Background: With greater awareness and increased screening, cancers are increasingly being diagnosed at stage I. Women with these small node-negative tumours have excellent survival prospects after surgery, but many women, especially those with triple-negative and human epidermal growth factor receptor (HER)-2-positive tumours, still receive adjuvant systemic treatments to reduce the recurrence risk. Aims: We review the outcomes of women diagnosed with stage I (T1N0M0) tumours in our unit and examine the effect of systemic chemotherapy with/without targeted therapy on recurrence patterns and survival outcomes. Results: We reviewed 643 women diagnosed with T1N0M0 disease over a 10-year period. Five-year recurrence-free survival (RFS) was 96.6% and the 10-year RFS was 95.5%. Recurrence occurred in 4.7% of the women and was limited to locoregional sites in two-thirds of the instances. Systemic recurrences developed in 12 women, all of whom had ER-positive/HER2-negative disease. The mode of surgery emerged as the only independent predictor of recurrence. Recurrence was highest in women treated with wide local excision (WLE) alone (p < 0.05), but not in those who had received breast radiation after WLE (p = 0.112). Systemic chemotherapy, with or without anti-HER2 therapy, was discussed with 334 women, of whom 50.6% received the treatment; these women were more often younger and had triple-negative or HER2-positive tumours (p < 0.001). Women who received chemotherapy showed a non-significant tendency to develop locoregional recurrence (p = 0.104), but the number of systemic recurrences were similar to those documented in women who had not received chemotherapy. Chemotherapy and/or targeted treatment was not observed to have a significant effect on 5-year recurrence-free survival (p = 0.444). Conclusions: Stage I cancers have excellent survival outcomes. An optimal local surgical treatment is important and we did not find chemotherapy and/or targeted therapy to produce any significant differences in survival.

BACKGROUND:There are concerns that tamoxifen is less effective in Asian women because of the high prevalence of impaired function cytochrome P450 2D6 (CYP2D6) polymor-phisms.AIM:To evaluate how knowledge of CYP2D6 genotype impacted the choice of hormonal agent and how CYP2D6 genotype and agent were associated with clinical outcomes.METHODS:Eighty-two women were recruited. Seventy-eight completed CYP2D6 genotyping and were categorized into poor, intermediate (IM) and extensive or ultra metabolizer phenotypes. Women with poor metabolizer and IM phenotypes were recommended aromatase inhibitors as the preferred agent.RESULTS:More than 70% of the women had an IM phenotype, 32% an extensive or ultra metabolizer phenotype, and 0% had a poor metabolizer phenotype. Regardless of genotype, more women opted for aromatase inhibitors. Overall, 80% of women completed 5 years of hormonal therapy. Five women developed recurrence, 3 contralateral breast cancer, 5 died, and 1 was diagnosed with a second primary cancer. Five-year recurrence-free and overall survival were slightly better in women with the extensive or ultra metabolizer phenotype compared to those with the IM phenotype, though not statistically significant [P = 0.743, hazard ratio (HR): 1.441, 95% confidence interval (CI): 0.191 to 10.17 and P = 0.798, HR: 1.327, 95%CI: 0.172 to 9.915, respectively]. Women receiving aromatase inhibitors also appeared to have a better, but also nonsignificant, 5-year recurrence-free and overall survival (P = 0.253, HR: 0.368, 95%CI: 0.031 to 0.258 and P = 0.292, HR: 0.252, 95%CI: 0.005 to 4.951, respectively).CONCLUSION:The IM phenotype was highly prevalent but was not associated with clinical outcome.

