Triple-negative breast cancer (TNBC) is a highly metastatic and deadly disease. TNBC tumors lack estrogen receptor (ERα), progesterone receptor (PR), and HER2 (ErbB2) and exhibit increased glutamine metabolism, a requirement for tumor growth. The G protein-coupled kisspeptin receptor (KISS1R) is highly expressed in patient TNBC tumors and promotes malignant transformation of breast epithelial cells. This study found that TNBC patients displayed elevated plasma kisspeptin levels compared with healthy subjects. It also provides the first evidence that in addition to promoting tumor growth and metastasis in vivo, KISS1R-induced glutamine dependence of tumors. In addition, tracer-based metabolomics analyses revealed that KISS1R promoted glutaminolysis and nucleotide biosynthesis by increasing c-Myc and glutaminase levels, key regulators of glutamine metabolism. Overall, this study establishes KISS1R as a novel regulator of TNBC metabolism and metastasis, suggesting that targeting KISS1R could have therapeutic potential in the treatment of TNBC.

The acquisition of cellular invasiveness by breast epithelial cells and subsequent transition from ductal carcinoma in situ (DCIS) to invasive breast cancer is a critical step in breast cancer progression. Little is known about the molecular dynamics governing this transition. We have previously shown that overexpression of the transcriptional regulator TBX3 in DCIS‐like cells increases survival, growth, and invasiveness. To explore this mechanism further and assess direct transcriptional targets of TBX3 in a high‐resolution, isoform‐specific context, we conducted genome‐wide chromatin‐immunoprecipitation (ChIP) arrays coupled with transcriptomic analysis. We show that TBX3 regulates several epithelial–mesenchymal transition (EMT)‐related genes, including SLUG and TWIST1 . Importantly, we demonstrate that TBX3 is a direct regulator of SLUG expression, and SLUG expression is required for TBX3‐induced migration and invasion. Assessing TBX3 by immunohistochemistry in early‐stage (stage 0 and stage I) breast cancers revealed high expression in low‐grade lesions. Within a second independent early‐stage non‐high‐grade cohort, we observed an association between TBX3 level in the DCIS and size of the invasive focus. Additionally, there was a positive correlation between TBX3 and SLUG, and TBX3 and TWIST1 in the invasive carcinoma. Pathway analysis revealed altered expression of several proteases and their inhibitors, consistent with the ability to degrade basement membrane in vivo . These findings strongly suggest the involvement of TBX3 in the promotion of invasiveness and progression of early‐stage pre‐invasive breast cancer to invasive carcinoma through the low‐grade molecular pathway. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

TBX3 is a member of the highly conserved family of T-box transcription factors involved in embryogenesis, organogenesis and tumor progression. While the functional role of TBX3 in tumorigenesis has been widely studied, less is known about the specific functions of the different isoforms (TBX3iso1 and TBX3iso2) which differ in their DNA-binding domain. We therefore sought to investigate the functional consequence of this highly conserved splice event as it relates to TBX3-induced tumorigenesis. By utilizing a nude mouse xenograft model, we have identified differential tumorigenic potential between TBX3 isoforms, with TBX3iso1 overexpression more commonly associated with invasive carcinoma and high tumor vascularity. Transcriptional analysis of signaling pathways altered by TBX3iso1 and TBX3iso2 overexpression revealed significant differences in angiogenesis-related genes. Importantly, osteopontin (OPN), a cancer-associated secreted phosphoprotein, was significantly up-regulated with TBX3iso1 (but not TBX3iso2) overexpression. This pattern was observed across three non/weakly-tumorigenic breast cancer cell lines (21PT, 21NT, and MCF7). Up-regulation of OPN in TBX3iso1 overexpressing cells was associated with induction of hyaluronan synthase 2 (HAS2) expression and increased retention of hyaluronan in pericellular matrices. These transcriptional changes were accompanied by the ability to induce endothelial cell vascular channel formation by conditioned media in vitro, which could be inhibited through addition of an OPN neutralizing antibody. Within the TCGA breast cancer cohort, we identified an 8.1-fold higher TBX3iso1 to TBX3iso2 transcript ratio in tumors relative to control, and this ratio was positively associated with high-tumor grade and an aggressive molecular subtype. Collectively, the described changes involving TBX3iso1-dependent promotion of angiogenesis may thus serve as an adaptive mechanism within breast cancer cells, potentially explaining differences in tumor formation rates between TBX3 isoforms in vivo. This study is the first of its kind to report significant functional differences between the two TBX3 isoforms, both in vitro and in vivo.

