Search

Despite advances in genomic classification of breast cancer, current clinical tests and treatment decisions are commonly based on protein level information. Formalin-fixed paraffin-embedded (FFPE) tissue specimens with extended clinical outcomes are widely available. Here, we perform comprehensive proteomic profiling of 300 FFPE breast cancer surgical specimens, 75 of each PAM50 subtype, from patients diagnosed in 2008-2013 (n = 178) and 1986-1992 (n = 122) with linked clinical outcomes. These two cohorts are analyzed separately, and we quantify 4214 proteins across all 300 samples. Within the aggressive PAM50-classified basal-like cases, proteomic profiling reveals two groups with one having characteristic immune hot expression features and highly favorable survival. Her2-Enriched cases separate into heterogeneous groups differing by extracellular matrix, lipid metabolism, and immune-response features. Within 88 triple-negative breast cancers, four proteomic clusters display features of basal-immune hot, basal-immune cold, mesenchymal, and luminal with disparate survival outcomes. Our proteomic analysis characterizes the heterogeneity of breast cancer in a clinically-applicable manner, identifies potential biomarkers and therapeutic targets, and provides a resource for clinical breast cancer classification. Protein level information enables the identification of potential biomarkers and therapeutic targets for breast cancer. Here, the authors perform proteomic analysis of 2 cohorts of breast cancer surgical specimens and identify distinct subtypes, immune features and survival outcomes. [ABSTRACT FROM AUTHOR]

Background: This pooled analysis of MONALEESA trials evaluated the safety of ribociclib plus endocrine therapy (RIB + ET) with a focus on dose reductions in first-line patients.Methods: In the dose reduction analysis, data were pooled from MONALEESA-2 (all patients), MONALEESA-3 (patients receiving treatment as first-line ET) and MONALEESA-7 (patients receiving combination therapy with an NSAI as initial ET). Efficacy was analysed by ribociclib relative dose intensity (DI). Safety was analysed in all patients in the trials (except those receiving tamoxifen in MONALEESA-7) and those with/without ≥1 ribociclib dose reduction.Results: Of 818 women who received first-line RIB + ET, 41.8% required ≥1 dose reduction due to AEs (most commonly, neutropenia). Median RIB relative DI in patients without and with dose reductions was 99.3% and 65.6% in MONALEESA-2, 98.4% and 67.8% in MONALEESA-3 and 98·0% and 66·3% in MONALEESA-7. Median PFS was 24.8, 24.9 and 29.6 months for patients who received ≤71% (30th percentile), 72-96% (60th percentile) and 97-100% (90th percentile) RIB relative DI, respectively. No new safety signals emerged in the pooled safety analysis.Conclusions: This analysis provides reassuring data showing that the clinical benefit of RIB is preserved when dose modifications are undertaken to manage AEs.Trial Registration: MONALEESA-2 (NCT01958021) first posted October 8, 2013; MONALEESA-3 (NCT02422615) first posted April 21, 2015; MONALEESA-7 (NCT02278120) first posted October 29, 2014. [ABSTRACT FROM AUTHOR]

Much remains unknown about the population history of early modern humans in southeast Asia, where the archaeological record is sparse and the tropical climate is inimical to the preservation of ancient human DNA1. So far, only two low-coverage pre-Neolithic human genomes have been sequenced from this region. Both are from mainland Hòabìnhian hunter-gatherer sites: Pha Faen in Laos, dated to 7939–7751 calibrated years before present (yr cal bp; present taken as ad 1950), and Gua Cha in Malaysia (4.4–4.2 kyr cal bp)1. Here we report, to our knowledge, the first ancient human genome from Wallacea, the oceanic island zone between the Sunda Shelf (comprising mainland southeast Asia and the continental islands of western Indonesia) and Pleistocene Sahul (Australia–New Guinea). We extracted DNA from the petrous bone of a young female hunter-gatherer buried 7.3–7.2 kyr cal bp at the limestone cave of Leang Panninge2 in South Sulawesi, Indonesia. Genetic analyses show that this pre-Neolithic forager, who is associated with the ‘Toalean’ technocomplex3,4, shares most genetic drift and morphological similarities with present-day Papuan and Indigenous Australian groups, yet represents a previously unknown divergent human lineage that branched off around the time of the split between these populations approximately 37,000 years ago5. We also describe Denisovan and deep Asian-related ancestries in the Leang Panninge genome, and infer their large-scale displacement from the region today.The palaeogenomic analysis of a pre-Neolithic skeleton associated with a Toalean burial context from Wallacea. [ABSTRACT FROM AUTHOR]

