Molecular subtyping of male breast cancer using alternative definitions and its prognostic impact

Influence of tumour grade on disease survival in male breast cancer patients: a systematic review

PURPOSE

Histological grading of tumours is a well-established biomarker used to guide treatment in female breast cancer. However, its significance in male breast cancer remains unclear. This systematic review investigates the prognostic significance of tumour grade in relation to breast cancer-specific survival (BCSS) in male breast cancer patients undergoing surgery.

METHODS

MEDLINE, PUBMED Central and EMBASE databases were searched to identify randomised trials and observational studies related to male breast neoplasms, tumour grading, recurrence, and survival.

RESULTS

A total of fifteen observational type studies were included in the review. A significant association between tumour grade and BCSS was reported in a majority of studies. This association was most evident with regard to high-grade (grade III) compared to low grade (grade I) tumours, with a significant relationship in 4 out of 4 studies. For intermediate-grade II tumours an association was demonstrated in a minority of studies.

CONCLUSIONS

This study confirms an association between high-grade male breast cancers and poorer disease-specific survival, however, the significance of intermediate-grade tumours remains unclear. Further research is required to investigate the biology of male breast cancer in relation to histological grade and optimally define intermediate-grade disease.

HER2 Low Expression in Primary Male Breast Cancer

Purpose

The introduction of HER2-targeting antibody drug conjugates (ADCs) offers new treatment options for female breast cancer patients (FBC) expressing low levels of HER2 (HER2 low). No evidence was found that HER2 low describes a new FBC subtype. There is a lack of studies determining the impact of HER2 low in male breast cancer (MBC). In this study, we evaluate the prevalence of HER2 low in primary MBC and correlate the results with patient characteristics.

Patients and Methods

In this study, histological specimens were obtained from 120 male patients diagnosed and treated for primary invasive breast cancer from 1995 to 2022 at Breast Cancer Units in Bergisch Gladbach, Chemnitz, and Zwickau, Germany. HER2 immunostaining and in situ hybridization were performed by central pathology and evaluated based on the ASCO/CAP guidelines. The correlation of expression of HER2 low with tumor biological characteristics and patient outcomes was investigated.

Results

Out of all cases, four patients (3.3%) showed HER2 positivity (3+), 39 (32.5%) patients were classified as HER2 low, 7 (5.8%) were HER2 2+ (no amplification), 32 (26.7%) were HER2 1+, and 77 (64.2%) were classified as HER2 zero. Out of 77 HER2 zero cases, 47 tumors (61.0%) showed incomplete staining, with <10% of tumor cells classified as HER2 ultralow. No statistical correlation between HER2 low and tumor biological characteristics and patients' survival was found.

Conclusion

Our findings show a notable, albeit lower, prevalence of HER2 low expression in primary MBC. However, tumors expressing HER2 low do not show specific tumor biological features to define a new breast cancer subtype in MBC. Our results suggest that a significant number of MBC patients could benefit from ADCs, as shown in FBC. Further studies are required to better understand HER2 low breast cancer, both generally and in MBC.

Adjuvant chemotherapy and survival in males aged 70 years or older with breast cancer: a population-based retrospective study

BACKGROUND

Male breast cancer constitutes a minority of breast cancer diagnoses, yet its incidence has been on the rise in recent decades. However, elderly male breast cancer patients have been inadequately represented in clinical trials, posing challenges in treatment decisions. This study seeks to clarify the efficacy of chemotherapy in this demographic and identify the population most likely to benefit from such intervention.

METHODS

We conducted a retrospective analysis using the Surveillance, Epidemiology, and End Results (SEER) database, encompassing a total of 1900 male breast cancer patients aged 70 years or older. Among them, 1652 were categorized in the no-chemotherapy group, while 248 were in the chemotherapy group. A multifactorial logistic regression model was employed to investigate the determinants influencing the administration of chemotherapy in elderly male breast cancer patients. Additionally, the multivariate Cox proportional hazards regression model was applied to identify factors associated with outcomes, with overall survival (OS) as the primary endpoint.

RESULTS

Multivariate logistic regression analysis revealed that grade, tumor size, and nodal status were robust predictors for elderly male breast cancer patients receiving chemotherapy. Furthermore, the multivariate analysis demonstrated that chemotherapy conferred benefits compared to the no-chemotherapy group (HR = 0.822, 95% CI: 0.682-0.991, p = 0.040). Stratified analyses indicated that individuals with N+, poorly/undifferentiated grade, and stage II/III disease could derive benefits from chemotherapy. Upon further investigation of progesterone receptor (PR) positive patients, it was found that only stage III patients experienced significant benefits from chemotherapy (HR = 0.571, 95% CI: 0.372-0.875, p = 0.010). Conversely, in PR negative patients, both stage II (HR = 0.201, 95% CI: 0.051-0.792, p = 0.022) and stage III patients (HR = 0.242, 95% CI: 0.060-0.972, p = 0.046) derived benefits from chemotherapy.

CONCLUSION

Adjuvant chemotherapy may benefit certain elderly male breast cancer patients, specifically those with positive lymph node status, poorly/undifferentiated grade, and PR-positive in stage III, as well as PR-negative expression in stage II/III. Given favorable physical tolerance, it is advisable not to hastily dismiss chemotherapy for these elderly male breast cancer patients.