Invadopodia are cell protrusions that mediate cancer cell extravasation but the microenvironmental cues and signaling factors that induce invadopodia formation during extravasation remain unclear. Using intravital imaging and loss of function experiments, we determined invadopodia contain receptors involved in chemotaxis, namely GABA receptor and EGFR. These chemotaxis capabilities are mediated in part by PAK1 which controls invadopodia responsiveness to ligands such as GABA and EGF via assembly, stability, and turnover of invadopodia in vivo. PAK1 knockdown rendered cells unresponsive to chemotactic stimuli present in the stroma, resulting in dramatically lower rates of cancer cell extravasation and metastatic colony formation compared to stimulated cancer cells. In an experimental mouse model of brain metastasis, inhibition of PAK1 significantly reduced overall tumor burden and reduced the average size of brain metastases. In summary, invadopodia contain chemotaxis receptors that can respond to microenvironmental cues to guide cancer cell extravasation, and when PAK1 is depleted, brain tropism of metastatic breast cancer cells is significantly reduced, blocking secondary colony growth at sites otherwise permissive for metastatic outgrowth.

Breast cancer is a leading cause of cancer mortality. In particular, triple negative breast cancer (TNBC) comprise a heterogeneous group of basal-like tumors lacking estrogen receptor (ERα), progesterone receptor (PR) and HER2 (ErbB2). TNBC represents 15-20% of all breast cancers and occurs frequently in women under 50 years of age. Unfortunately, these patients lack targeted therapy, are typically high grade and metastatic at time of diagnosis. The mechanisms regulating metastasis remain poorly understood. We have previously shown that the kisspeptin receptor, KISS1R stimulates invasiveness of TNBC cells. In this report, we demonstrate that KISS1R signals via the secreted extracellular matrix protein, fibulin-3, to regulate TNBC invasion. We found that the fibulin-3 gene is amplified in TNBC primary tumors and that plasma fibulin-3 levels are elevated in TNBC patients compared to healthy subjects. In this study, we show that KISS1R activation increases fibulin-3 expression and secretion. We show that fibulin-3 regulates TNBC metastasis in a mouse experimental metastasis xenograft model and signals downstream of KISS1R to stimulate TNBC invasion, by activating matrix metalloproteinase 9 (MMP-9) and the MAPK pathway. These results identify fibulin-3 as a new downstream mediator of KISS1R signaling and as a potential biomarker for TNBC progression and metastasis, thus revealing KISS1R and fibulin-3 as novel drug targets in TNBC.

Purpose: Radiation therapy (RT) after breast-conserving surgery (BCS) for Ductal Carcinoma in Situ (DCIS) halves the risk of local recurrence (LR). The omission of RT is often supported by the paradigm that patients who develop LR can be salvaged with further breast-conserving therapy leading to higher rates of breast preservation and improved quality of life. However, population-based, long-term rates of breast preservation in women treated by upfront BCS +/- RT are unknown. Methods and materials: Women diagnosed with pure DCIS from 1994 to 2003 treated with BCS +/- RT in Ontario were identified. Median follow-up is 12 years. The development and treatment of LR and contralateral breast cancers were determined by administrative databases with validation. The 10-year mastectomy-free survival was calculated using the Kaplan-Meier method. The impact of RT on breast preservation was determined by propensity-adjusted cox proportional hazards model. Results: The cohort includes 3303 women with DCIS; 1649 (50%) underwent BCS alone, 1654 (50%) underwent BCS thorn RT. Women treated by BCS alone were more likely to develop a LR compared to those treated by upfront BCS thorn RT (20.8% versus 15.5%, p < 0.001). Mastectomy was used to treat LR in 57.4% (197/343) of women who recurred after BCS alone and 67.6% (174/257) of those who recurred after BCS thorn RT. Women treated with upfront BCS thorn RT had higher rates of bilateral breast preservation at 10 years compared to those treated by BCS alone (87.3% vs. 82.7%, p = 0.0096). Conclusion: Local Recurrence after BCS alone does not favor breast preservation. (c) 2017 Elsevier Ltd. All rights reserved.

