Role of Coactivators and Corepressors in Steroid and Nuclear Receptor Signaling: Potential Markers of Tumor Growth and Drug Sensitivity

Nuclear receptors regulate target gene expression in response to steroid and thyroid hormones, retinoids, vitamin D and other ligands. These ligand-dependent transcription factors function by contacting various nuclear cooperating proteins, called coactivators and corepressors, which mediate local chromatin remodeling as well as communication with the basal transcriptional apparatus. Nuclear receptors and their coregulatory proteins play a role in cancer and other diseases, one leading example being the estrogen receptor pathway in breast cancer. Coregulators are often present in limiting amounts in cell nuclei and modifications of their level of expression and/or structure lead to alterations in nuclear receptor functioning, which may be as pronounced as a complete inversion of signaling, i.e. from stimulating to repressing certain genes in response to an identical stimulus. In addition, hemizygous knock-out of certain coactivator genes has been demonstrated to produce cancer-prone phenotypes in mice. Thus, assessment of coactivator and corepressor expression and structure in tumors may turn out to be essential to determine the role of nuclear receptors in cancer and to predict prognosis and response to therapy.

DNA Chips: The Future of Biomarkers

DNA chips are small, solid supports such as microscope slides onto which thousands of cDNAs or oligonucleotides are arrayed, representing known genes or simply EST clones, or covering the entire sequence of a gene with all its possible mutations. Fluorescently labeled DNA or RNA extracted from tissues is hybridized to the array. Laser scanning of the chip permits quantitative evaluation of each individual complementary sequence present in the sample.

DNA chip technology is currently being proposed for qualitative and quantitative applications, firstly for the detection of point mutations, small deletions and insertions in genes involved in human diseases or affected during cancer progression; secondly, to determine on a genome-wide basis the pattern of gene expression in tumors, as well as in a number of experimental situations.

The extraordinary power of DNA chips will have a strong impact on medicine in the near future, both in the molecular characterization of tumors and genetic diseases and in drug discovery and evaluation. Quantitative applications will soon spread through all fields of biology.

Laparoscopic surgery in the treatment of stage I adult granulosa cells tumors of the ovary: Results from the MITO-9 study

OBJECTIVE

Surgery represents the mainstay of treatment of stage I adult type granulosa cell tumors of the ovary (AGCTs). Because of the rarity and indolent course of the disease, no prospective trials are available. Open surgery has long been considered the traditional approach; oncological safety of laparoscopy is only supported by small series or case reports. The aim of this study was to compare the oncological outcomes between laparoscopic and open surgery in stage I AGCTs treated within the MITO (Multicenter Italian Trials in Ovarian cancer) Group.

METHODS

Data from patients with stage I AGCTs were retrospectively collected. Clinicopathological features were evaluated for association with relapse and death. Survival curves were calculated using the Kaplan-Meier method and compared with the log-rank test. The role of clinicopathological variables as prognostic factors for survival was evaluated using Cox's regression model.

RESULTS

223 patients were identified. Stage 1A, 1B and 1C were 61.5%, 1.3% and 29.6% respectively. 7.6% were apparently stage I. Surgical approach was laparoscopic for 93 patients (41.7%) and open for 130 (58.3%). 5-years DFS was 84% and 82%, 10-years DFS was 68% and 64% for the laparoscopic and open-group (p = 0.6).5-years OS was 100% and 99%, 10 years OS was 98% and 97% for the laparoscopic and open-surgery group (p = 0.8). At multivariate analyses stage IC, incomplete staging, site of primary surgery retained significant prognostic value.

CONCLUSION

The present study suggests that surgical route does not affect the oncological safety of patients with stage I AGCTs, with comparable outcomes between laparoscopic and open approach.

Abstract P5-07-03: Withdrawn

This abstract was withdrawn by the authors.

