Factors associated with circulating levels of insulin-like growth factor-I and insulin-like growth factor binding protein-3 in 740 women at risk for breast cancer

Fenretinide in Young Women at Genetic or Familial Risk of Breast Cancer: A Placebo-Controlled Biomarker Trial

Fenretinide, a retinoid with a low-toxicity profile that accumulates in the breast, has been shown to prevent second breast cancer in young women. Fenretinide exhibits apoptotic and antiinvasive properties and it improves insulin sensitivity in overweight premenopausal women with insulin resistance. This study aimed to further characterize its role in cancer prevention by measuring circulating biomarkers related to insulin sensitivity and breast cancer risk.Sixty-two women, ages 20 to 46 years, healthy or who had already undergone breast cancer surgery, with a known BRCA1/2 mutation or a likelihood of mutation ≥20% according to the BRCAPRO model, were randomly assigned to receive fenretinide (200 mg/day) or placebo for 5 years (trial registration: EudraCT No. 2009-010260-41). Fasting blood samples were drawn at baseline, 12 and 36 months, and the following biomarkers were analyzed: retinol, leptin, adiponectin, retinol-binding protein 4 (RBP-4), total cholesterol, high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol, triglycerides, glucose, insulin, insulin-like growth factor (IGF-1), IGF-binding protein 3, sex hormone binding globulin (SHBG), testosterone, and vascular endothelial growth factor (VEGF).After 12 months of treatment, we observed a favorable effect of fenretinide on glucose (decrease; P = 0.005), insulin (decrease; P = 0.03), homeostatic model assessment index (decrease; P = 0.004), HDL cholesterol (increase; P = 0.002), even though these effects were less prominent after 36 months. Retinol and retinol-binding protein 4 markedly decreased (P < 0.0001) throughout the study. None of the other measured biomarkers changed.

PREVENTION RELEVANCE

Fenretinide exhibits beneficial effects on the metabolic profile, supporting its clinical use in breast cancer prevention especially in premenopausal women with a positive family history and pathogenic variants in BRCA1/2 genes. This finding requires further investigations in larger trials to confirm its role in breast cancer prevention.

A Phenomic Perspective on Factors Influencing Breast Cancer Treatment: Integrating Aging and Lifestyle in Blood and Tissue Biomarker Profiling

Breast cancer is the most common malignancy among women worldwide. Over the last four decades, diagnostic and therapeutic procedures have improved substantially, giving patients with localized disease a better chance of cure, and those with more advanced cancer, longer periods of disease control and survival. However, understanding and managing heterogeneity in the clinical response exhibited by patients remains a challenge. For some treatments, biomarkers are available to inform therapeutic options, assess pathological response and predict clinical outcomes. Nevertheless, some measurements are not employed universally and lack sensitivity and specificity, which might be influenced by tissue-specific alterations associated with aging and lifestyle. The first part of this article summarizes available and emerging biomarkers for clinical use, such as measurements that can be made in tumor biopsies or blood samples, including so-called liquid biopsies. The second part of this article outlines underappreciated factors that could influence the interpretation of these clinical measurements and affect treatment outcomes. For example, it has been shown that both adiposity and physical activity can modify the characteristics of tumors and surrounding tissues. In addition, evidence shows that inflammaging and immunosenescence interact with treatment and clinical outcomes and could be considered prognostic and predictive factors independently. In summary, changes to blood and tissues that reflect aging and patient characteristics, including lifestyle, are not commonly considered clinically or in research, either for practical reasons or because the supporting evidence base is developing. Thus, an aim of this article is to encourage an integrative phenomic approach in oncology research and clinical management.

Biomarkers of Insulin and the Insulin-Like Growth Factor Axis in Relation to Breast Cancer Risk in Chinese Women

BACKGROUND

The interplay between biomarkers of insulin and the insulin-like growth factor (IGF) axis in the context of breast cancer risk is unclear.

METHODS

We measured the concentrations of insulin, C-peptide, IGF1, and IGF binding protein 3 (IGFBP3) and calculated the homeostasis model assessment of insulin resistance (HOMA-IR) index and the IGF1/IGFBP3 ratio among 2536 patients with breast cancer and 2528 patients with benign breast disease recruited from Ruijin Hospital, Shanghai, China, between 2012 and 2017.