HER2-Low Expression in Male Breast Cancer: Results from a Multicenter Series in Italy

In the field of breast cancer care, a significant breakthrough has occurred with the recognition of HER2-low expression as a target for novel anti-HER2 antibody-drug conjugates (ADC). This discovery is reshaping the treatment landscape, challenging previous perceptions that considered HER2-low as clinically insignificant. The ability to target HER2-low expression is expected to have substantial clinical implications, irrespective of gender, including in cases of male breast cancer (MBC). However, an estimate of the prevalence of the HER2-low subtype in MBC is missing. This retrospective, observational, multicenter study was aimed at characterizing the HER2-low subtype in MBC. For the purpose of this study, the three-tiered categorization of HER2 (HER2-0, HER2-low, and HER2-positive) was used to reclassify the HER2-negative group into HER-0 or HER2-low subtypes. In the whole series of 144 invasive MBCs, 79 (54.9%) were HER2-0 (IHC scores of 0), 39 (27.1%) HER2-low (IHC scores of 1+/2+ with negative ISH), and 26 (18.0%) HER2-positive (IHC scores of 3+/2+ with positive ISH). Specifically, among hormone receptor-positive (HR+) HER2-negative invasive MBCs, 34.8% were HER2-low and 65.2% HER2-0. Compared with HER2-0, HER2-low subtype was associated with a positive lymph node involvement (p = 0.01). Other pathologic characteristics including histology, staging, and grading did not show notable variations between the two subtypes. The presence of germline BRCA1/2 pathogenic variants (PVs) did not significantly differ between HER2-0 and HER2-low MBCs. However, about 13% of HER2-low MBCs had germline PVs in BRCA1/2 genes, mainly BRCA2, a clinically relevant observation in the context of combined target therapy. Overall, our data, which focused on the largest gender-specific breast cancer series, to our knowledge, confirm that the emerging three-tiered categorization of HER2 (HER2-0, HER2-low, and HER2-positive) can also be considered in MBC, to mitigate both the gender gap and the underrepresentation of males in clinical trials.

Case Series Analysis of Male Breast Cancer

Male breast cancer is a rare disease, accounting for less than 1% of all cases of breast cancer. However, the incidence of male breast cancer is increasing. In this study, we systematically analyzed the cases of male breast cancer and evaluated the management of operable male breast cancer in daily clinical practice according to the international clinical guidelines. Data of male breast cancer characteristics and management were recorded from our electronic database. We present a case series of male breast cancer patients treated at our institution between 2013 and 2021 and summarize the recommendations on management of male patients with breast cancer. Twenty-six patients met the search criteria. The majority of tumors were hormone-receptor positive and human epidermal growth factor receptor 2 negative. Two tumors were derived from axillary accessory breast. All patients underwent mastectomy. Fifteen patients received adjuvant chemotherapy containing anthracycline or taxane. Ten patients received adjuvant radiotherapy for lymph node metastasis. Twenty-five patients received adjuvant endocrine therapy. None of patients received anti-human epidermal growth factor receptor 2 therapy. During the median follow-up period of 37 months, one patient died of previous lung cancer recurrence and one patient developed lung metastases 2 years after breast surgery. No recurrence or distant metastasis occurred in the other twenty-four patients. The incidence of male breast cancer is low. In this study, we present twenty-six cases of male patients with operable breast cancer in our department. All of them received surgery and adjuvant treatment. Early diagnosis and combined therapy benefit male patients with breast cancer. Surgery together with adjuvant treatment can bring a good prognosis.

A systematic literature review of the management, oncological outcomes and psychosocial implications of male breast cancer

BACKGROUND

Although male breast cancer (MBC) is a rare disease, accounting for <1% of all breast cancers, it has significant oncological, survival and psychosocial implications for patients. The aim of this study is to assess the latest literature in the diagnosis, management, oncological outcomes, and psychosocial impact of MBC.

METHODS

A systematic literature review was conducted using the PRISMA guidelines (Moher et al., 2009) [1] to explore the management of MBC, with particular focus on investigative imaging, surgical management, oncological outcomes, survival, genetic screening and psychosocial effects. Electronic databases were searched for randomised control trials, cohort studies and case series involving more than 10 patients. Imaging and surgical techniques, local and distant disease recurrence, survival, genetic screening and psychosocial implications in the setting of MBC were assessed.

RESULTS

The search criteria identified 199 articles, of which 59 met the inclusion criteria. This included 39,529 patients, with a mean age of 64.5 years (55-71), and a mean follow-up of 66.3 months (26.2-115). Mastectomy remains the most frequently used surgical technique, with an average of 89.6%. Loco-regional and distant recurrence rate was 10.1% and 21.4% respectively. Disease-free survival (DFS) at 5 and 10 years was 66.8% and 54.5% respectively. Disease-specific survival (DSS) at 5 and 10 years was 87.1% and 67.1% respectively. Overall survival (OS) at 5 and 10 years was 72.7% and 50.7% respectively. Genetic screening was conducted in 38.6% of patients of which 4.8% and 15.8% were found to be BRCA1 and BRCA2 carriers respectively. Psychosocial studies were conducted mainly using questionnaire and interview-based methodology focusing primarily on awareness of breast cancer in men, support available and impact on gender identity.

CONCLUSIONS

This review demonstrates that men present with later stage disease with subsequent impact on survival outcomes. There remains a paucity of high-level evidence and prospective studies are required. There is a need for increasing awareness amongst the public and health care professionals in order to improve outcomes and reduce stigma associated with MBC.

Clinicopathological features and prognosis of male breast cancer

Objective

We aimed to describe the differences in clinicopathological characteristics and overall survival (OS) between male and female breast cancer patients, and to develop a prognostic nomogram to predict survival in patients with male breast cancer (MBC).

