Lactation and the risk of breast cancer

Some factors are suggested to have an association with an increased risk of breast cancer, which are called risk factors. Lactation is one of the risk factors that still needs to be studied because of conflicting findings in epidemiological studies and also uncertainty regarding biologic plausibility. Our objective was to study the relationship between lactation and the risk of breast cancer. A pair of unmatched case control studies was held among parous women at Dr. Soetomo Hospital (general hospital) and some private hospitals in the Surabaya municipality. There are 219 (51.9%) cases and 203 (48.1%) controls analyzed in this study. Age, age at menarche, regular menstruation and number of parity between both groups are not statistical different. When we divided the age at menarche (below 13), it was statistically different. The cases consisted of more women with menarche below 13 (p = 0.00038). Other factors showing statistical differences in the risk of breast cancer between case and control are age at first delivery, family history of breast cancer and age at menopause. Women who have lactated (more than 4-month duration of breast feeding) show a "protective effect" against breast cancer, OR 0.57 (95% CI 0.33-0.99). However, there was no clear duration of lactation and the risk of breast cancer. Logistic regression analysis showed that lactation was not any independent factor. Lactation exerts a "protective effect" against breast cancer. However, the duration of lactation did not show an influence in reducing the risk of breast cancer, and logistic regression analysis did not show that lactation was an independent factor in the risk of breast cancer.     

Pelvic radiotherapy,sex hormones,and breast cancer

Radiotherapy for malignant and benign gynecologic disease in middle age has been found to be associated inversely with the risk of breast cancer in several published studies. The ovaries received substantial doses of radiation from such treatments, in the tens of Gray (Gy) from radiotherapy for cervical cancer and one to 10 Gy from radiotherapy for benign gynecologic disease (BGD). The relative risk of breast cancer incidence or mortality decreased with increasing radiation dose to the ovaries between zero to six Gy but varied little with further increases in dose. Evidence of a protective effect even among women irradiated past the age of 50 suggests a mechanism other than that associated with induction of an early menopause. An inverse association with radiotherapy among women over age 50 was seen only for women with ovarian doses exceeding about four to five Gy, namely, those treated for cervical cancer or with external beam X-rays for BGD. Ovarian doses of two to three Gy from intrauterine radium (²²⁶Ra) treatments for BGD were not associated with an appreciably reduced risk of breast cancer, even though the treatments has the intended effect of inducing menopause in women in their mid-40s. The relevant target cells in the ovaries for radiologic menopause likely are those involved in estrogen production. Although the postmenopausal ovary has largely stopped producing estrogens, it continues to secrete androgens. Serum hormone measurements on a small sample of cervical cancer patients indicate that high-dose pelvic radiotherapy eliminates or greatly reduces this residual androgen-producing activity in ovaries of postmenopausal women. Taken together, these observations point to possible differential sensitivity to radiation inactivation of cells in the ovary that produces estrogens and androgens, respectively, and to the possible importance of continued androgen production by the postmenopausal ovary in the etiology or progression of breast cancer.     

Lactation after breast conserving therapy, including radiation therapy, for early breast cancer

Two patients who underwent breast conservation including radiotherapy for early breast carcinoma are described and who subsequently delivered healthy newborn infants. One of the two patients lactated from both the irradiated and the non-irradiated breast; whereas the other patient did not lactate from the irradiated side. The treatment and implications are discussed.     

Lactation following conservation surgery and radiotherapy for breast cancer

A 38-year-old woman with early stage invasive breast cancer was treated with wide excision of the tumor, axillary lymph node dissection, and breast irradiation. Three years later, she gave birth to a normal baby. She attempted breast feeding and had full lactation from the untreated breast. The irradiated breast underwent only minor changes during pregnancy and postpartum but produced small amounts of colostrum and milk for 2 weeks postpartum. There are only a few reports of lactation after breast irradiation. These cases are reviewed, and possible factors affecting breast function after radiotherapy are discussed. Because of scant information available regarding its safety for the infant, nursing from the irradiated breast is not recommended.     

