Abstract
The aims of the present study were to find the frequency of the most common BRCA1 mutations in women with ovarian tumours identified from a population-based cancer registry and in the general population, to estimate the relative risk of ovarian tumours among the mutation carriers, and to explore the value of using CA125 as a prediagnostic test. The study was designed as a nested case–control study within a cohort mainly consisting of participants in population-based health examinations. The data files of The Cancer Registry of Norway and the Janus serum bank were linked to identify cases with ovarian cancer and borderline tumours. Hereditary BRCA1 mutations were determined using archived serum samples and capillary electrophoresis. Altogether 478 ovarian cancer patients and 190 patients with borderline tumours were identified, and 1421 and 568 matching controls were selected. Odds ratios (OR) of developing ovarian cancer and borderline tumours in the presence of BRCA1 mutations and CA125 level were derived from conditional logistic regression models. Among the 478 ovarian cancer patients, 19 BRCA1 mutations were identified (1675delA, 1135insA, 816delGT and 3347delAG), none among the patients with borderline tumours. Only two of the 1989 controls were BRCA1 mutation carriers (0.10%). The risk of ovarian cancer among the mutation carriers was strongly elevated (OR=29, 95% CI=6.6–120). CA125 was a marker for ovarian cancer, but the sensitivity was low. This study showed that BRCA1 mutation carriers have a very high risk of ovarian cancer. However, since the prevalence of BRCA1 mutations in the Norwegian population was low, the proportion of ovarian cancers due to BRCA1 mutations seemed to be low, about 4%. The sensitivity of using CA125 only as a screening test for ovarian cancer was low.
Highlights
Ovarian cancer has a hereditary proportion exceeding 10% in some populations (Risch et al, 2001; Narod and Boyd, 2002)
Among the 478 ovarian cancer patients, 19 BRCA1 mutations were identified (4.0%) (Table 1), and no mutation was discovered among the 190 patients with borderline tumours
In the present seroepidemiological study, we showed that only 4% of the ovarian cancers in Norway were due to BRCA1 mutations (1675delA, 1135insA, 816delGT and 3347delAG), and none of the borderline tumours
Summary
Ovarian cancer has a hereditary proportion exceeding 10% in some populations (Risch et al, 2001; Narod and Boyd, 2002). Women with BRCA1 mutations are diagnosed at a younger age than noncarriers, and most tumours in the mutation carriers are of serous histology (Stratton et al, 1997; Risch et al, 2001). The two founder mutations (1675delA and 1135insA) have been shown to account for about half of all BRCA1 cases and for one-third of hereditary breast-ovarian cancers in Norway (Borg et al, 1999). CA125 has demonstrated its value in monitoring the treatment of patients with ovarian cancer (Makar, 1993) This marker has in combination with ultrasound been promising in screening for early detection of ovarian cancer (Jacobs et al, 1999). BRCA1 mutations and ovarian tumours T Bjrge et al1830 In Norway, the Janus serum bank was established in the early
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