Methods

Using the Surveillance, Epidemiology, and End Results database, we compared age, race, histological type, histological grade, tumor size, lymph node status, metastases, estrogen/progesterone receptor (ER/PR) and HER-2 status between male and female patients, and analyzed their relationships with OS. We established a nomogram and produced a calibration curve to observe its predictive effect.

Results

Age, race, T stage, N stage, bone and lung metastases, and histological type and grade differed between male and female patients. OS in male patients was related to age, tumor size, metastatic site, ER/PR status, and histological grade, but not to race or lymph node status. A nomogram was established, which showed good predictive performance for survival in MBC patients (area under the curve = 0.7).

Conclusion

MBC has a worse prognosis than female breast cancer, mainly characterized by late onset age, late staging, high proportion of invasive non-specific histological types, high histological grade, and luminal breast cancer.

Comparison between male and female breast cancer survival using propensity score matching analysis

Male breast cancer (MBC) is a rare disease. The few studies on MBC reported conflicting data regarding survival outcomes compared to women. This study has two objectives: to describe the characteristics of a single-cohort of MBC and to compare overall survival (OS) and disease-free survival (DFS) between men and women using the propensity score matching (PSM) analysis. We considered MBC patients (n = 40) diagnosed between January 2004 and May 2019. Clinical, pathological, oncological and follow-up data were analyzed. Univariate analysis was performed to determine the prognostic factors on OS and DFS for MBC. We selected female patients with BC (n = 2678). To minimize the effect of the imbalance of the prognostic factors between the two cohorts, the PSM method (1:3 ratio) was applied and differences in survival between the two groups were assessed. The average age of MBC patients was 73 years. The 5-year OS and DFS rates were 76.7% and 72.2% respectively. The prognostic factors that significantly influenced OS and DFS were tumor size and lymph node status. After the PSM, 5 year-OS was similar between MBC and FBC (72.9% vs 72.3%, p = 0.70) while we found a worse DFS for MBC (72.2% vs 91.4%, p  = 0.03). Our data confirmed previous reported MBC characteristics: we found a higher risk of recurrence in MBC compared to FMC but similar OS. MBC and FMC are different entities and studies are needed to understand its epidemiology and guide its management.

Prognostic relevance of Ki67 expression in primary male breast cancer: determination of cut-off points by different evaluation methods and statistical examinations

PURPOSE

1% of all breast cancer cases occur in men. There are significant differences regarding clinical behaviour and genetic profiles between female (FBC) and male breast cancer (MBC). Parameters for decision-making on treatment and prognosis are derived from FBC. Ki67 has a high value as a prognostic and predictive factor in FBC, but accurate Ki67 cut-off points for MBC are missing. In this study, we aimed to evaluate adequate examination methods and reliable cut-off points for Ki67 to assess the highest prognostic value for patient's overall survival (OS).

METHODS

In this multicentric retrospective study, histological specimens were obtained from 104 male patients who were diagnosed and treated for primary invasive breast cancer. We applied three methods of Ki67 analysis: Tumor average scoring (TA), tumor border scoring (TB) and hot-spot scoring (HS). Calculated Ki67 cut-off points for each method were assessed as a threshold for patients' overall survival (OS).

RESULTS

Ki67 cut-off points were 13.5 for the TA group, 22.5 for the HS group and 17.5 for the TB group. Only Ki67 TA cut-off calculations demonstrated statistical significance (p = 0.04). Ki67 expression analysis of TA showed that more than 90% of patients with low Ki67 levels (< 13.5) were alive after 5-year follow-up.

CONCLUSION

Our findings demonstrate that determination of Ki67 expression in TA is the most reliable to define a cut-off point with high prognostic value. A Ki67 cut-off point of 13.5 shows highest statistical power to define luminal A subgroup and OS.

Poor prognosis of male triple-positive breast Cancer patients: a propensity score matched SEER analysis and molecular portraits

Background

The purpose of this study was to explore clinicalpathology features, molecular features and outcome of male breast cancer patients who expressed ER, PR as well as HER-2, namely triple-positive male breast cancer (TP-MBC), and compared them with triple-positive female breast cancer patients (TP-FBC).

Methods

TP-MBC and TP-FBC from 2010 to 2017 were selected from the Surveillance, Epidemiology, and End Results database (SEER). Kaplan-Meier plotter and multivariable Cox regression model were applied to analyse the difference between TP-MBC and TP-FBC on cancer-specific survival (CSS) and overall survival (OS). Propensity score matched (PSM) analysis was used to ensure well-balanced characteristics. 7 cases TP-MBC and 174 cases TP-FBC patients with the genomic and clinical information were identified from the cohort of The Cancer Genome Atlas (TCGA) and the Memorial Sloan Kettering (MSK).

Result

336 TP-MBC and 33,339 TP-FBC patients were taken into the study. The percentages of TP-MBC in MBC patients were higher than the rates of TP-FBC in FBC patients from 2010 to 2017 except 2012. Compared with TP-FBC, more TP-MBC were staged III (17.9% vs. 13.5%) or stage IV (11.0% vs. 6.9%). TP-MBC were more frequently to be older than 65-years-old (47.0% vs. 29.3%), Balck (15.2% vs. 10.8%), ductal carcinoma (91.7% vs. 84.4%) and metastases to lung (4.5% vs. 2.1%) or bone (8.6% vs. 4.7%). TP-MBC had worse OS and CSS than TP-FBC in all stages (P < 0.001). In multivariable prediction model of TPBC, male patients had a higher risk than female. Lastly, the worse OS (P < 0.001) and CSS (P = 0.013) were seen in the 1:3 PSM analysis between TP-MBC and TP-FBC. Genomic analysis revealed that TP-MBCs have some notable rare mutations, like ERBB2, ERBB3, RB1, CDK12, FGFR2, IDH1, AGO2, GATA3, and some of them are not discovered in TP-FBC.

