Reproductive and Hormonal Factors and Breast Cancer in a Northern Italian Population

Abstract

Between January 1980 and March 1983, data were collected to evaluate risk factors for breast cancer in a case-control study based on 368 women with breast cancer admitted to the General Hospital of Pordenone (a district in North Eastern Italy with a particularly high breast cancer mortality rate), and 373 age-matched controls. Nulliparity or low parity, late age at first birth and later menopause were associated with an increased risk of breast cancer. The elevated risk associated with nulliparity could be almost completely explained by marital status, thus pointing to a specific protection given by parity, rather than some putative influence of infertility or subfertility in breast cancer cases. Likewise, risk did not vary materially according to history of abortions when marital status was controlled for. Increased risk associated with later age at first birth, on the other hand, was not accounted for by marital status or parity. The population studied, though frequently multiparous, showed late average at first birth: this might, at least partly, explain its high mortality rate from breast cancer. The risk estimate was higher if menarche occurred below age 15; however, there was no evidence of a trend for the relative risk to rise with lower age at menarche. The use of oral contraceptives or other female hormones (such as oestrogen replacement therapy) did not appear to be related to the risk of breast cancer. The role of the major menstrual and reproductive variables considered (age at menarche, parity, age at first birth) was apparently stronger in pre-menopausal women, thus suggesting an influence of these factors (and possibly, their hormonal correlates) on one of the latter stages of the process of carcinogenesis.

Risk of breast cancer in relation to reproductive factors in Denmark

“…Three previous studies (Wynder et al, 1978;Talamini et al, 1985;Hislop et al, 1986) have reported results similar to the present, but others (Stravraky & Emmons, 1974;Lubin et al, 1982) have found that age at first birth influenced breast cancer risk in postmenopausal women only. In the majority of studies, however, the effect of age at first birth has been consistent over all age groups.…”

The pattern of risk factors for breast cancer in a southern France population. Interest for a stratified analysis by age at diagnosis

“…Besides, there is an advantage of hospital based case-control studies: it is expected that they have similar motivation for answering since both cases and controls are patients in a hospital. In our total sample, the reproductive factors have shown the same pattern as that described in other populations all over the world (Helmrich et al, 1983;Lubin et al, 1982;Ewertz et al, 1990;Talamini et al, 1985;Le et al, 1984;Plesko et al, 1985;Thein-Hlaing et al, 1978;Mirra et al, 1971). However, parity was not found completely in line with what has been generally reported, since have two or three children was associated with a somewhat elevated OR compared with having no child and have more than three children was not significantly associated with a protective effect.…”

“…There is agreement by most authors on a list of 'established' (Kelsey & Gammon, 1990) risk factors, made up of reproductive and menstrual variables, socioeconomic status, family history of BC and previous benign breast disease. These have been found in most countries where studies have been conducted: North America (Helmrich et al, 1983;Lubin et al, 1987); Scandinavia (reviewed in Ewertz et al, 1990); Western Europe (Talamini et al, 1985;Le et al, 1984); Eastern Europe (Plesko et al, 1985); Asia (Thein & Theen et al, 1978) and South America (Mirra et al, 1971). However, in several studies, there is no risk increase associated with some of these established factors (Adami et al, 1980;East European Study of BC epidemiology, 1990).…”

Body mass index and post-menopausal breast cancer: an age-specific analysis

“…A total of 1556 incident, histologically confirmed cases were interviewed, together with 1473 controls admitted for acute, orthopaedic, medical or surgical conditions unrelated to risk factors for breast cancer and to long-term modification of diet (such as peptic ulcer and other gastric disorders, Crohn's disease or ulcerative colitis, diabetes mellitus, hyperuricaemia or any other metabolic condition). The second study (Talamini et al, 1985) was based on 373 breast cancer cases recruited between 1980 and 1983 at the General Hospital of Pordenone, north eastern Italy. Cases were matched for age (± 5 years) with 368 controls recruited in the same region and admitted to the same hospital for acute, non-neoplastic and non-hormone-related conditions that were unrelated to nutrition or diet.…”