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This study confirms the many previous studies showing that immediate
referral to colposcopy of women with low grade cervical cytology will
detect more cases of pre-invasive disease more quickly than cytological
surveillance - but that is not the main issue.
What really matters is whether cytological surveillance increases the
risk of invasive cancer. In what I think is the largest study of its kind,
Dr Fletcher and I showed that the average rate of invasive cancer was
208/100,000 women years in 5 studies of cytological surveillance and we
estimated that this was about 20 times greater than the incidence in women
of a similar age group at that time. Indeed, the only one of the five
studies to have attempted to measure the size of the increase directly,
calculated that these women had a 62 fold greater risk of invasive
With only 4476 women randomised in the TOMBOLA trial, there are too
few with invasive cancer to answer this crucial question. None the less,
the immediate colposcopy group did have fewer cases of invasive cancer
than the cytological surveillance group with 1 v 3 cases of Stage Ib or
worse disease and 3 v 7 of Stage Ia or worse disease. Assuming all those
who attended for exit examination had 3 year's follow up, a conservative
estimate of the rate of invasive disease in the surveillance group is
180/100,00 women years - very similar to the average rate we reported in
As the available evidence suggests that cytological surveillance is
associated with a high rate of invasive cancer, immediate referral to
colposcopy would seem to be the safer option.
(1)Soutter WP and Fletcher A. Invasive cancer of the cervix in women
with mild dyskaryosis followed up cytologically. BMJ 1994; 308:1421-3.
(2)Fletcher A, Metaxas N, Grubb C, Chamberlain J. Four and a half year
follow up of women with dyskaryotic cervical smears. BMJ 1990; 301:641-4