Purpose: The optimal time interval from neoadjuvant chemotherapy (NAC) to surgery in patients with breast cancer has not been established. We investigated whether different time intervals impact the rate of pathologic complete response (pCR), disease free survival (DFS), overall survival (OS), surgical complications, and rates of conversion from mastectomy to breast conserving surgery (BCS) in this population. Methods: We identified patients who received NAC at the BC Cancer Agency followed by surgery from May 2012 to April 2018. Patients were grouped based on time interval between NAC and surgery: < 4 weeks, 4–8 weeks, and > 8 weeks. Kaplan Meier method was used to estimate DFS and OS. Rates of pCR between the time intervals were also compared. Results: Of the 343 patients, 78 (22.8%) received surgery < 4 weeks, 233 (67.9%) received surgery between 4–8 weeks, and 32 (9.3%) received surgery > 8 weeks after NAC, with a median time to surgery (TTS) of 5.0 weeks. pCR was observed in 32.1%, 32.2%, and 28.1%, respectively (p = 0.90). Median follow-up time was 3.3 years. The 5-year DFS was 76%, 78%, and 70% (p = 0.89), respectively. The 5-year OS was 83%, 82%, and 78% (p = 0.33), respectively. No statistically significant differences were seen in surgical complications (p = 0.90), or rates of conversion from mastectomy to BCS (p = 0.19). Conclusions: There were no statistically significant differences in pCR, DFS, OS, surgical complications, and rates of conversion from mastectomy to BCS, among breast cancer patients receiving surgery < 4 weeks, 4–8 weeks, or > 8 weeks after the last dose of NAC. [ABSTRACT FROM AUTHOR]

Summary: Introduction Given the high level of uncertainty surrounding the outcomes of early phase clinical trials, whole genome and transcriptome analysis (WGTA) can be used to optimize patient selection and study assignment. In this retrospective analysis, we reviewed the impact of this approach on one such program. Methods Patients with advanced malignancies underwent fresh tumor biopsies as part of our personalized medicine program (NCT02155621). Tumour molecular data were reviewed for potentially clinically actionable findings and patients were referred to the developmental therapeutics program. Outcomes were reviewed in all patients, including those where trial selection was driven by molecular data (matched) and those where there was no clear molecular rationale (unmatched). Results From January 2014 to January 2018, 28 patients underwent WGTA and enrolled in clinical trials, including 2 patients enrolled in two trials. Fifteen patients were matched to a treatment based on a molecular target. Five patients were matched to a trial based upon single-gene DNA changes, all supported by RNA data. Ten cases were matched on the basis of genome-wide data (n = 4) or RNA gene expression only (n = 6). With a median follow-up of 6.7 months, the median time on treatment was 8.2 weeks. Discussion When compared to single-gene DNA-based data alone, WGTA led to a 3-fold increase in treatment matching. In a setting where there is a high level of uncertainty around both the investigational agents and the biomarkers, more data are needed to fully evaluate the impact of routine use of WGTA. [ABSTRACT FROM AUTHOR]

