Cervical cytology screening in two Yorkshire areas: results of testing

Withdrawing low risk women from cervical screening programmes: mathematical modelling study

OBJECTIVE

To evaluate the impact of policies for removing women before the recommended age of 64 from screening programmes for cervical cancer in the United Kingdom.

DESIGN

A mathematical model of the clinical course of precancerous lesions which accounts for the influence of infection with the human papillomavirus, the effects of screening on the progression of disease, and the accuracy of the testing procedures. Two policies are compared: one in which women are withdrawn from the programme if their current smear is negative and they have a recent history of regular, negative results and one in which women are withdrawn if their current smear test is negative and a simultaneous test is negative for exposure to high risk types of human papillomavirus.

SETTING

United Kingdom cervical screening programme.

MAIN OUTCOME MEASURES

The incidence of invasive cervical cancer and the use of resources.

RESULTS

Early withdrawal of selected women from the programme is predicted to give rise to resource savings of up to 25% for smear tests and 18% for colposcopies when withdrawal occurs from age 50, the youngest age considered in the study. An increase in the incidence of invasive cervical cancer, by up to 2 cases/100 000 women each year is predicted. Testing for human papillomavirus infection to determine which women should be withdrawn from the programme makes little difference to outcome.

CONCLUSIONS

This model systematically analyses the consequences of screening options using available data and the clinical course of precancerous lesions. If further audit studies confirm the model's forecasts, a policy of early withdrawal might be considered. This would be likely to release substantial resources which could be channelled into other aspects of health care or may be more effectively used within the cervical screening programme to counteract the possible increase in cancer incidence that early withdrawal might bring.

Preventive Pap-smears: balancing costs, risks and benefits

The pattern of spontaneous screening for cervical cancer by general practitioners and gynaecologists in The Netherlands is compared with an efficient screening policy resulting from a cost-effective study. Spontaneous screening tends to start and stop too early in a woman's life, and leaves too many women overscreened or unprotected. The combination in young age of a low incidence of invasive cancer and a high incidence of regressive lesions explains relative ineffectiveness and harmfulness of present screening practice. When screening would take place between ages 30 and at least 60, with intervals of about 5 years, as many lives could be saved for half the costs and with only 60% of the unnecessary referrals and treatments. Much attention should be paid to the coverage of the target population. Therapeutic follow-up policies for dysplastic lesions should be restrained.

Screening colposcopy in genitourinary medicine

A prospective study of new female patients attending the Genitourinary Medicine Department in Doncaster was carried out to look at the value of colposcopic examination at their first attendance. Of the 100 randomized patients studied 41 showed evidence of colposcopically detected cervical abnormality. Twenty-seven patients had colposcopically directed biopsies. These showed evidence of cervical intraepithelial neoplasia (3 cases), flat condyloma (16 cases), exophytic wart (2 cases), chronic inflammation (2 cases) and normal epithelium (4 cases). Colposcopic cervical abnormalities were significantly associated, with a history of anogenital warts, sexual contact with anogenital warts and the presence of anogenital warts at presentation. Despite this, less than half the group showing colposcopic abnormalities had an association with anogenital warts. Demonstration of cervical abnormalities by colposcopy resulted in a greater patient compliance during follow-up. Screening or primary colposcopy may be incorporated into a genitourinary screen at the first visit. The procedure is both acceptable and beneficial to the patient, facilitating the detection of a range of cervical disease and enhancing the doctor-patient relationship.

Four and a half year follow up of women with dyskaryotic cervical smears

OBJECTIVE

To determine the proportion of women with mild or moderate dyskaryosis in cervical smears who (a) progress to cervical intraepithelial neoplasia grade III or worse or (b) regress.

DESIGN

Four and a half year cytological follow up study of women with mild or moderate dyskaryosis in cervical smears.

SETTING

666 Women (mean age 28 (SD 8) years; range 14-74) found to have borderline, mild, or moderate dyskaryosis on routine screening.

RESULTS

45 Women (6.8%) had a cone biopsy recommended on the basis of an abnormal follow up smear (severe dyskaryosis suggestive of cervical intraepithelial neoplasia grade III or invasive cancer), and in one patient cervical intraepithelial neoplasia grade III was reported in a biopsy specimen after dilatation and curettage. Life table analysis gave a 14% probability of a patient being recommended for a biopsy after four and a half years of follow up (95% confidence interval 12% to 15%). There was a significant excess incidence of invasive cancer of the cervix in the series compared with the general population (five cases observed compared with less than 0.1 expected). 157 Patients (24%) showed reversion to a normal cell pattern sustained in several smears over more than 18 months but a single negative smear was an unreliable indicator of apparent regression. Having two successive smears showing mild dyskaryosis or a smear at any time showing moderate dyskaryosis was a significant predictor of a subsequent severely dyskaryotic smear.

