Tumor-Infiltrating Lymphocytes in Triple-Negative Breast Cancer

Importance

The association of tumor-infiltrating lymphocyte (TIL) abundance in breast cancer tissue with cancer recurrence and death in patients with early-stage triple-negative breast cancer (TNBC) who are not treated with adjuvant or neoadjuvant chemotherapy is unclear.

Objective

To study the association of TIL abundance in breast cancer tissue with survival among patients with early-stage TNBC who were treated with locoregional therapy but no chemotherapy.

Design, Setting, and Participants

Retrospective pooled analysis of individual patient-level data from 13 participating centers in North America (Rochester, Minnesota; Vancouver, British Columbia, Canada), Europe (Paris, Lyon, and Villejuif, France; Amsterdam and Rotterdam, the Netherlands; Milan, Padova, and Genova, Italy; Gothenburg, Sweden), and Asia (Tokyo, Japan; Seoul, Korea), including 1966 participants diagnosed with TNBC between 1979 and 2017 (with follow-up until September 27, 2021) who received treatment with surgery with or without radiotherapy but no adjuvant or neoadjuvant chemotherapy.

Exposure

TIL abundance in breast tissue from resected primary tumors.

Main Outcomes and Measures

The primary outcome was invasive disease-free survival [iDFS]. Secondary outcomes were recurrence-free survival [RFS], survival free of distant recurrence [distant RFS, DRFS], and overall survival. Associations were assessed using a multivariable Cox model stratified by participating center.

Results

This study included 1966 patients with TNBC (median age, 56 years [IQR, 39-71]; 55% had stage I TNBC). The median TIL level was 15% (IQR, 5%-40%). Four-hundred seventeen (21%) had a TIL level of 50% or more (median age, 41 years [IQR, 36-63]), and 1300 (66%) had a TIL level of less than 30% (median age, 59 years [IQR, 41-72]). Five-year DRFS for stage I TNBC was 94% (95% CI, 91%-96%) for patients with a TIL level of 50% or more, compared with 78% (95% CI, 75%-80%) for those with a TIL level of less than 30%; 5-year overall survival was 95% (95% CI, 92%-97%) for patients with a TIL level of 50% or more, compared with 82% (95% CI, 79%-84%) for those with a TIL level of less than 30%. At a median follow-up of 18 years, and after adjusting for age, tumor size, nodal status, histological grade, and receipt of radiotherapy, each 10% higher TIL increment was associated independently with improved iDFS (hazard ratio [HR], 0.92 [0.89-0.94]), RFS (HR, 0.90 [0.87-0.92]), DRFS (HR, 0.87 [0.84-0.90]), and overall survival (0.88 [0.85-0.91]) (likelihood ratio test, P < 10e-6).

Conclusions and Relevance

In patients with early-stage TNBC who did not undergo adjuvant or neoadjuvant chemotherapy, breast cancer tissue with a higher abundance of TIL levels was associated with significantly better survival. These results suggest that breast tissue TIL abundance is a prognostic factor for patients with early-stage TNBC.

Automated mitotic spindle hotspot counts are highly associated with clinical outcomes in systemically untreated early-stage triple-negative breast cancer

Operable triple-negative breast cancer (TNBC) has a higher risk of recurrence and death compared to other subtypes. Tumor size and nodal status are the primary clinical factors used to guide systemic treatment, while biomarkers of proliferation have not demonstrated value. Recent studies suggest that subsets of TNBC have a favorable prognosis, even without systemic therapy. We evaluated the association of fully automated mitotic spindle hotspot (AMSH) counts with recurrence-free (RFS) and overall survival (OS) in two separate cohorts of patients with early-stage TNBC who did not receive systemic therapy. AMSH counts were obtained from areas with the highest mitotic density in digitized whole slide images processed with a convolutional neural network trained to detect mitoses. In 140 patients from the Mayo Clinic TNBC cohort, AMSH counts were significantly associated with RFS and OS in a multivariable model controlling for nodal status, tumor size, and tumor-infiltrating lymphocytes (TILs) (p < 0.0001). For every 10-point increase in AMSH counts, there was a 16% increase in the risk of an RFS event (HR 1.16, 95% CI 1.08-1.25), and a 7% increase in the risk of death (HR 1.07, 95% CI 1.00-1.14). We corroborated these findings in a separate cohort of systemically untreated TNBC patients from Radboud UMC in the Netherlands. Our findings suggest that AMSH counts offer valuable prognostic information in patients with early-stage TNBC who did not receive systemic therapy, independent of tumor size, nodal status, and TILs. If further validated, AMSH counts could help inform future systemic therapy de-escalation strategies.

Identification of a Notch transcriptomic signature for breast cancer

BACKGROUND

Dysregulated Notch signalling contributes to breast cancer development and progression, but validated tools to measure the level of Notch signalling in breast cancer subtypes and in response to systemic therapy are largely lacking. A transcriptomic signature of Notch signalling would be warranted, for example to monitor the effects of future Notch-targeting therapies and to learn whether altered Notch signalling is an off-target effect of current breast cancer therapies. In this report, we have established such a classifier.

METHODS

To generate the signature, we first identified Notch-regulated genes from six basal-like breast cancer cell lines subjected to elevated or reduced Notch signalling by culturing on immobilized Notch ligand Jagged1 or blockade of Notch by γ-secretase inhibitors, respectively. From this cadre of Notch-regulated genes, we developed candidate transcriptomic signatures that were trained on a breast cancer patient dataset (the TCGA-BRCA cohort) and a broader breast cancer cell line cohort and sought to validate in independent datasets.

RESULTS

An optimal 20-gene transcriptomic signature was selected. We validated the signature on two independent patient datasets (METABRIC and Oslo2), and it showed an improved coherence score and tumour specificity compared with previously published signatures. Furthermore, the signature score was particularly high for basal-like breast cancer, indicating an enhanced level of Notch signalling in this subtype. The signature score was increased after neoadjuvant treatment in the PROMIX and BEAUTY patient cohorts, and a lower signature score generally correlated with better clinical outcome.

CONCLUSIONS

The 20-gene transcriptional signature will be a valuable tool to evaluate the response of future Notch-targeting therapies for breast cancer, to learn about potential effects on Notch signalling from conventional breast cancer therapies and to better stratify patients for therapy considerations.

Clinical outcomes and prognostic factors in triple-negative invasive lobular carcinoma of the breast

PURPOSE

Triple-negative invasive lobular carcinoma (TN-ILC) of breast cancer is a rare disease and the clinical outcomes and prognostic factors are not well-defined.

METHODS

Women with stage I-III TN-ILC or triple-negative invasive ductal carcinoma (TN-IDC) of the breast undergoing mastectomy or breast-conserving surgery between 2010 and 2018 in the National Cancer Database were included. Kaplan-Meier curves and multivariate Cox proportional hazard regression were used to compare overall survival (OS) and evaluate prognostic factors. Multivariate logistic regression was performed to analyze the factors associated with pathological response to neoadjuvant chemotherapy.

RESULTS

The median age at diagnosis for women with TN-ILC was 67 years compared to 58 years in TN-IDC (p < 0.001). There was no significant difference in the OS between TN-ILC and TN-IDC in multivariate analysis (HR 0.96, p = 0.44). Black race and higher TNM stage were associated with worse OS, whereas receipt of chemotherapy or radiation was associated with better OS in TN-ILC. Among women with TN-ILC receiving neoadjuvant chemotherapy, the 5-year OS was 77.3% in women with a complete pathological response (pCR) compared to 39.8% in women without any response. The odds of achieving pCR following neoadjuvant chemotherapy were significantly lower in women with TN-ILC compared to TN-IDC (OR 0.53, p < 0.001).

CONCLUSION

Women with TN-ILC are older at diagnosis but have similar OS compared to TN-IDC after adjusting for tumor and demographic characteristics. Administration of chemotherapy was associated with improved OS in TN-ILC, but women with TN-ILC were less likely to achieve complete response to neoadjuvant therapy compared to TN-IDC.

Evaluation of Alisertib Alone or Combined With Fulvestrant in Patients With Endocrine-Resistant Advanced Breast Cancer: The Phase 2 TBCRC041 Randomized Clinical Trial

Importance

Aurora A kinase (AURKA) activation, related in part to AURKA amplification and variants, is associated with downregulation of estrogen receptor (ER) α expression, endocrine resistance, and implicated in cyclin-dependent kinase 4/6 inhibitor (CDK 4/6i) resistance. Alisertib, a selective AURKA inhibitor, upregulates ERα and restores endocrine sensitivity in preclinical metastatic breast cancer (MBC) models. The safety and preliminary efficacy of alisertib was demonstrated in early-phase trials; however, its activity in CDK 4/6i-resistant MBC is unknown.