Purpose: Sexual dysfunction is an important concern of premenopausal women with early breast cancer. We investigated predictors of sexual problems in two randomized controlled trials. Methods: A subset of patients enrolled in TEXT and SOFT completed global and symptom-specific quality-of-life indicators, CES-Depression and MOS-Sexual Problems measures at baseline, six, 12 and 24 months. Mixed models tested the association of changes in treatment-induced symptoms (baseline to 6 months), depression at 6 months, and age at randomization with changes in sexual problems over 2 years. Results: Sexual problems increased by 6 months and persisted at this level. Overall, patients with more severe worsening of vaginal dryness, sleep disturbances and bone or joint pain at 6 months reported a greater increase in sexual problems at all time-points. Depression scores were significantly associated with sexual problems in the short-term. All other symptoms had a smaller impact on sexual problems. Age was not associated with sexual problems at any time-point. Conclusion: Among several key symptoms, vaginal dryness, sleep disturbance, and bone and joint pain significantly predicted sexual problems during the first 2 years. Early identification of these symptoms may contribute to timely and tailored interventions. [ABSTRACT FROM AUTHOR]

The estrogen receptor (ER) is a key predictive biomarker in the treatment of breast cancer. There is uncertainty regarding the use of hormonal therapy in the setting of weakly positive ER by immunohistochemistry (IHC). We report intrinsic subtype classification on a cohort of ER weakly positive early-stage breast cancers. Consecutive cases of breast cancer treated by primary surgical resection were retrospectively identified from 4 centers that engage in routine external proficiency testing for breast biomarkers. ER-negative (Allred 0 and 2) and ER weakly positive (Allred 3-5) cases were included. Gene expression profiling was performed using qRT-PCR. Intrinsic subtype prediction was made based upon the PAM50 gene expression signature. 148 cases were included in the series: 60 cases originally diagnosed as ER weakly positive and 88 ER negative. Of the cases originally assessed as ER weakly positive, only 6 (10 %) were confirmed to be of luminal subtype by gene expression profiling; the remaining 90 % of cases were classified as basal-like or HER2-enriched subtypes. This was not significantly different than the fraction of luminal cases identified in the IHC ER-negative cohort (5 (5 %) luminal, 83(95 %) non-luminal). Recurrence-free, and overall, survival rates were similar in both groups ( p = 0.4 and 0.5, respectively) despite adjuvant hormonal therapy prescribed in the majority (59 %) of weakly positive ER cases. Weak ER expression by IHC is a poor correlate of luminal subtype in invasive breast cancer. In the setting of highly sensitive and robust IHC methodology, cutoffs for ER status determination and subsequent systemic therapy should be revisited. [ABSTRACT FROM AUTHOR]

Human cancers, including breast cancers, comprise clones differing in mutation content. Clones evolve dynamically in space and time following principles of Darwinian evolution, underpinning important emergent features such as drug resistance and metastasis. Human breast cancer xenoengraftment is used as a means of capturing and studying tumour biology, and breast tumour xenografts are generally assumed to be reasonable models of the originating tumours. However, the consequences and reproducibility of engraftment and propagation on the genomic clonal architecture of tumours have not been systematically examined at single-cell resolution. Here we show, using deep-genome and single-cell sequencing methods, the clonal dynamics of initial engraftment and subsequent serial propagation of primary and metastatic human breast cancers in immunodeficient mice. In all 15 cases examined, clonal selection on engraftment was observed in both primary and metastatic breast tumours, varying in degree from extreme selective engraftment of minor (<5% of starting population) clones to moderate, polyclonal engraftment. Furthermore, ongoing clonal dynamics during serial passaging is a feature of tumours experiencing modest initial selection. Through single-cell sequencing, we show that major mutation clusters estimated from tumour population sequencing relate predictably to the most abundant clonal genotypes, even in clonally complex and rapidly evolving cases. Finally, we show that similar clonal expansion patterns can emerge in independent grafts of the same starting tumour population, indicating that genomic aberrations can be reproducible determinants of evolutionary trajectories. Our results show that measurement of genomically defined clonal population dynamics will be highly informative for functional studies using patient-derived breast cancer xenoengraftment. [ABSTRACT FROM AUTHOR]

