Breast Cancer in Relation to Patterns of Oral Contraceptive Use

Abstract

A total of 112 white females residents of King County, Washington, aged 35-54 years, who had received a first diagnosis of invasive breast cancer between July 1977 add August 1978, were investigated concerning prior use of oral contraceptives. Their responses were compared with those of a random sample of 469 demographically comparable women from the same population. Overall, oral contraceptive use in cases and controls was similar. However, use of oral contraceptives in preparous women was more common among cases than controls, with the estimated risk of breast cancer associated with such use being 2.2 times that of nonusers (90% confidence interval = 1.1-4.6). This relationship could be explained only in part by the effect of oral contraceptives in postponing or preventing childbirth. The association of breast cancer with use of oral contraceptives prior to ever giving birth has been observed in three studies, including this one, suggesting that the susceptibility of breast tissue to hormonal factors that influence the development of malignancy may be altered by having been exposed to the events of pregnancy.

Risk of breast cancer in relation to reproductive factors in Denmark

“…Apart from these, other studies showing no association between breast cancer and age at first birth have been relatively small, with less than 200 cases (Herity et al, 1975;Thein-Hlang & Thein-MaungMyint, 1978;Adami et al, 1978;Pike et al, 1981;Harris et al, 1982;Storm et al, 1986) with a low statistical power of detecting an association, especially if it was weak. Selection bias related to childbearing in the control group may explain the lack of association in the study of Choi et al (1978).…”

“…Several studies have confirmed this, but some found an additional protective effect of high parity (Soini, 1977;Tulinius et al, 1978;Paffenbarger et al, 1980;Brinton et al, 1983;Helmrich et al, 1983; Pathak et al., 1986). Others have failed to demonstrate an association between breast cancer risk and age at first birth (Choi et al, 1978; Thein-Hlaing & Thein-Maung-Myint, 1978;Adami et al, 1980;Pike et al, 1981;Harris et al, 1982;Kvale et al, 1987b).…”

“…Several studies have confirmed this, but some found an additional protective effect of high parity (Soini, 1977;Tulinius et al, 1978;Paffenbarger et al, 1980;Brinton et al, 1983;Helmrich et al, 1983; Pathak et al., 1986). Others have failed to demonstrate an association between breast cancer risk and age at first birth (Choi et al, 1978; Thein-Hlaing & Thein-Maung-Myint, 1978;Adami et al, 1980;Pike et al, 1981;Harris et al, 1982;Kvale et al, 1987b).Conflicting evidence also exists in the literature regarding the role of early terminated pregnancies. Two reports (Pike et al, 1981;Hadjimichael et al, 1986) suggested that a first trimester abortion (induced or spontaneous) before the fullterm pregnancy might elevate the risk of breast cancer, while such an effect was not seen in two other studies (Vessey et al, 1982;Brinton et al, 1983).…”

Oral contraceptives and breast cancer: Final report of an epidemiological study

“…Since the appearance of our last detailed report (Vessey et al, 1979), the results of a considerable number of additional epidemiological studies of the possible association between oral contraceptive use and breast cancer have been published (Paffenbarger et al, 1979;Ravnihar et al, 1979;Jick et al, 1980;Matthews et al, 1981;Pike et al, 1981;Royal College of General Practitioners, 1981;Vessey et al, 1981;Trapido, 1981;Harris et In our last full analysis (Vessey et al, 1979), we noted that a smaller proportion of women with breast cancer than of matched controls reported never having used any method of birth control at all. The addition of data for a further 555 pairs of patients has left this association unchanged.…”

Oral contraceptives and breast cancer: results from an expanded case-control study

“…In particular, there is evidence that oral contraceptives may alter the risk of breast cancer in women with a family history of breast cancer (Black et al, 1980;Brinton et al, 1982), women with prior benign breast lesions (Fasal & Paffenbarger, 1975, 1977Lees et al, 1978;Brinton et al, 1982;Janerich et al, 1983), young women with extended periods of use before a first live birth (Paffenbarger et al, 1977(Paffenbarger et al, , 1980Pike et al, 1981;Harris et al, 1982;McPherson et al, 1983McPherson et al, , 1987Meirik et al, 1986) or before age 25 (Pike et al, 1983;Olsson et al, 1985;Meirik et al, 1986), women under 35 years of age at diagnosis (Kay & Hannaford, 1988) and older women who used oral contraceptives around the perimenopausal period (Vessey et al, 1979;Jick et al, 1980;Paffenbarger et al, 1980;Kay, 1981;Brinton et al, 1982;Henneken et al, 1984). These relationships, however, have not been consistently found (Vessey et al, 1981(Vessey et al, , 1982Stadel et al, 1985;Miller et al, 1986;Prentice & Thomas, 1987;Schlesselman et al, 1988).…”