Conclusion

TP-MBC had a worse survival than TP-FBC, and there were different genomic features between two groups. Current knowledge and treatment to TP-MBC maybe inadequate and remain to be explored.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08267-9.

Male breast cancer: A closer look at patient and tumor characteristics and factors associated with survival

Background

The prognostic effect of molecular subtypes on male breast cancer (MBC) remains unclear. The aim of this study was to evaluate the clinicopathological and prognostic factors of MBC patients.

Methods

From 1 January 1990 to 31 December 2014, the data of 152 MBC and 304 female breast cancer (FBC) patients were identified and extensively compared.

Results

Compared with the FBC group, MBC patients were found to have a higher rate of cancer family history (30.9% vs. 18.4%, P = 0.001), mass around the areola area (37.5% vs. 5.6%, P = 0.000), lymph node invasion (44.1% vs. 34.2%, P = 0.006) and hormonal receptor positivity (66.4% vs. 49.3%, P = 0.027). Luminal A was the most common subtype accounting for 69.8%, whereas HER2‐positive (12.7%) and TNBC (1.6%) subtypes were rare in the MBC group. However, it was significantly lower for MBC than for FBC who received endocrine therapy (38.8% vs. 49.3%, P = 0.041). MBC showed the worse overall survival (OS) and disease‐free survival (DFS) than those of FBC patients. However, 10‐year OS and DFS were similar between MBC and FBC patients in the subgroups of nonluminal subtype (P < 0.001), but worse in MBC patients than those in FBC patients in the subgroups of luminal A (P = 0.004 for OS; P = 0.002 for DFS) and luminal B (P = 0.006 for OS; P = 0.003 for DFS). Multivariate analysis indicated tumor size, radical mastectomy and endocrine therapy as independent risk factors for OS and DFS of MBC patients.

Conclusions

Our study determined that MBC patients possessed a worse prognosis, usually with lymph node invasion, and were estrogen receptor (ER), progesterone receptor (PR)‐positive and human epidermal growth factor receptor (HER2)‐negative. Molecular subtypes based on FBC did not provide the same prognostic information in MBC, even in the luminal groups.

Subtyping of male breast cancer by PAM50 and immunohistochemistry: a pilot study of a consecutive Danish cohort

Male breast cancer (MBC) is a rare disease that is still to be fully understood. In female breast cancer, molecular subtyping by gene expression has proven its significance. In this study, we characterize a consecutive cohort of MBC patients surgically treated from 1997 to 2017, identified at our institution (N = 37), and report the association between molecular subtypes found by a surrogate panel of immunohistochemical (IHC) markers, and the PAM50 signature, as well as risk of recurrence score and overall survival for the different subtypes. PAM50 subtypes were determined using the nCounter FLEX system instrument and software. The distribution of molecular subtypes according to the PAM50 signature was as follows: 56% luminal B, 39% luminal A, and 5% basal-like. None of the tumors were HER2-enriched. Using IHC surrogate markers, we found 80% luminal B-like, 15% luminal A-like, and 5% basal-like. None were HER2-positive (non-luminal). We found a strong statistical association between subtypes found by PAM50 signature and the IHC surrogate markers (p < 0.001). Furthermore, we found luminal A tumors to be smaller in size compared to luminal B tumors (p = 0.04). Patients with luminal A subtype tumors had the lowest ROR scores with a mean of 39, whereas patients with luminal B subtype tumors had a mean ROR score of 69. Significant worse overall survival for luminal B tumors compared to luminal A tumors was seen (p = 0.02). Male breast cancer seems to be a mainly luminal disease, with luminal B being the most frequent subtype. Further studies are needed to ensure correct therapeutic strategies for this select group of patients.

M. Dinjens W, van Deurzen CHM. Loss of Y-Chromosome during Male Breast Carcinogenesis

Loss of Y-chromosome (LOY) is associated with increased cancer mortality in males. The prevalence of LOY in male breast cancer (BC) is unknown. The aim of this study is to assess the presence and prognostic effect of LOY during male BC progression. We included male BC patients diagnosed between 1989 and 2009 (n = 796). A tissue microarray (TMA) was constructed to perform immunohistochemistry and fluorescent in situ hybridization (FISH), using an X and Y probe. We also performed this FISH on a selected number of patients using whole tissue slides to study LOY during progression from ductal carcinoma in situ (DCIS) to invasive BC. In total, LOY was present in 12.7% (n = 92) of cases, whereby LOY was associated with ER and PR negative tumors (p = 0.017 and p = 0.01). LOY was not associated with the outcome. Using whole slides including invasive BC and adjacent DCIS (n = 22), we detected a concordant LOY status between both components in 17 patients. In conclusion, LOY is an early event in male breast carcinogenesis, which generally starts at the DCIS stage and is associated with ER and PR negative tumors.

Male Breast Cancer in Australia

AIMS

Male breast cancer is rare and treatment recommendations are based on female breast cancer guidelines. We analyzed an Australian dataset of patients with early breast cancer (including ductal carcinoma in situ, DCIS) for demographic, pathological and treatment information. The primary objective was to compare treatment delivery for males versus females.

METHODS

Australian data from the BreastSurgANZ Quality Audit (BQA) from 1 October 2006 and 30 September 2016 were analyzed. Demographic and pathological information was obtained and compared between males and females. Treatment recommendations were compared to BreastSurgANZ Key Performance Indicators (KPIs) and National Comprehensive Cancer Network (NCCN) guidelines to assess for adherence to national and international guidelines, respectively.