Objective

To assess the effect of adding fulvestrant to alisertib on objective tumor response rates (ORRs) in endocrine-resistant MBC.

Design, Setting, and Participants

This phase 2 randomized clinical trial was conducted through the Translational Breast Cancer Research Consortium, which enrolled participants from July 2017 to November 2019. Postmenopausal women with endocrine-resistant, ERBB2 (formerly HER2)-negative MBC who were previously treated with fulvestrant were eligible. Stratification factors included prior treatment with CDK 4/6i, baseline metastatic tumor ERα level measurement (<10%, ≥10%), and primary or secondary endocrine resistance. Among 114 preregistered patients, 96 (84.2%) registered and 91 (79.8%) were evaluable for the primary end point. Data analysis began after January 10, 2022.

Interventions

Alisertib, 50 mg, oral, daily on days 1 to 3, 8 to 10, and 15 to 17 of a 28-day cycle (arm 1) or alisertib same dose/schedule with standard-dose fulvestrant (arm 2).

Main Outcomes and Measures

Improvement in ORR in arm 2 of at least 20% greater than arm 1 when the expected ORR for arm 1 was 20%.

Results

All 91 evaluable patients (mean [SD] age, 58.5 [11.3] years; 1 American Indian/Alaskan Native [1.1%], 2 Asian [2.2%], 6 Black/African American [6.6%], 5 Hispanic [5.5%], and 79 [86.8%] White individuals; arm 1, 46 [50.5%]; arm 2, 45 [49.5%]) had received prior treatment with CDK 4/6i. The ORR was 19.6%; (90% CI, 10.6%-31.7%) for arm 1 and 20.0% (90% CI, 10.9%-32.3%) for arm 2. In arm 1, the 24-week clinical benefit rate and median progression-free survival time were 41.3% (90% CI, 29.0%-54.5%) and 5.6 months (95% CI, 3.9-10.0), respectively, and in arm 2 they were 28.9% (90% CI, 18.0%-42.0%) and 5.4 months (95% CI, 3.9-7.8), respectively. The most common grade 3 or higher adverse events attributed to alisertib were neutropenia (41.8%) and anemia (13.2%). Reasons for discontinuing treatment were disease progression (arm 1, 38 [82.6%]; arm 2, 31 [68.9%]) and toxic effects or refusal (arm 1, 5 [10.9%]; arm 2, 12 [26.7%]).

Conclusions and Relevance

This randomized clinical trial found that adding fulvestrant to treatment with alisertib did not increase ORR or PFS; however, promising clinical activity was observed with alisertib monotherapy among patients with endocrine-resistant and CDK 4/6i-resistant MBC. The overall safety profile was tolerable.

Trial Registration

ClinicalTrials.gov Identifier: NCT02860000.

Advances in systemic therapies for triple negative breast cancer

Triple negative breast cancer (TNBC) continues to be the subtype of breast cancer with the highest rates of recurrence and mortality. The lack of expression of targetable proteins such as the estrogen receptor and absence of HER2 amplification have made relying on cytotoxic chemotherapy necessary for decades. In the operable setting, efforts to improve outcomes have focused on escalation of systemic therapy and a shift toward preoperative delivery followed by a response adapted approach to postoperative systemic therapy. An improved understanding of tumor biology has resulted in the identification of subsets of patients with specific molecular features, leading to testing and approval of multiple new targeted therapies for this disease. Furthermore, advances in drug development have led to the approval of antibody-drug conjugates that are redefining classification schemes for breast cancer. This review focuses on the modern management of TNBC, with particular focus on recent updates in the treatment of operable disease, and an overview of the most recent promising advances in the therapeutic landscape of metastatic disease. It discusses the practical challenges and unanswered questions resulting from the approval of neoadjuvant immunotherapy and shares an approach in the clinic on topics for which evidence is lacking. In addition, it provides a glimpse into the future, highlighting challenges and opportunities for biomarker based right-sizing of preoperative therapy, refining evaluation of response to preoperative therapy after surgery, early diagnosis and detection of relapse, and areas of needed research for metastatic TNBC.

Distinct spatial immune microlandscapes are independently associated with outcomes in triple-negative breast cancer

The utility of spatial immunobiomarker quantitation in prognostication and therapeutic prediction is actively being investigated in triple-negative breast cancer (TNBC). Here, with high-plex quantitative digital spatial profiling, we map and quantitate intraepithelial and adjacent stromal tumor immune protein microenvironments in systemic treatment-naïve (female only) TNBC to assess the spatial context in immunobiomarker-based prediction of outcome. Immune protein profiles of CD45-rich and CD68-rich stromal microenvironments differ significantly. While they typically mirror adjacent, intraepithelial microenvironments, this is not uniformly true. In two TNBC cohorts, intraepithelial CD40 or HLA-DR enrichment associates with better outcomes, independently of stromal immune protein profiles or stromal TILs and other established prognostic variables. In contrast, intraepithelial or stromal microenvironment enrichment with IDO1 associates with improved survival irrespective of its spatial location. Antigen-presenting and T-cell activation states are inferred from eigenprotein scores. Such scores within the intraepithelial compartment interact with PD-L1 and IDO1 in ways that suggest prognostic and/or therapeutic potential. This characterization of the intrinsic spatial immunobiology of treatment-naïve TNBC highlights the importance of spatial microenvironments for biomarker quantitation to resolve intrinsic prognostic and predictive immune features and ultimately inform therapeutic strategies for clinically actionable immune biomarkers.

Abstract P2-11-34: Mitotic spindle hotspot counting using deep learning networks is highly associated with clinical outcomes in patients with early-stage triple-negative breast cancer who did not receive systemic therapy

Background: Triple-negative breast cancers (TNBC) exhibit high rates of recurrence and mortality. However, recent studies suggest that a subset of patients (pts) with early-stage TNBC enriched in tumor-infiltrating lymphocytes (TILs) have excellent clinical outcomes even in the absence of systemic therapy. Additional histological biomarkers that could identify pts for future systemic therapy escalation/de-escalation strategies are of great interest. TNBC are frequently highly proliferative with abundant mitoses. However, classic markers of proliferation (manual mitosis counting and Ki-67) appear to offer no prognostic value. Here, we evaluated the prognostic effects of automated mitotic spindle hotspot (AMSH) counting on RFS in independent cohorts of systemically untreated early-stage TNBC.

Methods: AMSH counting was conducted with a state-of-the-art deep learning algorithm trained on the detection of mitoses within 2 mm2 areas with the highest mitotic density (i.e. hotspots) in digital H&E images. Details of the development, training and validation of the algorithm were published previously [1] in a cohort of unselected TNBC. We obtained AMSH counts in a centrally confirmed TNBC cohort from Mayo Clinic [2] and focused our analysis on pts who received locoregional therapy but no systemic therapy. Using a fractional polynomial analysis with a multivariable proportional hazards regression model, we confirmed the assumption of linearity in the log hazard for the continuous variable AMSH and evaluated whether AMSH counts were prognostic of RFS. We corroborated our findings in an independent cohort of systemically untreated TNBC pts from the Radboud University Medical Center in the Netherlands (Radboud Cohort). Results are reported at a median follow-up of 8.1 and 6.7 years for the Mayo and Netherlands cohorts, respectively.

Results: Among 182 pts with who did not receive systemic therapy in the Mayo Cohort, 140 (77%) with available AMSH counts were included. The mean age was 61 (range: 31-94), 71% were postmenopausal, 67% had tumors ≤ 2cm, and 83% were node-negative. As expected, most tumors were Nottingham grade 3 (84%) and had a high Ki-67 proliferation index (54% with Ki-67 &gt;30%). Most tumors (73%) had stromal TILs ≤ 30%. The median AMSH count was 18 (IQR: 8, 42). AMSH counts were linearly associated with grade and tumor size, with the proportion of pts with grade 3 tumors and size &gt; 2 cm increasing as the AMSH counts increased (p=0.007 and p=0.059, respectively). In a multivariate model controlling for nodal status, tumor size, and stromal TILs, AMSH counts were independently associated with RFS (p&lt; 0.0001). For every 10-point increase in the AMSH count, we observed a 17% increase in the risk of experiencing an RFS event (HR 1.17, 95% CI 1.08-1.26). We corroborated our findings in the Radboud Cohort (n=126). The mean age was 68 (range: 40-96), and 81% were node-negative. While the median AMSH count was 36 (IQR: 16-63), higher than in the Mayo Cohort (p=0.004), the prognostic impact was similar, with a significant association between AMSH count and RFS (p=0.028) in a multivariate model corrected for nodal status, tumor size, and stromal TILs. For every 10-point increase in the AMSH count in the Netherlands cohort, we observed a 9% increase in the risk of experiencing an RFS event (HR 1.09, 95% CI 1.01-1.17). RFS rates according to AMSH counts for both cohorts are shown in the Table.