RESULTS

Multivariable-adjusted odds ratios (ORs) for breast cancer associated with the highest quartiles versus the lowest quartiles of insulin and IGF factors were 1.45 (95% CI, 1.20-1.75) for insulin, 1.32 (1.08-1.60) for C-peptide, 1.53 (1.26-1.85) for HOMA-IR, and 1.27 (1.05-1.53) for IGF1; these associations did not differ substantially across stratifications of age, body mass index, age at menarche, or menopausal status (all P for interaction >0.05). In the joint analysis, the highest quartile of IGF1 was associated with the greatest risk of breast cancer in the highest quartiles of insulin (OR, 1.77; 95% CI, 1.29-2.44), C-peptide (1.60; 1.17-2.20), and HOMA-IR (1.90; 1.38-2.62), compared with the risks associated with the combination of the lowest quartiles of IGF1 and each insulin factor. In stratification analysis, the positive association between IGF1 and breast cancer was stronger in the highest quartiles of insulin (P[interaction] = 0.29), C-peptide (P[interaction] = 0.020), and HOMA-IR (P[interaction] = 0.075).

CONCLUSION

Our findings indicate effect modifications of insulin, C-peptide, and insulin resistance on the relationship between IGF1 and breast cancer risk in Chinese women.

Menstrual cycle characteristics and steroid hormone, prolactin, and growth factor levels in premenopausal women

PURPOSE

Menstrual cycle characteristics are markers of endocrine milieu. However, associations between age at menarche and adulthood sex steroid hormone levels have been inconsistent, and data on menstrual characteristics and non-sex steroid hormones are sparse.

METHODS

We assessed the relations of menstrual characteristics with premenopausal plasma sex steroid hormones, sex hormone binding globulin (SHBG), prolactin, and growth factors among 2,745 premenopausal women (age 32-52) from the Nurses' Health Study II. Geometric means and tests for trend were calculated using multivariable general linear models.

RESULTS

Early age at menarche was associated with higher premenopausal early-follicular free estradiol (percent difference < 12 vs. > 13 years = 11%), early-follicular estrone (7%), luteal estrone (7%), and free testosterone (8%) (all p trend < 0.05). Short menstrual cycle length at age 18-22 was associated with higher early-follicular total (< 26 vs. > 39 days = 18%) and free estradiol (16%), early-follicular estrone (9%), SHBG (7%), lower luteal free estradiol (- 14%), total (- 6%), and free testosterone (- 15%) (all p trend < 0.05). Short adult menstrual length was associated with higher early-follicular total estradiol (< 26 vs. > 31 days = 14%), SHBG (10%), lower luteal estrone (- 8%), progesterone (- 9%), total (- 11%) and free testosterone (- 25%), and androstenedione (- 14%) (all p trend < 0.05). Irregularity of menses at 18-22 was associated with lower early-follicular total (irregular vs. very regular = - 14%) and free estradiol (- 14%), and early-follicular estrone (- 8%) (All p trend < 0.05). Irregularity of adult menstrual cycle was associated with lower luteal total estradiol (irregular vs. very regular = - 8%), SHBG (- 3%), higher total (8%), and free testosterone (11%) (all p trend < 0.05).

CONCLUSIONS

Early-life and adulthood menstrual characteristics are moderately associated with mid-to-late reproductive year's hormone concentrations. These relations of menstrual characteristics with endogenous hormone levels could partially account for associations between menstrual characteristics and reproductive cancers or other chronic diseases.

A pooled analysis of CYP2D6 genotype in breast cancer prevention trials of low-dose tamoxifen

