Long-term oral contraceptive use increases breast cancer risk in women over 55 years of age: The DOM cohort

Abstract

The role of past oral contraceptive use in the development of breast cancer is unclear, particularly in postmenopausal women. The authors investigated this relationship among pre-and postmenopausal middle-aged women in a nested case-control study within the population-based DOM cohort, Utrecht, the Netherlands. Among a total population of 12,184 women followed up for an average of 7.5 years, 309 breast cancer cases aged 42 to 63 years, diagnosed from November 1982 through May 1996, and 610 controls were examined. Overall, duration of oral contraceptive use was not clearly related to breast cancer. In women older than 55 years, however, oral contraceptive use for more than 10 years was associated with a 2-fold increased risk of breast cancer (odds ratio (OR) 2.1, 95% confidence interval (CI) 1.1-4.0). We conclude that long duration of oral contraceptive use increases the risk of breast cancer in women over 55 years of age but not in younger women.

Previous oral contraceptive use and breast cancer risk according to hormone replacement therapy use among postmenopausal women

“…In agreement with our results, recent studies of older or postmenopausal women [6,17] found no increase in breast cancer risk with OC use. One recent nested case-control study of women aged over 55 years [7] found an increased risk of breast cancer with past OC use, but the increase in risk might be due to HRT use which was not taken into account. Furthermore, since older women are more likely to have stopped using OCs more than ten years ago [16], results on long time since last use should be in line with results for older women.…”

“…women for whom the maximum induction period might have passed, observed a decreased risk of breast cancer when OC use a Adjusted for age at menarche (£12, 13-14, ‡15 years), age at first birth and parity (nulliparous, <30 years, ‡30 years and one child, ‡30 years and two or more children), family history of breast cancer, BMI (continuous variable), frequency of pap smear exams (i.e. percentage of questionnaires reporting a pap smear exam), history of benign breast disease, alcohol consumption (£2.5 g/day, >2.5 g/day, missing), time since menopause (<5 years, [5][6][7][8][9][10] years, ‡10 years). Further adjusted for OC use (never/ever) or HRT use (never/ever), depending on the variable(s) studied.…”

“…Two other case-control studies [4,5] found no association between long-term use of OCs and breast cancer risk in young women, although an increased risk of breast cancer was associated with early age of use. Results for older or postmenopausal women are inconsistent: although a case-control study [6] based on a large population of women 45 years of age or older found no significant association between breast cancer risk and long duration of OC use, a nested casecontrol study [7] treating postmenopausal women as a separate group concluded that their risk of breast cancer increased with increasing duration of OC use but analyses were not adjusted for HRT use.…”

“…percentage of questionnaires reporting a pap smear exam), history of benign breast disease, alcohol consumption (£2.5 g/day, >2.5 g/day, missing), time since menopause (<5 years,[5][6][7][8][9][10] years, ‡10 years) HRT use (never/ever). b Time-dependent variable in Cox models.…”

Management of risk of breast carcinoma in postmenopausal women.

“…Most of these data consider cancers developing during the pre-or perimenopausal period; the possible correlation between OC use and breast carcinoma in postmenopausal women has still to be elucidated. Two cohort studies have shown that the RR is almost doubled in women with breast carcinoma diagnosed after 55 years and who had previously used OCs for long periods (Schuurman et al 1995, Van Hoften et al 2000.…”