CONCLUSIONS

Women found to have mild or moderate dyskaryosis in cervical smears should be kept under regular surveillance. The optimum management of these patients--by cytology or colposcopy--needs to be determined by randomised controlled trials.

Cervical-cancer screening: attendance and cost-effectiveness

The influence of attendance on the health effects and cost-effectiveness of cervical-cancer screening was studied, both for organized screening programmes and for spontaneous screening. The asymmetric distribution of smears among the female population and the higher risk incurred by women who never or only occasionally attend screening appear crucial in determining the health effects of screening. An increase in attendance rate induces a substantial rise in health effects and a less than proportionate rise in costs, thus improving cost-effectiveness. Wider screening coverage, in order to increase the number of life-years saved, is achieved more efficiently by encouraging a greater number of women to attend than by inviting the same number of women to attend more often, i.e., with a shorter interval between successive screens. Spontaneous screening is characterized by high coverage for younger women and low coverage for middle-aged and older women. This leads to a small amount of health effects and poor cost-effectiveness as compared with organized screening.

An evaluation of screening policies for cervical cancer in England and Wales using a computer simulation model

Several screening policies have been recommended for implementation in England and Wales in the last 20 years, although no evidence as to their relative effectiveness or efficiency has been provided. Using a computer simulation model, the outcomes expected from those policies had they been implemented over a 30 year period (1961-90) have been examined. The original policies based on five-yearly testing of women aged over 35 appear to be the most cost-effective, and extension of screening to younger age groups leads to loss of efficiency. Attempts to use non-screening health care contacts in order to take cervical smears (eg, during pregnancy, family planning, at gynaecology clinics) produce few advantages and considerably complicate the establishment of regular testing for the individual. The achievement of higher attendance rates is as important to the outcome of screening as concentration on more intensive or complex policies.

A computer simulation model for the practical planning of cervical cancer screening programmes

There is ample evidence of the efficacy of cytological screening in the prevention of cervical cancer but disagreement on the form which screening programmes should take. Simulation models have been used as a convenient and rapid method of exploring the outcome of different screening policies and of demonstrating the importance and interrelationships of the variables concerned. However, most such models are either too abstract or too simplistic to be of practical value in planning screening programmes. A model is described which reproduces demographic events in a female population (that of England and Wales) over a 30 year period, and onto this superimposes the natural history of cervical carcinoma, using data derived from published studies. A microsimulation approach--each individual in the population being retained as a unit--allows factors such as disease onset and screening uptake to be dependent upon personal characteristics and past events. Screening can be offered as part of a routine programme, or incidentally--for example during pregnancy or hospital attendance. The model allows quantitative evaluation of the complex patterns of screening that are actually observed and the relative importance of the different components of such screening programmes. Assumptions about natural history can thus be studied.

Cervical smear histories of 500 women with invasive cervical cancer in Yorkshire

The smear histories of 312 women with cancer of the cervix have been determined. Eighty nine women had had at least one negative smear reported in the 10 years before a diagnosis of cancer and 14 had had more than one negative smear. Fifty six of the 89 women had had a negative smear in the three years preceding the diagnosis of cancer. The highest number of negative smears (61) reported was among the 115 women aged under 45. Fifty eight slides reported as negative were submitted to independent review; 13 were subsequently reported as negative, 11 as unsatisfactory, and 34 as abnormal. These findings may in part explain why in this region there has been a disappointing reduction in the incidence of clinically invasive cervix cancer, and our findings may also apply elsewhere. Nevertheless, the confirmed negative smears chiefly occurred within three years of clinical cancer, particularly in the younger women, and this finding suggests that these women may have a short preinvasive phase.

Incidence and prevalence of preclinical carcinoma of cervix in a British population

Quantitative knowledge of the natural history of cancer of the cervix is essential to the design of optimal screening programmes. We have estimated the incidence and prevalence of cervical intraepithelial neoplasia in a population of women receiving cytological examinations, and compared the results with those from other series. Relative risk of disease is reported in relation to easily identified variables (marital status, parity, contraceptive use, symptoms) which are likely to be of practical value in defining selective screening policies.