Decreased CYP2D6 activity is associated with lower levels of active tamoxifen metabolites. We examined the impact of CYP2D6 genotype on tamoxifen pharmacokinetics, biomarker activity, and efficacy in a pooled analysis of low-dose tamoxifen. Four randomized breast cancer prevention trials of very-low-dose (1 mg/day, n = 52 or 10 mg/week, n = 152) or low-dose tamoxifen (5 mg/day, n = 171) were pooled. DNA from 367 subjects was genotyped for CYP2D6 alleles associated with absent (PM allele: *3, *4, *5, *6, *7, *8, *12, and *14), reduced (IM allele: *9, *10, *17, *29, *41), normal (EM allele), or increased (UM: *XN) enzyme activity. Associations of tamoxifen, metabolites, activity biomarkers, and event-free survival with rapid (UM/EM, UM/IM, EM/EM, EM/IM, or EM/PM alleles) versus slow metabolizers (PM/IM or PM/PM) were investigated through random effects models, with 'study' as the random factor, and Cox regression models, adjusting for confounders. Rapid metabolizers had higher endoxifen levels than slow metabolizers: 15.3 versus 12.2 ng/mL (P = 0.018) with 5 mg/day, and 3.8 versus 2.8 ng/mL (P = 0.004) with 1 mg/day or 10 mg/week tamoxifen. The IGF-I decrease correlated with endoxifen (P = 0.002) and 4-hydroxytamoxifen levels, demonstrating steeper decreases at higher metabolite levels (P = 0.001). After a median follow-up of 12 years, rapid metabolizers with prior history of breast neoplasms allocated to tamoxifen 5 mg/day had a 60 % reduction of risk of recurrences (HR = 0.40, 95 % CI: 0.16-0.99) compared to slow metabolizers. CYP2D6 genotype may have an impact on tamoxifen efficacy at low doses. Trials investigating tamoxifen dose adjustments based on the woman's hormonal context and CYP2D6 genotype are warranted.

Increased Igf-I/Igfbp-3 Ratios in Postmenopausal Taiwanese with Breast Cancer, Irrespective of Er and Pr Statuses and Her2 Expression in a Case-Control Study

BACKGROUND

In most research, there were positive associations between the insulin-like growth factor I (IGF-I) status, including IGF-I, insulin-like growth factor binding protein-3 (IGFBP-3), and ratio of IGF-I/IGFBP-3, and risks of breast cancer (BC), which was influenced by many factors, including hormone statuses and ethnicity. Therefore, the alterations of the IGF-I status in Taiwanese women with BC by menopausal statuses and hormone receptors were investigated.

METHODS

The levels of IGF-I and IGFBP-3 were determined by the enzyme-labeled chemiluminescent immunometric assay, and the protein expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor 2 (HER2) on paraffin-embedded sections of tissues with BC were analyzed by the immunohistochemical method.

RESULTS

The ratios of IGF-I/IGFBP-3 were significantly higher in the women with BC than those in the controls, but not of the levels of IGF-I and IGFBP-3; furthermore, the significantly higher ratios were found only in the postmenopausal status. In addition, there was no significant difference between the IGF-I status and ER and PR statuses, and HER2 expression, respectively, in the women with BC.

CONCLUSIONS

The ratios of IGF-I/IGFBP-3 were increased in postmenopausal Taiwanese women with BC, irrespective of their ages, ER and PR statuses, and HER2 expression.

A comparison of hormonal profiles between breast cancer and benign breast disease: a case-control study

BACKGROUND

Benign breast disease (BBD), particularly proliferative BBD, is an established breast cancer risk factor. However, there has been no systematic attempt to compare the hormonal profiles of the two conditions. In a case-control investigation in Athens, Greece, we compared levels of estrogens, testosterone and insulin-like growth factor-1 (IGF-1), as well as their principal binding proteins, between breast cancer patients, women with BBD by histological type (proliferative and nonproliferative) and women with no breast pathology.

PATIENTS AND METHODS

We studied 466 women with incident breast cancer, 704 women with BBD and 244 healthy women. We used multiple regression to compare log-transformed serum hormone levels of breast cancer patients with those of healthy women and women with BBD by histological type (proliferative and nonproliferative BBD).

RESULTS

The hormonal profile of breast cancer in our study was in line with the generally accepted hormonal profile of this disease, as reported from large cohort studies. Compared with healthy women, breast cancer patients tended to have higher levels of steroid hormones. The evidence was strong for estrone (difference 21.5%, P < 0.001), weaker for testosterone (difference 15.8%, P = 0.07) and weaker still for estradiol (difference 12.0%, P = 0.18). Also compared with healthy women, breast cancer patients had barely higher levels of IGF-1 (difference 2.0%, P = 0.51), but had significantly lower levels of IGF binding protein 3 (IGFBP-3) (difference -6.7%, P = 0.001). Compared with women with BBD, breast cancer patients had nonstatistically significantly lower levels of steroid hormones, but they had higher levels of IGF-1 [difference 5.5%, 95% confidence interval (CI) 0.7% to 10.6%] and lower levels of IGFBP-3 (difference -3.7%, 95% CI -6.7% to -0.7%). Differences were more pronounced when breast cancer patients were contrasted to women with proliferative BBD.

CONCLUSIONS

Our findings suggest that high levels of IGF-1 may be an important factor toward the evolution of BBD to breast cancer.