Objectives To evaluate the potential of contrast-enhanced spectral mammography (CESM) in reducing benign breast biopsy rate, thereby improving resource utilization. To explore its potential as a value-adding modality in the management of BI-RADS 4/5 lesions. Materials and Methods This was a prospective study conducted between July 2016 and September 2018. Patients with BI-RADS 4/5 lesions detected on conventional imaging (mammogram, digital breast tomosynthesis, and ultrasound) were enrolled for adjunct CESM. Histopathologic correlation was done for all lesions. Additional suspicious lesions detected on CESM were all identified on second-look ultrasound and subsequently biopsied. Images were evaluated independently by two radiologists trained in breast imaging using BI-RADS classification. Presence of enhancement on CESM, BI-RADS score, and histopathology of each lesion were analyzed and tested with the chi-square/fisher-exact test for statistical significance. Results The study included 105 lesions in 63 participants—1 man and 62 women, an average age of 53.7 ± 10.8 years. On CESM, 22 (20.9%) of the lesions did not show enhancement. All 22 lesions had been classified as BI-RADS 4A and were subsequently proven to be benign. Of the remaining 83 enhancing lesions, 54 (65.1%) were malignant and 29 (34.9%) were benign (p < 0.05). CESM detected 6 additional lesions which were not identified on initial conventional imaging. Four of these were proven malignant and were in a different quadrant than the primary lesion investigated. Conclusion There is evidence that the absence of enhancement in CESM strongly favors benignity. It may provide the reporting radiologist with greater confidence in imaging assessment, especially in BI-RADS 4A cases, where a proportion of them are in actuality BI-RADS 3. Greater accuracy of BI-RADS grading can reduce nearly half of benign biopsies and allow better resource allocation. CESM also increases the detection rate of potentially malignant lesions, thereby changing the treatment strategies.

Background: The hypothesis that breast cancer (BC) susceptibility variants are linked to chemotherapy-induced toxicity has been previously explored. Here, we investigated the association between a validated 313-marker-based BC polygenic risk score (PRS) and chemotherapy-induced neutropenia without fever and febrile neutropenia (FNc) in Asian BC patients. Methods: This observational case-control study of Asian BC patients treated with chemotherapy included 161 FNc patients, 219 neutropenia patients, and 936 patients who did not develop neutropenia. A continuous PRS was calculated by summing weighted risk alleles associated with overall, estrogen receptor- (ER-) positive, and ER-negative BC risk. PRS distributions neutropenia or FNc cases were compared to controls who did not develop neutropenia using two-sample t-tests. Odds ratios (OR) and corresponding 95% confidence intervals were estimated for the associations between PRS (quartiles and per standard deviation (SD) increase) and neutropenia-related outcomes compared to controls. Results: PRS distributions were not significantly different in any of the comparisons. Higher PRSoverall quartiles were negatively correlated with neutropenia or FNc. However, the associations were not statistically significant (PRS per SD increase OR neutropenia: 0.91 [0.79–1.06]; FNc: 0.87 [0.73–1.03]). No dose-dependent trend was observed for the ER-positive weighted PRS (PRSER-pos) and ER-negative weighted PRS (PRSER-neg). Conclusion: BC PRS was not strongly associated with chemotherapy-induced neutropenia or FNc.

Background A breast cancer polygenic risk score (PRS) comprising 313 common variants reliably predicts disease risk. We examined possible relationships between genetic variation, regulation, and expression to clarify the molecular alterations associated with these variants. Methods Genome-wide methylomic variation was quantified (MethylationEPIC) in Asian breast cancer patients (1152 buffy coats from peripheral whole blood). DNA methylation (DNAm) quantitative trait loci (mQTL) mapping was performed for 235 of the 313 variants with minor allele frequencies > 5%. Stability of identified mQTLs (p < 5e-8) across lifetime was examined using a public mQTL database. Identified mQTLs were also mapped to expression quantitative trait loci (eQTLs) in the Genotype-Tissue Expression Project and the eQTLGen Consortium. Results Breast cancer PRS was not associated with DNAm. A higher proportion of significant cis-mQTLs were observed. Of 822 significant cis-mQTLs (179 unique variants) identified in our dataset, 141 (59 unique variants) were significant (p < 5e-8) in a public mQTL database. Eighty-six percent (121/141) of the matched mQTLs were consistent at multiple time points (birth, childhood, adolescence, pregnancy, middle age, post-diagnosis, or treatment). Ninety-three variants associated with DNAm were also cis-eQTLs (35 variants not genome-wide significant). Multiple loci in the breast cancer PRS are associated with DNAm, contributing to the polygenic nature of the disease. These mQTLs are mostly stable over time. Conclusions Consistent results from DNAm and expression data may reveal new candidate genes not previously associated with breast cancer.

