Effectiveness of Breast-Conserving Surgery and 3-Dimensional Conformal Partial Breast Reirradiation for Recurrence of Breast Cancer in the Ipsilateral Breast: The NRG Oncology/RTOG 1014 Phase 2 Clinical Trial

Importance

Mastectomy is standard for recurrence of breast cancer after breast conservation therapy with whole breast irradiation. The emergence of partial breast irradiation led to consideration of its application for reirradiation after a second lumpectomy for treatment of recurrence of breast cancer in the ipsilateral breast.

Objectives

To assess the effectiveness and adverse effects of partial breast reirradiation after a second lumpectomy and whether the treatment is an acceptable alternative to mastectomy.

Design, Setting, and Participants

The NRG Oncology/Radiation Therapy Oncology Group 1014 trial is a phase 2, single-arm, prospective clinical trial of 3-dimensional, conformal, external beam partial breast reirradiation after a second lumpectomy for recurrence of breast cancer in the ipsilateral breast after previous whole breast irradiation. The study opened on June 4, 2010, and closed June 18, 2013. Median follow-up was 5.5 years. This analysis used all data received at NRG Oncology through November 18, 2018. Eligible patients experienced a recurrence of breast tumor that was less than 3 cm and unifocal in the ipsilateral breast more than 1 year after breast-conserving therapy with whole breast irradiation and who had undergone excision with negative margins.

Interventions

Adjuvant partial breast reirradiation, 1.5 Gy twice daily for 30 treatments during 15 days (45 Gy), using a 3-dimensional conformal technique.

Main Outcomes and Measures

The main outcomes of the present study were the predefined secondary study objectives of recurrence of breast cancer in the ipsilateral breast, late adverse events (>1 year after treatment), mastectomy incidence, distant metastasis-free survival, overall survival, and circulating tumor cell incidence.

Results

A total of 65 women were enrolled, with 58 evaluable for analysis (mean [SD] age, 65.12 [9.95] years; 48 [83%] white). Of the recurrences of breast cancer in the ipsilateral breast, 23 (40%) were noninvasive and 35 (60%) were invasive. In all 58 patients, 53 (91%) had tumors 2 cm or smaller. All tumors were clinically node negative. A total of 44 patients (76%) tested positive for estrogen receptor, 33 (57%) for progesterone receptor, and 10 (17%) for ERBB2 (formerly HER2 or HER2/neu) overexpression. Four patients had breast cancer recurrence, with a 5-year cumulative incidence of 5% (95% CI, 1%-13%). Seven patients underwent ipsilateral mastectomies for a 5-year cumulative incidence of 10% (95% CI, 4%-20%). Both distant metastasis-free survival and overall survival rates were 95% (95% CI, 85%-98%). Four patients (7%) had grade 3 and none had grade 4 or higher late treatment adverse events.

Conclusions and Relevance

For patients experiencing recurrence of breast cancer in the ipsilateral breast after lumpectomy and whole breast irradiation, a second breast conservation was achievable in 90%, with a low risk of re-recurrence of cancer in the ipsilateral breast using adjuvant partial breast reirradiation. This finding suggests that this treatment approach is an effective alternative to mastectomy.

The Implications of Genetic Testing on Radiation Therapy Decisions: A Guide for Radiation Oncologists

The advent of affordable and rapid next-generation DNA sequencing technology, along with the US Supreme Court ruling invalidating gene patents, has led to a deluge of germline and tumor genetic variant tests that are being rapidly incorporated into clinical cancer decision-making. A major concern for clinicians is whether the presence of germline mutations may increase the risk of radiation toxicity or secondary malignancies. Because scarce clinical data exist to inform decisions at this time, the American Society for Radiation Oncology convened a group of radiation science experts and clinicians to summarize potential issues, review relevant data, and provide guidance for adult patients and their care teams regarding the impact, if any, that genetic testing should have on radiation therapy recommendations. During the American Society for Radiation Oncology workshop, several main points emerged, which are discussed in this manuscript: (1) variants of uncertain significance should be considered nondeleterious until functional genomic data emerge to demonstrate otherwise; (2) possession of germline alterations in a single copy of a gene critical for radiation damage responses does not necessarily equate to increased risk of radiation-induced toxicity; (3) deleterious ataxia-telangiesctasia gene mutations may modestly increase second cancer risk after radiation therapy, and thus follow-up for these patients after indicated radiation therapy should include second cancer screening; (4) conveying to patients the difference between relative and absolute risk is critical to decision-making; and (5) more work is needed to assess the impact of tumor somatic alterations on the probability of response to radiation therapy and the potential for individualization of radiation doses. Data on radiosensitivity related to specific genetic mutations is also briefly discussed.

Association of Transforming Growth Factor β Polymorphism C-509T With Radiation-Induced Fibrosis Among Patients With Early-Stage Breast Cancer: A Secondary Analysis of a Randomized Clinical Trial

Importance

Whether genetic factors can identify patients at risk for radiation-induced fibrosis remains unconfirmed.

Objective

To assess the association between the C-509T variant allele in the promoter region of TGFB1 and breast fibrosis 3 years after radiotherapy.

Design, Setting, and Participants

This is an a priori-specified, prospective, cohort study nested in an open-label, randomized clinical trial, which was conducted in community-based and academic cancer centers to compare hypofractionated whole-breast irradiation (WBI) (42.56 Gy in 16 fractions) with conventionally fractionated WBI (50 Gy in 25 fractions) after breast-conserving surgery. In total, 287 women 40 years or older with pathologically confirmed stage 0 to IIA breast cancer treated with breast-conserving surgery were enrolled from February 2011 to February 2014. Patients were observed for a minimum of 3 years. Outcomes were compared using the 1-sided Fisher exact test and multivariable logistic regression.

Exposures

A C-to-T single-nucleotide polymorphism at position -509 relative to the first major transcription start site (C-509T) of the TGFB1 gene.

Main Outcomes and Measures

The primary outcome was grade 2 or higher breast fibrosis as assessed using the Late Effects Normal Tissue/Subjective, Objective, Medical Management, Analytic scale (range, 0 to 3) three years after radiotherapy.

