eMJA: How much cervical cancer is being prevented?

To the Editor: It was estimated in 1989 that cervical screening in Australia was preventing only 46% of squamous malignancies, against a theoretical capacity of 90%.1 This suboptimal achievement after almost 25 years of cervical screening led to a major reorganisation of the program.

The 1989 analysis has been repeated, using the most recent year (1998) for which incidence rates have been published (Box). The more recent figures suggest that cervical screening in Australia is now preventing 70% of squamous carcinoma of the cervix.

This remarkable improvement can probably be attributed to the improved participation by women in regular screening, improved standards within laboratories, and better follow-up of cytological abnormalities. While there is still scope for improvement, there is clear evidence of a substantially better gain from cervical screening. Continued efforts to increase the participation rate among women aged 60–69 years is appropriate given that the prevented proportion appears to be lower in this age range.

Percentage of squamous carcinoma of the cervix prevented, by age group, Australia 1998

Age group	Number of women (estimated number with a cervix*) in Australia2	Expected rate (per 100 000 women) of squamous carcinoma without screening†	Expected number of squamous carcinomas‡	Estimated number of squamous carcinomas observed in 1998§	Percentage prevented

20–24	665 691 (665 025)	5	33.3	9.6	71.1%
25–29	733 145 (732 412)	15	109.9	34.8	68.3%
30–34	706 925 (687 838)	25	172.0	62.9	63.4%
35–39	748 913 (728 692)	45	327.9	74.7	77.2%
40–44	702 629 (608 477)	45	273.8	76.2	72.2%
45–49	649 539 (562 501)	45	253.1	81.4	67.8%
50–54	570 287 (410 607)	45	184.8	48.1	74.0%
55–59	431 183 (310 452)	45	139.7	40.7	70.9%
60–64	370 123 (251 314)	45	113.1	40.7	64.0%
65–69	348 707 (236 772)	45	106.6	44.4	58.3%
Total	5 927 142 (5 194 090)		1714	514	70.0%

* Calculated by multiplying the number of women in Australia by the estimated age-specific hysterectomy fractions.3 † Methodology as for the study by the International Agency for Research on Cancer,4 using incidence in Norway at a time when the rates would have been little affected by screening. ‡ Calculated by multiplying the estimated number of women in Australia with a cervix by the expected rate of squamous carcinoma of the cervix in the absence of screening.4 § Calculated by multiplying the number of cases of cervical cancer observed in 1998 by 0.74, which was the proportion of all cervical cancers that were squamous.5