In this article, we report for the first time, the detection of circulating miRNA as a breast cancer biomarker in patient sera using surface plasmon resonance imaging biosensor. The advantage of this approach lies in the rapid, label-free and sensitive detection. The sensor excites plasmonic resonance on the gold sensor surface and specific DNA-miRNA molecular bindings elucidate responses in the plasmonic resonance image. Experiments of detecting synthetic miRNA molecules (miR-1249) were performed and the sensor resolution was found to be 63.5 nM. The sensor was further applied to screen 17 patient serum samples from National Cancer Centre Singapore and Tan Tock Seng Hospital. Sensor intensity response was found to differ by 20% between malignant and benign cases and thus forms, a potential and an important metric in distinguishing benignity and malignancy.

Abstract Background Mutations in certain genes are known to increase breast cancer risk. We study the relevance of rare protein-truncating variants (PTVs) that may result in loss-of-function in breast cancer susceptibility genes on tumor characteristics and survival in 8852 breast cancer patients of Asian descent. Methods Gene panel sequencing was performed for 34 known or suspected breast cancer predisposition genes, of which nine genes (ATM, BRCA1, BRCA2, CHEK2, PALB2, BARD1, RAD51C, RAD51D, and TP53) were associated with breast cancer risk. Associations between PTV carriership in one or more genes and tumor characteristics were examined using multinomial logistic regression. Ten-year overall survival was estimated using Cox regression models in 6477 breast cancer patients after excluding older patients (≥75years) and stage 0 and IV disease. Results PTV9genes carriership (n = 690) was significantly associated (p < 0.001) with more aggressive tumor characteristics including high grade (poorly vs well-differentiated, odds ratio [95% confidence interval] 3.48 [2.35–5.17], moderately vs well-differentiated 2.33 [1.56–3.49]), as well as luminal B [HER−] and triple-negative subtypes (vs luminal A 2.15 [1.58–2.92] and 2.85 [2.17–3.73], respectively), adjusted for age at diagnosis, study, and ethnicity. Associations with grade and luminal B [HER2−] subtype remained significant after excluding BRCA1/2 carriers. PTV25genes carriership (n = 289, excluding carriers of the nine genes associated with breast cancer) was not associated with tumor characteristics. However, PTV25genes carriership, but not PTV9genes carriership, was suggested to be associated with worse 10-year overall survival (hazard ratio [CI] 1.63 [1.16–2.28]). Conclusions PTV9genes carriership is associated with more aggressive tumors. Variants in other genes might be associated with the survival of breast cancer patients. The finding that PTV carriership is not just associated with higher breast cancer risk, but also more severe and fatal forms of the disease, suggests that genetic testing has the potential to provide additional health information and help healthy individuals make screening decisions.