RESULTS

A total of 99,768 breast cancer episodes were analyzed, comprising 585 males (544 invasive; 41 DCIS) and 99 183 (99.4%) females (85 596 invasive; 13 525 DCIS; 62 unknown). Compared with females, males were older at diagnosis, more likely to be hormone receptor-positive and lymph node-positive disease, and more likely to have mastectomy. The proportion of males undergoing breast conserving surgery receiving radiotherapy was the only BreastSurgANZ KPI that was not met. Males were less likely to receive adjuvant chemotherapy than females using NCCN guidelines.

CONCLUSION

Australian males with breast cancer account for 0.6% of breast cancer incidence and have similar clinico-pathological features as reported internationally. Overall, there is good compliance with the surgical KPIs, and adherence to NCCN guidelines for adjuvant systemic treatment is similar to previous international studies.

Male breast cancer: a neglected disease

Male breast cancer (MBC) is rare, tending to afflict sedentary men, with adolescent obesity being a risk factor. Men fare worse compared with matched females with breast cancer. The preponderance of ER+ve disease affects the molecular profile: most cases have luminal A tumors. Through male ignorance and risk-taking, delay is frequent and this lacuna needs addressing with health education. The major gene mutation responsible for MBC is BRCA2. Five single nucleotide polymorphisms (SNPs) are significantly and uniquely associated with MBC risk with two located in the 8q24.21 regions. Mastectomy is being gradually replaced by nipple-preserving surgery and radiotherapy but this trend could be expedited with neoadjuvant endocrine therapy. Significant advances will occur only after expansion of collaborative groups and this is a matter of pressing importance.

Current state of surgical management for male breast cancer

Management guidelines for male breast cancer have long been extrapolated from those for female breast cancer, which are based on large, randomised-controlled trials. While there are no randomised-controlled trials for male breast cancer management mainly due to the rarity of the disease, the only type of evidence available comes from retrospective studies, subject to selection biases and small sample sizes. Male breast cancer, while similar to female breast cancer in many respects, has some important differences that can affect management choices. Most cancers are oestrogen and progesterone receptor positive, and usually more advanced at presentation than female breast cancer. This is likely due to less breast parenchyma in male patients and delay to diagnosis. The classical management option for male patients with breast cancer is mastectomy, due to small tumour-to-breast ratio and often central position of the tumour. Breast conserving surgery is still useful in selected cases and has similar outcomes when compared to mastectomies in these patients. For patients with clinically negative lymph nodes, sentinel lymph node biopsy offers the same prognosis as axillary lymph node dissection, but with less associated morbidity. Endocrine therapy is of particular use, due to high levels of receptor positivity. Adjuvant endocrine therapy seems to significantly improve overall survival of male patients with breast cancer and while no prospective evidence exists for neoadjuvant hormonal therapy, there is hope that this is a useful management option as well. Radiotherapy is also useful in an adjuvant setting, particularly when combined with endocrine therapy. Better identification of patients, less delay from presentation to diagnosis and more collaborative efforts are key in improving the management, prognosis and outcomes of patients with male breast cancer.

Characterization of male breast cancer: results of the EORTC 10085/TBCRC/BIG/NABCG International Male Breast Cancer Program

Background

Male breast cancer (BC) is rare, managed by extrapolation from female BC. The International Male BC Program aims to better characterize and manage this disease. We report the results of part I, a retrospective joint analysis of cases diagnosed during a 20-year period.

Methods

Patients with follow-up and tumor samples, treated between 1990 and 2010, in 93 centers/9 countries. Samples were centrally analyzed in three laboratories (the United Kingdom, the Netherlands and the United States).

Results

Of 1822 patients enrolled, 1483 were analyzed; 63.5% were diagnosed between 2001 and 2010, 57 (5.1%) had metastatic disease (M1). Median age at diagnosis: 68.4 years. Of 1054 M0 cases, 56.2% were node-negative (N0) and 48.5% had T1 tumors; 4% had breast conserving surgery (BCS), 18% sentinel lymph-node biopsy; half received adjuvant radiotherapy; 29.8% (neo)adjuvant chemotherapy and 76.8% adjuvant endocrine therapy (ET), mostly tamoxifen (88.4%). Per central pathology, for M0 tumors: 84.8% ductal invasive carcinomas, 51.5% grade 2; 99.3% estrogen receptor (ER)-positive; 81.9% progesterone receptor (PR)-positive; 96.9% androgen receptor (AR)-positive [ER, PR or AR Allred score ≥3]; 61.1% Ki67 expression low (<14% positive cells); using immunohistochemistry (IHC) surrogates, 41.9% were Luminal-A-like, 48.6% Luminal-B-like/HER-2-negative, 8.7% HER-2-positive, 0.3% triple negative. Median follow-up: 8.2 years (0.0-23.8) for all, 7.2 years (0.0-23.2), for M0, 2.6 years (0.0-12.7) for M1 patients. A significant improvement over time was observed in age-corrected BC mortality. BC-specific-mortality was higher for men younger than 50 years. Better overall (OS) and recurrence-free survival (RFS) were observed for highly ER+ (P = 0.001), highly PR+ (P = 0.002), highly AR+ disease (P = 0.019). There was no association between OS/RFS and HER-2 status, Ki67, IHC subtypes nor grade.

Conclusions

Male BC is usually ER, PR and AR-positive, Luminal B-like/HER2-negative. Of note, 56% patients had T1 tumors but only 4% had BCS. ER was highly positive in >90% of cases but only 77% received adjuvant ET. ER, PR and AR were associated with OS and RFS, whereas grade, Ki67 and IHC surrogates were not. Significant improvement in survival over time was observed.