Results

Among 287 women enrolled in the trial, TGFB1 genotype and 3-year radiotherapy-induced toxicity data were available for 174 patients, of whom 89 patients (51%) with a mean (SD) age of 60 (8) years had at least 1 copy of C-509T. Grade 2 or higher breast fibrosis was present in 12 of 87 patients with C-509T (13.8%) compared with 3 of 80 patients without the allele variant (3.8%) (absolute difference, 10.0%; 95% CI, 1.7%-18.4%; P = .02). The results of multivariable analyses indicated that only C-509T (odds ratio, 4.47; 95% CI, 1.25-15.99; P = .02) and postoperative cosmetic outcome (odds ratio, 7.09; 95% CI, 2.41-20.90; P < .001) were significantly associated with breast fibrosis risk.

Conclusions and Relevance

To date, this study seems to be the first prospective validation of a genomic marker for radiation fibrosis. The C-509T allele in TGFB1 is a key determinant of breast fibrosis risk. Assessing TGFB1 genotype may facilitate a more personalized approach to locoregional treatment decisions in breast cancer.

Trial Registration

ClinicalTrials.gov identifier: NCT01266642.

Safety and Efficacy of Panitumumab Plus Neoadjuvant Chemotherapy in Patients With Primary HER2-Negative Inflammatory Breast Cancer

Importance

Combining conventional chemotherapy with targeted therapy has been proposed to improve the pathologic complete response (pCR) rate in patients with inflammatory breast cancer (IBC). Epidermal growth factor receptor (EGFR) expression is an independent predictor of low overall survival in patients with IBC.

Objective

To evaluate the safety and efficacy of the anti-EGFR antibody panitumumab plus neoadjuvant chemotherapy in patients with primary human epidermal growth factor receptor 2 (HER2)-negative IBC.

Design, Setting, and Participants

Women with primary HER2-negative IBC were enrolled from 2010 to 2015 and received panitumumab plus neoadjuvant chemotherapy. Median follow-up time was 19.3 months. Tumor tissues collected before and after the first dose of panitumumab were subjected to immunohistochemical staining and RNA sequencing analysis to identify biomarkers predictive of pCR.

Intervention

Patients received 1 dose of panitumumab (2.5 mg/kg) followed by 4 cycles of panitumumab (2.5 mg/kg), nab-paclitaxel (100 mg/m2), and carboplatin weekly and then 4 cycles of fluorouracil (500 mg/m2), epirubicin (100 mg/m2), and cyclophosphamide (500 mg/m2) every 3 weeks.

Main Outcomes and Measures

The primary end point was pCR rate; the secondary end point was safety. The exploratory objective was to identify biomarkers predictive of pCR.

Results

Forty-seven patients were accrued; 7 were ineligible. The 40 enrolled women had a median age of 57 (range, 23-68) years; 29 (72%) were postmenopausal. Three patients did not complete therapy because of toxic effects (n = 2) or distant metastasis (n = 1). Nineteen patients had triple-negative and 21 had hormone receptor-positive IBC. The pCR and pCR rates were overall, 11 of 40 (28%; 95% CI, 15%-44%); triple-negative IBC, 8 of 19 (42%; 95% CI, 20%-66%); and hormone receptor-positive/HER2-negative IBC, 3 of 21 (14%; 95% CI, 3%-36%). During treatment with panitumumab, nab-paclitaxel, and carboplatin, 10 patients were hospitalized for treatment-related toxic effects, including 5 with neutropenia-related events. There were no treatment-related deaths. The most frequent nonhematologic adverse event was skin rash. Several potential predictors of pCR were identified, including pEGFR expression and COX-2 expression.

Conclusions and Relevance

This combination of panitumumab and chemotherapy showed the highest pCR rate ever reported in triple-negative IBC. A randomized phase 2 study is ongoing to determine the role of panitumumab in patients with triple-negative IBC and to further validate predictive biomarkers.

Trial Registration

ClinicalTrials.gov Identifier: NCT01036087.

Mixture theory modeling for characterizing solute transport in breast tumor tissues

Background

Tumor numerical models have been used to quantify solute transport with a single capillary embedded in an infinite tumor expanse, but measurements from different mammalian tumors suggest that a tissue containing a single capillary with an infinite intercapillary distance assumption is not physiological. The present study aims to investigate the limits of the intercapillary distance within which nanoparticle transport resembles solute extravasation in a breast tumor model as a function of the solute size, the intercapillary separation, and the flow direction in microvessels.

Methods

Solute transport is modeled in a breast tumor for different vascular configurations using mixture theory. A comparison of a single capillary configuration (SBC) with two parallel cylindrical blood vessels (2 BC) and a lymph vessel parallel to a blood vessel (BC_LC) embedded in the tissue cylinder is performed for five solute molecular weights between 0.1 kDa and 70 kDa. The effects of counter flow (CN) versus co-current flow (CO) on the solute accumulation were also investigated and the scaling of solute accumulation-decay time and concentration was explored.

Results

We found that the presence of a second capillary reduces the extravascular concentration compared to a single capillary and this reduction is enhanced by the presence of a lymph vessel. Varying the intercapillary distance with respect to vessel diameter shows a deviation of 10-30% concentration for 2 BC and 45-60% concentration for BC_LC configuration compared to the reference SBC configuration. Finally, we introduce a non-dimensional time scale that captures the concentration as a function of the transport and geometric parameters. We find that the peak solute concentration in the tissue space occurs at a non-dimensional time, T peak ∗ = 0.027 ± 0.018, irrespective of the solute size, tissue architecture, and microvessel flow direction.

Conclusions

This work suggests that the knowledge of such a unique non-dimensional time would allow estimation of the time window at which solute concentration in tissue peaks. Hence this can aid in the design of future therapeutic efficacy studies as an example for triggering drug release or laser excitation in the case of photothermal therapies.

The impact of Ki-67 in the context of multidisciplinary care in primary inflammatory breast cancer

Background: Research on the prognostic or predictive value of Ki-67 among patients with inflammatory breast cancer (IBC) is limited.

