Return to work, work productivity loss and activity impairment in Chinese breast cancer survivors 12-month post-surgery: a longitudinal study.

Introduction: Existing evidence of returning-to-work (RTW) after cancer comes predominately from Western settings, with none prospectively examined since the initial diagnostic phase. This study prospectively documents RTW-rate, time-to-RTW, work productivity loss, and activity impairment, within the first-year post-surgery among Chinese women with breast cancer (BCW) and identify potential causal co-variants. Methods: This observational longitudinal study followed 371 Chinese BCW who were employed/self-employed at the time of diagnosis at 4-week post-surgery (baseline). RTW-status and time-to-RTW were assessed at baseline (T1), 4-month (T2), 6-month (T3), and 12-month (T4) post-baseline. WPAI work productivity loss and activity impairment were assessed at T4. Baseline covariates included demographics, medical-related factors, work satisfaction, perceived work demand, work condition, RTW self-efficacy, B-IPQ illness perception, COST financial well-being, EORTC QLQ-C30 and QLQ-BR23 physical and psychosocial functioning, and HADS psychological distress. Results: A 68.2% RTW-rate (at 12-month post-surgery), prolonged delay in RTW (median = 183 days), and significant proportions of T4 work productivity loss (20%), and activity impairment (26%), were seen. BCW who were blue-collar workers with lower household income, poorer financial well-being, lower RTW self-efficacy, poorer job satisfaction, poorer illness perception, greater physical symptom distress, impaired physical functioning, and unfavorable work conditions were more likely to experience undesired work-related outcomes. Discussion: Using a multifactorial approach, effective RTW interventions should focus on not only symptom management, but also to address psychosocial and work-environmental concerns. An organizational or policy level intervention involving a multidisciplinary team comprising nurses, psychologists, occupational health professionals, and relevant stakeholders in the workplace might be helpful in developing a tailored organizational policy promoting work-related outcomes in BCW.

Rare Breast Cancer Histotypes-A Retrospective Study and Literature Review.

Breast cancer is the most common cancer among women globally and can be classified according to various histological subtypes. Current treatment strategies are typically based on the cancer stage and molecular subtypes. This article aims to address the knowledge gap in the understanding of rare breast cancer. A retrospective study was conducted on 4393 breast cancer patients diagnosed from 1992 to 2012, focusing on five rare subtypes: mucinous, invasive lobular, papillary, mixed invasive and lobular, and pure tubular/cribriform carcinomas. Our analysis, supplemented by a literature review, compared patient characteristics, disease characteristics, and survival outcomes of rare breast cancer patients with invasive carcinoma (not otherwise specified (NOS)). Comparative analysis revealed no significant difference in overall survival rates between these rare cancers and the more common invasive carcinoma (NOS). However, mucinous, papillary, and tubular/cribriform carcinomas demonstrated better disease-specific survival. These subtypes presented with similar characteristics such as early detection, less nodal involvement, more hormonal receptor positivity, and less human epidermal growth factor receptor 2 (HER2) positivity. To conclude, our study demonstrated the diversity in the characteristics and prognosis of rare breast cancer histotypes. Future research should be carried out to investigate histotype-specific management and targeted therapies, given their distinct behavior.

Surgical margin and local recurrence of ductal carcinoma in situ.

PURPOSE: This study aims to evaluate the association between surgical margin status and local recurrence of DCIS. METHODS: A retrospective analysis of a prospectively maintained 20-year DCIS database was performed. >=2 mm margin was defined as clear margin. Local relapse rate between the patients with clear versus close margins were analyzed with Kaplan-Meier analyses. RESULTS: 654 patients were analyzed. Median age was 46.5 (Range 18 - 80). 205 (31.3%) were high grade, 194 (29.7%) were intermediate grade, 143 (21.9%) were low grade. 112 (18.3%) were unknown. 202 (30.9%) were estrogen receptor positive, 49 (7.4%) were negative, 403 (61.6%) patients were unknown. 403 (61.6%) patients received mastectomy while 251 (38.4%) patients received BCS and radiotherapy. 549 (83.9%) patients had clear surgical margin, 50 (7.7%) patients had involved (positive) resection margin, 55 (8.4%) had close margin (<2 mm margin). All patients with involved margin received re-excision of margin, while 21 patients (out of 55 who had close resection margins) received re-excision of margin. Negative surgical margins were achieved after the re-excision. 34 patients with close resection margin decided not to receive re-excision but to undergo adjuvant radiotherapy. After median follow-up of 128 months, the 10-year ipsilateral breast tumor relapse (IBTR) was 4.5% (N = 28), Of which 27 (96.4%) patients had clear margin after the initial surgical treatment of DCIS. 1 (3.6%) patient had close surgical margin. Difference in IBTR between the two groups was not statistically significant (p = 0.692). CONCLUSION: Close surgical margin for DCIS is not associated with increased risk of IBTR.

