Insulin resistance and breast-cancer risk.

Life-style has a major influence on the incidence of breast cancer. To evaluate the effects of life-style related metabolic-endocrine factors on breast cancer risk we conducted a case-control study comparing 223 women aged 38 to 75 years presenting with operable (stage I or II) breast cancer and 441 women of the same age having no breast cancer, who participated in a population-based breast cancer screening program. Women reporting diabetes mellitus were excluded. Sera from 110 women of the same age group presenting with early stage melanoma, lymphoma or cervical cancer were used as a second 'other-cancer control group'. Serum levels of C-peptide were significantly higher in early breast cancer cases compared to controls. The same was found for the ratios C-peptide to glucose or C-peptide to fructosamine, indicating insulin resistance. Sex hormone binding globulin was inversely, triglycerides and available estradiol were positively related to C-peptide. Serum C-peptide levels were related to body mass index (BMI), and to waist/hip ratio (WHR), in particular in controls. However, the relative increase of C-peptide, C-peptide to glucose or C-peptide to fructosamine in cases was independent of BMI or WHR. The log relative risk was linearly related to the log C-peptide levels. Relative risk according to quintiles, and adjusted for age, family history, BMI and WHR, for women at the 80% level was 2.9 as compared with those at the 20% level for C-peptide. Elevated C-peptide or C-peptide to fructosamine values were not observed in the sera from women belonging to the 'other-cancer control group'. This study suggests that hyperinsulinemia with insulin resistance is a significant risk factor for breast cancer independent of general adiposity or body fat distribution.

Body measurements, estrogen availability and the risk of human breast cancer: a case-control study.

Recent studies on lifestyle-related mechanisms involved in cardiovascular risk offer important clues for a better understanding of breast-cancer epidemiology. Central body-fat distribution promoted by an affluent dietary intake and a sedentary lifestyle over many years is related to elevated serum triglycerides and free fatty acids, with lower levels of sex-hormone-binding globulin (SHBG). The resulting greater availability of estradiol not bound to SHBG could help to explain the high breast-cancer incidence in Western industrialized countries. We conducted a case-control study comparing 225 women aged 38 to 75 years with operable (stage I or II) breast cancer and 441 women of the same age having no breast cancer who participated in a population-based breast-cancer screening program. Body fatness, as measured by body mass index (BMI), fat distribution as measured by waist-to-hip girth ratio (WHR), body height, serum lipids, SHBG and the available fraction of estradiol were analyzed in a conditional logistic regression, together with family history for breast cancer, reproductive history and smoking. Post-menopausal cases showed no difference in body fatness (BMI), but a significant preponderance of central adiposity (WHR). In contrast, pre-menopausal cases were significantly leaner, but had a similar body-fat distribution as compared with controls. In all women, WHR, and less strongly BMI, was positively correlated with serum levels of triglycerides and available estradiol fractions. An independent, positive linear correlation between body height and relative risk (RR) was observed. Moreover, a significant correlation between SHBG and menarcheal age was seen in cases, but not in controls. These data support our hypothesis that lifestyle relates to breast-cancer risk by metabolic-endocrine mechanisms which modulate the availability of individual sex-steroid concentrations in plasma. The findings of height as a risk factor and adult SHBG levels being correlated with menarcheal age suggest that lifestyle factors promoting breast-cancer development already act around puberty. The leanness of pre-menopausal cases awaits further explanation.

Bone mineral density after adjuvant chemotherapy for premenopausal breast cancer.

Lumbar bone mineral density (BMD) determination by dual photon absorptiometry was used to study the influence of adjuvant chemotherapy for premenopausal breast cancer on the risk of premature osteoporosis. Six cycles of combination chemotherapy caused ovarian failure in 31 of 44 (71%) women, amenorrhoea mostly already beginning during treatment. In contrast, only seven of 44 (16%) women, who were pair-matched for age and year of breast cancer surgery and had not been treated with chemotherapy, were post-menopausal at the time of measurement. The mean interval after breast surgery was 3.5 years. The significantly decreased BMD in the treated group (1.17 compared to 1.29 g cm-2) could only be explained by the high incidence of menopause in these women, which on average occurred 10 years prematurely. Extrapolation of these findings suggests that adjuvant chemotherapy may precipitate osteoporotic fractures by some 10 years in a considerable proportion of women cured of premenopausal breast cancer.

Low dose aminoglutethimide without hydrocortisone for the treatment of advanced postmenopausal breast cancer.