Biomarkers of bone turnover, including urine N-telopeptide (uNTx), have been used as surrogate measures of response to bone-targeted therapies. Vascular endothelial growth factor (VEGF) levels correlate with extent of bone metastases. We assessed whether vandetanib, an inhibitor of VEGF, epidermal growth factor receptor and RET signalling, improved uNTx response when added to fulvestrant (F) in breast cancer patients with bone metastases. Postmenopausal patients with bone predominant, hormone-receptor-positive metastatic breast cancer were randomised to F (500 mg IM days 1, 15, 29, then monthly) with either vandetanib (100 mg PO OD) (FV) or placebo (FP). The primary objective was uNTx response. Secondary objectives included PFS, OS, RECIST response, pain scores and toxicity. Sixty-one patients were allocated to FV and 68 to FP. Out of 127 analyzable patients, an uNTx response occurred in 66 % for FV and 54 % for FP ( p = 0.21). No difference was detected between groups for PFS; HR = 0.95 (95 % CI 0.65-1.38) or OS HR = 0.69 (95 % CI 0.37-1.31). For the 62 patients with measurable disease, clinical benefit rates were 41 and 43 %, respectively ( p = 0.47). Serious adverse events were similar, 3.3 % for FV versus 5.9 % for FP. Elevated baseline uNTx (>65 nM BCE/mmol Cr) was prognostic for PFS, HR = 1.55 (95 % CI 1.04-2.30) and for OS, HR = 2.32 (95 % CI 1.25-4.33). The addition of vandetanib to fulvestrant did not improve biomarker response, PFS or OS in patients with bone metastases. Baseline bone turnover was prognostic for PFS and OS. [ABSTRACT FROM AUTHOR]

Over the last few decades, the angiogenesis mechanism has increasingly been studied and implicated in cancer pathophysiology. At present, it is known that angiogenesis plays a relevant role in tumor growth, and more importantly many new molecules exists can potentially interfere with this process. Bevacizumab, a humanized monoclonal antibody targeting the vascular endothelial growth factor A (VEGF-A) now commonly used in the treatment of colorectal, renal cell, and brain cancer, is the first anti-angiogenesis drug delivered in combination with chemotherapy that has consistently shown clinical efficacy in the treatment of breast cancer. Since the ECOG 2100 trial has shown that bevacizumab added to paclitaxel as a first-line treatment for advanced breast cancer nearly doubled the time to progression and tumor response rate, its approval was granted almost worldwide. However, other phase III trials revealed a smaller absolute improvement in progression-free survival (PFS) and response rates, and no trials yet have demonstrated survival enhancement which led to a great controversy and debate over the use of bevacizumab. The discrepancy between PFS and overall survival also raises the question of whether or not bevacizumab has been applied sub-optimally in some of the studies, if a predictive biomarker(s) exists to select the group of patients whom would receive the greatest benefit and what is the appropriate clinical end-point for approval and funding of new targeted agents. In this article we will review the bevacizumab mechanism of action and the clinical trials that assessed its benefit in the treatment of metastatic breast cancer (MBC). [ABSTRACT FROM AUTHOR]