INTRODUCTION:Idiopathic granulomatous mastitis (IGM) is a rare, benign, chronic breast condition that can cause repeated abscesses or mass formation in bilateral breasts. The condition can severely impact the quality of life of affected women. This study aims to evaluate effective treatment modalities, as well as understand the demographics and clinical presentation of patients with IGM.METHODS:An 11-year retrospective review was performed of patients diagnosed with IGM from 1 January 2008 to 31 December 2018 at a tertiary breast unit.RESULTS:A total of 77 patients were included in the study. The median age at presentation was 36 years old. IGM presented most commonly as a breast lump (98.1%). The median number of flares was 2 (1-12). Of the 77 patients, 68.8% (53) were treated with antibiotics, 50.6% (39) with steroids, and 44.2% (34) underwent surgery, in the course of their IGM treatment. Forty-five (59.2%) of the 76 patients with IGM required a multimodal treatment approach to achieve remission. There was no significant difference in the number of flares no matter the initial treatment (P=0.411), or subsequent treatment modality (P=0.343). Smokers had 10 times greater odds of having a "high flare" of IGM compared to those who did not smoke (P=0.031, odds ratio 10.444, 95% confidence interval 1.092-99.859).CONCLUSION:IGM is a clinical diagnosis. It is a rare, relapsing breast inflammatory condition that affects young females with no superior treatment modality. Smoking is associated with higher number of flares of IGM and should be discouraged in IGM patients.

Background: Breast Magnetic Resonance Imaging (MRI) has been shown superior to mammography and ultrasound in terms of cancer detection and tumour size estimation. However, breast MRI is seldom done at our unit because of its cost. Aims: We reviewed 31 women (32 cancers) who had preoperative MRI and evaluated the impact of additional MRIdetected lesions on surgical planning and margin status. Results: Breast MRI was done to evaluate suitability for breast conservation in 20 women and as further evaluation of inconclusive or discordant mammography and ultrasound findings in the other 11. Additional lesions were detected in 24 of 31 (77.4%) women. Additional cancer foci occult on mammography and ultrasound were detected in 10 women (32.2%); with additional cancers found in the contralateral breast in 3 of these women. Surgical margins were found inadequate in 5 of 18 (27.8%) women who underwent wide local excision, in whom a larger, but statistically nonsignificant, difference between imaging and actual pathological tumour size was observed. Both ultrasound and MRI tumour size estimation correlated significantly with actual pathological tumour size, with tumour size estimation on breast MRI being most precise (P <0.001, rho=0.732, 95% CI: 0.505 – 0.864). Ultrasound tended to underestimate tumour size more frequently compared to breast MRI (P <0.001 and P=0.956 respectively). Conclusion: Breast MRI detected tumours occult on mammography and ultrasound and estimated tumour size most accurately. Two-thirds of additional lesions detected on MRI were non-malignant. Breast conservation rate was high in those with normal or benign MRI findings.

Mammography is extensively used for breast cancer screening but has high false-positive rates. Here, prospectively collected blood samples were used to identify circulating microRNA (miRNA) biomarkers to discriminate between malignant and benign breast lesions among women with abnormal mammograms. The Discovery cohort comprised 72 patients with breast cancer and 197 patients with benign breast lesions, while the Validation cohort had 73 and 196 cancer and benign cases, respectively. Absolute expression levels of 324 miRNAs were determined using RT-qPCR. miRNA biomarker panels were identified by: (1) determining differential expression between malignant and benign breast lesions, (2) focusing on top differentially expressed miRNAs, and (3) building panels from an unbiased search among all expressed miRNAs. Two-fold cross-validation incorporating a feature selection algorithm and logistic regression was performed. A six-miRNA biomarker panel identified by the third strategy, had an area under the curve (AUC) of 0.785 and 0.774 in the Discovery and Validation cohorts, respectively, and an AUC of 0.881 when differentiating between cases versus those with benign lesions or healthy individuals with normal mammograms. Biomarker panel scores increased with tumor size, stage and number of lymph nodes involved. Our work demonstrates that circulating miRNA signatures can potentially be used with mammography to differentiate between patients with malignant and benign breast lesions.

