Influence of pregnancy and lactation on serum and breast fluid estrogen levels: Implications for breast cancer risk

Nl, Petrakis; Mr, Wrensch; Vl, Ernster; Miike, Rei; Murai, James T.; Simberg, Niklas; Pk, Srivastava

doi:10.1002/ijc.2910400502

Cited by 121 publications

(78 citation statements)

References 27 publications

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“…Several investigations have suggested that women with extensive breastfeeding histories may be at reduced endometrial cancer risk (Rosenblatt and Thomas, 1995;Salazar-Martinez et al, 1999;Newcomb and Trentham-Dietz, 2000;Wernli et al, 2006), possibly from suppression of ovarian hormones (Petrakis et al, 1987). Although we initially observed reduced risk among subjects who breastfed for 2 or more years, this relation disappeared after adjustment for other risk factors.…”

Section: Discussionmentioning

confidence: 38%

Reproductive risk factors for endometrial cancer among Polish women

et al. 2007

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We conducted a population-based case -control study of reproductive factors in Warsaw and Ló qź, Poland, in 551 incident endometrial cancer cases and 1925 controls. The reproductive variable most strongly related to risk was multiparity, with subjects with three or more births having a 70% lower risk than the nulliparous women. The reduced risk was particularly strong below 55 years of age. Subjects with older ages at a first birth were also at reduced risk even after adjustment for number of births. Ages at last birth or intervals since last birth were not strongly related to risk. Spontaneous abortions were unrelated to risk, but induced abortions were associated with slight risk increases (odds ratios ¼ 1.28, 95% confidence intervals 0.8 -2.1 for 3 þ vs no abortions). The absence of effects on risk of later ages at, or short intervals since, a last birth fails to support the view that endometrial cancer is influenced by mechanical clearance of initiated cells. Alternative explanations for reproductive effects should be sought, including alterations in endogenous hormones.

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Section: Discussionmentioning

confidence: 38%

Reproductive risk factors for endometrial cancer among Polish women

et al. 2007

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“…A prolonged period of lactation is associated with a longer period of lactational amenorrhoea and thus exposure to total estrogens, which has been related to proliferative and carcinogenic effects, is reduced 24 ; breast fluid estrogen levels, independent of serum estrogen levels, were found to be lower in breastfeeding premenopausal women compared with never lactated (parous or nulliparous), and it took several years after the last breastfeeding to reach levels found in nulliparous women 25 ; in lactating women, oxytocin causes contraction of myoepithelial cells in response to suction, and it was reported that oxytocin inhibits cell proliferation and tumor growth in animal models, although this latter mechanism would be relevant mainly for short-term risk. 26 In conclusion, this is the largest case-control study on breast cancer to date in India; it revealed a strongly decreased risk for breast cancer in premenopausal women with long duration of breastfeeding.…”

Section: Discussionmentioning

confidence: 99%

Breastfeeding and breast cancer risk in India: A multicenter case‐control study

Gajalakshmi

Mathew

Brennan

et al. 2009

Intl Journal of Cancer

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Breast cancer incidence is low in India compared with highincome countries, but it has increased in recent decades, particularly among urban women. The reasons for this pattern are not known although they are likely related to reproductive and lifestyle factors. Here, we report the results of a large case-control study on the association between breastfeeding and breast cancer risk. The study was conducted in 2 areas in South India during [2002][2003][2004][2005] and included 1,866 cases and 1,873 controls. Detailed information regarding menstruation, reproduction, breastfeeding and physical activity was collected through in-person interview. Odds ratios (OR) and 95% confidence intervals (CI) were estimated by unconditional logistic regression models. Breastfeeding for long duration was common in the study population. Lifetime duration of breastfeeding was inversely associated with breast cancer risk among premenopausal women (p-value of linear trend, 0.02). No such protective effect was observed in postmenopausal women, among whom a protective effect of parity was suggested. A reduction of breast cancer risk with prolonged breastfeeding was shown among premenopausal women. Health campaign focusing on breastfeeding behavior by appropriately educating women would contribute to reduce breast cancer burden. ' UICCKey words: breastfeeding; breast cancer; India Breast cancer is the most common cancer in women worldwide with nearly 1,000,000 new cases each year, representing over 20% of all malignancies. 1 There are striking geographic variations in breast cancer incidence with more than a 10-fold difference between low rates in rural African and Asian populations and high rates in North American and Western European populations.Age-standardized breast cancer incidence rates in India range from 15 to 29 per 100,000 and have been increasing in recent decades, especially among urban women, and India is now the country with the largest estimated number of breast cancer deaths worldwide. 1 The reasons for the low incidence of breast cancer among Indian women and the increasing incidence in recent years are not completely understood, although are likely to be explained by reproductive and lifestyle factors. Only few epidemiological studies have been conducted to determine the risk factors of breast cancer in Indian women. [2][3][4] Although it is well established that prolonged breastfeeding decreases the risk of breast cancer, 5 most of the evidence derives from studies conducted in high-income countries. Data from lowincome countries, where prolonged breastfeeding is prevalent, are needed to better quantify the effect of long-term breastfeeding.The World Health Organization (WHO) 6 conducted a study on breastfeeding in India between 1975 and 1978, and found sociocultural factors such as education, employment and income to be the strongest determinants of the length of breastfeeding; 96% of mothers in the urban areas and 100% in rural areas breastfed their infants. Data from National Family Health Survey-2 show that in ...