Magee Equation Recurrence Score Is Associated With Distal Metastatic Risk in Male Breast Carcinomas: Experience From Two Institutions

OBJECTIVES

To conduct a clinicopathologic study of male breast carcinoma with Magee equation recurrence score (RS).

METHODS

Seventy-four cases of male invasive breast cancers (MBCs) were studied, including 63 hormone receptor (HR)-positive, 10 human epidermal growth factor receptor 2-positive, and one triple-negative breast cancers.

RESULTS

Among 63 HR-positive MBC patients, nine patients developed distal metastasis. Statistical analysis demonstrated distal metastasis was significantly associated with positive lymph node, high Nottingham grade, and increased Magee equation RS. All HR-positive MBCs were further stratified into two categories (low RS <18; intermediate/high RS ≥18). There was a significantly increased risk for distal metastasis in MBCs with intermediate/high Magee equation RS, but no increased risk for lymph node metastasis.

CONCLUSIONS

Our data suggest Magee equation RS may be useful to predict distal metastatic risk in MBC patients.

Ghrelin expression is associated with a favorable outcome in male breast cancer

Ghrelin and obestatin are two gastrointestinal peptides, derived from a common precursor. Expression of both peptides have been found in breast cancer tissue and ghrelin has been associated with breast cancer development. Ghrelin expression is associated with longer survival in women diagnosed with invasive and node negative breast cancer. The clinical implications of the peptide expression in male breast cancer are unclear. The aim of this study was to investigate the role and potential clinical value of ghrelin and obestatin in male breast cancer. A tissue microarray of invasive male breast cancer specimens from 197 patients was immunostained with antibodies versus the two peptides. The expression of the peptides was correlated to previously known prognostic factors in breast cancer and to the outcome. No strong correlations were found between ghrelin or obestatin expression and other known prognostic factors. Only ghrelin expression was statistically significantly correlated to breast cancer-specific survival (HR 0.39, 95% CI 0.18–0.83) in univariate analyses and in multivariate models, adjusted for tumor size and node status (HR 0.38, 95% CI 0.17–0.87). HR for obestatin was 0.38 (95% CI 0.11–1.24). Ghrelin is a potential prognostic factor for breast cancer death in male breast cancer. Patients with tumors expressing ghrelin have a 2.5-fold lower risk for breast cancer death than those lacking ghrelin expression. Drugs targeting ghrelin are currently being investigated in clinical studies treating metabolic or nutritional disorders. Ghrelin should be further evaluated in forthcoming studies as a prognostic marker with the aim to be included in decision algorithms.

Male breast cancer: correlation between immunohistochemical subtyping and PAM50 intrinsic subtypes, and the subsequent clinical outcomes

Male breast cancer is a rare disease that is still poorly understood. It is mainly classified by immunohistochemistry as a luminal disease. In this study, we assess for the first time the correlation between molecular subtypes based on a validated six-marker immunohistochemical panel and PAM50 signature in male breast cancer, and the subsequent clinical outcome of these different subtypes. We collected 67 surgical specimens of invasive male breast cancer from four different Spanish pathology laboratories. Immunohistochemical staining for the six-marker panel was performed on tissue microarrays. PAM50 subtypes were determined in a research-use-only nCounter Analysis System. We explored the association of immunohistochemical and PAM50 subtypes. Overall survival and disease-free survival were analyzed in the different subtypes of each classification. The distribution of tumor molecular subtypes according PAM50 was: 60% luminal B, 30% luminal A and 10% human epidermal growth factor receptor 2 (Her2) enriched. Only one Her2-enriched tumor was also positive by immunohistochemistry and was treated with trastuzumab. None of the tumors were basal-like. Using immunohistochemical surrogates, 51% of the tumors were luminal B, 44% luminal A, 4% triple-negative and 1% Her2-positive. The clinicopathological characteristics did not differ significantly between immunohistochemical and PAM50 subtypes. We found a significant worse overall survival in Her2-enriched compared with luminal tumors. Male breast cancer seems to be mainly a genomic luminal disease with a predominance of the luminal B subtype. In addition, we found a proportion of patients with Her2-negative by immunohistochemistry but Her2-enriched profile by PAM50 tumors with a worse outcome compared with luminal subtypes that may benefit from anti-Her2 therapies.

The biology of male breast cancer

Important differences have begun to emerge concerning the molecular profile of female and male breast cancer which may prove to be of therapeutic value. This review examined all the available data on the genomics of MBC. Most male cancers are ER+ve but without a corresponding increase in PR positivity and only a weaker association with estrogen-controlled markers such as PS2, HSP27 and Cathepsin-D. HER2 +ve cancers are rare in males and the role of androgen receptor is controversial. Although the Luminal A phenotype was the most frequent in both MBC and FBC, no Luminal B or HER2 phenotypes were found in males and the basal phenotype was very rare. Using hierarchical clustering in FBC, ERα clustered with PR, whereas in MBC, ERα associated with ERβ and AR. Based on limited data it appears that Oncotype DX is effective in determining recurrence risk in selected MBC. In future, tailored therapies based on genomics will probably yield the most promising approach for both MBC and FBC.