This article aims to provide a detailed description of the Singapore Breast Cancer Cohort (SGBCC), an ongoing multi-ethnic cohort established with the overarching goal to identify genetic markers for breast cancer risk, prognosis and treatment response, as well as to understand the ethnic differences in disease risk and outcome in an Asian setting. The cohort comprises of breast cancer patients aged 21 years and above from six public hospitals which diagnose and treat nearly 76% breast cancer cases in Singapore. Self-reported data on sociodemographic and lifestyle, reproductive risk factors, medical history and family history of breast or ovarian cancer is collected using a structured questionnaire. Clinical data on tumour characteristics, and treatment modalities are obtained through medical record. Bio-specimens (blood or saliva) is collected at recruitment. Follow-up on survival information is done through routine linkage with the Registry of Births and Deaths. As of 31 December 2016, 7,768 subjects have been recruited to the study with 76% subjects contributed bio-specimens. The SGBCC provides a valuable platform which offers a unique, large and rich resource for new research ideas on breast cancer related phenotypic risk factors and genetic markers.

INTRODUCTION:Advanced breast cancer (ABC) remains common in Singapore. In 2019, 22.1% of breast cancer patients presented with ABC in our institution. Despite increasing affluence and the advent of national mammographic screening, the incidence of ABC has not changed significantly. This suggests inherent differences in women who present late. We aim to explore the socio-economic background, knowledge and attitudes of women who present with ABC.METHODS:Between December 2013 and July 2015, 100 patients who presented consecutively with ABC in a tertiary institution in Singapore were recruited to participate in an interviewer-led questionnaire exploring psychosocial and economic issues.RESULTS:Among the 100 patients, 63 and 37 presented with stages 3 and 4 breast cancer respectively. Median age was 57 (27-86), 52% had at least secondary education, 53% had no formal employment and 71% were married; 88% were aware of breast cancer symptoms, 82% were aware that mammography can help detect cancer, 82% believed that current treatment modality for breast cancer is effective, 96% had never undergone a mammography and 52.9% felt mammograms were unnecessary. A total of 64% presented symptomatic from the breast tumour, with a median duration of 3 months. Many of the patients were aware of breast cancer symptoms and the utility of mammography. However, a group of patients did not comply with screening. This may be due to poor understanding about breast screening and detection in its asymptomatic phase.CONCLUSION:Further public education to improve understanding of breast cancer and screening mammography may help to improve rates for earlier detection of breast cancer.

Polygenic risk scores (PRS) have been shown to predict breast cancer risk in European women, but their utility in Asian women is unclear. Here we evaluate the best performing PRSs for European-ancestry women using data from 17,262 breast cancer cases and 17,695 controls of Asian ancestry from 13 case-control studies, and 10,255 Chinese women from a prospective cohort (413 incident breast cancers). Compared to women in the middle quintile of the risk distribution, women in the highest 1% of PRS distribution have a ~2.7-fold risk and women in the lowest 1% of PRS distribution has ~0.4-fold risk of developing breast cancer. There is no evidence of heterogeneity in PRS performance in Chinese, Malay and Indian women. A PRS developed for European-ancestry women is also predictive of breast cancer risk in Asian women and can help in developing risk-stratified screening programmes in Asia.

Objectives: Although Triple Negative Breast Cancers (TNBCs) are known as a particularly aggressive subtype, some women have a favorable prognosis and recurrence after the initial few years is uncommon. In this study, we reviewed the outcome of women with TNBC and evaluated factors potentially useful for risk stratification. Methods: Retrospective review was performed of 345 patients diagnosed with TNBC at two local institutes from 2006 to 2011. Detailed analyses focused on 315 women without metastasis. Results: TNBC accounted for 11.3% of cancers diagnosed and was most prevalent among Indian women. Disease recurrence was a significant determinant of overall survival (P<0.001) and apart from the disease stage (P<0.001), it was independently associated with ethnicity (P=0.011). Recurrence was two-fold higher among Malay and Indian women compared to Chinese women (P=0.027) and 5-year recurrence-free survival was significantly shorter compared to Chinese women (P=0.031, HR 2.575, 95% CI 0.165 to 0.915; P=0.034, HR 2.090, 95% CI 0.514 to 0.929). On the other hand, 5-year recurrence-free survival was similar between Malay and Indian women (P=0.987). This survival difference could not be attributed to differences in disease factors or stage at presentation, and apart from more Malay women receiving radiation (P=0.020), due to higher rates of breast conservation in this group, the women all received similar treatments. Conclusions: Ethnicity and disease stage were identified as independent predictors of disease recurrence in women with TNBC, with Chinese women having better survival outcomes.