Conclusions: AMSH counting is a new proliferation biomarker that provides prognostic value independent of nodal status, tumor size, and stromal TILs in systemically untreated early-stage TNBC. Plans are underway to evaluate AMSH counts in additional cohorts of systemically untreated TNBC, and in other disease settings such as prior to neoadjuvant systemic therapy. If validated, this biomarker should be prospectively evaluated as a potential selection biomarker in clinical trials of systemic therapy de-escalation.

References:

1. PMID: 29994086

2. PMID: 28913760

Table RFS according to AMSH counts in the Mayo and Radboud Cohorts

Citation Format: Roberto A. Leon-Ferre, Jodi M. Carter, David Zahrieh, Jason P. Sinnwell, Roberto Salgado, Vera Suman, David Hillman, Judy C. Boughey, Krishna R. Kalari, Fergus J. Couch, James N. Ingle, Maschenka Balkenkohl, Francesco Ciompi, Jeroen van der Laak, Matthew P. Goetz. Mitotic spindle hotspot counting using deep learning networks is highly associated with clinical outcomes in patients with early-stage triple-negative breast cancer who did not receive systemic therapy [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-11-34.

Abstract PD9-05: Stromal tumor-infiltrating lymphocytes identify early-stage triple-negative breast cancer patients with favorable outcomes at 10-year follow-up in the absence of systemic therapy: a pooled analysis of 1835 patients

Background: The prognostic value of stromal tumor-infiltrating lymphocytes (TILs) as a biomarker for triple-negative breast cancer (TNBC) has been extensively demonstrated in patients (pts) receiving (neo)adjuvant systemic therapy. In addition, several small studies suggest that a subset of pts with early-stage TNBC and high TILs have excellent long-term outcomes, even in the absence of systemic therapy [1-3]. However, data on the absolute risk of TNBC recurrence according to TIL levels in the absence of systemic therapy are limited and critical to inform the design of future systemic therapy de-escalation clinical trials.

Methods: We conducted an individual patient data pooled analysis of 12 international cohorts of pts with TNBC treated with locoregional therapy but no systemic therapy. TNBC was defined as tumors with estrogen and progesterone receptor of &lt; 1% and HER2 negative (IHC 0, 1+ or IHC 2+ and FISH negative) per local evaluation. TILs were locally assessed in hematoxylin & eosin-stained slides according to the International Immuno-Oncology Biomarker Working Group guidelines (www.tilsinbreastcancer.org). We used the Kaplan-Meier method to assess survival outcomes according to prespecified TIL thresholds: 30% and 50%. Confidence intervals (CI) for survival probabilities were calculated using a percentile bootstrap method. The primary endpoint was invasive disease-free survival (iDFS, STEEP 2.0 definition). Key secondary outcomes included recurrence-free survival (RFS), distant disease-free survival (DDFS) and overall survival (OS).

Results: 1,835 pts diagnosed with TNBC between 1982 and 2017 who did not receive systemic therapy were included. The median age at diagnosis was 56 (IQR 38-71). Menopausal status was known in 1,184 women, of whom 78% were post-menopausal. The median tumor size was 2.0 cm (IQR 1.2-2.6). Most pts (87%) had no axillary lymph node involvement (N0). Most tumors were invasive ductal carcinoma (74%) and grade 3 (70%). The median level of TILs was 15% (IQR 5-40). The median duration of follow-up was 30.4 years (95% CI 29.9, 31.1). A total of 950 (52%) iDFS, 828 (45%) RFS, 767 (42%) DDFS events, and 604 (33%) deaths were observed. In multivariable analyses, higher TILs were independently associated with improved iDFS, RFS, DDFS, and OS beyond clinicopathological factors (likelihood ratio p&lt; 10e-6). Each 10% increment in stromal TILs was associated with an 8% (95% CI: 6-11), 10% (95% CI: 7-13), and 13% (95% CI: 10-15) reduction in the risk of experiencing an iDFS, RFS or DDFS event, and with a 12% (95% CI: 9-15) reduction in the risk of death. iDFS, RFS, DDFS and OS rates according to different TIL thresholds and nodal status are shown in the Table. Of note, the RFS estimates (which exclude second non-breast primaries and contralateral breast cancers) were consistently higher than the iDFS counterparts (which include both), consistent with a high rate of contralateral breast cancers and second primary tumors in this cohort. Notably, patients with node-negative—and especially stage I—TNBC with high TILs had excellent survival rates at 10-year follow-up.

Conclusion: TILs are highly prognostic in pts with systemically untreated early-stage TNBC. Pts with pN0 (and especially stage I) TNBC with high TILs exhibited very favorable long-term outcomes even in the absence of systemic therapy. These data define the natural history of TIL-rich TNBC pts and are crucial to identifying the optimal patient population for future chemotherapy and immunotherapy de-escalation clinical trials.

References:

[1] Leon-Ferre et al, 2017, PMID: 28913760

[2] Park et al, 2019, PMID: 31566659

[3] de Jong et al, 2022, PMID: 35353548

Table 5 and 10-year survival endpoints according TIL level, nodal status, and stage

Citation Format: Roberto A. Leon-Ferre, Sarah Flora Jonas, Roberto Salgado, Sherene Loi, Vincent De Jong, Jodi M. Carter, Torsten Nielson, Samuel Leung, Nazia Riaz, Giuseppe Curigliano, Carmen Criscitiello, Vincent Cockenpot, Matteo Lambertini, Vera Suman, Barbro Linderholm, John WM Martens, Carolien HM van Deurzen, Mieke Timmermans, Tatsunori Shimoi, Shu Yazaki, Masayuki Yoshida, Sung-Bae Kim, Hee Jin Lee, Maria Vittoria Dieci, Guillaume Bataillon, Anne Salomon, Fabrice Andre, Marleen Kok, Sabine Linn, Matthew P. Goetz, Stefan Michiels. Stromal tumor-infiltrating lymphocytes identify early-stage triple-negative breast cancer patients with favorable outcomes at 10-year follow-up in the absence of systemic therapy: a pooled analysis of 1835 patients [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD9-05.

Abstract P4-07-56: Mayo Clinic Enterprise patterns of growth-factor utilization for sacituzumab govitecan (SG)-induced neutropenia among patients with metastatic triple negative breast cancer

Background: SG was approved in 2020 for the treatment of metastatic triple negative breast cancer (TNBC). The most common grade 3/4 adverse event in the ASCENT trial was neutropenia (51.2%) with a 6% incidence of febrile neutropenia. 1 Package insert recommendations do not endorse primary prophylactic growth factor support, rather only initiating if severe neutropenia occurs on treatment.2

Objective: This study retrospectively reviewed the utilization of growth factor support in patients (pts) with metastatic TNBC initiated on SG at each Mayo Clinic Enterprise site.

Methods: We performed a multi-center, retrospective review of all pts with TNBC who received SG from January 2021 to December 2021 at Mayo Clinic sites in Minnesota, Florida, Arizona, and its community-based health system network. Data collected included history of neutropenia with previous cycles of SG resulting in a treatment delay, number of cycles, grade of neutropenia and cycle/day of treatment plan when growth factor added. Pts who received only one dose of SG were excluded. The Fisher’s exact test was utilized to compare the difference in the use of primary prophylaxis between sites.

Results: 67 pts received at least two doses of SG. Within this cohort, 42 pts (63%) received growth factor support during treatment with SG. Growth factor support was most often added during the first two cycles (59.5%). A total of 12 patients initiated growth factor with no history of delays related to neutropenia and without neutropenia at the time of administration. Eleven of these pts had growth factor support added on Cycle 1 as primary prophylaxis. Primary prophylaxis was most common at Mayo Clinic – Rochester compared to the other sites (Table 1), however there was not a statistically significant difference (p=0.27). There were 26 pts (39%) with a treatment delay due to neutropenia while receiving SG, of which 21 (81%) were managed with the addition of growth factor (13 pegfilgrastim, 8 filgrastim). The median number of cycles for all pts was 5 (range: 1-25). Pts who received growth factor were treated with a median of 5 cycles (range: 1-25) and pts who did not receive growth factor were treated with a median of 4 cycles (range: 1-19) (p=0.10).

Conclusions: We observed wide variability in the use of prophylactic growth factor between Mayo Clinic sites with SG. The optimal practice of growth factor use with SG warrants further exploration.