Additional file 2. External file sources used in study.

Abstract Background: Ductal Carcinoma in Situ (DCIS) is a non-invasive breast cancer often treated with breast-conserving surgery (BCS) with or without radiotherapy (RT). It is unclear if the presence of microinvasion (MI) (invasion ≤1mm) is associated with an increased risk of LR (DCIS or invasive) or invasive LR compared to women with pure DCIS. In addition, the impact of multiple foci (>2) of MI compared to pure DCIS is also unknown; therefore, it is unclear if some women with MI require more aggressive treatment. We evaluated the impact of the presence of MI and the number of foci of MI on the risks of any LR and invasive LR in a population of women with DCIS with and without MI treated with BCS. Methods: The cohort includes all women diagnosed with pure DCIS or DCIS with MI in Ontario from 1994-2003 treated with BCS +/- RT. All cases had systematic pathology review to confirm the presence and number of foci of MI. Treatment and outcomes were ascertained through administrative databases and validated by chart review. Cox proportional hazards model was used to evaluate the impact of MI and the number of foci of MI (1 vs >2 foci) on the development of any LR and invasive LR compared to cases with pure DCIS. The 10-yr local recurrence-free survival (LRFS) and invasive LRFS rates were calculated using the Kaplan-Meier approach with differences compared using the log-rank test. Results: The population cohort includes 2,988 women with DCIS treated by BCS (N=2,721 pure DCIS, N= 267 DCIS with MI). Median follow-up (12 years; p=.23) and median age at diagnosis (58 years; p=.17) were similar in both groups. RT was given in 58% of cases with MI and 51% of cases with pure DCIS (p=.03). Hormonal therapy was utilized in 7.1% of women with MI and 5.3% of women with pure DCIS (p=.22). LR developed in 59 (22.1%) cases with MI and 530 (19.6%) cases of pure DCIS. Women with MI were more likely to have high nuclear grade (p<.001), and larger tumor size (p<.001) compared to those without MI. On multivariable analyses adjusted for age, the presence of 1 focus of MI(HR=.92, 95% CI: .64-1.33) or ≥2 foci of MI (HR=1.26, 95% CI: .85-1.85) was not associated with an increased risk of any LR compared to cases with pure DCIS. Factors associated with any LR were age <50 years at diagnosis, RT, multifocality and high nuclear grade. The presence of 1 focus of MI (HR=.86, 95% CI: .52-1.40) or > 2 foci of MI (HR=1.45, 95% CI: .90-2.32) was also not associated with an increased risk of invasive LR compared to cases of pure DCIS. Among women treated with BCS alone, the 10 year LRFS rates were 80%, 75% and 73% for women with pure DCIS, 1 focus, >2 foci of MI (p=.10). The invasive LRFS rates were 89%, 91% and 85% (p=.26). Among women treated with BCS+RT, the 10 year LRFS rates were 87%, 88% and 80% (p=0.32) for women with pure DCIS, 1 focus or ≥2 foci of MI. The invasive LRFS rates were 93%, 90% and 86% (p=.44). There was no interaction between the presence of MI and RT. Conclusions: Women with DCIS with one or multiple foci of microinvasion (<1mm) treated by breast conserving therapy do not have an increased risk of LR or invasive LR compared to women with pure DCIS. Citation Format: Lalani N, Paszat L, Sutradhar R, Gu S, Fong C, Nofech-Mozes S, Hanna W, Tuck A, Youngson B, Miller N, Done SJ, Chang MC, Sengupta S, Elavathil L, Jani PA, Bonin M, Rakovitch E. The presence of one or multiple foci of microinvasion is not associated with an increased risk of local recurrence in women with ductal carcinoma in situ treated with breast conserving therapy [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P4-15-05.

Additional file 7. Gene-list of targets which bind TDG and are regulated by E2.