TMSB4Y is a candidate tumor suppressor on the Y chromosome and is deleted in male breast cancer

Male breast cancer comprises less than 1% of breast cancer diagnoses. Although estrogen exposure has been causally linked to the development of female breast cancers, the etiology of male breast cancer is unclear. Here, we show via fluorescence in situ hybridization (FISH) and droplet digital PCR (ddPCR) that the Y chromosome was clonally lost at a frequency of ~16% (5/31) in two independent cohorts of male breast cancer patients. We also show somatic loss of the Y chromosome gene TMSB4Y in a male breast tumor, confirming prior reports of loss at this locus in male breast cancers. To further understand the function of TMSB4Y, we created inducible cell lines of TMSB4Y in the female human breast epithelial cell line MCF-10A. Expression of TMSB4Y resulted in aberrant cellular morphology and reduced cell proliferation, with a corresponding reduction in the fraction of metaphase cells. We further show that TMSB4Y interacts directly with β-actin, the main component of the actin cytoskeleton and a cell cycle modulator. Taken together, our results suggest that clonal loss of the Y chromosome may contribute to male breast carcinogenesis, and that the TMSB4Y gene has tumor suppressor properties.

Male breast cancer is not congruent with the female disease

It has become customary to extrapolate from the results of treatment trials for female breastcancer and apply them to males with the disease. In the absence of results from national and international randomised trials for male breast cancer (MBC) this appears superficially to be an appropriate response. Closer examination of available data reveals that aspects of the aetiology and treatment of MBC do not fit the simplistic model that men usually have endocrine sensitive tumours which behave like those in postmenopausal women. Most females and males with breast cancer have none of the recognised risk factors, indicating the gaps in our knowledge of the epidemiology of this disease. Several studies have compared epidemiological risk factors for MBC and female breast cancer (FBC) but many have been blighted by small numbers. In comparison with FBC there is a larger proportion of BRCA2 tumours, (occurring in 10% of MBC), and underrepresentation of BRCA1 tumours (found in only 1%), suggesting significant differences in the genetic aetiology of MBC and FBC. Genome-wide association studies in FBC reported single nucleotide polymorphisms (SNPs) in 12 novel independent loci were consistently associated with disease but for MBC 2 SNPs had a significantly increased risk. Molecular profiles of matched cancers in males and females showed a gender-associated modulation of major processes including energy metabolism, regulation of translation, matrix remodelling and immune recruitment. Immunohistochemistry for kinase inhibitor proteins (KIPs) p27Kip1 and p21Waf1 indicate a significant difference in the immunostaining of tumours from male patients compared with females. MBC is almost always estrogen receptor positive (ER+ve) and so systemic treatment is usually endocrine. With evidence in FBC that aromatase inhibitors are more effective than tamoxifen in the postmenopausal it was seemingly logical that the same would be true for MBC. Results however suggest less efficacy with AIs and an increase in risk of mortality compared to tamoxifen. The overall survival in male breast cancer was significantly better after adjuvant treatment with tamoxifen compared to an aromatase inhibitor. These important biological differences point the way to the development of new therapies for MBC based on differences rather than similarities with FBC.

Genome methylation patterns in male breast cancer - Identification of an epitype with hypermethylation of polycomb target genes

Male breast cancer (MBC) is a rare disease that shares both similarities and differences with female breast cancer (FBC). The aim of this study was to assess genome-wide DNA methylation profiles in MBC and compare them with the previously identified transcriptional subgroups of MBC, luminal M1 and M2, as well as the intrinsic subtypes of FBC. Illumina's 450K Infinium arrays were applied to 47 MBC and 188 FBC tumors. Unsupervised clustering of the most variable CpGs among MBC tumors revealed two stable epitypes, designated ME1 and ME2. The methylation patterns differed significantly between the groups and were closely associated with the transcriptional subgroups luminal M1 and M2. Tumors in the ME1 group were more proliferative and aggressive than ME2 tumors, and showed a tendency toward inferior survival. ME1 tumors also displayed hypermethylation of PRC2 target genes and high expression of EZH2, one of the core components of PRC2. Upon combined analysis of MBC and FBC tumors, ME1 MBCs clustered among luminal B FBC tumors and ME2 MBCs clustered within the predominantly luminal A FBC cluster. The majority of the MBC tumors remained grouped together within the clusters rather than being interspersed among the FBC tumors. Differences in the genomic location of methylated CpGs, as well as in the regulation of central canonical pathways may explain the separation between MBC and FBC tumors in the respective clusters. These findings further suggest that MBC is not readily defined using conventional criteria applied to FBC.

Molecular profiling of male breast cancer - lost in translation?

Breast cancer is the most common cancer form in women and it has been extensively studied on the molecular level. Male breast cancer (MBC), on the other hand, is rare and has not been thoroughly investigated in terms of transcriptional profiles or genomic aberrations. Most of our understanding of MBC has therefore been extrapolated from knowledge of female breast cancer. Although differences in addition to similarities with female breast cancer have been reported, the same prognostic and predictive markers are used to determine optimal management strategies for both men and women diagnosed with breast cancer. This review is focused on prognosis for MBC patients, prognostic and predictive factors and molecular subgrouping; comparisons are made with female breast cancer. Information was collected from relevant literature on both male and female breast cancer from the MEDLINE database between 1992 and 2014. MBC is a heterogeneous disease, and on the molecular level many differences compared to female breast cancer have recently been revealed. Two distinct subgroups of MBC, luminal M1 and luminal M2, have been identified which differ from the well-established intrinsic subtypes of breast cancer in women. These novel subgroups of breast cancer therefore appear unique to MBC. Furthermore, several studies report inferior survival for men diagnosed with breast cancer compared to women. New promising prognostic biomarkers for MBC (e.g. NAT1) deserving further attention are reviewed. Further prospective studies aimed at validating the novel subgroups and recently proposed biomarkers for MBC are warranted to provide the basis for optimal patient management in this era of personalized medicine. This article is part of a Directed Issue entitled: Rare Cancers.