References:

1. Bardia A, Hurvitz SA, Tolaney SM, et al. Sacituzumab govitecan in metastatic triple-negative breast cancer. N Engl J Med. 2021;384(16):1529-1541

2. Immunomedics, Inc. Trodelvy (sacituzumab govitecan-hziy) [package insert]. Foster City, CA: Gilead Sciences; 2020.

Table 1: Grade of neutropenia for patients receiving SG when growth factor initiated

Citation Format: Kaylee Clark, Jamie L. Carroll, Alvaro Moreno-Aspitia, Brenda Ernst, Farah Raheem, Ashley Heil, Beth Boyer, Kristin Mara, Matthew P. Goetz, Roberto A. Leon-Ferre, Karthik V. Giridhar, Jodi Taraba. Mayo Clinic Enterprise patterns of growth-factor utilization for sacituzumab govitecan (SG)-induced neutropenia among patients with metastatic triple negative breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-07-56.

Abstract P4-01-22: Clinical outcomes of metastatic breast cancer patients treated with poly (adenosine diphosphate-ribose) polymerase inhibitors (PARPi): the Mayo Clinic experience

Background: Two poly (adenosine diphosphate-ribose) polymerase inhibitors (PARPi) are currently FDA-approved for the treatment of HER2-negative metastatic breast cancer (MBC) in carriers of germline pathogenic variants (PVs) in BRCA1 or BRCA2 (BRCA1/2). This study explores the clinical outcomes of MBC patients treated with a PARPi. Methods: In this retrospective study, we included MBC patients treated with a PARPi between January 2017 and February 2022 at Mayo Clinic (Minnesota, Arizona, Florida, and Mayo Clinic Health Systems). We used the Kaplan Meier method to estimate the time-to-treatment-failure (TTF) and the log-rank test to compare different subsets. In addition, predictors of TTF were identified in a multivariate cox-proportional hazard regression model, including age at PARPi initiation, race, ethnicity, histology, estrogen receptor (ER), progesterone receptor (PR), and HER2 expression of the tumor, the number of prior therapies, type of PARPi, and PV carrier status (germline BRCA1/2 or PALB2 vs. somatic BRCA1/2 vs. other). Results: Sixty-five patients treated with PARPi (olaparib: 51; talazoparib: 14) were included in the final analysis. Fifty-five patients were carriers of germline PVs in BRCA1 (n=24, 37%), BRCA2 (n=27, 42%) or PALB2 (n=4, 6%), whereas ten patients (15%) had no germline PVs but the tumor had a somatic mutation in the homologous recombination-related (HRR) genes (7 in BRCA1/2, 2 in ATM, and 1 in CDKN2A and CDH1). At the data cutoff, 48 (74%) patients had discontinued PARPi due to progression or death. Fifteen (23%) patients required a dose reduction due to side effects. Occurrence of grade ≥ 3 side effects: anemia in 8, fatigue in 4, neutropenia in 2, and thrombocytopenia in 2 patients. Eight (15.7%) patients in the olaparib group and seven (50%) patients in the talazoparib group required a dose reduction for side effects. No patient on olaparib required drug discontinuation due to side effects, whereas two patients on talazoparib were switched to olaparib due to cytopenias and could tolerate olaparib. Median TTF in the overall population was 8 months (95% confidence interval [CI]: 6.4 – 9.6), and there was no difference (p=0.64) in TTF between the olaparib and talazoparib groups. Median TTF in the germline BRCA1, BRCA2, and PALB2 PV carriers were 7, 8, and 11 months, respectively (p=0.57). Among patients with somatic BRCA1/2 mutations, the median TTF was 4 months. Numerically, patients with HER2-positive tumors (n=8) had a shorter TTF compared to HER2-negative tumors (Median TTF: 4 vs. 8 months, p=0.098). No significant difference in TTF was observed by ER or PR status of the tumor, age at initiation of PARPi, the number of prior therapies, and prior use of platinum-based chemotherapy or CDK4/6 inhibitors. In multivariate analysis, HER2 positivity (hazard ratio [HR]: 8.0, 95% CI: 2.2 – 29.4, p=0.002), somatic BRCA1/2 mutations (HR: 7.6, 95% CI: 1.2 – 50.0, p=0.03) and somatic mutations in other HRR genes (HR: 19.1, 95% CI: 3.1 – 118.6, p=0.002) were associated with worse TTF. Conclusions: In the real world, PARPi were well-tolerated with promising time-to-treatment-failure (TTF) benefits comparable to data from clinical trials. Notably, relatively shorter TTF was observed in patients with somatic BRCA1/2 and other HRR gene mutations and HER2-positive MBC. These findings improve our understanding of the role of PARPi in MBC and will help to guide treatment decisions with PARPi in the clinical setting.

Citation Format: Nusrat Jahan, Jodi Taraba, Karthik V. Giridhar, Roberto A. Leon-Ferre, Amye J. Tevaarwerk, Elizabeth Cathcart-Rake, Ciara C. O’Sullivan, Prema Peethambaram, Timothy J. Hobday, Kathryn Ruddy, Lida A. Mina, Pooja Advani, Felipe Batalini, Matthew P. Goetz, Tufia C. Haddad, Fergus J. Couch, Siddhartha Yadav. Clinical outcomes of metastatic breast cancer patients treated with poly (adenosine diphosphate-ribose) polymerase inhibitors (PARPi): the Mayo Clinic experience [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-01-22.

Surveillance mammography after treatment for male breast cancer

PURPOSE

To identify the practice patterns related to use of surveillance mammography in male breast cancer (MaBC) survivors.

METHODS

Using administrative claims data from OptumLabs Data Warehouse, we identified men who underwent surgery for breast cancer during 2007-2017. We calculated the proportion of men who had at least one mammogram (a) within 13 months for all patients and (b) within 24 months amongst those who maintained their insurance coverage for at least that length of time after surgery. Multivariate logistic regression modeling was used to identify factors associated with mammography within each timeframe.

RESULTS

Out of 729 total MaBC survivors, 209 (29%) underwent mammography within 13 months after surgery. Among those who had lumpectomy, 41% underwent mammography, whereas among those who had mastectomy, 27% had mammography. Amongst 526 men who maintained consistent insurance coverage for 24 months after surgery, 215 (41%) underwent mammography at least once during that 24-month period. In this cohort, the proportion who had at least one mammogram during the 24-month period was 49% after lumpectomy and 40% after mastectomy. In a multivariate logistic regression model, more recent diagnosis (2015+) and older age at diagnosis were associated with lower odds of undergoing mammography, while receipt of radiation was associated with higher odds of undergoing mammography.

CONCLUSIONS

Although recent ASCO guidelines recommend surveillance mammography after lumpectomy, a minority of MaBC survivors undergo surveillance mammography, even after lumpectomy. This is likely due to the paucity of data regarding the true benefits and harms of surveillance/screening mammography for MaBC.

Luminal androgen receptor breast cancer subtype and investigation of the microenvironment and neoadjuvant chemotherapy response

Triple-negative breast cancer (TNBC) is the most aggressive breast cancer subtype with low overall survival rates and high molecular heterogeneity; therefore, few targeted therapies are available. The luminal androgen receptor (LAR) is the most consistently identified TNBC subtype, but the clinical utility has yet to be established. Here, we constructed a novel genomic classifier, LAR-Sig, that distinguishes the LAR subtype from other TNBC subtypes and provide evidence that it is a clinically distinct disease. A meta-analysis of seven TNBC datasets (n = 1086 samples) from neoadjuvant clinical trials demonstrated that LAR patients have significantly reduced response (pCR) rates than non-LAR TNBC patients (odds ratio = 2.11, 95% CI: 1.33, 2.89). Moreover, deconvolution of the tumor microenvironment confirmed an enrichment of luminal epithelium corresponding with a decrease in basal and myoepithelium in LAR TNBC tumors. Increased immunosuppression in LAR patients may lead to a decreased presence of cycling T-cells and plasma cells. While, an increased presence of myofibroblast-like cancer-associated cells may impede drug delivery and treatment. In summary, the lower levels of tumor infiltrating lymphocytes (TILs), reduced immune activity in the micro-environment, and lower pCR rates after NAC, suggest that new therapeutic strategies for the LAR TNBC subtype need to be developed.