Pregnancy-related breast cancer: 14-year experience in a tertiary institution in Hong Kong.

BACKGROUND: The incidence of pregnancy-associated breast cancer (PABC) is increasing. Its tumor characteristics and overall survival compared with those in nonpregnant patients remain controversial. While there have been suggestions that PABC patients have a 40 % increase in the risk of death compared to non-pregnant patients, other studies suggested similar disease outcomes. This study aims to review our local experience with PABC. METHODS: Twenty-eight patients diagnosed with PABC and twenty-eight patients diagnosed at premenopausal age randomly selected by a computer-generated system during the same period were recruited. Background characteristics, tumor features, and survival were compared. RESULTS: Among the twenty-eight pregnant patients, seventeen were diagnosed during pregnancy, and eleven were diagnosed in the postpartum period. Compared to the non-pregnant breast cancer patients, they presented with less progesterone receptor-positive tumor (35.7 % vs. 64.2 %, p = 0.03). Although there was no statistically significant difference in tumor size (p = 0.44) and nodal status (p = 0.16), the tumor tended to be larger in size (2.94 +/- 1.82 vs 2.40 +/- 1.69 cm) and with more nodal involvement (35.7 % vs 25.0 %). There was also a trend of delayed presentation to medical attention, with a mean duration of 13.1 weeks in the PABC group and 8.6 weeks in the control group. However, the overall survival did not differ (p = 0.63). CONCLUSION: PABC is increasing in incidence. They tend to have more aggressive features, but overall survival remains similar. A multidisciplinary approach is beneficial for providing the most appropriate care.

Implementing a nurse-led screening clinic for symptom distress with community-based referral for cancer survivors: A feasibility study.

INTRODUCTION: This prospective, single-arm, pragmatic implementation study evaluated the feasibility of a nurse-led symptom-screening program embedded in routine oncology post-treatment outpatient clinics by assessing (1) the acceptance rate for symptom distress screening (SDS), (2) the prevalence of SDS cases, (3) the acceptance rate for community-based psychosocial support services, and (4) the effect of referred psychosocial support services on reducing symptom distress. METHODS: Using the modified Edmonton Symptom Assessment System (ESAS-r), we screened patients who recently completed cancer treatment. Patients screening positive for moderate-to-severe symptom distress were referred to a nurse-led community-based symptom-management program involving stepped-care symptom/psychosocial management interventions using a pre-defined triage system. Reassessments were conducted at 3-months and 9-months thereafter. The primary outcomes included SDS acceptance rate, SDS case prevalence, intervention acceptance rate, and ESAS-r score change over time. RESULTS: Overall, 2988/3742(80%) eligible patients consented to SDS, with 970(32%) reporting ≥1 ESAS-r symptom as moderate-to-severe (caseness). All cases received psychoeducational material, 673/970(69%) accepted psychosocial support service referrals. Among 328 patients completing both reassessments, ESAS-r scores improved significantly over time (p < 0.0001); 101(30.8%) of patients remained ESAS cases throughout the study, 112(34.1%) recovered at 3-month post-baseline, an additional 72(22%) recovered at 9-month post-baseline, while 43(12.2%) had resumed ESAS caseness at 9-month post-baseline. CONCLUSION: Nurse-led SDS programs with well-structured referral pathways to community-based services and continued monitoring are feasible and acceptable in cancer patients and may help in reducing symptom distress. We intend next to develop optimal strategies for SDS implementation and referral within routine cancer care services.

Knowledge, attitudes and intention on fertility preservation among breast cancer patients.

Breast cancer is the most common cancer in reproductive age women. The aim of this study is to assess the knowledge, attitude and intention on fertility preservation among women diagnosed to have breast cancer. This is a multi-centre cross-sectional questionnaire study. Reproductive age women diagnosed with breast cancer attending Oncology, Breast Surgery and Gynaecology Clinics and support groups were invited to participate. Women filled in paper or electronic form of the questionnaire. 461 women were recruited and 421 women returned the questionnaire. Overall, 181/410 (44.1%) women had heard of fertility preservation. Younger age and higher education level were significantly associated with increased awareness of fertility preservation. Awareness and acceptance of the different fertility preservation methods in reproductive age women with breast cancer was suboptimal. However, 46.1% women felt that their fertility concerns affected their decision for cancer treatment in some way.

