Short term increase in risk of breast cancer after full term pregnancy

Abstract

To determine whether there is a short term increase in the risk of breast cancer after a full term birth data from two hospital based, case-control studies in Italy were pooled. Analysis was restricted to women aged under 50 with two or more children (573 women with cancer and 570 controls). A relative risk for breast cancer of 2*66 was seen in women who had given birth during the three years preceding the interview compared with women whose last birth had occurred 10 or more years before, after adjustment for age, age at first birth, and parity. The relative risk slowly decreased for women who had last given birth three to 10 years before. Multivariate analyses confirmed the protective effect of an early age at first birth and the age dependent effect of parity on the risk of breast cancer-that is, a direct relation below age 40 and an inverse one in older women. These data provide epidemiological evidence that a full term birth is foliowed by a transient increase in the risk of breast cancer, which for some time contrasts with and overcomes the long term protection of pregnancy at an early age. They therefore confirm predictions from animal studies and theoretical models that pregnancy prevents the early stages of breast carcinogenesis but promotes the late stages of the process. Introduction The role of several reproductive factors in the risk of

Oral contraceptives and breast cancer in Northern Italy. Final report from a case-control study

“…This resembles the transient increase in the risk of breast cancer found after a full-term pregnancy (Bruzzi et al, 1988;La Vecchia et al, 1990). These findings are not in agreement with most previous evidence referring to the pattern of risk in younger women (<40 years) (Lubin et al, 1982;Meirik et al, 1986;McPherson et al, 1987;Kay & Hannaford, 1988;Miller et al, 1989;Olsson et al, 1989;Peto, 1989; UK National Case-Control Study Group, 1989;Romieu et al, 1990;Delgado-Rodriguez et al, 1991;Weinstein et al, 1991;Rushton & Jones, 1992;Ursin et al, 1992), and in those who used OC at a younger age or before first birth (Pike et al, 1981;Meirik et al, 1986;McPherson et al, 1987).…”

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

“…This has also been observed by Kvale et al (1987);Negri et al (1990) and Williams et al (1990). Since we do not have information about the date of the last pregnancy, we cannot say for sure that this increased risk is related to the detrimental effect of a recent pregnancy (Bruzzi et al, 1988). However, it is very likely, because the increased risk is restricted to the youngest groups.…”

Breastfeeding history, pregnancy experience and risk of breast cancer

“…Although the long-term effect of pregnancy is clearly to reduce breast cancer risk, there is a hypothesized dual effect of pregnancy on risk: a transient increase in risk for roughly three years following the pregnancy, followed by a long-term reduction in risk (Woods et al, 1980;Bruzzi et al, 1988;Adami et al, 1990;Williams et al, 1990;Vatten and Kvinnsland 1992;Cummings et al, 1994;Hsieh et al, 1994;Lambe et al, 1994;Albrektsen et al, 1995;Leon et al, 1995). Because the women in this study were premenopausal and may have experienced a recent pregnancy, we analysed the breastfeeding-breast cancer association separately for women whose most recent full-term pregnancy was within 5 years of their breast cancer diagnosis (or within 5 years of the case's diagnosis for controls) and for women whose most recent full-term pregnancy was 5 years or more before the date of diagnosis (Table 2).…”