Invasive cervical cancer audit: a relative increase in interval cancers while coverage increased and incidence declined.

OBJECTIVE

To examine screening histories of women with invasive cervical cancer in a 12-year period during the introduction of organised screening to assess its effectiveness.

STUDY DESIGN

Screening histories were classified into six categories: no cytology record (1), previous cytology more than 5 years before diagnosis (2) and previous cytology within 5 years of diagnosis (3-6). Categories 3-6 were described as interval cancers and comprised previous negative cytology (3), previous repeats for low-grade cytology (4), previous recommendations for investigation (5) and previous treatment (6).

SETTING

Southampton and South West Hampshire (SSWH).

POPULATION

Women resident in SSWH registered with invasive cervical carcinoma between 1985 and 1996.

METHODS

Data were held for analysis on an anonymous spreadsheet.

MAIN OUTCOME MEASURES

Association of screening history categories with 3-year time period, age group, type and stage of cancer and route to diagnosis; incidence per 100,000 women aged 25-64 years screened and not screened within 5 years in 1991-93 and 1994-96.

RESULTS

Interval cancers increased as a proportion of all cancers from 31.5% in 1985-87 to 48.6% in 1994-96 (P= 0.002) and showed a peak in 1991-93. Their incidence decreased from 20.1 to 10.9 per 100 000 eligible women aged 25-64 years screened within 5 years (P= 0.008) between 1991-93 and 1994-96, while incidence in women not screened within 5 years was unchanged (44.2 and 40.4). Factors other than previous negative smears were recorded in 50.9% of interval cancers. Interval cancers were more likely to be low stage, screen detected and were diagnosed in younger women (P < 0.00001).

CONCLUSIONS

Interval cancers should be assessed as a proportion of eligible women screened within the same period of time and not as a proportion of all cancers. This audit demonstrates the importance of accurate cytology, appropriate follow up, prompt investigation and effective treatment of high-grade precancerous lesions.