Quantitative Real-Time RT-PCR Analysis of Eight Novel Estrogen-Regulated Genes in Breast Cancer

Background

Biological markers capable of predicting the risk of recurrence and the response to treatment in breast cancer are eagerly awaited. Estrogen and progesterone receptors (ER, PgR) in tumor cells mark cancers that are more likely to respond to endocrine treatment, but up to 40% of such patients do not respond. Here, the expression of a group of estrogen-regulated genes, previously identified by microarray analysis of in vitro models, was measured in breast tumors and possible associations with other clinicopathological variables were investigated.

Methods

The expression of CD24, CD44, HAT-1, BAK-1, G1P3, TIEG, NRP-1 and RXRα was measured by quantitative real-time RT-PCR on RNA from eighteen primary breast tumors. Statistical analyses were used to identify correlations among the eight genes and the available clinicopathological data.

Results

Variable expression levels of all the genes were observed in all the samples examined. Significant associations of CD24 with tumor size, CD44 with lymph node invasion, and HAT-1 and BAK-1 with ER positivity were found. The possible combinatorial value of these genes was assessed. Unsupervised hierarchical clustering analysis demonstrated that the expression profile of these genes was able to predict ER status with an acceptable approximation.

Conclusions

Eight novel potential markers for breast cancer have been preliminarily characterized. As expected from in vitro data, their expression is able to discriminate ER- versus ER+ tumors.

Fractional CO2 laser therapy: a new challenge for vulvovaginal atrophy in postmenopausal women

OBJECTIVE

To evaluate the effects of CO₂ laser in the treatment of vulvovaginal atrophy (VVA) in postmenopausal women.

METHODS

VVA was assessed in 87 postmenopausal women (mean age 58.6 ± 6.9 years) before and after the treatment. The protocol consisted of three monthly treatments and included the treatment of vulva. Subjective measures included VAS (Visual Analog Scale) both for vaginal dryness and dyspareunia; DIVA (Day-by-day Impact of Vaginal Aging); a questionnaire on treatment satisfaction and one about the degree of pain during the procedure. Objective measures included VHI (Vaginal Health Index) and VVHI (Vulvo-Vaginal Health Index). Time points of the study were at the screening visit (T0), at baseline (T1), at week 4 (T2), at week 8 (T3), after 3 months since the last laser application (T4), after 6 months (T5), after 9 months (T6), after 12 months (T7) and after 15 months (T8).

RESULTS

Treatment induced significant improvement in the VAS score. After treatment, VHI and VVHI indicated no VVA and this improvement was long lasting. Multivariate analysis showed that the time of follow-up was correlated with better VHI and VVHI (p < 0.001). DIVA improved over time (p < 0.001).

CONCLUSIONS

This study shows that CO₂ laser treatment induces a significant and long-lasting improvement of symptoms.

Vasomotor symptoms in menopause: a biomarker of cardiovascular disease risk and other chronic diseases?

Menopausal disorders may include shorter-term symptoms, such as hot flushes and night sweats (vasomotor symptoms, VMS) and longer-term chronic conditions such as cardiovascular disease (CVD), osteoporosis, and cognitive impairment. Initially, no clear link between the shorter-term symptoms and longer-term chronic conditions was evident and these disorders seemed to occur independently from each other. However, there is a growing body of evidence demonstrating that VMS may be a biomarker for chronic disease. In this review, the association between VMS and a range of chronic postmenopausal conditions including CVD, osteoporosis, and cognitive decline is discussed. Prevention of CVD in women, as for men, should be started early, and effective management of chronic disease in postmenopausal women has to start with the awareness that VMS during menopause are harbingers of things to come and should be treated accordingly.