HER2 gene amplification and topoisomerase IIα gene ( TOP2A) alteration have been associated with increased benefit from anthracycline compared to non-anthracycline containing adjuvant breast cancer chemotherapy in some but not other studies. Chromosome 17 centromere (CEP17) duplication was measured on TMAs from formalin-fixed paraffin-embedded specimens obtained from 639 of 716 premenopausal women with node positive breast cancer who received cyclophosphamide, epirubicin and fluorouracil (CEF) or cyclophosphamide, methotrexate and fluorouracil (CMF) in the randomized controlled mammary 5 (MA.5) adjuvant trial. The prognostic impact of CEP17 duplication and its interactions with treatment were studied for relapse-free survival (RFS) and overall survival (OS). Overall, CEP17 duplication was not significantly associated with RFS or OS in multivariate analysis. For patients whose tumours had normal CEP17 copy number there were no apparent benefits for CEF compared to CMF for RFS (HR 0.98; 95% CI 0.68-1.42) or OS (HR 1.10; 95% CI 0.72-1.69). For patients whose tumours had CEP17 duplication, there was significant benefit for CEF compared to CMF for RFS (HR 0.54; CI 0.33-0.89) and a trend towards significance for OS (HR 0.64; CI 0.37-1.09). The adjusted P values for interaction between treatment and CEP17 duplication were 0.09 for RFS and 0.13 for OS. This study suggests that CEP17 duplication has a borderline association with clinical responsiveness to anthracycline containing chemotherapy similar to previous results seen with HER2 amplification and TOP2A alteration in MA.5. An appropriately powered meta-analysis is required to discriminate the predictive value of these three candidate markers. [ABSTRACT FROM AUTHOR]

The prognostic implication of breast cancer with nodal micrometastases measuring >0.2 mm but ≤2 mm (pNmic) is unclear. This study evaluates survival in pNmic relative to node-negative (N0) and macroscopic node-positive (pNmac) disease in a large population-based series. Subjects were 9,637 women diagnosed between 1989 and 1999, referred to the British Columbia Cancer Agency with pT1–2, node-negative and node-positive, M0 breast cancer. Kaplan–Meier breast-cancer-specific survival (BCSS) and overall survival (OS) were compared between patients with pN0 ( n = 7,988), pNmic ( n = 491), and pNmac disease ( n = 1,158), according to the number of positive nodes and the lymph node ratio (LNR) of positive to excised nodes. Cox regression and recursive partitioning analyses were performed to identify significant factors associated with survival. Median follow-up was 8.2 years. Patients with pNmic disease had significantly poorer outcomes compared with pN0 cancers, with progressively lower BCSS and OS with increasing number of positive nodes and with LNR > 0.25. On multivariable analysis, histologic subtype, T stage, number of positive nodes, LNR, grade, lymphovascular invasion, estrogen receptor status, and systemic therapy use were factors significantly associated with BCSS and OS. Recursive partitioning trees for BCSS and OS both selected the pN/LNR variable at the first split, indicating that this variable provided the strongest prognostic separation. Patients with nodal micrometastases are a heterogeneous population with varying breast cancer mortality risks. The number of positive nodes and the LNR should be considered in conjunction with tumor factors in risk estimates and treatment decisions for patients with nodal micrometastatic breast cancer. [ABSTRACT FROM AUTHOR]

Estrogen receptor status in breast cancer is associated with response to hormonal therapy and clinical outcome. The additional value of progesterone receptor (PR) has remained controversial. We examine the value of PR for prognosis and response to tamoxifen on a population-based series of 4,046 invasive early stage breast cancer patients. Clinical information for age at diagnosis, stage, pathology, treatment and outcome was assembled for the study cohort; the median follow-up was 12.4 years. PR status was determined by immunohistochemistry using a rabbit monoclonal antibody on tissue microarrays built from breast tumor surgical excisions. Survival analyses, Kaplan–Meier functions and Cox proportional hazards regression models were applied to assess the associations between PR and breast cancer specific survival. Progesterone receptor was positive in 51% of all cases and 67% of estrogen receptor positive (ER+) cases. Survival analyses for both the whole cohort and ER+ cases given tamoxifen therapy showed that patients with PR+ tumors had 24% higher relative probability for breast cancer specific survival as compared to PR− patients, adjusted for ER, HER2, age at diagnosis, grade, tumor size, lymph node status and lymphovascular invasion covariates. Higher PR expression showed stronger association with patient survival. Log-likelihood ratio tests of multivariate Cox proportional hazards regression models demonstrated that PR was an independent statistically significant factor for breast cancer specific survival in both the whole cohort and among ER+ cases treated with tamoxifen. PR adds significant prognostic value in breast cancer beyond that obtained with estrogen receptor alone. [ABSTRACT FROM AUTHOR]