Background: Breast tumors with low Estrogen Receptor (ER) expression cluster more closely with ER-negative tumors on a molecular level and may not derive the same benefit from hormonal therapy as ER-positive tumors. In this study, we examined the effect of hormonal therapy on survival outcomes in low ER-positive tumors. Methods: Retrospective review was done of 2872 women diagnosed with breast cancer at Tan Tock Seng Hospital from 2001 to 2012. Low ER-positive tumors were defined as tumors where 1% to 9% of cells stained positive for ER. Results: Low ER-positive tumors were found in 171 women, 70% of whom received hormonal therapy. Compared to tumors demonstrating at least 10% ER expression, low ER-positive tumors were more common in younger (P<0.001), non-Chinese (P=0.018) women and were more likely to be high grade (P=0.003 and P<0.001 for DCIS and invasive cancers respectively), Progesterone Receptor (PR)-negative (P<0.001) and human epidermal growth factor receptor (HER)-2 overexpressing (P<0.001). Distant disease-free survival among low ER-positive tumors was significantly worse compared to tumors expressing at least 10% ER (P=0.005), but closely overlapped that of ER-negative tumors (P=0.574). Nevertheless, hormonal therapy was still found to reduce disease recurrence, both locoregional and distant, in women with low ER-positive tumors (P=0.042 and P<0.001 respectively) and improved 10-year distant disease-free and overall survival outcomes (P<0.001 and P=0.004 respectively). An advanced stage at presentation (P=0.002,), PR-negativity (P=0.042) and the omission of hormonal therapy (P<0.001) increased the risk of distant recurrence in women with low ER-positive tumors. Conclusion: Hormonal therapy conferred clinical benefit in low ER-positive tumors and should be considered especially in those with advanced or PR-negative tumors who are at high risk of distant recurrence.

Although mammography is the gold standard for breast cancer screening, the high rates of false-positive mammograms remain a concern. Thus, there is an unmet clinical need for a non-invasive and reliable test to differentiate between malignant and benign breast lesions in order to avoid subjecting patients with abnormal mammograms to unnecessary follow-up diagnostic procedures. Serum samples from 116 malignant breast lesions and 64 benign breast lesions were comprehensively profiled for 2,083 microRNAs (miRNAs) using next-generation sequencing. Of the 180 samples profiled, three outliers were removed based on the principal component analysis (PCA), and the remaining samples were divided into training (n = 125) and test (n = 52) sets at a 70:30 ratio for further analysis. In the training set, significantly differentially expressed miRNAs (adjusted p < 0.01) were identified after correcting for multiple testing using a false discovery rate. Subsequently, a predictive classification model using an eight-miRNA signature and a Bayesian logistic regression algorithm was developed. Based on the receiver operating characteristic (ROC) curve analysis in the test set, the model could achieve an area under the curve (AUC) of 0.9542. Together, this study demonstrates the potential use of circulating miRNAs as an adjunct test to stratify breast lesions in patients with abnormal screening mammograms.