Estrogen receptor beta repurposes EZH2 to suppress oncogenic NFκB/p65 signaling in triple negative breast cancer

Triple Negative Breast Cancer (TNBC) accounts for 15-20% of all breast cancer cases, yet is responsible for a disproportionately high percentage of breast cancer mortalities. Thus, there is an urgent need to identify novel biomarkers and therapeutic targets based on the molecular events driving TNBC pathobiology. Estrogen receptor beta (ERβ) is known to elicit anti-cancer effects in TNBC, however its mechanisms of action remain elusive. Here, we report the expression profiles of ERβ and its association with clinicopathological features and patient outcomes in the largest cohort of TNBC to date. In this cohort, ERβ was expressed in approximately 18% of TNBCs, and expression of ERβ was associated with favorable clinicopathological features, but correlated with different overall survival outcomes according to menopausal status. Mechanistically, ERβ formed a co-repressor complex involving enhancer of zeste homologue 2/polycomb repressive complex 2 (EZH2/PRC2) that functioned to suppress oncogenic NFκB/RELA (p65) activity. Importantly, p65 was shown to be required for formation of this complex and for ERβ-mediated suppression of TNBC. Our findings indicate that ERβ+ tumors exhibit different characteristics compared to ERβ- tumors and demonstrate that ERβ functions as a molecular switch for EZH2, repurposing it for tumor suppressive activities and repression of oncogenic p65 signaling.

Abstract OT2-19-05: A phase I/II trial of abemaciclib and T-DM1 in women and men with HER2-positive advanced or metastatic breast cancer that has progressed on treatment with a taxane, trastuzumab and pertuzumab (THP) (ACCRU-BR-1801)

Background: Although major advances have been made in the treatment of HER2+ metastatic breast cancer (MBC), the goal of care remains largely palliative, therefore better treatments are needed. Given encouraging preclinical and clinical data, the combination of cyclin dependent 4/6 kinase inhibitors and HER2-directed therapy is further being evaluated in this trial. Trial Design: In this phase I/II multicenter trial, we will determine the maximum tolerated dose (MTD) of abemaciclib (Abem) combined with T-DM1. Three Abem dose levels will be examined, 50 mg, 100 mg and 150 mg. The phase 2 portion of this trial will examine whether PFS is increased with addition of Abem to T-DM1 in two pt cohorts - those with ER+ HER2+ MBC and those with ER-HER2+ MBC. For phase 2, a pre-registration biopsy is required to confirm ER and HER2-status and to determine levels of tumor infiltrating lymphocytes; vimentin (an epithelial-mesenchymal transition marker); and CD8 and FOXP3 expression. Blood samples will be collected pretreatment , at 6 weeks, and at progression for all pts. Eligibility Criteria: Phase I&II: All pts must have HER2+ MBC per ASCO-CAP guidelines and prior treatment with a taxane, trastuzumab and pertuzumab. For the phase Iportion, pts can have measurable or non-measurable disease with no restriction on the number of prior lines of therapy. In the phase II portion, pts must have measurable disease with ≤1-2 prior lines of chemotherapy alone, ≤1 HER2-directed therapy alone, and/or chemotherapy with HER2-directed therapies. There is no limit on prior endocrine therapy. Specific Aims: The primary objective of the phase II trial is to assess whether addition of Abem to T-DM1 increases PFS in one or both patient cohorts. Secondary objectives include an assessment of toxicity, objective response rates and overall survival. Correlative studies will assess the association between baseline TIL levels, vimentin expression, and CD8/FOXP3 expression with PFS. Changes in peripheral blood mononuclear cells, CTCs, ctDNA and serum thymidine kinase 1 during the course of treatment will be examined to determine if there is a link with PFS outcomes overall and separately for each cohort. Pharmacogenomic studies will determine if pts with the FCGR3A-158 polymorphism derive less benefit from T-DM1 and have inferior PFS outcomes compared with pts who do not have this polymorphism. Statistical Methods:Phase I: Standard 3+3 design, with dose limiting toxicities as per protocol. Phase II: For each pt cohort, a stratified randomization scheme will be used to assign pts to treatment with liver mets as a stratification factor.

For each pt cohort, a stratified log rank test will be used to assess whether PFS is increased with the addition of Abem to T-DM1. A non-binding futility analysis will be applied in each cohort after 58 events in the ER+ HER2+ MBC study cohort and 48 events in the ER- HER2+ MBC study cohort. Present Accrual: 0; target accrual: minimal 120 pts., maximal 140 pts

CohortOne-sidedalphaPowerAccrual Period (accrual rate)Follow-up after close of enrollmentPFS with T-DM1PFS with abema and T-DM1Number of eligible patientsER+/HER2+0.100.912 months (5-6 pts per month)12 months12 weeks24 weeks64 (32 per arm)ER-/HER2+0.100.8512 months (3-4 pts per month)12 months6 weeks12 weeks50 (25 pts per arm)

Citation Format: Ciara C O Sullivan, Jun He, Vera J Suman, Krishna R Kalari, Roberto A Leon-Ferre, Jose C Villasboas-Bisneto, Pratima Chalasani, Demet Gokalp Yasar, Daniel M Anderson, Philip J Stella, Anthony J Jaslowski, Susan H Tannenbaum, Angela Saverimuthu, Donald Northfelt, Alvaro Moreno-Aspitia, Jodi M Carter, Minetta C Liu, Liewei Wang, Zhenkun Lou, Matthew P Goetz. A phase I/II trial of abemaciclib and T-DM1 in women and men with HER2-positive advanced or metastatic breast cancer that has progressed on treatment with a taxane, trastuzumab and pertuzumab (THP) (ACCRU-BR-1801) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr OT2-19-05.

Abstract P3-08-02: The frequency and somatic mutation landscape of Fibroblast growth factor receptor (FGFR) alterations in breast cancer

Background: FGFR dysregulation is observed in multiple cancers and targeting FGFR is an emerging therapeutic strategy with FDA approved treatments in bladder and cholangiocarcinoma. Here we examined the prevalence of FGFR mutations, fusions, and high-level amplifications in breast cancer, stratified by receptor subtype and local/metastatic status, in both Foundation Medicine (FM) and institutional Mayo Clinic (MC) cohorts. Methods: For the FM cohort, comprehensive genomic profiling (CGP) examining at least 324 genes for all classes of alterations, including FGFR1-4 was carried out for 32,048 breast cancers during the course of routine clinical care in a Clinical Laboratory Improvement Amendments (CLIA)-certified lab (Foundation Medicine Inc., Cambridge, MA, USA). Tumor mutational burden (TMB) was determined on up to 1.1 Mb, microsatellite instability high (MSI-High) was determined on up to 114 loci and predicted ancestry from &gt;10,000 SNPs. Estrogen receptor (ER) and HER2 status were available for a subset of FM samples. Additionally, 131 patients with metastatic breast cancer from a subset of patients at three Mayo Clinic sites (MC cohort) with clinical characteristics and cancer-panel DNA sequencing data from a CLIA-certified lab (Tempus, Chicago, IL) were included. Results: In the FM cohort, the prevalence of FGFR1-4 high-level amplification (CN≥10) was 10.1%, while mutations (1.5%) and fusions (0.72%) were rare. Most amplifications occurred in FGFR1 (9.2%); most fusions and mutations occurred in FGFR2 (0.46%, 0.77%). FGFR alteration prevalence was highest in ER+/HER2- subtype (14.4%) and lowest in HER2+ disease (7.7%). FGFR alterations were more common in IDC (11.7%) than ILC (7.7%), p&lt;3E-08. FGFR alterations were more prevalent in the metastatic setting relative to breast-biopsied disease (13.6% v 10.1%; OR = 1.4; p=2E-17), especially in the HER2+ (OR =1.9, p=0.004) and ER-/HER2- (OR = 1.9, p = 0.05) disease; no enrichment was seen in the ER+/HER2- metastases (OR =1.0, p = 1). FGFR amplifications were observed at a higher prevalence in patients with predicted East Asian ancestry, relative to patients with European ancestry (12.1% v 10.0%; p = 0.03). Overall, the most common activating mutations in FGFR were FGFR2 N549K (n=85), FGFR1 N546K (n=78), FGFR4 V510M (n=28), FGFR2 K659E (n=28), FGFR4 V510L (n=20), and FGFR2 Y375C (n=15). The most common recurrent fusions were FGFR3:TACC3 (n=36), FGFR2:TACC2 (n=17), FGFR1:TACC1 (n=9), FGFR1:BAG4 (n=6), and FGFR2:ATE1 (n=5). In patients with FGFR amplifications, the most frequently co-occurring alterations were ZNF703 (78.4%), TP53 (51.5%), CCND1 (36.1%), FGF3/4/19 (32.9 - 34.4%), PIK3CA (30.7%), MYC (29.6%), ESR1 (17.2%), EMSY (16.3%), and PTEN (10.6%). Significant co-occurrence was observed for a number of genes including FGF3/4/19, CDK4, and CDK8 (all OR&gt;2, p&lt;1E-07); mutual exclusivity was observed with PIK3R1, BRCA1, and BRCA2 (all OR &lt;0.5, p&lt;4E-13), among other genes. In the 131 metastatic tumors from MC, the prevalence of FGFR1-4 high-level amplifications was 19.8% [FGFR1 (12.4%), FGFR2 (7.4%), and FGFR3 (0.8%)]. The prevalence of high-level FGFR amplifications did not differ by clinical subtypes: HR-/HER2- (7/31), HR+/HER2- (15/79), and HER2+ (2/11), p=0.68. Conclusions: High-level FGFR amplifications are observed in &gt;11% of breast cancers, especially the ER+/HER2- subtype, while mutations/fusions are rare. These data support the ongoing studies evaluating targeted therapies for FGFR amplified ER + breast cancer. Correlations with clinical information (MC cohort) and associations with actionable alterations are ongoing and may inform potential combination strategies.