Fulvestrant use in pretreated metastatic breast cancer patients is associated with variable response rates. This study aimed to characterize these responses and to develop a prediction model to identify those patients who could potentially derive the most clinical benefit. A nationwide review of patients enrolled in a Canadian compassionate use program from 1999 to 2006 was performed. Prior therapy with tamoxifen, steroidal, and nonsteroidal aromatase inhibitors was mandatory. The dependent variable in the analysis was the proportion of patients requiring chemotherapy at 3 months following the start of fulvestrant. General Linear Mixed modeling was used to identify factors significantly associated with this dependant variable and to subsequently develop the prediction model. Three hundred and five women received at least one dose of fulvestrant; 207 went on to receive chemotherapy (68%). Median duration of fulvestrant treatment was 4.1 months (range 0.8–63.1). Factors predictive of being chemotherapy free at 3 months included older age, no prior adjuvant hormonal therapy, and the absence of lung or brain metastases at the start of therapy. A receiver operating characteristic (ROC) curve analysis had an area under the curve of 0.70 (95% CI 0.60–0.80). This model was able to identify risk information that could be helpful in assessing which patients would most likely benefit from fulvestrant as an intervention with the objective being a delay in chemotherapy. [ABSTRACT FROM AUTHOR]

Five cases of an unusual encapsulated apocrine papillary tumour are reported. All presented as cystic masses in the breast of women aged 44-84 years. Imaging studies showed a complex cyst often with one or more mural nodules. The key histological features are similar to those of classical encapsulated papillary carcinoma in that myoepithelial cells were absent within the papillary structures and at the periphery of the cyst. All were pure apocrine in type and showed variable degrees of cytological atypia and mitotic activity. All lacked evidence of malignancy in the breast tissue outside of the lesion. Sentinel lymph node biopsies performed in three of the cases were negative for metastases, and all have behaved in a benign fashion. [ABSTRACT FROM AUTHOR]

Purpose BCIRG 001 demonstrated prolonged disease-free (DFS) and overall survival (OS) but increased toxicity for adjuvant docetaxel, doxorubicin, and cyclophosphamide (TAC) versus 5-fluorouracil, doxorubicin, cyclophosphamide (FAC) in women with node positive breast cancer (BC). This study evaluates quality-adjusted survival and cost-effectiveness of adjuvant TAC versus FAC, taking downstream decisions and events into account, including palliative chemotherapy with taxanes. Methods We developed a Markov model for a cohort of women with node positive BC eligible for adjuvant anthracyclines. Data input included clinical and resource utilization data collected prospectively from BCIRG 001. Treatment decisions and outcomes with disease recurrence were based on a systematic literature review with validity reviewed by a national panel of Canadian BC oncologists. Direct costs for resource utilization following Canadian practice patterns were included. Unit costs were obtained from provincial cost list and published drug list prices. Utility scores were derived from the literature. An incremental cost-effectiveness ratio (ICER) in cost per quality-adjusted life-years (QALY) gained for TAC versus FAC was calculated. Results For 1,000 women with node positive BC, the model showed that TAC would lead to a gain of 313 QALY (370 life years) at an additional cost of $5.8 Million Canadian dollars (Cdn) compared to FAC, over a 10-year time horizon. The ICER of TAC versus FAC was $18,505.54 Cdn per QALY gained. Sensitivity analyses supported the robustness of the model. By one-way sensitivity analyses of over 50 model variables, 95% of the cumulative ICER variation was from $6,000 to $28,000 Cdn/QALY. By multivariate Monte Carlo simulation, there was a 70% probability that the ICER would be under $50,000 CdN/QALY. Conclusion For women with node positive BC, TAC improves DFS and OS compared to FAC and is a cost-effective adjuvant chemotherapy strategy. [ABSTRACT FROM AUTHOR]