Methods: Using the comprehensive database of the Morgan Welch Inflammatory Breast Cancer Research Program at MD Anderson Cancer Center, we identified a cohort of breast cancer patients who were diagnosed with IBC between 1992 and 2012. Distributions of survival outcomes were estimated by the Kaplan-Meier method and compared by log-rank tests and Cox models.

Results: Among a total of 257 patients with stage III IBC, the mean percentage of tumor cells that stained positive for Ki-67 was 48%, (range, 4% to 100%). Using a cutoff of 20% as being Ki-67 positive, this characteristic tended to be associated with worse overall survival (p=0.07) in the univariate analysis. After controlling for hormone receptor (HR) status, human epidermal growth factor receptor 2 (HER2) status and having received trimodality treatment, the association between Ki-67 status and overall survival remained marginally significant (p=0.07). The effects of trimodality treatment on overall survival were statistically significantly different between patients with Ki-67-positive tumors (hazard ratio=0.26, 95% confidence interval [CI]=0.15-0.44, p<0.01) and those with Ki-67-negative tumors (hazard ratio =2.04, 95% CI=0.45-9.29, p=0.36) after adjusting for other tumor characteristics (p=0.01).

Conclusion: IBC patients with Ki-67-positive tumors tended to have worse overall survival, but were more likely to benefit from trimodality treatment, with better overall survival and distant metastasis-free survival. Patients with Ki-67-negative tumors had similar survival distributions, regardless of whether they received trimodality treatment.

Excellent Locoregional Control in Inflammatory Breast Cancer With a Personalized Radiation Therapy Approach

PURPOSE

Inflammatory breast cancer (IBC) has been characterized by high locoregional recurrence (LRR) rates even after trimodality therapy. We recently reported excellent locoregional control among patients treated since formal dedication of an IBC-specific clinic and research program in 2006. Institutionally, a standard twice-daily (BID) dose escalation regimen for all patients with IBC was de-escalated in select cases in 2006 after review demonstrated that young age, incomplete response to neoadjuvant therapy, and positive margins identified subsets with maximal benefit from dose escalation. We report local control and toxicity rates specific to BID versus once-daily (QD) radiation therapy approaches.

METHODS AND MATERIALS

From a prospectively collected database, we identified 103 patients with nonmetastatic IBC who received trimodality therapy at our institution from 2007 to 2015. Descriptive statistics were used to describe the study cohort and compare retrospectively extracted rates of radiation therapy-associated toxicity. The actuarial rate of LRR-free survival was analyzed using the Kaplan-Meier method.

RESULTS

The median follow-up is 3.6 years. Thirty-nine patients (37.9%) received postmastectomy radiation therapy (PMRT) to the chest wall and undissected regional lymphatics in QD fractions (median dose, 50.0 Gy in 25 fractions [fx]; median boost dose, 10.0 Gy in 5 fx) and 64 patients (62.1%) received BID PMRT (median dose, 51.0 Gy in 34 fx; median boost dose, 15.0 Gy in 10 fx). Crude rates of toxicity were not different between patients treated with QD or BID PMRT. Two BID patients (3.1%) and no QD patients (0.0%) experienced LRR (P = .53). The 3- and 5-year LRR-free survival were 95.1% and 100.0% for BID and QD patients, respectively (P = .25).

CONCLUSIONS

Tailoring radiation therapy to clinical risk factors was associated with excellent locoregional control. De-escalation of PMRT from BID to QD was not clearly associated with reduced toxicity compared with BID, although retrospective data collection may limit this comparison.

Outcomes after adjuvant radiotherapy in breast cancer patients with and without germline mutations: A large, single-institutional experience

1502

Background: Women with germline mutations in DNA repair pathways are at an increased risk of developing breast cancer. We posit that tumors arising in these patients may be more sensitive to radiotherapy and, therefore, patients may experience improved locoregional control and survival outcomes following adjuvant radiotherapy as compared to patients without DNA repair pathway mutations. Methods: We evaluated the records of 2,221 women with stage 0-III de novo primary breast cancer treated with surgery and adjuvant radiotherapy who all underwent genetic testing at our institution from 1993 to 2018. Mutations were categorized as pathogenic variant, variant of unknown significance (VUS), or negative. The Kaplan-Meier method was used to estimate the locoregional recurrence rate (LRR), rate of distant metastasis (DM), disease-free survival (DSS), and overall survival (OS) from the time of surgery. Results: The median age at diagnosis was 45 years (range 19-84). Median follow-up time was 7 years (95% confidence interval 6.6-7.4). Among 1,960 patients with evaluable radiation records, 752 (38.4%) received breast only radiation, 12 (0.6%) received chest wall only radiation, and 1,196 (61.0%) received breast/chest wall and regional nodal radiation. A total of 255 (11.4%) and 162 (7.3%) patients had a pathogenic variant mutation and a VUS only, respectively. Pathogenic variant and VUS in BRCA1/2 mutations were detected in 216 (9.7%) and 82 (3.7%) patients, respectively. Perturbations in ATM, CHEK2, MLH, MSH2/6, MUTYH, PALB2, RAD50/51, and/or TP53 were detected in 71% (85/119) of patients who tested positive for a non- BRCA1/2 pathogenic variant or VUS. On univariate analysis, there was no significant association between BRCA1/2 mutation status or any genetic mutation and rate of LRR or DM, DSS, or OS ( p > 0.10 for all). Clinicopathological features including advanced stage and lymphovascular invasion were associated with higher cumulative incidence of LRR and DM as well as shorter DFS and OS ( p < 0.01 for all). Conclusions: Herein we report on the largest cohort of women with breast cancer treated with adjuvant radiotherapy at a single institution who have undergone germline testing. Our findings suggest that the overall prognosis of breast cancer treated with adjuvant radiotherapy in patients with germline BRCA1/2 or other genetic predisposition is similar to patients with sporadic breast cancer. Further investigation to evaluate acute or late toxicities and secondary cancers as a result of radiotherapy is warranted.