OBJECTIVE:Effective targeted therapies for patients with triple-negative breast cancer (TNBC) present an unmet clinical need. There is evidence that TNBCs often have increased expression of the epidermal growth factor receptor (EGFR) and of osteopontin (OPN). OPN-mediated signaling can activate EGFR-dependent signaling pathways. Here, we assessed OPN as a potential predictive biomarker for response to anti-EGFR therapy in TNBC.RESEARCH DESIGN AND METHODS:Using two different TNBC cell lines, MDA-MB-468 and MDA-MB-231, we investigated the impact of stable expression of OPN on efficacy of the EGFR inhibitor erlotinib in vitro.RESULTS:We observed that breast cancer cells engineered to overexpress OPN are more sensitive to growth inhibition by erlotinib than control cells. The level of response was related to the level of OPN expression, possibly due to increased phosphorylation status of EGFR Tyr1068.CONCLUSIONS:These results indicate that OPN expression levels are related to sensitivity of TNBC cells to growth inhibition by erlotinib. OPN thus is a promising predictive biomarker for anti-EGFR therapy in breast cancer.

Abstract Background: Most women diagnosed with DCIS will be treated by breast-conserving surgery (BCS) with or without radiotherapy (RT). Data on outcomes following breast-conserving therapy are predominantly based on women with small (<25mm) lesions. The paucity of data on outcomes of women with larger (>40mm) DCIS lesions leads to uncertainty of the appropriateness of breast-conserving therapy for women with larger lesions. Specifically, it is unclear if women with large tumors experience higher risks of local recurrence (LR) and invasive LR after BCS+/-RT that would preclude recommendations of breast-conserving therapy. We report the outcomes and evaluate the impact of large tumor size (>40mm) on recurrence risk in a population of women with pure DCIS treated by BCS alone or with RT. Methods: The cohort includes all women diagnosed with DCIS in Ontario from 1994-2003 treated with BCS +/- RT; 82% had pathology review. Treatment and outcomes were ascertained through administrative databases and validated by chart review. Cox proportional hazards model was used to evaluate the impact of tumor size (≤10mm,11-25mm, 26-39mm, ≥40mm) on the development of any LR (DCIS or invasive) and invasive LR. The 10 and 15-year LR-free survival (LRFS) and invasive LRFS rates were calculated using the Kaplan-Meier method with differences compared using the log-rank test. Results: The cohort includes 3262 women with DCIS treated by BCS (N=1635 had RT). Median age at diagnosis was 59 years (IQR 50-68 years). Median follow-up was 13 years (IQR 8-15 years). Distribution of tumor size: 707 (22%) ≤10mm, 524 (16%) 11-25mm, 107 (3%) 26-39mm, 84 (3%) ≥40mm, unable to determine in 1840 (56%). Women with lesions ≥ 40mm were more likely to be ≤50 years of age at diagnosis (p=.02), have high nuclear grade (p<.001), multifocality (p<.001), and positive margins (p<.001) compared to women with smaller lesions. On multivariable analyses adjusted for age and year of diagnosis, tumor size ≥40mm was significantly associated with an increased risk of LR compared to size ≤10mm (HR=2.5, 95%CI:1.64-3.81). Other factors associated with LR were age <50 years (p<.001), omission of RT (p<.001), high nuclear grade (p=.002), and multifocality (p=.0008). Tumor size ≥40mm was not significantly associated with an increased risk of invasive LR (HR=1.68, 95%CI:.94-3.04). Women with tumour size ≥40mm treated with BCS alone had lower 10 and 15 year LRFS (53% and 41%) and invasive LRFS rates (78% and 75%) compared to women with smaller lesions. However, women with larger lesions treated with RT had significantly higher LRFS and invasive LRFS rates Outcomes by tumour size for women with DCIS treated with BCS with or without RT ≤10mm N=70711-25mm N=52426-39mm N=107≥40mm N=84p-valueBCS AloneLRFS (%) 10 yr85797053<0.001 15 yr81746741 Invasive LRFS (%) 10 yr928786780.03 15 yr89838375 BCS + RTLRFS (%) 10 yr928874850.01 15 yr86847079 Invasive LRFS (%) 10 yr959492910.27 15 yr90918789 . There was a significant interaction between tumor size ≥40mm and RT (p=.02). Conclusions: Women with DCIS lesions ≥40mm treated by BCS alone experience significantly higher risks of LR and invasive LR compared to smaller lesions but this risk can be mitigated with the addition of RT. Citation Format: Lalani N, Paszat L, Nofech-Mozes S, Sutradhar R, Gu S, Hanna W, Fong C, Miller N, Youngson B, Done SJ, Tuck A, Chang MC, Sengupta S, Jani PA, Bonin M, Rakovitch E. Is breast-conserving therapy effective in women with large ductal carcinoma in situ (DCIS) lesions? A population-based analysis [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-12-02.

