Between 1968 and 1976 a total of 5162 women volunteers were enrolled into a prospective study conducted on the Island of Guernsey. Up to February 1990 145 women subsequently developed breast cancer. Blood samples were taken at the time of enrollment and prolactin levels were known for 85% of the volunteers. In calculating the relationship between blood prolactin levels and subsequent breast cancer risk, women were excluded if they had a hysterectomy or an oophorectomy or had cancer at any site before enrollment. The final analysis was based on 2596 premenopausal and 1180 naturally postmenopausal women and, of these respectively, there were 71 and 40 volunteers who subsequently developed breast cancer. The total follow-up for these two groups was 49,941 and 22,360 woman-years, respectively. In assessing the relationship between blood prolactin levels and risk of subsequent breast cancer the cohort was divided into quintiles according to prolactin concentration and relative risks (RR) were estimated. In calculating these values possible confounding by age at entry, age at menarche, parity, age at first birth, years since menopause, body build, history of benign breast disease and family history of breast cancer were taken into consideration. There was no significant relation between risk of breast cancer and prolactin in either pre- or postmenopausal women. Hence prolactin appears not to be an important determinant of breast cancer risk.
A prospective study has been conducted on 4954 female volunteers from the Island of Guernsey between 1977 and 1985 to examine risk factors for breast cancer and their relationship to mammographic parenchymal patterns as assessed by Wolfe's method of grading. Up to September 1988, 69 women had developed breast cancer, 11 of whom were prevalent cases being diagnosed within six months of mammography. The remaining incident cases were diagnosed six to 126 months (median 65 months) after entry to the study. Univariate analysis showed that the distribution of Wolfe grades in the population was significantly associated with menopausal status, age, parity, adiposity, age at menarche, age at first childbirth and use of oral contraception, but not with a family history of breast cancer. Multivariate analysis of the data for these variables from either pre- and/or post-menopausal women indicated that age, parity and adiposity were significantly related to Wolfe grade pattern. Age had an opposite effect in pre- compared with postmenopausal women thus the probability of either a P2 or DY pattern increased with increasing age in premenopausal but decreased in postmenopausal women so that incidence peaked around the menopause. Other variables did not achieve significance in the multivariate analysis. Odds ratios (ORs) were calculated for women with P2 or DY patterns using those with N1 or P1 grades as the reference group. The ORs were determined at two censoring times; one at five years and the other to include the most recent follow-up of this cohort. The ORs were adjusted for years of follow-up, age and adiposity and in postmenopausal women adjustment was also made for age at menarche.(ABSTRACT TRUNCATED AT 250 WORDS)
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