Duloxetine and escitalopram for hot flushes: efficacy and compliance in breast cancer survivors

Selective serotonin reuptake inhibitors (SSRI) and serotonin-norepinephrine reuptake inhibitors (SNRI) might be an effective treatment for hot flushes (HFs) in breast cancer survivors (BCSs). This study aims to compare the efficacy and tolerability of duloxetine (SNRI) versus escitalopram (SSRI) in reducing frequency and severity of HFs in BCSs and to assess the effect on depression. Thirty-four symptomatic BCSs with emotional impairment received randomly duloxetine 60 mg daily or escitalopram 20 mg daily for 12 weeks. Patients were asked to record in a diary HF frequency and severity at baseline and after 4 and 12 weeks of treatment. Depression was evaluated through validated questionnaires (Beck Depression Inventory and Montgomery Asberg Depression Rating Scale) at baseline and after 4 and 12 weeks of treatment. Both drugs showed a significant reduction of HF frequency and severity after 12 weeks of treatment with no significant difference between the two groups. A significant improvement in depression symptoms was observed at the end of the study period within both the groups, without difference between the two drugs. In conclusion, escitalopram and duloxetine are both effective treatment for the relief of HFs in BCSs, with similar beneficial effect. A significant improvement of depression was obtained with no major side effects.

Clinical and ethical issues in the diagnosis of hereditary breast cancer (review)

A small subset of breast and ovarian cancers is related to the mutation of dominant susceptibility genes. The recent isolation of BRCA1 and BRCA2 has created great interest and expectations among members of families with a positive history for breast/ovarian cancer. We reviewed the literature to explore the clinical implications of genetic testing for BRCA1 and BRCA2 mutations among high risk women. Both the value of the information provided by the test and the efficacy of the preventive and diagnostic measures presently available have been examined. We also specifically address the issue of ethical dilemmas arising from widespread availability of genetic information, including psycological reactions of those who receive the test, genetic discrimination by health insurance companies or employers and prenatal testing for BRCA1 mutations.

Clinical-pathologic features, long term-outcome and surgical treatment in a large series of patients with invasive lobular carcinoma (ILC) and invasive ductal carcinoma (IDC)

PURPOSE OF THE STUDY

A retrospective analysis on 1407 patients with invasive ductal carcinoma (IDC) and 243 invasive lobular carcinoma (ILC) was performed in order to compare the histological features, the immunohistochemical characteristics, the surgical treatment and the clinical outcome in the two groups.

RESULTS

ILC seems to be more likely multifocal, estrogen receptor positive, HER-2 negative and to have a lower proliferative index compared to IDC. ILC, when treated with conservative surgery, required more frequently re-excision and/or mastectomy because of positive resection margins. No difference was observed in terms of 5-year disease free survival and local relapse free survival between the two groups, in the whole series and in the subgroup of patients treated with breast-conserving treatment.

CONCLUSION

ILC can be safely treated with conservative surgery but a more accurate preoperative evaluation of tumor size and multifocality could be advocated, in order to reduce the re-excision rate.

Role of MRI (magnetic resonance imaging) versus conventional imaging for breast cancer presurgical staging in young women or with dense breast

AIMS

The role of magnetic resonance imaging (MRI) in the local staging of breast cancer is currently uncertain. The purpose of this prospective study is to evaluate the accuracy of preoperative MRI compared to conventional imaging in detecting breast cancer and the effect of preoperative MRI on the surgical treatment in a subgroup of women with dense breasts, young age, invasive lobular cancer (ILC) or multiple lesions.

METHODS

Between January 2006 and October 2007, 91 patients with newly diagnosed breast cancer underwent preoperative clinical breast examination, mammography, bilateral breast ultrasonography and high-resolution breast MRI. All patients had histologically verified breast cancer. The imaging techniques were compared using the final pathological report as gold standard.

RESULTS

The sensitivity of MRI for the main lesion was 98.9%, while for multiple lesions sensitivity was 90.7% and specificity 85.4%. After preoperative MRI, 13 patients (14.3%) underwent additional fine needle/core biopsies, 9 of whom had specimen positive for cancer. Preoperative MRI changed the surgical plan in 26 patients: in 19.8% of the cases breast conservative surgery was converted to mastectomy and in 7.7% of the patients a wider excision was performed. At a mean follow-up of 48 months, 2 local recurrences occurred (local failure rate = 2.5%).