NRG-BR002: A phase IIR/III trial of standard of care therapy with or without stereotactic body radiotherapy (SBRT) and/or surgical ablation for newly oligometastatic breast cancer (NCT02364557)

TPS1117

Background: This is a randomized Phase II/III trial to evaluate if stereotactic body radiotherapy (SBRT) and/or surgical resection (SR) of all metastatic sites in newly oligo-metastatic breast cancer who have received up to 12 months of first line systemic therapy without progression will significantly improve median progression free survival (PFS). If this aim is met the trial continues as a phase III to evaluate if SBRT/SR improves 5 year overall survival. Secondary aims include local control in the metastatic site, new distant metastatic rate, and technical quality. Translational primary endpoint is to determine whether < 5 CTCs is an independent prognostic marker for improved PFS and OS. Methods: Women with pathologically confirmed metastatic breast cancer to ≤ 4 sites who have been diagnosed within 365 days with metastatic disease and the primary tumor site disease is controlled. CNS metastases are ineligible. ER/PR and HER-2 neu status is required. Site radiation credentialing with a facility questionnaire and pre-treatment review of first case is required. Randomization is to standard systemic therapy with local radiotherapy/ surgery for palliation when necessary versus ablative therapy of all metastases with SBRT and/or SR. For the phase IIR portion to detect a signal for improved median PFS from 10.5 months to 19 months with 95% power and a 1-sided alpha of 0.15 and accounting for ineligible/lost patients, 128 patients will be required. For the Phase III, an additional 232 patients will be required to definitively determine if ablative therapy improves 5-year overall survival from 28% to 42.5% (HR=0.67), with 85% power and a one-sided type I error of 0.025. For the translational research assuming a two-sided probability of type I error of 0.05, the number of patients accrued in the Phase II-R and Phase III portions will provide sufficient power of at least 91% and 93% to detect whether < 5 CTC’s is prognostic for PFS and OS, respectively. Present accrual (1-31-2019): 105. Contact Information: Protocol: CTSU member web site https://www.ctsu.org . Enrollment: OPEN at https://open.ctsu.org . Support: This project is supported by NRG Oncology grants U10CA180868 and U10CA180822 from the National Cancer Institute (NCI). Translational science is supported by the Ludwig Foundation for Cancer Research. Clinical trial information: NCT02364557.

Elevated serum levels of sialyl Lewis X (sLeX) and inflammatory mediators in patients with breast cancer

PURPOSE

The carbohydrate sialyl Lewis^X (sLe^X) mediates cell adhesion, is critical in the normal function of immune cells, and is frequently over-expressed on cancer cells. We assessed the association, differential levels, and prognostic value of sLe^X and inflammatory cytokines/chemokines in breast cancer sera.

METHODS

We retrospectively measured sLe^X and a panel of cytokines/chemokines in the sera of 26 non-invasive ductal carcinoma in situ (DCIS), 154 invasive non-metastatic breast cancer (non-MBC), 63 metastatic breast cancer (MBC) patients, and 43 healthy controls. Differences in sLe^X and inflammatory cytokines among and between patient groups and healthy controls were assessed with nonparametric tests and we performed survival analysis for the prognostic potential of sLe^X using a cut-off of 8 U/mL as previously defined.

RESULTS

Median serum sLe^X was significantly higher than controls for invasive breast cancer patients (MBC and non-MBC) but not DCIS. In univariate analysis, we confirmed patients with serum sLe^X > 8 U/mL have a significantly shorter progression-free survival (PFS) (P = 0.0074) and overall survival (OS (P = 0.0003). Similarly, patients with high serum MCP-1 and IP-10 had shorter OS (P = 0.001 and P < 0.001, respectively) and PFS (P = 0.010 and P < 0.001, respectively). sLe^X, MCP-1 and IP-10 remained significant in multivariate survival analysis.

CONCLUSION

Elevated serum sLe^X was associated with invasive cancer but not DCIS. High serum sLe^X levels were associated with inflammatory mediators and may play a role in facilitating local invasion of breast tumor. Furthermore, serum MCP-1, IP-10 and sLe^X may have prognostic value in breast cancer.

Poor Response to Neoadjuvant Chemotherapy Correlates with Mast Cell Infiltration in Inflammatory Breast Cancer

Our understanding is limited concerning the tumor immune microenvironment of inflammatory breast cancer (IBC), an aggressive form of primary cancer with low rates of pathologic complete response to current neoadjuvant chemotherapy (NAC) regimens. We retrospectively identified pretreatment (N = 86) and matched posttreatment tissue (N = 27) from patients with stage III or de novo stage IV IBC who received NAC followed by a mastectomy. Immune profiling was performed including quantification of lymphoid and myeloid infiltrates by IHC and T-cell repertoire analysis. Thirty-four of 86 cases in this cohort (39.5%) achieved a pathologic complete response. Characterization of the tumor microenvironment revealed that having a lower pretreatment mast cell density was significantly associated with achieving a pathologic complete response to NAC (P = 0.004), with responders also having more stromal tumor-infiltrating lymphocytes (P = 0.035), CD8⁺ T cells (P = 0.047), and CD20⁺ B cells (P = 0.054). Spatial analysis showed close proximity of mast cells to CD8⁺ T cells, CD163⁺ monocytes/macrophages, and tumor cells when pathologic complete response was not achieved. PD-L1 positivity on tumor cells was found in fewer than 2% of cases and on immune cells in 27% of cases, but with no correlation to response. Our results highlight the strong association of mast cell infiltration with poor response to NAC, suggesting a mechanism of treatment resistance and a potential therapeutic target in IBC. Proximity of mast cells to immune and tumor cells may suggest immunosuppressive or tumor-promoting interactions of these mast cells.

Prediction of Bone Metastasis in Inflammatory Breast Cancer Using a Markov Chain Model

BACKGROUND

Inflammatory breast cancer (IBC) is a rare yet aggressive variant of breast cancer with a high recurrence rate. We hypothesized that patterns of metastasis differ between IBC and non-IBC. We focused on the patterns of bone metastasis throughout disease progression to determine statistical differences that can lead to clinically relevant outcomes. Our primary outcome of this study is to quantify and describe this difference with a view to applying the findings to clinically relevant outcomes for patients.

SUBJECTS, MATERIALS, AND METHODS

We retrospectively collected data of patients with nonmetastatic IBC (n = 299) and non-IBC (n = 3,436). Probabilities of future site-specific metastases were calculated. Spread patterns were visualized to quantify the most probable metastatic pathways of progression and to categorize spread pattern based on their propensity to subsequent dissemination of cancer.