Introduction: Locoregional Recurrence (LR) can still develop after breast conserving surgery despite adequate surgical margins and whole breast radiation, even with a boost to the tumour bed. In this study, we evaluated predictors of LR and examined its effect on survival. Methods: Retrospective review was performed of 713 women diagnosed with breast cancer from 2004 to 2011. Results: Locoregional recurrence developed in 74 women (10.4%) and occurred adjacent to the previous tumour bed in half the instances. Surgical margins (P<0.001), nodal involvement (P=0.002), radiation (P=0.003) and 5 years of hormonal therapy (P<0.001) were independent predictors of LR. While LR had no effect on overall survival in women with DCIS (P=0.756), it was associated with poorer distant recurrence-free and overall survival in women with invasive cancer (P<0.001, HR 114.200, 95% CI 40.630–320.900 and P<0.001, HR 14.210, 95% CI 5.651–35.720 respectively). Radiation and hormonal therapy improved survival, showing an additive effect. Radiation, without hormonal therapy, did not improve recurrence-free survival, both locoregional (P=0.190) and distant (P=0.189), nor overall survival (P=0.236) in node-positive disease. However, radiation conferred survival benefit even when given alone in node-negative disease. Conclusion: The rate of locoregional recurrence after breast conserving surgery was 10.4%. Adequate surgical margins and nodal disease were independently associated with LR and both radiation and hormonal therapy improved survival. Survival benefit was greatest in women who completed both radiation and 5 years of hormonal therapy.

Background: Complete resection of solitary metastasis can render a woman disease-free, raising the possibility that curative treatment is still possible even in metastatic breast cancer. However, there is no conclusive data in support of this and the actual value of metastasectomy is uncertain since it is often performed only in women expected to have a more favorable outcome. Aims: In this present study, we evaluated 13 women who underwent metastasectomy after relapsing with solitary metastasis. The endpoints of disease progression after metastasectomy and overall survival were specifically examined. Results: All 13 women had previously undergone curative treatment for breast cancer. Ten women were known to have locally advanced Stage III disease. The distant recurrence was diagnosed after new symptoms developed in 12 women; the remaining woman was found with asymptomatic mediastinal nodal recurrence on positron emission tomography-computed tomography. Complete resection of all gross tumour was done in all instances and 9 women received further systemic treatment after surgery. All 5 women with brain metastasis received whole brain radiation after surgery. New metastatic disease developed in 8 women and was adjacent to the previous resection bed in 3 women. No further surgery was done in these 8 women. Median overall survival for the 13 women was 74.70 months (ranging from 32.07 to 336.80 months) and the women survived a median of 30.57 months (ranging from 16.60 to 80.40 months) after metastasectomy. There was a non-significant trend towards better overall survival in these 13 women compared to others who had received only systemic treatments (P = 0.398). Conclusions: Reasonable survival was observed in women who had undergone metastasectomy. Complete resection of metastatic tumour can be considered in selected women with limited secondary metastases from breast cancer.

We aim to identify clinicopathologic predictors for response to neoadjuvant chemotherapy and to evaluate the prognostic value of pathologic complete response (pCR) on survival in Asia. This study included 915 breast cancer patients who underwent neoadjuvant chemotherapy at five public hospitals in Singapore and Malaysia. pCR following neoadjuvant chemotherapy was defined as 1) no residual invasive tumor cells in the breast (ypT0/is) and 2) no residual invasive tumor cells in the breast and axillary lymph nodes (ypT0/is ypN0). Association between pCR and clinicopathologic characteristics and treatment were evaluated using chi‐square test and multivariable logistic regression. Kaplan–Meier analysis and log‐rank test, stratified by other prognostic factors, were conducted to compare overall survival between patients who achieved pCR and patients who did not. Overall, 4.4% of nonmetastatic patients received neoadjuvant chemotherapy. The median age of preoperatively treated patients was 50 years. pCR rates were 18.1% (pCR ypT0/is) and 14.4% (pCR ypT0/is ypN0), respectively. pCR rate was the highest among women who had higher grade, smaller size, estrogen receptor negative, human epidermal growth factor receptor 2‐positive disease or receiving taxane‐based neoadjuvant chemotherapy. Patients who achieved pCR had better overall survival than those who did not. In subgroup analysis, the survival advantage was only significant among women with estrogen receptor‐negative tumors. Patients with poor prognostic profile are more likely to achieve pCR and particularly when receiving taxane‐containing chemotherapy. pCR is a significant prognostic factor for overall survival especially in estrogen receptor‐negative breast cancers.