CONCLUSIONS

Enhanced sensitivity of breast MRI may change the surgical approach, by increasing mastectomy rate or suggesting the need of wider local excision. MRI can play an important role in preoperative planning if used in selected patients with high risk of multifocal/multicentric lesions. However, the histologic confirmation of all suspicious findings detected by MRI is mandatory prior to definite surgery.

Clinical outcome of adjuvant endocrine treatment according to PR and HER-2 status in early breast cancer

Patients with estrogen receptor (ER)+/progesterone receptor (PR)- and/or HER-2 overexpressing breast carcinomas may derive lower benefit from endocrine treatment. We examined retrospectively data from 972 breast cancer patients who received tamoxifen (725), tamoxifen + Gn-RH analogs (127) and aromatase inhibitors (120) as adjuvant treatments. ER+/PR- versus ER+/PR+ tumours were characterised by larger size (P = 0.001), higher tumour grade (P = 0.001), higher Ki-67 expression (P = 0.001) and lower mean ER (P = 0.000) and HER-2 expression (P = 0.000). At univariate analysis, tumour grading [hazard ratio (HR) = 4.0; 95% confidence interval (CI) = 1.4-11.1; P = 0.007], nodal status (HR = 3.4; 95% CI 1.2-5.7; P = 0.000), tumour diameter (HR = 2.9; 95% CI 1.7-4.7; P = 0.000) lack of PR expression (HR = 2.1; 95% CI 1.3-3.4; P = 0.002) and HER-2 overexpression (HR = 1.9; 95% CI 1.0-3.5; P = 0.03), as well as Ki 67 expression (HR = 1.7; 95% CI 1.0-2.7; P = 0.04) were associated with shorter disease-free survival (DFS). At the multivariate analysis, nodal status (HR = 3.6; 95% CI 1.9-6.8; P = 0.0001), lack of PR expression (HR = 2.3; 95% CI 1.3-4.0; P = 0.003) and tumour diameter (HR = 2.1; 95% CI 1.1-3.8; P = 0.018) retained their prognostic significance, whereas HER-2 overexpression was associated with a trend towards shorter DFS that was of borderline statistical significance (HR = 2.0; 95 % CI 1.0-3.9; P = 0.05). Our data suggest that lack of PR expression and HER-2 overexpression are both associated with aggressive tumour features, but the prognostic information of PR status on the risk of recurrence in endocrine-treated breast cancer patients is stronger.

Evaluation of low-dose venlafaxine hydrochloride for the therapy of hot flushes in breast cancer survivors

OBJECTIVE

To evaluate the efficacy and tolerability of long-term treatment with venlafaxine at low dose for the reduction of vasomotor symptoms in breast cancer survivors.

DESIGN

Forty consecutive breast cancer patients suffering troublesome hot flushes have been treated for 8 weeks with venlafaxine XR 37.5 mg/day in an open-label study. Vasomotor symptoms have been evaluated before starting treatment and every 4 weeks with a hot flushes diary pointing out the number and the severity of vasomotor symptoms. A Beck Depression Inventory (BDI) was completed at baseline and at the end of the treatment.

RESULTS

Thirty patients had completed the first 4 weeks of treatment, reporting a reduction of hot flushes frequency of 39% as compared to baseline (p<0.001). After 8 weeks of treatment, a further significant reduction was observed both for the hot flushes frequency (-53%; p<0.001) and for the hot flushes score (-59%; p<0.001), a measure which reflects both the number and the severity of hot flushes. Very few side effects were reported, mostly nausea in the first 2 weeks of assumption and mouth dryness. Only 23 women had completed BDI at week 8; a reduction of 23% was observed (p=0.000).

CONCLUSION

Venlafaxine is an effective treatment for the relief of vasomotor symptoms in patients previously treated for breast cancer. A favourable effect is maintained also in those patients using tamoxifen as adjuvant therapy. The use of the low dose (37.5 mg/day) is associated with minimal side effects and produces a good improvement in hot flushes if pursued over 8 weeks.