Effect on Germline Mutation Rate in a High-Risk Chinese Breast Cancer Cohort after Compliance with The National Comprehensive Cancer Network (NCCN) 2023 v.1 Testing Criteria.

BACKGROUND: The National Comprehensive Cancer Network (NCCN) testing criteria for the high-penetrance breast cancer susceptibility genes, specifically BRCA1, BRCA2, CDH1, PALB2, PTEN, and TP53, have been recently modified in 2023 to 2023 v.1. The following criteria have been changed: (1) from a person diagnosed with breast cancer at ≤45 to ≤50; (2) from aged 45-50 of personal breast diagnosis to any age of diagnosis with multiple breast cancers; and (3) from aged ≥51 of personal breast diagnosis to any age of diagnosis with family history listed in NCCN 2022 v.2. METHODS: High-risk breast cancer patients (n = 3797) were recruited from the Hong Kong Hereditary Breast Cancer Family Registry between 2007 and 2022. Patients were grouped according to NCCN testing criteria 2023 v.1 and 2022 v.2. A 30-gene panel for hereditary breast cancer was performed. The mutation rates on high-penetrance breast cancer susceptibility genes were compared. RESULTS: About 91.2% of the patients met the 2022 v.2 criteria, while 97.5% of the patients met the 2023 v.1 criteria. An extra 6.4% of the patients were included after the revision of the criteria, and 2.5% of the patients did not meet both testing criteria. The germline BRCA1/2 mutation rates for patients meeting the 2022 v.2 and 2023 v.1 criteria were 10.1% and 9.6%, respectively. The germline mutation rates of all 6 high-penetrance genes in these two groups were 12.2% and 11.6%, respectively. Among the additional 242 patients who were included using the new selection criteria, the mutation rates were 2.1% and 2.5% for BRCA1/2 and all 6 high-penetrance genes, respectively. Patients who did not meet both testing criteria were those with multiple personal cancers, a strong family history of cancers not listed in the NCCN, unclear pathology information, or the patient's voluntary intention to be tested. The mutation rates of BRCA1/2 and the 6 high-penetrance genes in these patients were 5.3% and 6.4%, respectively. CONCLUSION: This study provided a real-world application of the revision of NCCN guidelines and its effect on the germline mutation rate in the Chinese population. Applying the updated criteria for further genetic investigation would increase the positive detection rate, and potentially more patients would benefit. The balance between the resource and outcome requires careful consideration.

Use of Superparamagnetic Iron Oxide (SPIO) Versus Conventional Technique in Sentinel Lymph Node Detection for Breast Cancer: A Randomised Controlled Trial.

BACKGROUND: The objective of this study is to compare the efficacy of the superparamagnetic iron oxide (SPIO)-guided and standard techniques for sentinel lymph node (SLN) detection in early breast cancer. Multiple inferiority trials have concluded the non-inferiority of SPIO to the conventional radioisotope technique, with or without blue dye, in detecting SLNs. PATIENTS AND METHODS: From July 2018 to August 2022, patients clinically diagnosed with node-negative invasive breast cancer were randomised into the study group (SPIO) and control group (radioisotope and blue dye). Patient data and disease characteristics were prospectively collected. SLN detection rates were compared between the two groups. RESULTS: A total of 282 patients undergoing 288 sentinel lymph node biopsy (SLNB) procedures were recruited, and 144 SLNB procedures were randomised into each group. The baseline patient and disease characteristics were comparable. SLN localisation failed in one patient in each group; the success rate of SLNB was 99.3%. The SPIO group demonstrated a higher mean number of SLNs harvested (3.3 versus 2.8, p = 0.039) and longer mean procedure duration (33.1 min versus 22.3 min, p = 0.01) than the control group did. In the study group, the concordance rates per patient and node were 99.3% and 94.6%, respectively. Sixty-seven positive SLNs were detected in 37 patients. The concordance rates per malignant SLNB procedure and positive SLN were 97.3% and 96.8%, respectively. CONCLUSION: Single-tracer SPIO-guided SLNB was non-inferior to the dual technique (radioisotope and blue dye) and could safely replace the gold standard for SLN mapping in early breast cancer.

