Cancer diagnosis after a report of negative cervical cytology

1. To determine the annual rate of interval squamous cancer of the cervix after a negative Papanicolaou smear report. 2. To evaluate the proportion of women with cervical cancer who received negative cervical smear reports during the three years before the cancer diagnosis.

Objective 1. A prospective study of the incidence of squamous cervical cancer from 1990 to 1993 among women who received negative cervical smear results in Victoria in 1990. Objective 2. A retrospective audit of preceding cervical smear results from 1990 to 1993 in women diagnosed with cervical cancer in Victoria in 1993.

The average interval cervical rate was 2.54 squamous cancers per 100000 women per year (95% confidence interval, 1.75-3.67) during the first three years after a negative smear report. The interval cancer rate did not vary by age group nor by the endocervical status of the negative smear report. Of the 233 cases of cervical cancer diagnosed during 1993, 56 women (24%) had negative cervical cytology reported during the preceding three years. The frequency of preceding negative cervical cytology was greater for non-squamous cancer (22 women [33%] from 66 cases) than for squamous cancer (34 women [20%] from 167 cases.

The rate of interval cancer diagnosis is very low compared with expected rates in the absence of screening, indicating the effectiveness of the cervical screening program in Victoria.