Citation Format: Karthik V Giridhar, Ethan S Sokol, Peter T Vedell, Jason P Sinnwell, Aakash Desai, Tufia C Haddad, Ciara C O’Sullivan, Roberto A Leon-Ferre, Siddhartha Yadav, Kostandinos Sideras, Brenda Ernst, Minetta C Liu, Abe Eyman Casey, Xiaojia Tang, Zoe Fleischmann, Karthikeyan Murugesan, Krishna R Kalari, Matthew P Goetz. The frequency and somatic mutation landscape of Fibroblast growth factor receptor (FGFR) alterations in breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-08-02.

Abstract P1-04-01: Digital spatial profiling of immune-related proteins in luminal androgen receptor (LAR) vs non-LAR triple-negative breast cancer (TNBC)

Background: The importance of the antitumor immune response in TNBC is well established. TNBC with higher TILs are less likely to recur and more responsive to systemic therapy. Likewise, PD-L1+ TNBC are more likely to benefit from chemoimmunotherapy. However, TNBC is highly heterogeneous. Of the TNBC molecular subtypes, LAR TNBC is less sensitive to systemic therapy, has lower TILs and lower rates of PD-L1 positivity. The role of other immune related proteins in LAR TNBC is not well established. Here, we evaluated differentially expressed (DE) immune related proteins in the stromal and intratumoral compartments of LAR vs non-LAR TNBC tumors. Methods: We used the Nanostring GeoMX DSP platform to quantitate 58 proteins within spatially distinct intraepithelial, cytokeratin (CK)-positive tumor segments and adjacent CK-negative/nuclei-positive stromal segments in 248 TNBC tumors included in a tissue microarray generated from a cohort of pts with centrally confirmed TNBC who underwent breast surgery without prior neoadjuvant therapy. A subset (n=111) underwent bulk tumor RNA sequencing and were classified as LAR or non-LAR TNBC. DE proteins were identified using a negative binomial generalized linear model (SNR&gt;2, p&lt;0.05). A targeted set of DE proteins was dichotomized at the 80th percentile. Results: Of 111 TNBC tumors, 17 (15%) were LAR and 94 (85%) non-LAR. Compared to non-LAR TNBC, pts with LAR TNBC were older (age ≥50: 82% vs 52%, p&lt;0.01), with tumors that were more often of apocrine histology (35% vs 0%, p &lt;0.01), grade 1-2 (24% vs 1%, p&lt;0.01), and had lower Ki67 (Ki67 ≤15: 24% vs 11%, p=0.06). Most tumors were T1-2 (94% vs 93%, p=0.82) and N0 (53% vs 62%, p=0.09), respectively. As expected, expression of most immune-related proteins was higher in the stromal vs the intratumoral compartment for both LAR and non-LAR TNBC. When focusing on the stromal compartment, expression of multiple immune related proteins was significantly lower in LAR compared to non-LAR TNBC, including the pan-leukocyte marker CD45 (log-2 fold change [log2FC]: 0.552, p=0.05), the macrophage marker CD14 (log2FC: 0.834, p=0.06), CD44 (lof2FC: 0.637, p=0.07), and the immune checkpoint proteins IDO1 (log2FC: 0.914, p=0.04), VISTA (log2FC: 0.471, p=0.07), ICOS (log2FC: 0.444, p=0.08), and STING (log2FC: 0.544, p=0.09). Proteins with expression levels too low for comparisons included PD-L1, LAG3, FOXP3 and BCL-2. When focusing on the intratumoral compartment, expression of most immune-related proteins was very low in both LAR and non-LAR TNBC. Like in the stromal compartment, CD45 expression was lower in LAR TNBC (log2FC: 0.78, p=0.02). Expression of the immune checkpoint B7-H3 was lower in LAR TNBC (log2FC: 0.737, p=0.02), while expression of the T cell marker CD127 was higher (log2FC: -0.528, p=0.34). With regards to relevant non-immune markers, expression of Ki67 was lower in LAR TNBC (log2FC: 0.5498, p=0.05), consistent with the clinical assay. Conclusion: In this ultra high-plex spatial analysis, we provide first insights into the differential expression at the protein level of several targetable immune checkpoint molecules in LAR vs non-LAR TNBC. The lower expression of several immune related proteins in LAR TNBC is consistent with the hypothesis that LAR TNBC exhibits a “cold” immune microenvironment compared to other TNBC subtypes, potentially rendering itself less susceptible to immunotherapy-based strategies. These data support the need to consider TNBC molecular subtypes in future evaluations of immune-based therapeutic approaches. Funding: This work was supported by NIH grant P50CA116201 to RLF, JMC, KRK, FJC, DZ, JNI, and MPG; BCRF grant 19-161 to EAT and NCATS grant CTSA KL2 TR002379 to RLF. The contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIH

Citation Format: Roberto A Leon-Ferre, Jodi M. Carter, David M. Zahrieh, David W. Hillman, Saranya Chumsri, Yaohua Ma, Jennifer M. Kachergus, Xue Wang, Judy C. Boughey, Minetta C. Liu, James N. Ingle, Krishna R. Kalari, Jose C. Villasboas Bisneto, Fergus J. Couch, E. Aubrey Thompson, Matthew P. Goetz. Digital spatial profiling of immune-related proteins in luminal androgen receptor (LAR) vs non-LAR triple-negative breast cancer (TNBC) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-04-01.

Abstract P5-13-22: Serum thymidine kinase 1 activity (TKa) levels and progression-free survival (PFS) in patients (pts) with hormone receptor positive (HR+) HER2-negative metastatic breast cancer (MBC) on palbociclib (Pb) and endocrine therapy (ET)

Background: Cyclin dependent 4/6 kinase inhibitors (CDK4/6i) and endocrine therapy (ET) have improved progression-free survival (PFS) and overall survival in HR+ MBC, but progression of disease ultimately occurs. Apart from HR+ status, there are no clinically available biomarkers that enable oncologists to determine prognosis and predict response to CDK4/6i. An emerging biomarker is serum thymidine kinase 1 (TK1), a secreted marker of proliferation that is prognostic in pts with HR+ HER2- MBC. High levels of TKa are associated with inferior PFS, whereas pts with low TKa levels pretreatment, or TKa levels that decrease on ET and a CDK4/6i, have superior PFS. Notably, TKa levels rebound ≥ 5 days off Pb, with resumption of cell cycling. PROMISE (NCT0281902) is a prospective study that enrolled women with HR+ MBC starting Pb + letrozole (L) in the 1st line [FL] or Pb + fulvestrant in the 2nd line [SL] setting. The trial includes a comprehensive “omic” assessment of blood, tumor, urine and the fecal microbiome to identify novel genomic variants and pathways associated with an early decline in TKa (measured after 2 months or end of cycle [C]2) and PFS. Here, we report the association between i) pre-treatment TKa (pre-TKa) levels and PFS (i.e. from registration to the 1st disease event) and ii) TKa levels at the end of C2 (C2-TKa) and PFS-2 (i.e. from the start of C3 to the 1st disease event).Methods: TKa testing was performed using the DiviTum assay (Biovica). TKa+ disease was defined as ≥ 200 Du/L and TKa- disease as below limit of detection to 200 Du/L. Log-rank test and univariate Cox modeling were used to assess the association between pre-TKa levels and PFS and between end of C2-TKa levels and PFS-2. The database was locked on June 28, 2021. Results: Of 68 pts enrolled, 4 were ineligible and pre-TKa data was unavailable for 4. Of the remaining 60 pts (45 FL, 15 SL), the percentage of pts with pre-TKa+ disease was 33.3% in FL (15/45, 95% CI: 20.0-49.0%), and 46.7% (7/15, 95% CI: 21.4-71.9%) in the SL. The median follow-up time for pts on study was 24 months (range: 2-42 months). There were 22 disease events (13 in FL, 9 in SL). In the FL setting, PFS was significantly shorter for preTKa+ pts compared to preTKa- pts (HR: 4.15, 95% CI:1.35-12.74; p=0.007), but not for SL pts (HR: 1.11, 95% CI: 0.30-4.18, p=0.875). End of C2 TKa data was obtained for pts while on Pb (n=5), or after stopping Pb as follows: 1-4 days (n=9), 5-8 days (n=28) and 9-36 days (n=11). PFS-2 was not associated with C2-TKa in the FL (p=0.834) or SL (p=0.454) settings. An analysis of TKa levels by metastatic site will be presented at the meeting.Conclusions: A secreted biomarker of proliferation (TK1) obtained prior to initiating CDK4/6i and ET for the treatment of HR+ MBC is associated with PFS in pts receiving 1st line Pb + L, but not in those receiving 2nd line Pb + fulvestrant. While the end of C2 TKa levels were not associated with PFS, the interpretability of these data are limited, given treatment delays (0-36 days) prior to starting C3 that may result in TKa rebound. Future studies evaluating the predictive nature of TKa and Pb response should focus on earlier timepoints while on drug.