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“…Lactation has also been proposed to protect against breast cancer through hormonal mechanisms by postponing the resumption of ovulatory menstrual cycles after a pregnancy, by increasing the differentiation of breast tissue (Russo and Russo, 1994) or by altering oestrogen levels in the breast (Petrakis et al, 1987). In addition, it has been proposed that lactation also has a direct mechanical effect by which carcinogenic agents are excreted from the breast ductal tissue (Murrell, 1991).…”

Section: Discussionmentioning

confidence: 99%

“…The protective effects of lactation may occur because of both hormonal (Petrakis et al, 1987;Russo and Russo, 1994) and nonhormonal mechanisms (Murrell, 1991). It has previously been proposed that hormonal breast cancer risk factors ought to be predominantly associated with tumours that express oestrogen (ER) and progesterone (PR) receptors, and less so with receptor-negative tumours (McTiernan et al, 1986;Stanford et al, 1987;Potter et al, 1995;Enger et al, 2000;Ursin et al, 2002).…”

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confidence: 99%

Reproductive factors and subtypes of breast cancer defined by hormone receptor and histology

et al. 2005

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Reproductive factors are associated with reduced risk of breast cancer, but less is known about whether there is differential protection against subtypes of breast cancer. Assuming reproductive factors act through hormonal mechanisms they should protect predominantly against cancers expressing oestrogen (ER) and progesterone (PR) receptors. We examined the effect of reproductive factors on subgroups of tumours defined by hormone receptor status as well as histology using data from the NIHCD Women's Contraceptive and Reproductive Experiences (CARE) Study, a multicenter case -control study of breast cancer. We estimated odds ratios (ORs) and 95% confidence intervals (CIs) as measures of relative risk using multivariate unconditional logistic regression methods. Multiparity and early age at first birth were associated with reduced relative risk of ER þ PR þ tumours (P for trend ¼ 0.0001 and 0.01, respectively), but not of ERÀPRÀ tumours (P for trend ¼ 0.27 and 0.85), whereas duration of breastfeeding was associated with lower relative risk of both receptor-positive (P for trend ¼ 0.0002) and receptor-negative tumours (P ¼ 0.0004). Our results were consistent across subgroups of women based on age and ethnicity. We found few significant differences by histologic subtype, although the strongest protective effect of multiparity was seen for mixed ductolobular tumours. Our results indicate that parity and age at first birth are associated with reduced risk of receptor-positive tumours only, while lactation is associated with reduced risk of both receptor-positive and -negative tumours. This suggests that parity and lactation act through different mechanisms. This study also suggests that reproductive factors have similar protective effects on breast tumours of lobular and ductal origin.

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Influence of pregnancy and lactation on serum and breast fluid estrogen levels: Implications for breast cancer risk

Cited by 121 publications

References 27 publications

Reproductive risk factors for endometrial cancer among Polish women

Reproductive risk factors for endometrial cancer among Polish women

Breastfeeding and breast cancer risk in India: A multicenter case‐control study

Reproductive factors and subtypes of breast cancer defined by hormone receptor and histology

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