One hundred and one postmenopausal patients with advanced breast cancer were enrolled in a randomized phase II clinical trial to investigate the clinical and hormonal response to aminoglutethimide administered at daily doses of 2 x 125 mg, 3 x 125 mg or 2 x 250 mg, with no addition of hydrocortisone. Among 71 evaluable patients 25% showed objective tumor response (three complete, 15 partial), at all three dose levels and irrespective of the major tumor site. Previous treatment with Tamoxifen had been successful in 75%. Out of the 18 responding patients 10 had estrogen receptor positive, four had estrogen receptor negative tumors; the receptor status was unknown in four other patients. Progression-free interval was more than 700 days in 50% of the responders. Drowsiness caused early drug withdrawal in one patient. Side-effects were very mild, comparing favorably with standard therapy of 250 mg aminoglutethimide q.i.d. plus hydrocortisone. Plasma estrogen levels were reduced by all doses to the same 50% or less as in patients on standard treatment. In nine out of 27 patients a further decrease of estrone levels could be monitored with clinically improved results in five. Plasma cortisol and mineralocorticoids remained normal throughout more than 6 months. The original role of hydrocortisone administration to suppress a reflex rise of ATH in 'medical adrenalectomy' with standard dose aminoglutethimide is no longer tenable. Further phase III comparative clinical results pending, low dose aminoglutethimide as an aromatase inhibitor may at present be considered as an appropriate second-line endocrine treatment with low toxicity and expense.

Tamoxifen, serum lipoproteins and cardiovascular risk.

The influence of tamoxifen on plasma lipids and lipoproteins was monitored in 46 postmenopausal and 8 premenopausal women treated for advanced breast cancer up till 6 months. Total cholesterol (total-C) did not significantly change. However, high density lipoprotein cholesterol (HDL-C) and the HDL-C/total-C ratio rose significantly. Low density lipoprotein cholesterol was significantly decreased. Triglycerides and free fatty acids did not change markedly. The concomitant rise of sex hormone binding globulin and thyroxine binding globulin indicates that the increase of HDL-C with prolonged use of tamoxifen is compatible with an intrinsic oestrogenic effect of tamoxifen on the liver. The increased HDL-C/total-C ratio lends no support to the concern that long-term administration of this anti-oestrogenic drug might lead to an increased cardiovascular risk.

Why is breast cancer so frequent in The Netherlands?

The very high incidence rate of breast cancer in The Netherlands, and in other Western industrialized countries, has to be explained by promoting environmental factors. The possible contributions by hormones and nutrition are reviewed. It is concluded that the promotion of breast cancer is likely to occur during breast development and several subsequent decades. A hypothesis is discussed which could explain how the affluent Western diet, a relative lack of physical activity and possibly also an overall increase of stress lead to a greater bio-availability of oestrogens at normal plasma concentrations. In this model the decrease of sex hormone binding globulin and a change of the binding equilibrium between oestrogens and plasma proteins in the presence of free fatty acids are central. Intra-abdominal fat accumulation, or frank central obesity, would favour this mechanism. Leads to further investigation and preliminary results are presented.

Comparison of circulating MAM-6 and CEA levels and correlation with the estrogen receptor in patients with breast cancer.

MAM-6 and CEA serum levels of 136 staged breast cancer patients were determined concomitantly. The sensitivities of the MAM-6 assay using monoclonal antibody (MAb) 115D8 and a polyclonal CEA assay were equally low and only a limited number of patients with early stages of breast cancer showed elevated antigen levels. However, the sensitivity rose to 75% for MAM-6 and to 60% for CEA in stage-IV patients. The levels of both antigens correlated well in the sera of these patients, although MAM-6 serum levels were elevated more frequently, while only in a few cases were MAM-6-negative sera CEA-positive. A group of stage-II breast cancer patients who eventually developed distant metastases was followed in a longitudinal study. Tumor progression or regression was clinically determined and compared with the MAM-6 and CEA serum levels in order to establish the value of each assay for the monitoring of breast cancer. The course of the disease correlated significantly better with changes in MAM-6 antigen levels than with changes in CEA levels (p less than 0.05), being 79% and 42% respectively. The lower correlation of CEA levels with the course of the disease was mainly due to a lower sensitivity of the CEA assay for advanced breast cancer. The specificity of changing MAM-6 and CEA levels was not significantly different. The main advantage of the MAM-6 assay over the CEA assay is the higher sensitivity of the former. In a preliminary study among stage-IV patients a correlation was found between elevated MAM-6 levels and the presence of the estrogen receptor in the primary tumor.

MAM-6 antigen, a new serum marker for breast cancer monitoring.

Almost all carcinomas contain a cell surface antigen, MAM-6, which has been defined by several monoclonal antibodies, including 115D8 (Hilkens et al., Int. J. Cancer, 34: 197-206, 1984). A quantitative sandwich radioimmunoassay, using 115D8 as catcher and as tracer antibody, has been developed to detect MAM-6 in serum. To quantitate the MAM-6 level, pooled human milk was used as a standard, and arbitrary units were chosen. Less than 5% of the sera of apparently healthy individuals contained more than 5 units/ml. In sera of patients with benign breast lesions, the same low levels were detected. However, concentrations over 5 units/ml were found in 24, 21, 43, and 79% of the sera of patients with pathological Stages I, II, III, and IV breast cancer, respectively. MAM-6 levels were also increased in almost all sera tested from patients with advanced stages of ovarian carcinoma, but in a low percentage of sera from patients with other advanced cancers. A longitudinal study was carried out to test the MAM-6 assay as clinical marker to monitor the therapeutic response of breast cancer. Increasing or decreasing MAM-6 serum levels correlated in 93% of the cases with breast cancer progression or regression, indicating that the assay can be used to monitor the course of the disease during therapy. In some breast cancer patients, elevated MAM-6 levels were observed prior to any clinical indication of tumor recurrence.