The influence of hormone replacement therapy on the pathology of breast cancer

AIM OF THE STUDY

To assess whether the pathological characteristics of breast carcinomas arising in post-menopausal women who ever used hormonal replacement therapy (HRT) differ from those of post-menopausal patients who never used HRT.

MATERIALS AND METHODS

Six hundred and forty three consecutive breast cancer patients were entered in a case control-study. Cases were represented by 111 breast cancer patients who had used or were using HRT at the time of diagnosis, while the remaining 532 patients who never used HRT were chosen as controls.

RESULTS

Tumour diameter was smaller in HRT users (17.6 vs 22.1 mm; p=0.002) and tumours of lobular histology were almost twice more frequent among HRT users as in 'never users' (21 vs 12%; p=0.01). No differences were found in grading, hormonal receptor status and axillary nodal status. The expression of c-erb B-2, p53, Ki67 and PS2 measured by immunohistochemistry was similar in the two groups.

CONCLUSIONS

Our findings suggest that HRT use may modify the pathological presentation of breast cancer. Further studies are indicated, while other clinical-pathological characteristics did not differ according to HRT use.

Management of risk of breast carcinoma in postmenopausal women

Breast carcinoma is the most frequent tumor in the female population. Many factors can influence the risk of breast cancer; some of them, such as old age and breast cancer 1/2 (BRCA1/BRCA2) gene mutations, are associated with a fourfold increase in risk. A previous diagnosis of atypical ductal or lobular hyperplasia or having a first-degree relative with a carcinoma are factors associated with a two- to fourfold increase in risk. A relative risk between 1 and 2 is associated with longer exposure to endogenous hormones as a result of early menarche, late menopause and obesity, or with recent and prolonged use of hormone replacement therapy (HRT) or with behavioural factors such as high alcohol and fat intake. Is it possible to modify breast cancer risk in postmenopausal women? Risk factors related to lifestyle can be changed, even if it is not clear whether modifying these behavioural factors during the postmenopausal period will influence the overall breast cancer risk. For instance, the influence of exogenous hormones throughout life (both oral contraceptives and HRT) should be evaluated according to the individual risk-benefit ratio. The problem is even more complex for women who carry genetic mutations and for those who have close relatives with breast cancer, who may be candidates for risk reduction strategies. Prophylactic bilateral mastectomy is still controversial, but is frequently offered to or requested by this group of women and may be indicated in BRCA1/BRCA2 carriers. Chemoprevention with tamoxifen and with the new selective estrogen receptor modulators, namely raloxifene, is very promising and deserves a thorough discussion for all high-risk women.

Sentinel node dissection as definitive treatment for node negative breast cancer patients

AIMS

Negative sentinel node may predict tumour-free axillary nodes in breast cancer. We report the performance of sentinel node dissection at our Institution.

METHODS

We analysed data from 212 consecutive women with primary invasive breast tumours less than 3 cm in diameter and no axillary lymphadenopathy who underwent radioguided sentinel node dissection by means of 99mTc-colloidal albumin between 1999 and 2002. Completion axillary node dissection was performed if sentinel nodes contained metastases or if no sentinel nodes were identified.

RESULTS

Sentinel nodes were identified in 207/212 of the patients. Fifty-seven patients had tumour-positive sentinel nodes. Only tumour diameter showed significant association with sentinel node status (p<0.000). Per-operative histologic evaluation had a sensitivity of 67.3% and a negative predictive value of 90.4%. No subset of sentinel node positive patients was identified for whom axillary node dissection could be safely avoided. No recurrences were detected at a median follow-up of 15 months.

CONCLUSION

Radioguided sentinel node dissection offers a reliable way to assess nodal status in most breast cancer patients. In our experience, both preoperative lymphoscintigraphy and intraoperative histologic evaluation add useful information to the procedure.

