CASE-CONTROL STUDY OF GASTRIC-CANCER SCREENING IN VENEZUELA

A screening programme for early gastric cancer was introduced in the s tate of Tachira, Venezuela, in 1980. Screening was performed by photof luorography, using two mobile units. The efficacy of this programme in reducing mortality from stomach cancer was evaluated by means of a ca se-control study. Cases were 241 individuals who died from stomach can cer in the period 1985-89. Ten live controls per case were drawn from the electoral rolls, matched by sex, age and residence. Exposure to th e screening examination of cases and controls was assessed through ind ividual linkage with the programme's centralised database. After the e xclusion of examinations occurring within the 6 months preceding the c ase's diagnosis, the odds ratio (OR) of dying from stomach cancer for those screened was 1.26 (CI 0.83-1.91) and the OR in females was lower than in males: 0.77 (CI 0.33-1.78) and 1.52 (CI 0.94-2.47) respective ly. Odds ratios associated with years since last test and number of te sts did not differ significantly from 1. These results show the ineffi cacy of the programme in reducing mortality from gastric cancer in the area. In an attempt to determine whether this result was due to selec tion bias, an analysis restricted to subjects who had been screened at least once was performed. When examinations occurring after an index date at various intervals before the case's diagnosis were excluded, t he screening test appeared to protect from death, although confidence intervals of the odds ratios are large, for example OR = 0.47 (CI 0.24 -0.98) when excluding tests within 1 month.