Prospective Clinical Trial on Expanding Indications for Cryosurgery for Early Breast Cancers.

INTRODUCTION: This is a prospective single arm clinical trial on cryosurgery for early breast cancers, to evaluate the expanded criteria to tumors larger than 1.5 cm and non-luminal breast cancers. METHODS: Inclusion criteria include Solitary T1 breast cancers of any immunohistotypes. Cryosurgery was performed using the IceCure ProSense Cryoablation System. Lumpectomy of the cryoablated tumor was then performed 8 weeks after cryosurgery. RESULTS: Fifteen patients underwent cryosurgery followed by lumpectomy (BCS). Median age was 53 years old 5 (33.3%) patients had ductal carcinoma in situ (DCIS), while 10 (66.7%) patients had invasive ductal carcinoma (IDC), of which 5 (50%) patients had luminal type cancers of which 3 (60%) were luminal A and 2 (40%) luminal B, 3 (30%) patients had HER2 enriched invasive carcinoma and 2 (20%) patients had triple negative IDC. Median tumor size was 13mm (Range 8.6-18mm). Seven (46.7%) patients were found to have residual cancer in the post-cryosurgery lumpectomy specimen. All residual cancers were found at the periphery of the cryoablated breast tissue. All breast cancers were otherwise completely ablated centrally as confirmed by routine histopathology, immunochemistry and TUNEL assay for evaluation of cell viability. None of the tumor factors such as tumor biology, as well as surgical factors such as ablation time and iceball size, were associated with risk of residual cancer. None of the 15 patients developed post-operative complications. CONCLUSION: Residual cancer occurs at the periphery of the cryoablation site, careful pre-operative planning and intra-operative monitoring is crucial to ensure complete cryoablation.

Study protocol of ConquerFear-HK: a randomised controlled trial of a metacognition-based, manualised intervention for fear of cancer recurrence among Chinese cancer survivors.

INTRODUCTION: Fear of cancer recurrence (FCR) is a prevalent and frequently debilitating response to a cancer diagnosis, affecting a substantial proportion of cancer survivors. Approximately 30% of local Hong Kong Chinese cancer survivors in a recent survey reportedly experienced persistent high FCR over the first-year post-surgery. This was associated with lower levels of psychological well-being and quality of life. A manualised intervention (ConquerFear) developed primarily based on the Self-Regulatory Executive Function Model and the Rational Frame Theory, has been found to reduce FCR effectively among Caucasian cancer survivors. The intervention now has been adapted to a Chinese context; ConquerFear-HK. The primary aim of this study is to evaluate its efficacy vs a standard-survivorship-care control (BasicCancerCare) in FCR improvement in a randomised control trial (RCT). METHODS AND ANALYSIS: In this RCT, using the sealed envelope method, 174 eligible Chinese cancer survivors will be randomised to either the ConquerFear-HK or BasicCancerCare intervention. Both interventions include six sessions over 10 weeks, which will be delivered via face to face or online by trained therapists. The ConquerFear-HK intervention incorporates value classification, metacognitive therapy, attentional training, detached mindfulness and psychoeducation; BasicCancerCare includes relaxation training, dietary and physical activity consultations. Participants will be assessed at prior randomisation (baseline; T0), immediately postintervention (T1), 3 months (T2) and 6 months postintervention (T3) on the measures of FCR (Fear of Cancer Recurrence Inventory) as a primary outcome; metacognition (30-item Metacognitions Quesionnaire) and cognitive attentional syndrome (Cognitive-attentional Syndrome Questionnaire) as process outcomes; psychological distress (Hospital Anxiety and Depression Scale), cancer-related distress (Chinese Impact of Events Scale), quality of life (European Organisation for Research and Treatment of Cancer Quality of Life Core Questionnaire) and treatment satisfaction are secondary outcomes. ETHICS AND DISSEMINATION: Ethics approval has been obtained from HKU/HA HKW Institutional Review Board (ref: UW19-183). The patients/participants provide their written informed consent to participate in this study. The study results will be disseminated through international peer-review publications and conference presentations. TRIAL REGISTRATION NUMBER: NCT04568226.

Molecular characteristics of Asian male BRCA-related cancers.