RESULTS

In patients with IBC, the probabilities of developing bone metastasis after chest wall, lung, or liver metastasis as the first site of progression were high: 28%, 21%, and 21%, respectively. For patients with non-IBC, the probability of developing bone metastasis was fairly consistent regardless of initial metastasis site.

CONCLUSION

Metastatic patterns of spread differ between patients with IBC and non-IBC. Selection of patients with IBC with known liver, chest wall, and/or lung metastasis would create a population in whom to investigate effective methods for preventing future bone metastasis.

IMPLICATIONS FOR PRACTICE

This study demonstrated that the patterns of metastasis leading to and following bone metastasis differ significantly between patients with inflammatory breast cancer (IBC) and those with non-IBC. Patients with IBC had a progression pattern that tended toward the development of bone metastasis if they had previously developed metastases in the liver, chest wall, and lung, rather than in other sites. Selection of patients with IBC with known liver, chest wall, and/or lung metastasis would create a population in whom to investigate effective methods for preventing future bone metastasis.

Outcomes of Curative-Intent Treatment for Patients With Breast Cancer Presenting With Sternal or Mediastinal Involvement

PURPOSE

Optimal treatment of patients diagnosed with de novo metastatic breast cancer limited to the mediastinum or sternum has never been delineated. Herein, we sought to determine the efficacy of multimodality treatment, including metastasis-directed radiation therapy, in curing patients with this presentation.

METHODS AND MATERIALS

This is a single-institution retrospective cohort study of patients with de novo metastatic breast cancer treated from 2005 to 2014, with a 50-month median follow-up for the primary cohort. The primary patient cohort had metastasis limited to the mediastinum/sternum treated with curative intent (n = 35). We also included a cohort of patients with stage IIIC disease treated with curative intent (n = 244). Additional groups included a mediastinal/sternal palliative cohort (treatment did not include metastasis-directed radiation therapy; n = 14) and all other patients with de novo stage IV disease (palliative cohort; n = 1185). The primary study outcomes included locoregional recurrence-free survival (LRRFS), recurrence-free survival (RFS), and overall survival (OS), which were calculated using the Kaplan-Meier method. Cox multivariable models compared survival outcomes across treatment cohorts adjusted for molecular subtype, age, and race.

RESULTS

For the mediastinal/sternal curative-intent cohort, 5-year LRRFS was 85%, RFS was 52%, and OS was 63%. After adjustment, there was no statistically significant difference in LRRFS (hazard ratio [HR], 0.39; 95% confidence interval [CI], 0.13-1.13; P = .08), RFS (HR, 0.87; 95% CI 0.50-1.49; P = .61), or OS (HR, 0.79; 95% CI 0.44-1.43; P = .44) between the stage IIIC cohort and the mediastinal/sternal curative-intent cohort (referent). In contrast, RFS was worse for the mediastinal/sternal palliative cohort (HR, 2.29; 95% CI 1.05-5.00; P = .04). OS was worst for the de novo stage IV palliative cohort (HR, 2.61; 95% CI 1.50-4.53; P < .001).

CONCLUSIONS

For select patients presenting with breast cancer metastatic to the sternum and/or mediastinum, curative-intent treatment with chemotherapy, surgery, and radiation yields outcomes similar to those of stage IIIC disease and superior to de novo stage IV breast cancer treated with palliative intent.

Abstract P2-01-03: Lipocalin 2 promotes inflammatory breast cancer tumorigenesis and skin invasion

Background: Inflammatory breast cancer (IBC) is the most lethal form of primary breast cancer and accounts for a significant 10 % of breast cancer deaths in the USA owing to its aggressive proliferation and metastasis, and a lack of effective therapeutic options. Unraveling the underlying mechanisms of growth and metastasis of this aggressive disease could lead to effective therapeutic strategies for an improved outcome in IBC patients. We recently generated in vitro and in vivo IBC models for brain metastasis studies [Debeb et al. JNCI, 2016] and observed an upregulation of Lipocalin 2 (LCN2), a small, secreted iron-trafficking protein which plays a significant role in immune and inflammatory responses and the promotion of malignant progression. The purpose of this study was to investigate the function of LCN2 in IBC tumorigenesis and metastasis.

Methods: Stable knockdown (KD) of LCN2 in IBC cell lines was achieved with lentiviral vectors. Proteomic and gene expression profiling were performed using RPPA and Affymetrix Clariom D microarray. For in vivo studies, control and LCN2 KD IBC cells were transplanted into the cleared mammary fat pad of SCID/Beige mice. Tumor-skin involvement was assessed visually during primary tumor growth and tumor excision. LCN2 gene expression levels in clinical samples were analyzed from the IBC Consortium as well as public data sets. LCN2 serum levels in IBC patients were measured using ELISA and were correlated with clinicopathological variables and outcome data.

Results: LCN2 gene expression is higher in IBC versus non-IBC patients (p=0.00036), independently of the molecular subtypes, and higher in more aggressive (TNBC and HER2+) than hormone receptor-positive subtypes (p&lt;0.00001). LCN2 expression in patient tissues is correlated with reduced overall survival (p&lt;0.00001) and metastasis-free survival (p=0.04) in non-IBC; however, LCN2 was not associated with overall survival in IBC patient serum samples. LCN2 expression was also significantly higher in IBC cell lines, in their culture media, and in brain metastasis sublines compared to non-IBC cell lines (p=0.004). In IBC cell lines, LCN2 KD reduced proliferation, colony formation, migration, and cancer stem cell properties. In vivo silencing of LCN2 in SUM149 cells inhibited primary tumor growth (p=0.001)and resulted in a well-differentiated tumor histology. Additionally, SUM149 LCN2 KD significantly reduced skin invasion/recurrence (LCN2 control vs LCN2 KD: 88 % vs 25 %, p=0.01) suggesting LCN2 is a mediator of tumorigenesis. Analysis of proteomics data showed changes in major signaling pathways including PI3K-Akt signaling and EGF/EGFR signaling pathways. Mechanistically, LCN2 depletion in SUM149 abrogated EGF-induced EGFR phosphorylation and ERK activation.