Primary hypothyroidism in breast cancer patients with irradiated supraclavicular lymph nodes.

Since the treatment of postmenopausal breast cancer patients with aminoglutethimide caused hypothyroidism with an unexpectedly high frequency previous treatment was suspected to contribute to hypofunction of the thyroid. Serum thyrotropin, triiodothyronine and free thyroxine index were compared between breast cancer patients who had undergone irradiation of regional lymph nodes and non-irradiated breast cancer patients, as well as patients having endometrial or colorectal carcinoma. Subclinical and clinical primary hypothyroidism was significantly more frequent in breast cancer patients who had previously received irradiation on supraclavicular lymph nodes comprising a minor part of the thyroid. Testing for the presence of autoantibodies against thyroid tissue components gave no evidence for radiation-induced autoimmune thyroiditis. Drugs suppressing thyroid hormone synthesis like aminoglutethimide may frequently cause myxedema in such irradiated women, especially at postmenopausal age.

Influence of ACTH on aminoglutethimide induced reduction of plasma steroids in postmenopausal breast cancer.

In postmenopausal women estrogens are mainly produced by aromatase mediated conversion of adrenal 4-ene-steroids in peripheral tissue, a process which is inhibited by aminoglutethimide (AG). To assess possible fluctuations in adrenocortical steroid secretion and the impact on plasma estrogen levels the effect of physiological ACTH doses was studied in 24 postmenopausal women with advanced breast cancer treated with AG 4 X 250 mg and hydrocortisone 2 X 10 + 1 X 20 mg daily. Synthetic 1-24 ACTH (Synacthen) 0.5 mg was injected i.m. at 8.30 a.m. (t0), 10 h after the last AG + hydrocortisone dose. A definite decrease of t0 levels of the 5-ene-steroids dehydroepiandrosterone and its sulphate, and androstenediol was found at 1 month, with no further decrease at 2 months. 5-Ene-steroids responded decreasingly to ACTH under treatment. The 4-ene-steroids progesterone, androstenedione and testosterone, before and after ACTH were not suppressed by 1 or 2 months of treatment. Basal (t0) cortisol remained normal. Cortisol response to ACTH (delta max) was drastically diminished, but still present. Plasma estrogens were decreased. Estradiol (E2) at t0, being low from the start, fell by 50%. Estrone (E1) at t0 dropped to 30%. ACTH had measurable influence on E2, but did cause a transient increase of E1 (mean delta max 40% of baseline value) under treatment. The following conclusions are drawn: Treatment with AG + hydrocortisone for postmenopausal breast cancer reduces plasma estrogens, particularly E1. Plasma E1 reduction is not stable as demonstrated by the response to a physiological ACTH dose. The responses of 4-ene-steroids to ACTH are not affected by treatment, except for the response of cortisol which is significantly diminished.

Pros and cons of aminoglutethimide for advanced postmenopausal breast cancer.

In a phase II clinical trial, 38 postmenopausal women with advanced breast cancer were treated with aminoglutethimide and replacement hydrocortisone. All women had previously received up to 4 modalities of endocrine therapy. Seventeen patients had also been treated with cytostatic drugs. Twenty-five percent of the 29 evaluable patients experienced objective tumor regression, lasting from 11 to more than 18 months. In 29% the disease was stabilized for 3 to more than 15 months. Toxicity was significant, necessitating drug withdrawal in 3 patients. One patient died within 3 weeks of therapy from multiple perforated gastric ulcers. Two patients developed herpes zoster within 4 weeks of treatment. Many side effects were minor and transient. However, treatment resulted in overt primary hypothyroidism in 25% of the evaluable patients and in a strongly increased need of acenocoumarin in all 3 patients on anticoagulant therapy.

Plasma prolactin and its relationship to risk factors in human breast cancer.

The prolactin concentration has been determined in plasma from ostensibly healthy women living on the Island of Guernsey. There were 102, 42, and 41 women who had a mother, sister or maternal aunt, respectively, with breast cancer. The remaining 184 women in this study claimed to have no known family history of breast cancer and were used as a control group. The increased risk of breast cancer due to family history was not associated with a raised mean prolactin level compared to the control group. However, in the luteal phase of the menstrual cycle, daughters of breast cancer patients had significantly raised levels of prolactin at 19.00 h. There were no abnormalities in the mean plasma prolactin levels for the above groups associated with differences in age at first child, age at menarche, interval between age at menarche and first child, and body weight of post-menopausal women. (All these factors have been reported to influence breast cancer risk). It is concluded that prolactin has no obvious function in the aetiology of breast cancer. If it is involved, the mechanism by which it acts must be subtle and concerned with the homeostatic control governing nycthemeral prolactin rhythms.