Background The estrogen receptor (ER) is a ligand-dependant transcription factor expressed in many breast cancers and is the target of many endocrine-based cancer therapies. Genome-wide studies have shown that the ER binds to gene-specific enhancer regions in response to β-estradiol (E2) which undergo transcription producing noncoding enhancer RNA (eRNA). While eRNAs are important for transcriptional activation of neighboring genes, the mechanism remains poorly understood. Results Using ChIP-Seq we generate a global profile of thymine DNA glycosylase (TDG), an ER coactivator that plays an essential role in DNA demethylation, in response to E2 in the MCF7 breast cancer cell line. Remarkably, we found that in response to E2 TDG localized to enhancers which also recruit ERα, RNA Pol II and other coregulators and which are marked by histone modifications indicative of active enhancers. Importantly, depletion of TDG inhibits E2-mediated transcription of eRNAs and transcription of ER-target genes. Functionally, we find that TDG both sensitizes MCF7 cells to tamoxifen-mediated cytostasis and increases migration and invasion of MCF7 cells. Conclusions Taken together we find that TDG plays a central role in mediating transcription at a subset of enhancers and governs how MCF7 cells respond to both estrogenic and anti-estrogenic compounds and may be an effective therapeutic target.

Purpose: To evaluate whether concurrent neoadjuvant radiation added to standard chemotherapy could increase the pathologic complete response (pCR) to treatment for locally advanced breast cancer (LABC). Methods and Materials: This prospective phase 2 trial recruited 32 LABC patients from 2009 to 2011. Patients received neoadjuvant every-3-weekly 5-fluorouracil (500 mg/m(2)), epirubicin (100 mg/m(2)), and cyclophosphamide (500 mg/m(2)) for 3 cycles, followed by weekly docetaxel (35 mg/m(2)) for 9 cycles. Regional radiation (45 Gy/25 plus 5.4 Gy/5) was delivered concurrently with docetaxel, then modified radical mastectomy. Patients were matched post hoc by a blinded statistician to a concurrent cohort treated with neoadjuvant chemotherapy, modified radical mastectomy, and adjuvant regional radiation. Results: Thirty of 32 patients completed treatment. Twenty-seven were successfully matched by propensity score to 81 control patients by age, stage, and molecular subtype. The concurrent chemoradiation produced a significant increase in pCR (14% vs 22%, P<. 001) but no statistically significant difference in disease-free and overall survival at 3 years (respectively, 69% vs 81%, PZ. 186, hazard ratio 0.51; and 74% vs 89%, PZ. 162, hazard ratio 0.46). Toxicity included 25% of patients with grade 3 pneumonitis and 25% of patients with dermatitis, and 1 death. Conclusions: Concurrent neoadjuvant radiation added to radiosensitizing chemotherapy significantly improved pCR. A prospective randomized clinical trial is warranted to exploit the improved response seen with concurrent therapy but using another radio-sensitizing taxane, to better minimize treatment-related toxicity and determine its impact on overall survival. (C) 2017 Elsevier Inc. All rights reserved.