Conclusions: Our findings suggest that LCN2 may drive IBC tumor progression and skin invasion/recurrence potentially via the EGFR signaling pathway.Future studies will determine the role of LCN2 in metastasis and pinpoint the detailed mechanisms of LCN2-mediated IBC tumorigenesis and recurrence.

Citation Format: Villodre ES, Larson R, Hu X, Stecklein SR, Gomez K, Finetti P, Krishnamurthy S, Ivan C, Su X, Ueno NT, Van Laere S, Bertucci F, Tripathy D, Vivas-Mejía P, A Woodward W, Debeb BG. Lipocalin 2 promotes inflammatory breast cancer tumorigenesis and skin invasion [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-01-03.

Abstract P5-05-04: Myc as a poor prognostic marker for ER+ inflammatory breast cancer (IBC): Quantitative estrogen receptor (ER) expression analysis and gene expression analysis in ER+ IBC vs non-IBC

Background

Estrogen receptor-positive (ER+) primary inflammatory breast cancer (IBC) has a poorer prognosis than ER+ primary non-IBC. Our objective was to determine the association between ER positivity and survival outcome in order to elucidate the biological reason that ER+ IBC is more aggressive than non-IBC.

Methods

We retrospectively determined the relationship between ER expression by immunohistochemistry staining and neoadjuvant chemotherapy response as well as survival outcome for 189 patients with ER+ and HER2-negative (HER2-) IBC and 896 case-matched patients with stage III non-IBC seen at MD Anderson Cancer Center between January 1989 and April 2015. We performed gene expression (GE) analysis for 39 patients with ER+/HER2- IBC and 40 patients with non-IBC to detect genes that are specifically overexpressed in IBC. Logistic regression and Cox proportional hazards model were used to determine the predictive and prognostic value of percentages of cells positive for ER and progesterone receptor (PR) among the patients with ER+/HER2- IBC and non-IBC. Recursive partitioning analysis (RPA) was used to determine the optimal cutoff points for ER% and progesterone receptor (PR) % that maximized differences in survival. The identified cutoff points were tested in an external cohort of 192 ER+/HER2- IBC patients from Institut Paoli-Calmettes in France.

Results

The median values for ER% for IBC and non-IBC were 85 (range, 1-100) and 90 (range, 1-100), respectively. The logistic regression model demonstrated a lack of a relationship of ER% with pathological complete response rate to neoadjuvant chemotherapy both in IBC (P=0.29) and non-IBC (P=0.14). Expression of ER was significantly associated with distant disease-free survival (DDFS); hazard ratio (HR), 0.56 [95% CI, 0.37-0.83] per 50% increase in ER%; P&lt;0.05). Also, ER% was significantly associated with overall survival (OS) (HR, 0.40 [95% CI, 0.25-0.63] per 50% increase in ER%; P&lt;0.05). RPA showed that 91.5% and 9.0% were the optimal cutoff points for ER% and PR%, respectively, for DDFS and overall survival in IBC patients. However, the cutoff points could not be validated in the French external cohort. In the GE study, 84 genes were detected as significantly distinguishing ER+ IBC from non-IBC. Among the top 15 canonical pathways shown by IPA, the ERK/MAPK signaling pathway, PDGF pathway, insulin receptor signaling pathway, and IL-7 signaling pathway were associated with the ER signaling pathway. MYC upregulation was observed in three of these four pathways. Indeed, ER+/HER- IBC had significantly higher MYC amplification compared to those with non-IBC (P&lt;0.05) and higher MYC level was associated with poor relapse free survival for IBC (HR, 1.85 [95% CI, 1.05-2.70], P&lt;0.05).

Conclusions

Increased ER positivity was significantly associated with improved survival in ER+/HER- IBC patients. ER+/HER- IBC had several activated pathways with MYC upregulation compared to non-IBC. MYC upregulation was associated with a poor survival outcome for ER+/HER- IBC. The results indicate that MYC is a key gene for understanding the aggressive biological behavior of ER+/HER- IBC.

Citation Format: Iwase T, Harano K, Masuda H, Kida K, Espinosa Fernandez JR, Hess KR, Wang Y, Woodward WA, Layman RM, Dirix L, Van Laere SJ, Bertucci F, Ueno NT. Myc as a poor prognostic marker for ER+ inflammatory breast cancer (IBC): Quantitative estrogen receptor (ER) expression analysis and gene expression analysis in ER+ IBC vs non-IBC [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-05-04.

Targeting the Tumor Microenvironment in Radiation Oncology: Proceedings from the 2018 ASTRO-AACR Research Workshop

The development of cancers and their response to radiation are intricately linked to the tumor microenvironment (TME) in which they reside. Tumor cells, immune cells, and stromal cells interact with each other and are influenced by the microbiome and metabolic state of the host, and these interactions are constantly evolving. Stromal cells not only secrete extracellular matrix and participate in wound contraction, but they also secrete fibroblast growth factors (FGF), which mediate macrophage differentiation. Tumor-associated macrophages migrate to hypoxic areas and secrete vascular endothelial growth factor (VEGF) to promote angiogenesis. The microbiome and its byproducts alter the metabolic milieu by shifting the balance between glucose utilization and fatty acid oxidation, and these changes subsequently influence the immune response in the TME. Not only does radiation exert cell-autonomous effects on tumor cells, but it influences both the tumor-promoting and tumor-suppressive components in the TME. To gain a deeper understanding of how the TME influences the response to radiation, the American Society for Radiation Oncology and the American Association of Cancer Research organized a scientific workshop on July 26-27, 2018, to discuss how the microbiome, the immune response, the metabolome, and the stroma all shift the balance between radiosensitivity and radioresistance. The proceedings from this workshop are discussed here and highlight recent discoveries in the field, as well as the most important areas for future research.

Three-Year Outcomes With Hypofractionated Versus Conventionally Fractionated Whole-Breast Irradiation: Results of a Randomized, Noninferiority Clinical Trial

PURPOSE

The adoption of hypofractionated whole-breast irradiation (HF-WBI) remains low, in part because of concerns regarding its safety when used with a tumor bed boost or in patients who have received chemotherapy or have large breast size. To address this, we conducted a randomized, multicenter trial to compare conventionally fractionated whole-breast irradiation (CF-WBI; 50 Gy/25 fx + 10 to 14 Gy/5 to 7 fx) with HF-WBI (42.56 Gy/16 fx + 10 to 12.5 Gy/4 to 5 fx).