Citation Format: Ciara C O'Sullivan, Jun He, Jason Sinnwell, Vera J Suman, Krishna R Kalari, Peter T Vedell, Ann M Moyer, Xiaojia Tang, Kevin J Thompson, Abe Eyman Casey, Alvaro Moreno-Aspitia, Donald W Northfelt, Minetta C Liu, Tufia C Haddad, Saranya Chumsri, Brendan McMenomy, Prema Peethambaram, Kathryn J Ruddy, Karthik V Giridhar, Roberto A Leon-Ferre, Mattias Bergqvist, Adrian Nordmark, Richard M Weinshilboum, Liewei Wang, Matthew P Goetz. Serum thymidine kinase 1 activity (TKa) levels and progression-free survival (PFS) in patients (pts) with hormone receptor positive (HR+) HER2-negative metastatic breast cancer (MBC) on palbociclib (Pb) and endocrine therapy (ET) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-13-22.

Abstract P4-01-03: Multiomics data reveal novel biomarkers for CDK4/6 resistance

Background: Cyclin-dependent 4/6 kinase inhibitors (CDK4/6i) and endocrine therapy (ET) have improved progression-free survival (PFS) and overall survival in hormone-receptor-positive (HR+) metastatic breast cancer (MBC), but endocrine resistance is a major challenge. PROMISE [NCT0281902; n=63] is a multicenter study that enrolled women with HR+ HER2- MBC commencing palbociclib (Pb) with letrozole (1st line [1L]) or fulvestrant (2nd line [2L]), and was designed to perform a comprehensive “omic” assessment of prospectively collected biospecimens (pre-treatment (M1), at 2 months (M2), and at disease progression). The goal is to identify novel genomic variants and pathways associated with resistance to CDK4/6i and ET and PFS outcomes. Here we report the association between the proteomic, metabolomics, and lipidomics data generated from pre-Pb and 2-month serum samples and PFS. Methods: Untargeted mass spectrometry data was generated from Metabolon, assaying 1308 metabolites and 831 lipids. Additionally, 1436 proteins were assayed on the Olink platform. Cox proportional hazard models were used to evaluate the univariate hazard ratio (HR) for all features with respect to PFS. The analyses were performed on samples from 45 patients (N=33 1Lwith 9 progression events and 12 2L with 8 progression events), obtained from M1 and M2 timepoints on Pb + ET. Enrichment analysis p-values are calculated using Fisher’s exact test. Results: Proteomics: In the M1 timepoint, 93 and 43 proteins were associated with PFS in the 1L and 2L settings, respectively; inflammation genes were enriched among the 1L setting (p= 0.034); 33 proteins presented HRs ranging between 0.026 and 0.56. The FABP9 protein (HR of 1.98, 95% CI 1.02-3.83) was associated with worse PFS. Conversely, inflammation genes were not observed to be enriched in 2L. In the M2 timepoint, we observed 60 and 21 proteins significantly associated with PFS, but no biological function was enriched in 1L and 2L. Metabolites: In the M1 timepoint, metabolism of the sulfur-containing amino acids (methionine, cysteine, SAM and taurine) were enriched in the 1L setting (p= 0.035, HR range 0.15-0.33); and the branched-chain amino acids (leucine, isoleucine, and valine) were significantly associated with PFS in the 2L setting (p= 0.028, HR range 0.013-0.33). At the M2 timepoint, the amino acids were no longer enriched, but fatty acid metabolism was significantly enriched for both 1L and 2L (p= 0.048 and 0.067, respectively). Pathways involving lipids, amino acids, and xenobiotics were enriched in metabolites related to PFS (p &lt;0.05) for both treatment lines at M1 and M2. Lipidomics: In the M1 timepoint, 10 and 19 lipids were associated with PFS for 1L and 2L, respectively. The most notable lipid associated with worse PFS in the 1L was an 18 carbon phosphatidylinositol, PI(18:1/18:2), (HR 7.34 (CI 1.27-42.50); 8 triglycerides were associated with improved PFS (HR range 0.39 and 0.55). In 2L, the 19 lipids associated with PFS included 12 phosphatidylcholines (enrichment p = 5.6X10-8). In the M2 timepoint, 15 and 8 lipids were significantly associated with PFS for 1L and 2L. An enrichment of phosphatidylinositols was observed in 1L (p= 1.2X10-5); none were observed in the 2L.Future Directions: Networks are being constructed using the proximity scores of the proteins, lipids, and metabolites associated with PFS in M1 and M2 for 1L and 2L. Network similarities and analyses will be conducted.Conclusion: Distinct multi-omic changes identified in serum samples obtained from PROMISE participants M1 and M2 on Pb correlate with disease progression in both 1L and 2L settings. Additionally, validation studies will determine the significance of these findings.

Citation Format: Krishna R. Kalari, Kevin J. Thompson, Jason Sinnwell, Xiaojia Tang, Vera J. Suman, Jun He, Seul Kee Byeon, Akhilesh Pandey, Abe Eyman Casey, Peter T. Vedell, Ann M. Moyer, Alvaro Moreno-Aspitia, Donald W. Northfelt, Minetta C. Liu, Tufia C. Haddad, Saranya Chumsri, Prema Peethambaram, Kathryn J. Ruddy, Karthik V. Giridhar, Roberto A. Leon-Ferre, Richard M. Weinshilboum, Liewei Wang, Ciara C. O’ Sullivan, Matthew P. Goetz. Multiomics data reveal novel biomarkers for CDK4/6 resistance [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P4-01-03.

Characteristics and Spatially Defined Immune (micro)landscapes of Early-stage PD-L1-positive Triple-negative Breast Cancer

PURPOSE

Programmed death ligand 1 [PD-(L)1]-targeted therapies have shown modest survival benefit in triple-negative breast cancer (TNBC). PD-L1+ microenvironments in TNBC are not well characterized and may inform combinatorial immune therapies. Herein, we characterized clinicopathologic features, RNA-based immune signatures, and spatially defined protein-based tumor-immune microenvironments (TIME) in early-stage PD-L1+ and PD-L1- TNBC.

EXPERIMENTAL DESIGN

From a large cohort of chemotherapy-naïve TNBC, clinicopathologic features, deconvoluted RNA immune signatures, and intraepithelial and stromal TIME (Nanostring GeoMX) were identified in subsets of PD-L1+ and PD-L1- TNBC, as defined by FDA-approved PD-L1 companion assays.

RESULTS

228 of 499 (46%) TNBC were PD-L1+ (SP142: ≥1% immune cells-positive). Using PD-L1 22C3, 46% had combined positive score (CPS) ≥ 1 and 16% had CPS ≥10. PD-L1+ TNBC were higher grade with higher tumor-infiltrating lymphocytes (TIL; P < 0.05). PD-L1 was not associated with improved survival following adjustment for TILs and other variables. RNA profiles of PD-L1+ TNBC had increased dendritic cell, macrophage, and T/B cell subset features; and decreased myeloid-derived suppressor cells. PD-L1+ stromal and intraepithelial TIMEs were highly enriched in IDO-1, HLA-DR, CD40, and CD163 compared with PD-L1-TIME, with spatially specific alterations in CTLA-4, Stimulator of Interferon Genes (STING), and fibronectin. Macrophage- and antigen presentation-related proteins correlated most strongly with PD-L1 protein.

