S) and biopsies (-B); and 3) the frequency of HPV types according to the grade of the cyto- and histopathologic findings. Of all cases, 95% were positive with all HPV tests combined. The HCA (HPV: 16, 18, 31, 33, 35, 45, 51, 52 and 56) and the PCR-S and PCR-B (HPV: 16, 18, 31, 33 and 35) tests for high-risk HPV exhibited sensitivities of 57%, 56% and 48%, respectively. The high-grade smears and the high-risk PCR-S HPV had about 80% sensitivity for histologic high-grade lesions compared with around 70% for HCA and the PCR-B. Combining the high-grade smears and the high-risk HPV increased the sensitivity to 93-96%. Among the cervical intraepithelial neoplasia I (CIN I) and the atypical squamous cells of undetermined significance (ASCUS) smears the sensitivity of high-risk HPV for high-grade histologic lesions was 63% for the HCA and 79% for the PCR-S. No correlation was found between the relative amount of HPV DNA detected by HCA and the grade of cyto- and histological lesions. We conclude that the results strongly indicate that HCA is less sensitive than PCR in the diagnosis of high-risk HPV, that swabs are more sensitive than biopsies as a sampling method, that high-risk HPV and high-grade smears are complementary for the diagnosis of high-grade histologic lesions and that the present role of HPV testing in screening could be limited to identifying women with low-grade smears and koilocytotic or low-grade colposcopic biopsies that are at risk of concealing or developing high-grade histologic lesions.