Objective To assess the clinical significance of screen-detected cancer compared with symptomatic cervical cancer during the introduction of organized screening.
Study design Screen-detected and symptomatic cancers were analysed according to International Federation of Obstetrics and Gynecology stage and histological type of cancer and age of women during four 3-year periods.
Setting Southampton and South West Hampshire (SSWH).
Population Women resident in SSWH registered with invasive cervical carcinoma between 1985 and 1996.
Methods Screen-detected and symptomatic cancers were defined on the basis of clinical information obtained at the time of diagnosis and recorded together with date of diagnosis, age group, histology and cytology results. Data were held for analysis on an anonymous spreadsheet.
Main outcome measures Incidence of screen-detected and symptomatic cancers per 100 000 women; association between route to diagnosis, age group, stage of cancer and screening history during four 3-year periods.
Results Of 382 cancers, 256 were symptomatic, 78 screen-detected fully invasive and 48 screen-detected microinvasive. Incidence of symptomatic cancers fell from 13.0 to 6.4 per 100 000 total female population (P = 0.0005), and there was a trend towards screen-detected cancers as a proportion of all cancers (P = 0.002). By the latest period of the study (1994–96), the likelihood of cancers being screen-detected was strongly associated with younger age groups (P = 0.001). Screen-detected fully invasive cancers were significantly less likely (P = 0.001) to be diagnosed at stage II or above (16.6%) compared with symptomatic cancers (63.3%). Women with screen-detected microinvasive cancers were significantly more likely (P < 0.001) to have been screened within 5 years (83.3%) than screen-detected fully invasive cancers (60.2%) or symptomatic cancers (33.6%).
Conclusion Screen-detected cancers were more likely to be diagnosed at an earlier stage, in younger women and in women who had previously been screened and became relatively more frequent as symptomatic cancers declined.