PATIENTS AND METHODS

From 2011 to 2014, 287 women with stage 0 to II breast cancer were randomly assigned to CF-WBI or HF-WBI, stratified by chemotherapy, margin status, cosmesis, and breast size. The trial was designed to test the hypothesis that HF-WBI is not inferior to CF-WBI with regard to the proportion of patients with adverse cosmetic outcome 3 years after radiation, assessed using the Breast Cancer Treatment Outcomes Scale. Secondary outcomes included photographically assessed cosmesis scored by a three-physician panel and local recurrence-free survival. Analyses were intention to treat.

RESULTS

A total of 286 patients received the protocol-specified radiation dose, 30% received chemotherapy, and 36.9% had large breast size. Baseline characteristics were well balanced. Median follow-up was 4.1 years. Three-year adverse cosmetic outcome was 5.4% lower with HF-WBI ( Pnoninferiority = .002; absolute risks were 8.2% [n = 8] with HF-WBI v 13.6% [n = 15] with CF-WBI). For those treated with chemotherapy, adverse cosmetic outcome was higher by 4.1% (90% upper confidence limit, 15.0%) with HF-WBI than with CF-WBI; for large breast size, adverse cosmetic outcome was 18.6% lower (90% upper confidence limit, -8.0%) with HF-WBI. Poor or fair photographically assessed cosmesis was noted in 28.8% of CF-WBI patients and 35.4% of HF-WBI patients ( P = .31). Three-year local recurrence-free survival was 99% with both HF-WBI and CF-WBI ( P = .37).

CONCLUSION

Three years after WBI followed by a tumor bed boost, outcomes with hypofractionation and conventional fractionation are similar. Tumor bed boost, chemotherapy, and larger breast size do not seem to be strong contraindications to HF-WBI.

Rates of immune cell infiltration in patients with triple-negative breast cancer by molecular subtype

In patients with triple-negative breast cancer (TNBC), tumor-infiltrating lymphocytes (TILs) are associated with improved survival. Lehmann et al. identified 4 molecular subtypes of TNBC [basal-like (BL) 1, BL2, mesenchymal (M), and luminal androgen receptor (LAR)], and an immunomodulatory (IM) gene expression signature indicates the presence of TILs and modifies these subtypes. The association between TNBC subtype and TILs is not known. Also, the association between inflammatory breast cancer (IBC) and the presence of TILs is not known. Therefore, we studied the IM subtype distribution among different TNBC subtypes. We retrospectively analyzed patients with TNBC from the World IBC Consortium dataset. The molecular subtype and the IM signature [positive (IM+) or negative (IM-)] were analyzed. Fisher’s exact test was used to analyze the distribution of positivity for the IM signature according to the TNBC molecular subtype and IBC status. There were 88 patients with TNBC in the dataset, and among them 39 patients (44%) had IBC and 49 (56%) had non-IBC. The frequency of IM+ cases differed by TNBC subtype (p = 0.001). The frequency of IM+ cases by subtype was as follows: BL1, 48% (14/29); BL2, 30% (3/10); LAR, 18% (3/17); and M, 0% (0/21) (in 11 patients, the subtype could not be determined). The frequency of IM+ cases did not differ between patients with IBC and non-IBC (23% and 33%, respectively; p = 0.35). In conclusion, the IM signature representing the underlying molecular correlate of TILs in the tumor may differ by TNBC subtype but not by IBC status.

Prospective Comparison of Toxicity and Cosmetic Outcome After Accelerated Partial Breast Irradiation With Conformal External Beam Radiotherapy or Single-Entry Multilumen Intracavitary Brachytherapy

PURPOSE

This study aimed to prospectively characterize toxicity and cosmesis after accelerated partial breast irradiation (APBI) with 3-dimensional conformal radiation therapy (CRT) or single-entry, multilumen, intracavitary brachytherapy.

METHODS AND MATERIALS

A total of 281 patients with pTis, pT1N0, or pT2N0 (≤3.0 cm) breast cancer treated with segmental mastectomy were prospectively enrolled from December 2008 through August 2014. APBI was delivered using 3-dimensional CRT (n = 29) or with SAVI (n = 176), Contura (n = 56), or MammoSite (n = 20) brachytherapy catheters. Patients were evaluated at protocol-specified intervals, at which time the radiation oncologist scored cosmetic outcome, toxicities, and recurrence status using a standardized template.

RESULTS

The median follow-up time is 41 months. Grade 1 seroma and fibrosis were more common with brachytherapy than with 3-dimensional CRT (50.4% vs 3.4% for seroma; P < .0001 and 66.3% vs 44.8% for fibrosis; P = .02), but grade 1 edema was more common with 3-dimensional CRT than with brachytherapy (17.2% vs 5.6%; P = .04). Grade 2 to 3 pain was more common with 3-dimensional CRT (17.2% vs 5.2%; P = .03). Actuarial 5-year rates of fair or poor radiation oncologist-reported cosmetic outcome were 9% for 3-dimensional CRT and 24% for brachytherapy (P = .13). Brachytherapy was significantly associated with inferior cosmesis on mixed model analysis (P = .003). Significant predictors of reduced risk of adverse cosmetic outcome after brachytherapy were D0.1cc (skin) ≤102%, minimum skin distance >5.1 mm, dose homogeneity index >0.54, and volume of nonconformance ≤0.89 cc. The 5-year ipsilateral breast recurrence was 4.3% for brachytherapy and 4.2% for 3-dimensional CRT APBI patients (P = .95).

CONCLUSIONS

Brachytherapy APBI is associated with higher rates of grade 1 fibrosis and seroma than 3-dimensional CRT but lower rates of grade 1 edema and grade 2 to 3 pain than 3-dimensional CRT. Rates of radiation oncologist-reported fair or poor cosmetic outcomes are higher with brachytherapy. We identified dosimetric parameters that predict reduced risk of adverse cosmetic outcome after brachytherapy-based APBI. Ipsilateral breast recurrence was equivalent for brachytherapy and 3-dimensional CRT.