Sentinel node biopsy for breast cancer: yes, less surgery is better surgery

Breast surgery evolves towards always more precise, but less invasive techniques. The halstedian concept of radical surgery has been abandoned and the majority of patients are now allowed to preserve their breasts provided they receive radiation therapy after surgery. In many institutions standard axillary lymph-node dissection is being replaced by the less invasive and probably also more accurate staging technique known as sentinel-node dissection. Nevertheless, the procedure requires interdisciplinary collaboration and rigorous quality control monitoring to provide optimal results. Many issues, some of which will be discussed in the light of our personal experience, still need to be tested in clinical controlled trials.

The androgen-regulated gene human kallikrein 15 (KLK15) is an independent and favourable prognostic marker for breast cancer

Many kallikrein genes were found to be differentially expressed in various malignancies, and prostate specific antigen (encoded by the KLK3 gene) is the best tumour marker for prostate cancer. Prostate specific antigen has recently been shown to be an independent favourable prognostic marker for breast cancer. KLK15 is newly discovered kallikrein gene that is located adjacent to KLK3 on chromosome 19q13.4. KLK15 has 41% similarity to KLK3 and the encoded protein, hK15, can activate pro-prostate specific antigen. We studied the expression of KLK15 by real-time quantitative reverse transcriptase-polymerase chain reaction in 202 tissues from patients with breast carcinoma of various stages, grades and histological types. KLK15 expression was found to be a significant predictor of progression-free survival (hazard ratio of 0.41 and P=0.011) and overall survival (hazard ratio of 0.34 and P=0.009). When all other known confounders were controlled in the multivariate analysis, KLK15 retained its prognostic significance. Higher concentrations of KLK15 mRNA were found more frequently in node negative patients (P=0.042). No association was found between KLK15 expression and any other clinicopathological variable. Further, KLK15 is an independent prognostic factor of progression-free survival and overall survival in the subgroup of patients with lower grade and those with oestrogen receptor and progesterone receptor negative tumours in both univariate and multivariate analysis. KLK15 levels of expression were slightly higher (although not statistically significant) in the oestrogen receptor negative and progesterone receptor negative subgroups of patients. KLK15 is up-regulated by androgens in breast cancer cell lines. Time-course and blocking experiments suggest that this regulation is mediated through the androgen receptor.

Quantitative analysis of human kallikrein gene 14 expression in breast tumours indicates association with poor prognosis

KLK14 (formerly known as KLK-L6) is a recently identified member of the human kallikrein gene family. This family harbours several genes aberrantly expressed in various cancers as well as established (PSA/hK3, hK2) and potential (hK6, hK10) cancer markers. Similar to other kallikrein genes, KLK14 was found to be regulated by steroid hormones, particularly androgens and progestins, in breast and ovarian cancer cell lines. Preliminary studies indicated that KLK14 is differentially expressed in breast, ovarian, prostatic and testicular tumours. Given the above, we determined the prognostic significance of KLK14 expression in breast cancer. We studied KLK14 expression in 178 histologically confirmed epithelial breast carcinomas by quantitative reverse transcription-polymerase chain reaction and correlated with clinicopathological variables (tumour stage, grade, histotype etc.) and with outcome (disease-free survival and overall survival), monitored over a median of 76 months. KLK14 mRNA levels ranged from 0 to 1,219 arbitrary units in breast cancer tissues, with a mean+/-s.e. of 136+/-22. An optimal cutoff value of 40.5 arbitrary units was selected, to categorise tumours as KLK14-positive or negative. Higher concentrations of KLK14 mRNA were more frequently found in patients with advanced stage (III) disease (P=0.032). No statistically significant association was found between KLK14 and the other clinicopathological variables. KLK14 overexpression was found to be a significant predictor of decreased disease-free survival (hazard ratio of 2.31, P=0.001) and overall survival (hazard ratio of 2.21, P=0.005). Cox multivariate analysis indicated that KLK14 was an independent prognostic indicator of disease-free survival and overall survival. KLK14 also has independent prognostic value in subgroups of patients with a tumour size </=2 cm and positive nodal, oestrogen receptor and progestin receptor status. We conclude that KLK14 expression, as assessed by quantitative reverse transcription-polymerase chain reaction, is an independent marker of unfavourable prognosis for breast cancer.