Endogenous sex hormones, prolactin, and breast cancer in premenopausal women

Forty-one women with breast cancer and 119 controls participated in a case-control study of the relation of endogenous sex hormones to breast carcinoma in premenopausal women. During the follicular phase of the menstrual cycle, one overnight urine specimen was collected. During the luteal phase, urine and blood specimens were obtained. 17 beta-Estradiol, sex hormone-binding globulin, progesterone, and prolactin were measured in plasma, whereas estrogen metabolites (estrone, estradiol, and estriol) and pregnanediol were assessed in the urine. Breast cancer was associated with high-plasma estradiol and prolactin and with low progesterone. Similar but weaker associations were observed for urinary estrogens and pregnanediol in the luteal phase.     

Lactation and the risk of breast cancer in an Italian population

The relation between breast feeding and breast cancer was investigated in a multicentric case-control study conducted in Italy on 2,167 parous women with histologically confirmed breast cancer, diagnosed within 1 year, and 2,208 parous control women admitted to hospitals in the same catchment areas of cases for acute, non-neoplastic, non-gynecological non-hormone-related diseases. Compared with women who had never tried to lactate, those who had always failed had a multivariate odds ratio (OR; adjusted for parity, education and several other potential confounding factors) of 0.94, and those who had lactated had an OR of 1.17. The multivariate ORs of women who had breast fed 1, 2 and 3 or more children were, respectively, 1.14, 1.18 and 1.32, compared with women who had never lactated. None of these ORs was statistically significant. Compared with women who had never breast fed, the multivariate ORs were 1.19 for women reporting less than 6 months of breast feeding, 1.15 for 6–11 months, 1.34 for 12–17 months, 1.10 for 18–23 months and 0.86 for 24 months or more. No appreciable difference was evident across strata of age, menopausal status, parity and age at first birth, while there was a hint of interaction with education. Our study therefore excluded any appreciable protective role for lactation in breast cancer risk, with the patterns of lactation in this European population, aside from the protective role of parity on breast carcinogenesis. © 1996 Wiley-Liss, Inc.     

Lactation and breast cancer risk: a case-control study in Connecticut

In this report, we examined the relationship between lactation and breast cancer risk, in a case-control study of breast cancer, conducted in Connecticut between 1994 and 1998. Included were 608 incident breast cancer cases and 609 age frequency matched controls, aged 30-80 years old. Cases and controls were interviewed by trained study interviewers, using a standardized, structured questionnaire, to obtain information on lactation and other major risk factors. Parous women who reported ever lactation had a borderline significantly reduced risk of breast cancer (OR = 0.83, 95% CI, 0.63-1.09). An OR of 0.53 (95% CI, 0.27-1.04) was observed in those having breastfed more than 3 children compared to those who never lactated. Women having breastfed their first child for more than 13 months had an OR of 0.47 (95% CI, 0.23-0.94) compared to those who never breastfed. Lifetime duration of lactation also showed a risk reduction while none of the ORs were statistically significant. Further stratification by menopausal status showed a risk reduction related to lactation for both pre- and postmenopausal women, while the relationship is less consistent for the latter. These results support an inverse association between breastfeeding and breast cancer risk.     

Socioeconomic status, lactation and breast cancer risk of parous women in Taiwan

The objective of this study was to evaluate effects of socioeconomic status and lactation on breast cancer of parous women in Taiwan. A total of 102 parous incident cases of female breast cancer in Taipei City were recruited from National Cancer Registry. Another 102 community parous controls individually matched with each case on residential area and age (within five years) were randomly selected from household registration profiles. Socioeconomic status including ethnic group, schooling years, family income, and religion, reproductive risk factors, lactation and body size risk factors for breast cancer were collected from a structured questionnaire interview. Conditional logistic regression was used to estimate the multivariate-adjusted odds ratio of each risk factor. Family income was positively and significantly associated with breast cancer, showing a significant dose-response trend. High parity above three showed a significant protective effect. There was a prominent protective effect from breast feeding. The longer the duration, the smaller the risk of breast cancer. The protective effect of breast feeding was significant only in women who had more than three deliveries.     