Triple-negative breast cancer (TNBC) lacks the expression of estrogen receptor α, progesterone receptor and human epidermal growth factor receptor 2 (HER2). TNBC patients lack targeted therapies, as they fail to respond to endocrine and anti-HER2 therapy. Prognosis for this aggressive cancer subtype is poor and survival is limited due to the development of resistance to available chemotherapies and resultant metastases. The mechanisms regulating tumor resistance are poorly understood. Here we demonstrate that the G protein-coupled kisspeptin receptor (KISS1R) promotes drug resistance in TNBC cells. KISS1R binds kisspeptins, peptide products of the KISS1 gene and in numerous cancers, this signaling pathway plays anti-metastatic roles. However, in TNBC, KISS1R promotes tumor invasion. We show that KISS1 and KISS1R mRNA and KISS1R protein are upregulated in TNBC tumors, compared to normal breast tissue. KISS1R signaling promotes drug resistance by increasing the expression of efflux drug transporter, breast cancer resistance protein (BCRP) and by inducing the activity and transcription of the receptor tyrosine kinase, AXL. BCRP and AXL transcripts are elevated in TNBC tumors, compared to normal breast, and TNBC tumors expressing KISS1R also express AXL and BCRP. Thus, KISS1R represents a potentially novel therapeutic target to restore drug sensitivity in TNBC patients.

Abstract This abstract was not presented at the symposium.

Abstract Background: Despite evidence that radiotherapy (RT) after breast-conserving surgery (BCS) for ductal carcinoma in situ (DCIS) halves the risk of recurrence, the benefit of RT in the management of DCIS continues to be a matter of controversy. One argument against the use of RT after BCS is that patients who develop ipsilateral local recurrence (LR) can be salvaged with further breast-conserving surgery such that the omission of RT will lead to high rates of breast preservation while minimizing exposure to RT. Breast preservation is an important determinant of quality of life for women with early stage breast cancer and DCIS. Yet the management of LR and the impact of RT on the resultant long-term risks of bilateral breast preservation in a population of women with DCIS are unclear. We assessed the treatment of LR, the impact of RT on the use of salvage mastectomy and the long-term risks of bilateral breast preservation achieved in a population of women with DCIS treated with BCS alone or BCS+RT. Methods: A population-based analysis of women diagnosed with DCIS from 1994-2003 treated with BCS alone or BCS+RT with pathology review. Treatment and outcomes, including the development of LR and contralateral breast events, were determined by administrative databases with validation by review of operative or pathology reports. Median follow-up was 10.2 years for cases treated by BCS alone, 11.6 years for those treated by BCS+RT. We used a propensity-adjusted Cox proportional hazards model to evaluate factors associated with the use of salvage mastectomy for LR and to evaluate factors associated with any mastectomy. We assessed the risk of long-term breast preservation by calculating the KM 10-year risk of ipsilateral mastectomy and any mastectomy. Results: The population cohort includes 3303 women with pure DCIS;1649 (50%) were treated by BCS alone, 1654 (50%) received BCS+RT. Women treated with RT had more high risk features of DCIS than those treated by BCS alone. LR developed in 343 (21%) women treated by BCS alone and in 257 (15.5%) women treated by BCS+RT (p<0.01). Most women who developed LR received salvage mastectomy, irrespective of age at diagnosis and histology. Salvage mastectomy was used in 57.4% (197/343) of cases that recurred after BCS alone and in 67.6% (173/257) that recurred after BCS+RT. The likelihood of receiving salvage mastectomy for LR was similar in patients initially treated by BCS+RT vs. those initially treated BCS alone. Most (90%) of mastectomies were performed for a LR. Overall, individuals initially treated by BCS+RT had a 29% lower probability of having a mastectomy at 10 years compared to those treated by BCS alone (HR=0.71, 95%CI: 0.60,0.84,p<0.0001). The 10 year mastectomy-free survival rates are 82.7% for women initially treated by BCS alone and 87.3% for those treated by BCS+RT (p=0.0096). Conclusion: Women who received RT after BCS for DCIS experience a greater likelihood of long-term bilateral breast preservation. This is attributable to the lower risks of LR and that most local recurrences after breast-conserving therapy are treated by salvage mastectomy. Long-term breast preservation should be considered in discussions weighing the benefits and risks of RT after conservative surgery for DCIS. Citation Format: Rakovitch E, Nofech-Mozes S, Hanna W, Gu S, Fong C, Tuck A, Sengupta S, Elavathil L, Jani P, Done S, Miller N, Youngson B, Bonin M, Chang M, Paszat L. Long-term rates of breast preservation after breast-conserving therapy for ductal carcinoma in situ [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-17-01.