PURPOSE: Germline mutations of BRCA1 or BRCA2 predispose men to develop various cancers, including breast cancers and prostate cancers. Male breast cancer (MBC) is a rare disease while prostate cancer (PRC) is uncommon in young men at the age of less than 40. The prevalence of BRCA genes in Asian male patients has to be elevated. METHODS: Germline mutations screening was performed in 98 high-risk Chinese MBC and PRC patients. RESULT: We have identified 16 pathogenic BRCA2 mutation carriers, 12 were MBC patients, 2 were PRC patients and 2 were patients with both MBC and PRC. The mutation percentages were 18.8%, 6.7% and 50% for MBC, PRC and both MBC and PRC patients, respectively. BRCA2 gene mutations confer a significantly higher risk of breast/prostate cancers in men than those with BRCA1 mutations. BRCA mutated MBC patients had a younger age of diagnosis and strong family histories of breast cancers while BRCA mutated PRC patients had strong family histories of ovarian cancers. CONCLUSION: Male BRCA carriers with breast cancers or prostate cancers showed distinct clinical and molecular characteristics, a male-specific genetic screening model would be useful to identify male cancer patients who have a high risk of BRCA mutation.

Delayed Sentinel Lymph Node Dissection in Patients with a Preoperative Diagnosis of Ductal Cancer In Situ by Preoperative Injection with Superparamagnetic Iron Oxide (SPIO) Nanoparticles: The SentiNot Study.

BACKGROUND: Difficulty in preoperatively assessing the risk for occult invasion or surgery that precludes future accurate axillary mapping in patients with ductal cancer in situ (DCIS) account for overutilization of SLND. METHODS: Prospective, multicenter, cohort study, including women with any DCIS planned for mastectomy or DCIS grade 2 and > 20 mm, any DCIS grade 3, any mass-forming DCIS and any planned surgery. Patients received an interstitial SPIO injection during breast surgery, but no upfront SLND was performed. If invasion was identified on final pathology, delayed SLND (d-SLND) was performed separately with the coadministration of isotope ± blue dye (BD). Study outcomes were proportion of upfront SLNDs that were avoided, detection rates during d-SLND, and impact on healthcare costs. RESULTS: In total, 78.7% of study participants (N = 254, mean age 60 years, mean DCIS size 37.8 mm) avoided upfront SLND. On d-SLND (median 28 days, range 9-46), SPIO outperformed Tc99 with (98.2% vs. 63.6%, p < 0.001) or without BD (92.7% vs. 50.9%, p < 0.001) and had higher nodal detection rate (86.9% vs. 32.3%, p < 0.001) and with BD (93.9% vs. 41.4%, p < 0.001). Only 27.9% of all SLNs retrieved were concordant for Tc99 and SPIO. Type of breast procedure (WLE vs. oncoplastic BCT vs. mastectomy) affected these outcomes and accounted for the low performance of Tc99 (p < 0.001). d-SLND resulted in a 28.1% total cost containment for women with pure DCIS on final pathology (4190 vs. 5828 USD, p < 0.001). CONCLUSIONS: Marking the SLN with SPIO may avoid overtreatment and allow for accurate d-SLND in patients with DCIS.

Axillary Reverse Mapping in the Prevention of Lymphoedema: A Systematic Review and Pooled Analysis.

BACKGROUND: This is a systematic review of randomized controlled trials (RCT) comparing the use of axillary reverse mapping (ARM) with conventional technique for axillary dissection (AD) in breast cancer surgery. METHODS: This review was written in line with the PRISMA protocol. Articles were retrieved from PubMed, EMBASE, CINAHL and Cochrane databases, using keywords ..úaxillary reverse mapping..Ñ and "axillary lymph node dissection". Non-RCT were excluded. Abstracts were screened independently by 2 reviewers. Data from eligible studies were retrieved for qualitative synthesis and pooled analysis. 73 publications were identified for initial screening. RESULTS: 68 articles were excluded from analysis according to the pre-defined systematic review protocol. 5 RCTS with 1696 subjects were included for analysis. 802 patients received ARM, 894 patients received AD. Pooled ARM node detection rate was 84.9% (Range 79.2 - 94.9%). There was a lower rate of post-operative lymphedema in ARM group patients across all 5 RCTs. The pooled lymphedema incidence in the ARM group was 4.8% (37/766) when compared to 18.8% (164/873) in the AD group (P < .0001). Axillary recurrence rate with median followof 37 months was 1.03% (8/778) in the ARM group, which was identical to 1.03% (9/870) in the AD group (P = 1). CONCLUSION: ARM resulted in decreased incidence of lymphedema. There was no significant increase in axillary recurrence at 37 months post-operation.