Plasma IGF-1 and IGFBP-3 may be imprecise surrogates for breast concentrations: an analysis of healthy women

We investigated insulin-like growth factor (IGF)-1 and IGF binding protein (IGFBP)-3 concentrations in histologically normal breast tissues and assessed their association with plasma concentrations, and breast cancer risk factors. IGF-1 and IGFBP-3 were assessed in plasma and breast tissues of 90 women with no history of any cancer and undergoing reduction mammoplasty. Pearson correlations and ANOVAs were used to describe plasma-breast associations and biomarker differences by breast cancer risk factors, respectively. Multivariable regression models were used to determine associations between risk factors, and breast IGF-1 and IGFBP-3. The mean age of the study sample was 37.3 years, 58 % were white, and generally these women were obese (mean BMI = 30.8 kg/m(2)). We observed no plasma-breast correlation for IGF-1, IGFBP-3, or IGF-1/IGFBP-3 (r = -0.08, r = 0.14, and r = 0.03, respectively; p-values >0.05). Through age- and BMI-adjusted analysis, BMI and years of oral contraceptive (OC) use were inversely associated with breast IGF-1 (p-values = 0.02 and 0.003, respectively) and age was associated with breast IGFBP-3 (p = 0.01), while breast IGF-1/IGFBP-3 was higher in blacks than whites (1.08 vs. 0.68, p = 0.04) and associated with age and BMI (p-values = 0.03 and 0.002, respectively). In multivariable-adjusted models, some breast cancer risk factors studied herein explained 24, 10, and 15 % of the variation in breast IGF-1, IGFBP-3, and IGF-1/IGFBP-3, respectively. While reasons for the lack of plasma-breast hormone correlations in these cancer-free women are unknown, several factors were shown to be associated with breast concentrations. The lack of correlation between blood and tissue IGF-1 and IGFBP-3 suggests that studies of breast cancer risk assessing blood IGF-1 and IGFBP-3 may have important limitations in understanding their role in breast carcinogenesis.

The Challenge of Growth Hormone Deficiency Diagnosis and Treatment during the Transition from Puberty into Adulthood

In children with childhood-onset growth hormone deficiency, replacement GH therapy is effective in normalizing height during childhood and achieving adult height within the genetic target range. GH has further beneficial effects on body composition and metabolism through adult life. The transition phase, defined as the period from mid to late teens until 6-7 years after the achievement of final height, represents a crucial time for reassessing children's GH secretion and deciding whether GH therapy should be continued throughout life. Evidence-based guidelines for diagnosis and treatment of growth hormone deficient children during transition are lacking. The aim of this review is to critically review the up-to-date evidence on the best management of transition patients in order to ensure the correct definitive diagnosis and establish the appropriate therapeutic regimen.

Evaluation of the insulin-like growth factors (IGF) IGF-I and IGF binding protein 3 in patients at high risk for breast cancer

Our data suggest that serum concentrations of insulin-like growth factor I and insulin-like growth factor binding protein 3 do not correlate with breast cancer development.

Insulin-like growth factor 1 (IGF1), IGF binding protein 3 (IGFBP3), and breast cancer risk: pooled individual data analysis of 17 prospective studies

BACKGROUND

Insulin-like growth factor 1 (IGF1) stimulates mitosis and inhibits apoptosis. Some published results have shown an association between circulating IGF1 and breast-cancer risk, but it has been unclear whether this relationship is consistent or whether it is modified by IGF binding protein 3 (IGFBP3), menopausal status, oestrogen receptor status or other factors. The relationship of IGF1 (and IGFBP3) with breast-cancer risk factors is also unclear. The Endogenous Hormones and Breast Cancer Collaborative Group was established to analyse pooled individual data from prospective studies to increase the precision of the estimated associations of endogenous hormones with breast-cancer risk.

METHODS

Individual data on prediagnostic IGF1 and IGFBP3 concentrations were obtained from 17 prospective studies in 12 countries. The associations of IGF1 with risk factors for breast cancer in controls were examined by calculating geometric mean concentrations in categories of these factors. The odds ratios (ORs) with 95% CIs of breast cancer associated with increasing IGF1 concentrations were estimated by conditional logistic regression in 4790 cases and 9428 matched controls, with stratification by study, age at baseline, and date of baseline. All statistical tests were two-sided, and a p value of less than 0.05 was considered significant.