Rearrangements of the neuregulin (NRG1) gene have been implicated in breast carcinoma oncogenesis. To determine the frequency and clinical significance of NRG1 aberrations in clinical breast tumors, a breast cancer tissue microarray was screened for NRG1 aberrations by fluorescent in situ hybridization (FISH) using a two-color split-apart probe combination flanking the NRG1 gene. Rearrangements of NRG1 were identified in 17/382 cases by FISH, and bacterial artificial chromosome array comparative genomic hybridization was applied to five of these cases to further map the chromosome 8p abnormalities. In all five cases, there was a novel amplicon centromeric to NRG1 with a minimum common region of amplification encompassing two genes, SPFH2 and FLJ14299. Subsequent FISH analysis for the novel amplicon revealed that it was present in 63/262 cases. Abnormalities of NRG1 did not correlate with patient outcome, but the novel amplicon was associated with poor prognosis in univariate analysis, and in multivariate analysis was of prognostic significance independent of nodal status, tumor grade, estrogen receptor status, and human epidermal growth factor receptor (HER)2 overexpression. Of the two genes in the novel amplicon, expression of SPFH2 correlated most significantly with amplification. This amplicon may emerge as a result of breakpoints and chromosomal rearrangements within the NRG1 locus.Oncogene (2005) 24, 7281–7289. doi:10.1038/sj.onc.1208892; published online 18 July 2005 [ABSTRACT FROM AUTHOR]

While the elevated lifetime risk of breast and ovarian cancer is well recognised for patients with a BRCA mutation, the implementation of effective risk reduction strategies has been fraught with challenges. This report from an international database and published in the British Journal of Cancer reveals suboptimal rates of utilisation of surveillance/preventative measures globally. [ABSTRACT FROM AUTHOR]

Objective: Residents of rural communities have decreased access to cancer screening and treatments compared to urban residents, though use of resources and patient outcomes have not been assessed with a comprehensive population-based analysis. The objectives of this study were to investigate whether breast cancer screening and treatments were utilized less frequently in rural BC and whether this translated into differences in outcomes., Methods: All patients diagnosed with breast cancer in British Columbia (BC) during 2002 were identified from the Cancer Registry and linked to the Screening Mammography database. Patient demographics, pathology, stage, treatments, mammography use and death data were abstracted. Patients were categorized as residing in large, small and rural local health authorities (LHAs) using Canadian census information. Use of resources and outcomes were compared across these LHA size categories. We hypothesized that mastectomy rates (instead of breast-conserving surgery) would be higher in rural areas, since breast conservation is standardly accompanied by adjuvant radiotherapy, which has limited availability in rural BC. In contrast we hypothesized that cancer screening and systemic therapy use would be similar, as they are more widely dispersed across BC. Exploratory analyses were performed to assess whether disparities in screening and treatment utilization translated into differences in survival., Results: 2,869 breast cancer patients were included in our study. Patients from rural communities presented with more advanced disease (p=0.01). On multivariable analysis, patients from rural, compared to urban, LHAs were less likely to be screening mammography attendees (OR=0.62; p<0.001). Women from rural communities were less likely to undergo breast-conserving surgery (multivariable OR=0.47; p<0.001). There was no significant difference in use of chemotherapy (p=0.54) or hormonal therapy (p=0.36). The 5-year breast cancer-specific survival for large, small and rural LHAs was 90%, 88% and 86%, respectively (p=0.08), while overall survival was 84%, 81% and 77%, respectively (p=0.01). On multivariable analysis with 7.4 years of median follow-up, neither breast cancer-specific survival (HR=1.16; 0.76-1.76; p=0.49) nor overall survival (HR=1.25; 0.92-1.70; p=0.16) was significantly worse for patients from rural compared to large LHAs., Conclusion: There was a significant difference in screening mammography use, stage distribution and loco-regional treatments use by population size of LHA. After controlling for differences in patient and tumour factors by LHA, survival was not significantly different.