Intramuscular depot medroxyprogesterone versus oral megestrol for the control of postmenopausal hot flashes in breast cancer patients: a randomized study

BACKGROUND

Hot flashes are frequent in postmenopausal breast cancer patients, especially when treated with tamoxifen. Estrogen replacement therapy is the most effective treatment for hot flashes, but its use is controversial in breast cancer survivors. Progestins may offer a good alternative for the control of hot flashes in this setting; in particular, oral megestrol acetate has been proven effective in a randomized, placebo-controlled clinical trial. With the aim of further improving these results, we have designed a randomized study comparing oral megestrol acetate with depot intramuscular (i.m.) medroxyprogesterone acetate (MPA) for the control of hot flashes in postmenopausal patients with a history of breast cancer.

PATIENTS AND METHODS

Seventy-one postmenopausal patients were randomized to receive an i.m. injection of depot MPA 500 mg on days 1, 14 and 28, or oral megestrol acetate 40 mg daily for 6 weeks. Patients recorded daily the number and severity of their hot flashes; response was defined as a > or =50% decrease in the number and severity of hot flashes.

RESULTS

At week 6, hot flashes were reduced by 86% on average in the whole group of patients, without significant differences between the two progestins. Response was obtained by 75 and 67% of patients receiving MPA or megestrol, respectively (P = 0.5). Responders were followed to assess maintenance of response (without further treatment), which was significantly better with i.m. MPA: in this group, 89% of responders still showed a benefit at week 24, compared with 45% in the megestrol group (P = 0.03).

CONCLUSIONS

Our study shows that a short cycle of i.m. depot MPA injections provides significant and long-lasting relief from postmenopausal hot flashes in patients with a history of breast cancer, offering an alternative to estrogen replacement therapy or prolonged administration of oral megestrol.

Breast cancer and hormone replacement therapy: putting the risk into perspective

Data on hormone replacement therapy and breast cancer risk come from a number of observational studies (mostly American studies). Those published up to 1995 were reanalyzed by the Collaborative Group on Hormonal Factors in Breast Cancer (CGHFBC). They involved populations where exceedingly high estrogen doses were used as first-line therapy, and a progestin was added in a minority of women. Overall, the CGHFBC reanalysis found that the relative risk increased by 0.023 for each year of use (with an absolute excess risk of two or six cases out of 1000 women treated for 5 or 10 years, respectively). Further American studies, published in 2000 and involving populations where lower doses were used, showed a risk increase of 0.01 per year of estrogen-only use. Both the CGHFBC reanalysis and the further studies did not find an increase of risk in treated overweight women. Possibly, overweight women already have a maximal estrogenic stimulus on the breast due to extraglandular estrogen production. An additional explanation could be that oral estrogens, through their hepatocellular effects, reverse some biological features of obesity (e.g. decreased sex hormone binding globulin level and increased insulin-like growth factor-I bioactivity) that potentially increase breast cancer risk, so balancing the estrogen stimulation. The CGHFBC reanalysis did not show a substantial difference in breast cancer risk between the majority using estrogen alone and the small minority using estrogen plus progestin. Conversely, Swedish studies and the recent American studies suggest that the risk increase could be higher with the addition of a progestin, compared with estrogen-only use. The biological effect of progesterone/progestins on the breast tissue is controversial. Even if the observed increase in risk could be partially ascribed to non-progesterone-like effects of some progestins (e.g. opposing the hepatocellular effects of oral estrogens) and also (in the American studies) to use-bias, a detrimental action due to progesterone-like effects cannot be excluded. However, the theoretical possibility exists that low doses of oral estrogens, plus a progestin providing progesterone-like effects only, will be shown to be associated with a limited breast cancer risk increase.