Assessing variability in breast cancer management across the world: results of a questionnaire survey amongst global international experts in breast cancer management.

Background: Breast cancer is the most common cancer in women worldwide with an estimated 2.3 million breast cancer cases diagnosed annually. The outcome of breast cancer management varies widely across the globe which could be due to a multitude of factors. Hence, a blanket approach in standardisation of care across the world is neither practical nor feasible. Aim: To assess the extent and type of variability in breast cancer management across the globe and to do a gap analysis of patient care pathway. Method: An online questionnaire survey and virtual consensus meeting was carried out amongst 31 experts from 25 countries in the field of breast cancer surgical management. The questionnaire was designed to understand the variability in diagnosis and treatment of breast cancer, and potential factors contributing to this heterogeneity. Result: The questionnaire survey shows a wide variation in breast surgical training, diagnosis and treatment pathways for breast cancer patients. There are several factors such as socioeconomic status, patient culture and preferences, lack of national screening programmes and training, and paucity of resources, which are barriers to the consistent delivery of high-quality care in different parts of the world. Conclusion: On-line survey platforms distributed to global experts in breast cancer care can assess gaps in the diagnosis and treatment of breast cancer patients. This survey confirms the need for an in-depth gap analysis of patient care pathways and treatments to enable the development of personalised plans and policies to standardise high quality care.

Inhibition of EP2 receptor suppresses tumor growth and chemoresistance of gastric cancer.

Gastric cancer is one of the leading causes of cancer death in the world. Early diagnosis and effective chemotherapy are vital to reduce the overall mortality. Prostaglandin E2 (PGE2) has been implicated as an important factor in gastric cancer carcinogenesis. ECF based regimen (epirubicin, cisplatin, 5-fluorouracil) is the first-line chemotherapy for advanced gastric cancer. However, patients develop resistance after chemotherapy. The aim of this study is sought to investigate the role of EP2 receptor, a PGE2 receptor, and the antagonism of EP2 receptor in response to ECF treatment. Expression of EP2 receptor was evaluated in gastric cancer tissue samples and cell lines. Cell proliferation and cell apoptosis assays were performed in vitro and in vivo, upon knockdown of EP2 receptor, antagonist of EP2 receptor and/or ECF treatment. Western Blot was applied for evaluation of proteins relating to cell cycle, apoptosis and drug transporter. Next generation sequencing and ingenuity pathway analysis were applied for screening for downstream targets of EP2 receptor. Expressions of the targets of EP2 receptor were further evaluated in gastric cancer cells and tissues. In this study, we found that expression of EP2 receptor was significantly upregulated in gastric cancer. Inhibition of EP2 receptor reduced gastric cancer cell proliferation, induced cell cycle arrest proteins, and enhanced cell apoptosis. Moreover, knockdown of EP2 receptor by siRNA or antagonist sensitized gastric cancer cells to ECF. Silence of EP2 receptor also significantly abrogated gastric cancer growth in a mice model. Analysis revealed that CAV1 was a downstream target of EP2 receptor in gastric cancer. Our findings illustrated that blocking EP2 receptor reduced tumor growth and induced apoptosis in gastric cancer. This novel study unraveled CAV1 was a downstream target of EP2 receptor. Antagonizing EP2 receptor could be a potential therapeutic target in gastric cancer, in particular those with high EP2 receptor expression.

Genome- and transcriptome-wide association studies of 386,000 Asian and European-ancestry women provide new insights into breast cancer genetics.

By combining data from 160,500 individuals with breast cancer and 226,196 controls of Asian and European ancestry, we conducted genome- and transcriptome-wide association studies of breast cancer. We identified 222 genetic risk loci and 137 genes that were associated with breast cancer risk at a p < 5.0 × 10-8 and a Bonferroni-corrected p < 4.6 × 10-6, respectively. Of them, 32 loci and 15 genes showed a significantly different association between ER-positive and ER-negative breast cancer after Bonferroni correction. Significant ancestral differences in risk variant allele frequencies and their association strengths with breast cancer risk were identified. Of the significant associations identified in this study, 17 loci and 14 genes are located 1Mb away from any of the previously reported breast cancer risk variants. Pathways analyses including 221 putative risk genes identified multiple signaling pathways that may play a significant role in the development of breast cancer. Our study provides a comprehensive understanding of and new biological insights into the genetics of this common malignancy.