FINDINGS

IGF1 concentrations, adjusted for age, were positively associated with height and age at first pregnancy, inversely associated with age at menarche and years since menopause, and were higher in moderately overweight women and moderate alcohol consumers than in other women. The OR for breast cancer for women in the highest versus the lowest fifth of IGF1 concentration was 1.28 (95% CI 1.14-1.44; p<0.0001). This association was not altered by adjusting for IGFBP3, and did not vary significantly by menopausal status at blood collection. The ORs for a difference in IGF1 concentration between the highest and lowest fifth were 1.38 (95% CI 1.14-1.68) for oestrogen-receptor-positive tumours and 0.80 (0.57-1.13) for oestrogen-receptor-negative tumours (p for heterogeneity=0.007).

INTERPRETATION

Circulating IGF1 is positively associated with breast-cancer risk. The association is not substantially modified by IGFBP3, and does not differ markedly by menopausal status, but seems to be confined to oestrogen-receptor-positive tumours.

FUNDING

Cancer Research UK.

Insulin-like growth factor-I (IGF-I) serum concentrations in healthy children and adolescents: relationship to level of contamination by DDT-derivative pesticides

CONTEXT

Serum levels of Insulin-like growth factor I (IGF-I) play a critical role in children growth and in the pathogenesis of several diseases. In addition, recent studies suggest that DDT-derivative organochlorine pesticides (OC-DDTs) could influence IGF levels in human beings.

OBJECTIVE AND DESIGN

Because it has been suggested that IGF-I peak levels at puberty could determine IGF-I levels in adulthood, we developed a cross-sectional study of the potential association between serum levels of OC-DDTs and IGF system in 160 serum samples from young people (81 boys and 79 girls) living in the Canary Islands (Spain).

RESULTS

Multivariate tests were used adjusting for confounding variables (age, height, and weight) and stratifying by gender and age: IGF-I serum levels were significantly lower in pre-pubertal male children (6-15years) who showed detectable values of p,p'-DDE, and p,p'-DDD than in pre-pubertal male children with undetectable levels of these OC-DDTs-metabolites (p=0.023 and p=0.049, respectively). In addition, in this multivariate model, a non-linear dose-response curve was observed between Total DDT body burden (sum of the three DDT-derivatives measured: p,p'-DDT, p,p'-DDE, and p,p'-DDD) and IGF-I in pre-pubertal male children (6-15years; p=0.043).

CONCLUSION

These findings suggest that OC-DDTs could modulate the IGF-system in a way that is highly influenced by gender and age. Improvements in our understanding of exogenous determinants of the IGF-system may provide new insights into the role played by environmental contaminants in IGF-related diseases.

IGF-I and IGFBP-3 polymorphisms in relation to circulating levels among African American and Caucasian women

Circulating insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 (IGFBP-3) levels have been associated with common diseases. Although family-based studies suggest that genetic variation contributes to circulating IGF-I and IGFBP-3 levels, analyses of associations with multiple IGF-I and IGFBP-3 single nucleotide polymorphisms (SNP) have been limited, especially among African Americans. We evaluated 30 IGF-I and 15 IGFBP-3 SNPs and estimated diplotypes in association with plasma IGF-I and IGFBP-3 among 984 premenopausal African American and Caucasian women. In both races, IGFBP-3 rs2854746 (Ala32Gly) was positively associated with plasma IGFBP-3 (CC versus GG mean difference among Caucasians, 631 ng/mL; 95% confidence interval, 398-864; African Americans, 897 ng/mL; 95% confidence interval, 656-1,138), and IGFBP-3 diplotypes with the rs2854746 GG genotype had lower mean IGFBP-3 levels than reference diplotypes with the CG genotype, whereas IGFBP-3 diplotypes with the CC genotype had higher mean IGFBP-3 levels. IGFBP-3 rs2854744 (-202 A/C) was in strong linkage disequilibrium with rs2854746 in Caucasians only, but was associated with plasma IGFBP-3 in both races. Eight additional IGFBP-3 SNPs were associated with >or=5% differences in mean IGFBP-3 levels, with generally consistent associations between races. Twelve IGF-I SNPs were associated with >or=10% differences in mean IGF-I levels, but associations were generally discordant between races. Diplotype associations with plasma IGF-I did not parallel IGF-I SNP associations. Our study supports that common IGFBP-3 SNPs, especially rs2854746, influence plasma IGFBP-3 levels among African Americans and Caucasians but provides less evidence that IGF-I SNPs affect plasma IGF-I levels.

