Risk factors for carcinoma of the fallopian tube in women with and without a germline BRCA mutation.

ABSTRACT

OBJECTIVE: The purpose of this study was to identify risk factors for fallopian tube cancer in women with and without a BRCA mutation. METHODS: Subjects with fallopian tube cancer were identified from two sources 1) a large international registry of women who carry a BRCA1 or BRCA2 mutation (n=56), and; 2) a population-based study of ovarian and fallopian tube cancer conducted in Ontario, Canada (n=66). BRCA mutation status was established for all subjects. Each subject was matched to one or more unaffected controls, for date of birth (within four years), for BRCA mutation status (negative, BRCA1, and BRCA2), for country of residence and for past history of breast cancer (yes/no). All subjects completed a questionnaire about medical history and lifestyle factors. Odds ratios and 95% confidence intervals were calculated for parity, oral contraceptive use, tubal ligation, hormone replacement therapy and body mass index, using conditional logistic regression. RESULTS: We studied 103 women with fallopian tube cancer (48 with a BRCA1 mutation, 12 with a BRCA2 mutation and 43 with no identified BRCA mutation) and 980 matched controls. Increasing parity was associated with a decreased risk of fallopian tube cancer in non-carriers (trend per birth odds ratio 0.71 (95% CI 0.52-0.97), p=0.03), in BRCA1 carriers (OR=0.79 (0.62-1.02) p=0.07) and in BRCA2 carriers (OR=0.62 (0.34-1.15), p=0.13), but was statistically significant only for non-carriers. Oral contraceptive use was associated with a reduced risk in BRCA1 carriers (trend per year of use odds ratio=0.91 (0.83-0.99), p=0.03) but not for non-carriers (OR=0.97 (0.87-1.09), p=0.64) or for BRCA2 carriers (OR=0.94 (0.80-1.11), p=0.47). Hormone replacement therapy was associated with an increased risk for fallopian tube cancer in all subjects (OR=1.07 (1.01-1.13), p=0.03), and in the subgroups stratified by mutation, however the association was not significant in the subgroups. Tubal ligation was associated with a decreased risk of fallopian tube cancer for all subjects (OR=0.64 (0.31-1.28), p=0.21), however the reduction was not significant. CONCLUSIONS: Parity and oral contraceptive use are associated with reduced risks of fallopian tube cancer. In contrast, hormone replacement therapy may be associated with an increase in the risk of fallopian tube cancer.