Author Correction: Inflammatory breast cancer biology: the tumour microenvironment is key

The originally published article contained an error in Table 1, in which two neoadjuvant clinical trials (NCT02876107 and NCT03101748) were not included. This omission has been corrected in the online and print versions of the manuscript through the addition of these two trials and their relevant details (agents, cohort details, targeted biology, main targeted pathway or characteristic and phase) to Table 1.

Inflammatory breast cancer biology: the tumour microenvironment is key

Inflammatory breast cancer (IBC) is a rare and aggressive disease that accounts for ~2-4% of all breast cancers. However, despite its low incidence rate, IBC is responsible for 7-10% of breast cancer-related mortality in Western countries. Thus, the discovery of robust biological targets and the development of more effective therapeutics in IBC are crucial. Despite major international efforts to understand IBC biology, genomic studies have not led to the discovery of distinct biological mechanisms in IBC that can be translated into novel therapeutic strategies. In this Review, we discuss these molecular profiling efforts and highlight other important aspects of IBC biology. We present the intrinsic characteristics of IBC, including stemness, metastatic potential and hormone receptor positivity; the extrinsic features of the IBC tumour microenvironment (TME), including various constituent cell types; and lastly, the communication between these intrinsic and extrinsic components. We summarize the latest perspectives on the key biological features of IBC, with particular emphasis on the TME as an important contributor to the aggressive nature of IBC. On the basis of the current understanding of IBC, we hope to develop the next generation of translational studies, which will lead to much-needed survival improvements in patients with this deadly disease.

Analysis of Hierarchical Organization in Gene Expression Networks Reveals Underlying Principles of Collective Tumor Cell Dissemination and Metastatic Aggressiveness of Inflammatory Breast Cancer

Clusters of circulating tumor cells (CTCs), despite being rare, may account for more than 90% of metastases. Cells in these clusters do not undergo a complete epithelial-to-mesenchymal transition (EMT), but retain some epithelial traits as compared to individually disseminating tumor cells. Determinants of single cell dissemination versus collective dissemination remain elusive. Inflammatory breast cancer (IBC), a highly aggressive breast cancer subtype that chiefly metastasizes via CTC clusters, is a promising model for studying mechanisms of collective tumor cell dissemination. Previous studies, motivated by a theory that suggests physical systems with hierarchical organization tend to be more adaptable, have found that the expression of metastasis-associated genes is more hierarchically organized in cases of successful metastases. Here, we used the cophenetic correlation coefficient (CCC) to quantify the hierarchical organization in the expression of two distinct gene sets, collective dissemination-associated genes and IBC-associated genes, in cancer cell lines and in tumor samples from breast cancer patients. Hypothesizing that a higher CCC for collective dissemination-associated genes and for IBC-associated genes would be associated with retention of epithelial traits enabling collective dissemination and with worse disease progression in breast cancer patients, we evaluated the correlation of CCC with different phenotypic groups. The CCC of both the abovementioned gene sets, the collective dissemination-associated genes and the IBC-associated genes, was higher in (a) epithelial cell lines as compared to mesenchymal cell lines and (b) tumor samples from IBC patients as compared to samples from non-IBC breast cancer patients. A higher CCC of both gene sets was also correlated with a higher rate of metastatic relapse in breast cancer patients. In contrast, neither the levels of CDH1 gene expression nor gene set enrichment analysis (GSEA) of the abovementioned gene sets could provide similar insights. These results suggest that retention of some epithelial traits in disseminating tumor cells as IBC progresses promotes successful breast cancer metastasis. The CCC provides additional information regarding the organizational complexity of gene expression in comparison to GSEA. We have shown that the CCC may be a useful metric for investigating the collective dissemination phenotype and a prognostic factor for IBC.

Abstract 2397: Intracellular cholesterol regulates the DNA damage response in inflammatory breast cancer

Purpose: Inflammatory breast cancer (IBC) is a highly aggressive form of breast cancer, and patients with IBC remain at high risk of locoregional recurrence after radiotherapy. We previously demonstrated that depleting intracellular cholesterol induces radiosensitivity in IBC cells in vitro, and that IBC patients with high levels of high-density lipoprotein (HDL) and those taking a statin, which inhibits de novo cholesterol biosynthesis, have improved locoregional control after radiotherapy. These results suggest that targeting cholesterol metabolism may improve the radiotherapeutic management of IBC. Here, we aimed to understand the molecular mechanism(s) linking cholesterol metabolism and radiation-induced DNA damage and DNA repair and to evaluate statin pharmacotherapy as a DNA repair inhibitor and radiotherapeutic adjunct in an in vivo pre-clinical model of IBC.

Methods: KPL4, SUM149, SUM190, and IBC3 IBC cell lines were used to examine the effect(s) of simvastatin and human serum lipoproteins on radiation-induced DNA damage induction, DNA damage signaling, DNA damage-associated G1, intra-S, and G2/M cell cycle checkpoint activation, and DNA double strand break (DSB) repair by homologous recombination (HR) and non-homologous end joining (NHEJ).

Results: We have generated multiple IBC cells lines with an integrated Traffic Light Reporter (TLR) that is capable of measuring HR and NHEJ, and demonstrate that depletion of intracellular cholesterol abrogates HR-mediated repair of DNA DSBs. We also show that intracellular cholesterol has pleiotropic effects on cell cycle distribution and DNA damage-associated cell cycle checkpoints. We also report a novel polycistronic dual bioluminescence reporter system that can robustly visualize and quantitate DNA DSB induction and repair in vitro and in vivo.

Conclusions: Cholesterol is an important determinant of intrinsic radiosensitivity in IBC, and appears to regulate repair of radiation-induced DNA DSBs. Targeting cholesterol metabolism is a potential strategy to overcome IBC radioresistance and improve the prognosis for this aggressive disease.

Citation Format: Shane R. Stecklein, Adam R. Wolfe, Bisrat G. Debeb, Richard A. Larson, Wendy A. Woodward. Intracellular cholesterol regulates the DNA damage response in inflammatory breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2397.