Circulating Insulin-Like Growth Factor-I and Binding Protein-3 and the Risk of Breast Cancer

Four meta-analyses and literature reviews have concluded that a positive association exists between circulating levels of insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 (IGFBP-3) and breast cancer risk for premenopausal but not postmenopausal women. Recently, a large prospective study reported an association with IGF-I and IGFBP-3 concentration for breast cancer diagnosed after, but not before, the age of 50 years; and in a large cohort of primarily premenopausal women, IGF-I and IGFBP-3 were not associated with breast cancer risk. We did a case-cohort study within the Melbourne Collaborative Cohort Study, which included a random sample of 1,901 women (subcohort) and 423 breast cancer cases diagnosed during a mean of 9.1 years of follow-up. IGF-I and IGFBP-3 concentrations were measured in plasma collected at baseline. The association between quartiles of IGF concentration and breast cancer risk was tested using a Cox model adjusted for known and potential confounders. The hazard ratio (HR) for breast cancer comparing the fourth with the first quartiles was 1.20 [95% confidence interval (95% CI), 0.87-1.65] for IGF-I and 1.09 (95% CI, 0.78-1.53) for IGFBP-3. Both associations varied with age: for IGF-I, the HRs for breast cancer comparing the fourth with the first quartiles were 0.60 (95% CI, 0.25-1.45) before age 50 and 1.61 (95% CI, 1.04-2.51) after age 60 (test for the log-linear trend of HR according to age, P = 0.05); for IGFBP-3, the HRs were 0.79 (95% CI, 0.34-1.83) before age 50 and 1.62 (95% CI, 1.03-2.55) after age 60 (test for log-linear trend, P = 0.08). IGF-I and IGFBP-3 were positively associated with breast cancer risk in older women but not in younger women. More prospective studies are needed to clarify the age dependence of the association between IGF-I and IGFBP-3 and breast cancer.

Insulin-like growth factor-I, insulin-like growth factor binding protein-3 and the risk of fibrocystic breast conditions among Chinese women

We investigated whether circulating insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding protein-3 (IGFBP-3) levels are associated with the risk of fibrocystic breast conditions (FBC), in a case-control study nested within a randomized trial of breast self-examination conducted in Shanghai, China. Participants were enrolled during 1989-1991 and were followed over 10 years for the development of breast diseases. Controls (n = 897) were frequency-matched by age to cases (n = 451), who were diagnosed with FBC between 1995 and 2000. Circulating IGF-I and IGFBP-3 levels and their molar ratio were positively associated with risk of FBC. The odds ratios (ORs) and 95% confidence intervals (CI) for the upper fourth of the distribution compared to the lowest fourth for IGF-I, IGFBP3 and their molar ratio were 3.02 (2.02-4.52), 1.92 (1.37-2.71) and 2.26 (1.52-3.36), respectively. The strength of the association between IGF-I levels and FBC was attenuated after adjustment for IGFBP-3 and that for IGFBP-3 was largely eliminated after adjustment for IGF-I. Increasing levels of IGF-I were particularly associated with increasing risk of FBC with proliferative elements (ORs and 95% CIs for the 2nd, 3rd and upper fourth of the distribution of IGF-I: 3.13 (1.50-6.53), 4.57 (2.22-9.39) and 6.30 (3.08-12.89), compared with the lowest fourth. Our results suggest that elevated levels of IGF-I may contribute to the development of FBC.

SERMs in chemoprevention of breast cancer

Selective estrogen receptor modulators (SERMs) play a key role in breast cancer chemoprevention. Tamoxifen has been shown to reduce breast cancer incidence by 30-40% in at-risk subjects in large phase III trials. However, toxicity may be a limiting factor. Thus, different strategies are being pursued to improve the risk: benefit ratio of using these compounds in chemoprevention. Firstly, the second generation SERM raloxifene is currently undergoing evaluation in comparison with tamoxifen in a large phase III trial. Also, lower doses of tamoxifen are being assessed in phase II-III trials. In addition, the combination of hormone replacement therapy (HRT) or aromatase inhibitors and tamoxifen at low doses may reduce the risks while retaining the benefits of either agents. Finally, new agents that interfere with the onset of ER-negative breast cancer are being sought for combination chemoprevention since almost a third of breast cancers will not be sensitive to hormonal modulation.