Obesity, body fat distribution, and sex hormones in breast cancer patients

This study addresses the relationship between female sex hormones, obesity, body fat distribution, and breast cancer. Increasing obesity correlated with a progressive fall in sex hormone-binding globulin (SHBG) level and an increase in testosterone level. Premenopausal breast cancer patients were found to have significantly lower levels of SHBG compared with age-matched and weight-matched controls. This difference in SHBG level was not noted in postmenopausal breast cancer patients. The SHBG level decreased with increasing upper body fat localization in breast cancer patients and controls. This effect was more marked in breast cancer patients which may explain our earlier finding that women with upper body fat localization are at increased risk for developing breast cancer.     

Nutrition, hormones, and breast cancer: Is insulin the missing link?

Breast cancer incidence rates are high in societies with a Western lifestyle characterized by low levels of physical activity, and by an energy-dense diet rich in total and saturated fat and refined carbohydrates. Epidemiologic studies, so far mostly on postmenopausal women, have shown that breast cancer risk is increased in hyperandrogenic women, with decreased levels of plasma sex-hormone binding globulin, and with increased levels of testosterone and of free estrogens. This paper describes the role of hyperinsulinemia as a physiologic link between nutritional lifestyle factors, obesity, and the development of a hyperandrogenic endocrine profile, and reviews evidence that may or may not support the theory that chronic hyperinsulinemia is an underlying cause of breast cancer. An hypothesis is presented, stipulating that breast cancer risk is increased not only in hyperandrogenic postmenopausal women, but also in premenopausal women with mild hyperandrogenism and normal (ovulatory) menstrual cycles. The author suggests further investigation as to whether there is a positive association between risk of breast cancer before menopause and subclinical forms of the polycystic ovary syndrome (PCOS), and to what extent diet and physical activity during childhood, by modulating the degree of insulin resistance during adolescence, may or may not be determinants of a PCO-like hyperandrogenic endocrine profile persisting into adulthood.Dr Kaaks is with the International Agency for Research on Cancer, Lyon, France. Address correspondence to Dr Kaaks, International Agency for Research on Cancer, 150 cours Albert-Thomas, 69372 Lyon Cedex 08, France.     

妊娠哺乳期乳腺癌20例临床分析

目的探讨妊娠哺乳期乳腺癌的临床特征和治疗方法。方法分析我院妊娠哺乳期乳腺癌20例,妊娠期乳腺癌8例,哺乳期12例;其中Ⅰ期1例,Ⅱ期9例,Ⅲ期8例,Ⅳ期2例。并与同期非妊娠哺乳期乳腺癌患者在诊断、TNM分期、治疗方法、5年生存率等方面相比较。结果妊娠哺乳期乳腺癌5年总生存率70.0%(14/20),比同期非妊娠哺乳期乳腺癌5年总生存率76.4%(1074/1405)低,但无统计学意义。结论妊娠哺乳期乳腺癌的治疗预后与非妊娠哺乳期乳腺癌患者相同,妊娠因素不能改变生存率。     

A case-control study of lactation and cancer of the breast.

We have examined the relation of lactation, by total duration, with breast cancer risk among pre- and post-menopausal women. In a hospital-based case-control study conducted in Athens (1989-91), involving 820 patients with confirmed breast cancer and 795 orthopaedic patient controls and 753 hospital visitor controls, logistic regression was used to analyse the data controlling for demographic, nutritional and reproductive factors, including parity and age at any birth. Among post-menopausal women, there was no association between breastfeeding and breast cancer risk, but among premenopausal women those who has breastfed for > or = 24 months had an odds ratio of 0.50 (95% confidence interval 0.23-1.41). A reduction of the odds ration was also evident among premenopausal women who had breastfed between 12 and 23 months (odds ratio 0.70; 95% confidence interval 0.34-1.60). In conjunction with several other recent reports these results support the hypothesis that breastfeeding of prolonged duration may reduce the risk of breast cancer among premenopausal women but not among post-menopausal women. The biology underlying this different effect remains unknown, and the practical implication of the finding is a marginal importance.