The landscape of candidate driver genes differs between male and female breast cancer

The rapidly growing collection of diverse genome-scale data from multiple tumor types sheds light on various aspects of the underlying tumor biology. With the objective to identify genes of importance for breast tumorigenesis in men and to enable comparisons with genes important for breast cancer development in women, we applied the computational framework COpy Number and EXpression In Cancer (CONEXIC) to detect candidate driver genes among all altered passenger genes. Unique to this approach is that each driver gene is associated with several gene modules that are believed to be altered by the driver. Thirty candidate drivers were found in the male breast cancers and 67 in the female breast cancers. We identified many known drivers of breast cancer and other types of cancer, in the female dataset (e.g. GATA3, CCNE1, GRB7, CDK4). In contrast, only three known cancer genes were found among male breast cancers; MAP2K4, LHP, and ZNF217. Many of the candidate drivers identified are known to be involved in processes associated with tumorigenesis, including proliferation, invasion and differentiation. One of the modules identified in male breast cancer was regulated by THY1, a gene involved in invasion and related to epithelial-mesenchymal transition. Furthermore, men with THY1 positive breast cancers had significantly inferior survival. THY1 may thus be a promising novel prognostic marker for male breast cancer. Another module identified among male breast cancers, regulated by SPAG5, was closely associated with proliferation. Our data indicate that male and female breast cancers display highly different landscapes of candidate driver genes, as only a few genes were found in common between the two. Consequently, the pathobiology of male breast cancer may differ from that of female breast cancer and can be associated with differences in prognosis; men diagnosed with breast cancer may consequently require different management and treatment strategies than women.

Therapeutic strategies in male breast cancer: clinical implications of chromosome 17 gene alterations and molecular subtypes

Male breast cancer (MBC) is a rare disease. To date, therapy is mainly based on studies and clinical experiences with breast cancer in women. Only little is known about molecular typing of MBC, particularly with regard to potential biological predictors for adjuvant therapy. In female breast cancer tumors with chromosome 17 centromere (CEP17) duplication, HER2 and/or Topoisomerase II alpha (Topo II-α) gene alterations have been suggested to be associated with poor prognosis and increased sensitivity to anthracycline-containing regimens. In a well characterized cohort of 96 primary invasive MBC, we studied CEP17, HER2 and Topo II-α alterations by fluorescence in-situ hybridization (FISH), and expression of hormone receptors (HR), HER2 and Ki67 by immunohistochemistry to define molecular subtypes. Tumor characteristics and follow-up data were available and correlated with molecular findings. HER2 amplification and Topo II-α amplification/deletion were exceptionally rare in MBC (6.3% and 3.1%, respectively). CEP17 polysomy were found in 9.4% of tumors. HER2, Topo II-α and CEP17 gene alterations were not correlated to patients outcome. 96.9% of our cases were HR positive. Triple negative tumors were found in only 3.1% of the cases. In nodal negative tumors luminal A subtypes were significantly associated with better overall survival. Our results provide evidence for a predominant male breast cancer phenotype, characterized by HR expression and a lack of HER2/Topo II-α alterations and CEP17 duplicates. Therefore, the impact of anthracycline sensitivity linked to HER2/Topo II-α alterations as found in female breast cancer has low clinical significance for this specific male breast cancer phenotype.

Gene expression profiling of primary male breast cancers reveals two unique subgroups and identifies N-acetyltransferase-1 (NAT1) as a novel prognostic biomarker

INTRODUCTION

Male breast cancer (MBC) is a rare and inadequately characterized disease. The aim of the present study was to characterize MBC tumors transcriptionally, to classify them into comprehensive subgroups, and to compare them with female breast cancer (FBC).

METHODS

A total of 66 clinicopathologically well-annotated fresh frozen MBC tumors were analyzed using Illumina Human HT-12 bead arrays, and a tissue microarray with 220 MBC tumors was constructed for validation using immunohistochemistry. Two external gene expression datasets were used for comparison purposes: 37 MBCs and 359 FBCs.

RESULTS

Using an unsupervised approach, we classified the MBC tumors into two subgroups, luminal M1 and luminal M2, respectively, with differences in tumor biological features and outcome, and which differed from the intrinsic subgroups described in FBC. The two subgroups were recapitulated in the external MBC dataset. Luminal M2 tumors were characterized by high expression of immune response genes and genes associated with estrogen receptor (ER) signaling. Luminal M1 tumors, on the other hand, despite being ER positive by immunohistochemistry showed a lower correlation to genes associated with ER signaling and displayed a more aggressive phenotype and worse prognosis. Validation of two of the most differentially expressed genes, class 1 human leukocyte antigen (HLA) and the metabolizing gene N-acetyltransferase-1 (NAT1), respectively, revealed significantly better survival associated with high expression of both markers (HLA, hazard ratio (HR) 3.6, P = 0.002; NAT1, HR 2.5, P = 0.033). Importantly, NAT1 remained significant in a multivariate analysis (HR 2.8, P = 0.040) and may thus be a novel prognostic marker in MBC.

CONCLUSIONS

We have detected two unique and stable subgroups of MBC with differences in tumor biological features and outcome. They differ from the widely acknowledged intrinsic subgroups of FBC. As such, they may constitute two novel subgroups of breast cancer, occurring exclusively in men, and which may consequently require novel treatment approaches. Finally, we identified NAT1 as a possible prognostic biomarker for MBC, as suggested by NAT1 positivity corresponding to better outcome.