Thh. Chen et al., Evaluation of a selective screening for colorectal carcinoma - The Taiwan Multicenter Cancer Screening (TAMCAS) project, CANCER, 86(7), 1999, pp. 1116-1128
BACKGROUND. Although the efficacy of mass screening for colorectal carcinom
a (CRC) with a fecal occult blood test has been demonstrated in several ran
domized trials, a mass screening approach used in countries with intermedia
te or low incidence of CRC might be costly. Screening high risk people may
be an alternative approach, to aid in the prevention of death from CRC. How
ever, the efficacy of CRC screening for high risk people in such countries
is uncertain.
METHODS. For this study, a multicenter design was devised to identify high
risk groups without clinical symptoms related to CRC; these subjects were i
dentified through the study of index cases of CRC in Taiwan. Colonoscopy, i
n combination with a fecal occult blood test or double-contrast barium enem
a, was used to screen high risk groups. A total of 8909 subjects were invit
ed to attend screening. Of 8909, 81 with asymptomatic CRC were detected in
one-shot screening. Markov models, in conjunction with a simulated approach
, were proposed to estimate relevant parameters in relation to disease prog
ression and to assess the effect of the interval between screenings on the
efficacy of CRC screening for these high risk groups.
RESULTS. The estimated preclinical incidence rate was 0.00396 (95% confiden
ce interval [CI], 0.002944-0.004985), which was 21 times that reported from
a cancer registry in 1994. The simultaneous estimations of mean sojourn ti
me (the average duration between the preclinical screen-detectable phase an
d the clinical phase) and sensitivity were 2.8 years (95% CI, 2.15-4.30) an
d 95.0% (95% CI, 24.4-99.9%), respectively. Predictions of mortality reduct
ion for people who received annual, biennial, and triennial screening regim
es compared with controls were 26% (95% CI, 0-50%), 23% (95% CI, 0-48%), an
d 21% (95% CI, 0-47%), respectively.
CONCLUSIONS. The efficacy of selective colorectal carcinoma screening has b
een demonstrated in this study. A high preclinical CRC incidence rate also
suggests that such a screening strategy might be cost-effective for countri
es with intermediate or low incidence of CRC. Methods proposed in this stud
y can be used to evaluate the efficacy of CRC screening in similar screenin
g trials. Cancer 1999;86:1116-28. (C) 1999 American Cancer Society.