Abstract Background: Most women with ductal carcinoma in situ (DCIS) will receive breast-conserving surgery (BCS) and radiation (RT). RT can be omitted for women at low risk of local recurrence (LR). The Oncotype DX DCIS score (DS) predicts LR risk after BCS alone. This study assesses the impact of RT and DS on LR risk. Methods: Population-based cohort analysis of individuals with DCIS treated by BCS ± RT from 1994–2003. Treatment and outcomes were determined by linkage and chart review. We used a propensity score–adjusted multivariable model to examine associations between DS and LR and evaluate the impact of RT. All statistical tests were two-sided. Results: The cohort includes 571 individuals treated by BCS alone, 689 cases treated with BCS + RT. Median follow-up was 9.4 years. On multivariable analysis, factors associated with LR include RT, age at diagnosis, tumor size, and multifocality. Adjusting for these factors, the DS risk group was statistically significantly associated with LR risk (hazard ratio high/intermediate = 1.75, 95% confidence interval = 1.28 to 2.41, P < .001). Women with a low-risk DS treated by BCS alone had an LR risk of 10.6% at 10 years and a small benefit from RT, while those with a high DS had a higher risk of LR (25.4%) after BCS alone and greater benefit from RT. A subgroup of patients with favorable clinicopathological features had a high-risk DS; these patients had a higher than expected risk of LR after BCS alone and a greater benefit with RT. Conclusions: The DS molecular assay improves risk stratification and estimates of RT benefit in individuals with DCIS treated with breast-conserving therapy.

The significance of microinvasion (MI) (invasive cancer ≤1mm) on the risk of local recurrence (LR) in women with ductal carcinoma in situ (DCIS) is unclear. We report a population-based analysis of women with DCIS with and without MI treated with breast-conserving surgery (BCS) alone or with radiotherapy (RT), and evaluated the impact of MI on the risks of any LR (DCIS or invasive) and invasive LR Cohort includes all women diagnosed with pure DCIS or DCIS with MI in Ontario from 1994-2003 that were treated with BCS +/- RT and had undergone expert pathology review. Treatments and outcomes were assessed through administrative databases and validated by chart review. Local recurrence-free survival (LRFS) was calculated using the Kaplan-Meier approach with differences compared using the log-rank test. The impact of MI on the development of LR was assessed using Cox proportional hazards model adjusted for propensity score to account for systematic differences in women treated with and without RT. Population cohort includes 2,988 women with DCIS treated by BCS (N=2,721 with pure DCIS, N= 267 DCIS with MI). Median follow-up was 13 years. Median age at diagnosis was 58 years. RT was given in 58% of cases with MI and 51% of cases with pure DCIS (p=.03). RT boost was given in 16.6% of women with MI and 14.4% of those with pure DCIS (p=.21). Women with MI were more likely to have high nuclear grade (p<.001), and larger tumour size (p<.001) versus pure DCIS. LR developed in 59 (22.1%) cases with MI and 530 (19.6%) cases of pure DCIS. Among women treated with BCS alone, the 15 year LRFS rate for DCIS with MI versus pure DCIS was 66% v 75% (p=.03) for any LR and 83% v 86% (p=.30) for invasive LR. Among women treated with BCS and RT, the 15 year LRFS rate for DCIS with MI versus pure DCIS was 82% v 82% (p=.74) for any LR and 88% v 88% (p=.84) for invasive LR. However, on multivariable analyses adjusted for age, propensity score and year of diagnosis, the presence of MI was not associated with an increased risk of any LR (HR=1.05, 95% CI: .80-1.38) or invasive LR (HR=1.08, 95% CI: .76-1.54). There was no significant interaction between the presence of MI and provision of RT for any LR (p=.15) or invasive LR (p=.67). Factors associated with any LR include RT (HR=.60, 95% CI: .51–.71), high nuclear grade (HR=1.21, 95% CI 1–1.45) and multifocality (HR=1.35, 95% CI: 1.12-1.64). Factors associated with invasive LR include RT (HR=.76, 95% CI: .61–.94) and multifocality (HR=1.40, 95% CI: 1.09-1.79). The presence of MI with DCIS is not associated with an increased risk of any LR or invasive LR after BCS with or without RT. The impact of number of foci of microinvasion on the risk of LR is in progress.