CONCLUSIONS

In this early-stage TNBC cohort, nearly 50% were PD-L1+ (SP142 companion assay) while 16% were PD-L1+ with the 22C3 companion assay. PD-L1+ TNBC had specific myeloid-derived and lymphoid features. Spatially defined PD-L1+ TIME were enriched in several clinically actionable immune proteins. These data may inform future studies on combinatorial immunotherapies for patients with PD-L1+ TNBC.See related commentary by Symmans, p. 5446.

A practical guide to endocrine therapy in the management of estrogen receptor-positive male breast cancer

The majority (more than 90%) of male breast cancers (MaBCs) are estrogen receptor-positive, such that endocrine therapy is the mainstay of MaBC treatment. Endocrine therapy has been associated with improved overall survival in observational studies on MaBC, though large randomized clinical trials have never been completed to confirm this benefit in this population. Tamoxifen is currently the preferred drug for both metastatic and adjuvant treatment of MaBC. Known differences in treatment patterns and hormonal milieu between men and women may warrant a unique approach to the management of toxicities in men. This review provides a detailed discussion of endocrine therapy for MaBC.

Abstract PS6-02: Spatially defined immune-related proteins and outcome in triple negative breast cancer in the FinXX trial and Mayo Clinic cohort

Background: Growing data established the pivotal role of preexisting immune response in triple negative breast cancer (TNBC). Conventionally, preexisting immune response can be evaluated by quantifying tumor infiltrating lymphocytes mainly in the stroma or gene expression analysis from the whole tumor section. Due to technical challenges with these conventional methods, limited data regarding specific subtypes and spatial distribution of these immune infiltrates are currently available. Methods: NanoString IO360 gene expression analysis and Digital Spatial Profiling (DSP) were used. DSP was used to quantify 29 immune-related proteins in stromal and tumor-enriched segments from 44 TNBC samples from the FinXX trial (NCT00114816) and 335 samples from the Mayo Clinic (MC) cohort of centrally reviewed TNBC (Leon-Ferre BCRT 2018). In FinXX trial, 22 patients with recurrence and 22 patients without recurrence were included. In MC cohort, 217/335 patients received adjuvant chemotherapy while 118 patients had surgery only without adjuvant chemotherapy. Regions were segmented based on pancytokeratin staining. The general linear model was used for statistical analysis of differential expression with recurrence free survival (RFS) as a categorical variable (recur yes or no). Kaplan-Meier (KM) estimates and Cox regression models were also used for analysis. Results: In the FinXX trial, there were 12 out of 29 proteins in tumor epithelial segments (intraepithelial) which were significantly expressed at higher levels among patients who were free of recurrence. These proteins include Beta-2 microglobulin, CD11c, CD20, CD40, CD56, CD8, Granzyme B, HLA-DR, ICOS, PD-L1, PD-L2, and TGFB1. In contrast, merely 5 out of 29 proteins in stromal segments were significantly differentially expressed in these 2 groups of patients. Granzyme B, IDO1, PD-L1, and PD-L2 in stroma were significantly higher and SMA was significantly lower in patients without recurrence. Using Cox regression models, intraepithelial CD56, CD40, and HLA-DR were significantly associated with outcome. When comparing between highest and lowest intraepithelial protein expression by tertile, intraepithelial CD56 (HR 0.12, 95%CI 0.03-0.39, p &lt; 0.001), CD40 (HR 0.13, 95%CI 0.04-0.46, p = 0.002), and HLA-DR (HR 0.24, 95%CI 0.06-0.89, p = 0.032) were significantly associated with improved outcome. However, expression of these same proteins in stroma was not associated with outcome. Using KM estimates, intraepithelial CD56 (p &lt; 0.0001), CD40 (p = 0.0006), and HLA-DR (p = 0.013) were also significantly associated with improved outcome. Nonetheless, RNA expression of these proteins by IO360 from whole tumor sections were not significantly associated with outcome (CD56 p = 0.27, CD40 p = 0.21, HLA-DR p = 0.48). Similar findings with DSP were observed in MC TNBC cohort. Comparing between the highest and lowest quartiles, there were significantly fewer patients who developed recurrence with high protein expression of intraepithelial CD56 (p &lt; 0.001), CD40 (p = 0.002), and HLA-DR (p = 0.006). Conclusions: Using an in-depth analysis with spatially defined context, we identify that there were numerically more intraepithelial immune-related proteins associated with outcome compared to proteins in stroma. Specifically, intraepithelial CD56, CD40, and HLA-DR were significantly associated with improved outcome in both FinXX and MC TNBC cohorts. However, neither expression of these proteins in stroma nor RNA expression from whole tumor were associated with outcome. Our study highlights the impact of spatial biology and the importance of evaluating each potential biomarker in a spatially defined manner. Support: W81XWH-15-1-0292, BCRF 19-161, P50CA116201-9, P50CA015083

Citation Format: Saranya Chumsri, Jodi M. Carter, Yaohua Ma, Douglas Hinerfeld, Heather Ann Brauer, Sarah Warren, Torsten O. Nielsen, Karama Asleh, Heikki Joensuu, Edith A. Perez, Roberto A. Leon-Ferre, David W. Hillman, Judy C. Boughey, Minetta C. Liu, James N. Ingle, Krishna R. Kalari, Fergus J. Couch, Keith L. Knutson, Matthew P. Goetz, E. A. Thompson. Spatially defined immune-related proteins and outcome in triple negative breast cancer in the FinXX trial and Mayo Clinic cohort [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS6-02.

Abstract PS5-24: Novel genomic variants and pathways associated with baseline serum thymidine kinase 1 levels in HR-positive HER2-negative MBC patients commencing palbociclib and letrozole

Background: Cyclin dependent 4/6 kinase inhibitors (CDK4/6i) and endocrine therapy (ET) have improved progression-free survival (PFS) and overall survival in hormone-receptor (HR)-positive metastatic breast cancer (MBC), but progression of disease is inevitable. Serum thymidine kinase-1 (TK1) is a secreted marker of proliferation that is prognostic in patients (pts) with HR-positive, HER2-negative MBC and may be predictive of ET and CDK 4/6i response. PROMISE (NCT0281902) is a prospective study enrolling women with HR-positive MBC starting palbociclib (Pb) + letrozole (L) (1st line) or Pb + fulvestrant (2nd line). We undertook a comprehensive “omic” assessment of blood, tumor, urine and the fecal microbiome in order to identify novel genomic variants and pathways associated with an early decline in TK1 (measured after 2 months) and PFS. Additionally, patient derived xenografts/organoids were generated at baseline and progression to test new therapeutic approaches to overcome resistance to CDK4/6i and ET. We report the initial association between the baseline genomic landscape and baseline TK1 levels. Methods: FFPE tumor biopsies were obtained for DNA/RNA sequencing (TempusTM) and blood samples for TK1 (Divitum® assay, Biovica) were collected pretreatment (pre-Pb) and after 2 cycles of Pb + ET (post-Pb2). Both whole-exome (exome capture) sequencing (WES) and RNA-Seq used the Integrated DNA Technologies xGen Exome Research Panel v1.0 capture kit. TK1+ disease was defined as &gt; 200 Du/L and TK1- disease as below limit of detection up to 200 Du/L. We tested the association between genomic and transcriptomic characteristics with baseline TK1 data in pretreatment samples where both WES and RNA-seq and TK1 was available. The data were analyzed using bioinformatics pipelines for somatic and germline mutations and copy number alterations. The current analysis focuses on baseline 1st-line pre-Pb omics data in conjunction with baseline TK1 levels. The database was locked for analysis on 5/29/2020. Results: Thirty-three pts (median age: 59 yrs.) were evaluable, with paired samples for TK1 in 32. Six pts had TK1+ disease pre-Pb and post-Pb2. Twenty-two pts had TK1- disease pre-Pb and post-Pb2. Four pts had a decrease in TK1 after 2 cycles of treatment that altered the classification from TK1+ to TK1-. Both baseline RNA seq and serum TK1 (n=16) were available for 4 TK1+ and 12 TK1- pts. In this group, 476 genes were differentially regulated (398 upregulated; 78 downregulated). Pathway analysis demonstrated enrichment in complement and coagulation cascade pathway, PPAR signaling pathway, and metabolism-related pathways related to up-regulation of CYP and UGT gene families. Further testing for the association of WES data with baseline TK1+ (n=8) and TK1- (n=16) disease demonstrated somatic copy number variations on chromosomes 6, 11, 12 and 15. CDK4 copy number gains were observed in 3/8 TK1+ pts and 0/16 TK1- pts. We also observed that somatic mutations (LOH, copy number and/or SNV/INDELs) were more prevalent in the TK1+ compared to the TK1- pre-Pb group in several cancer-associated genes (FAS [p=0.06] PTEN, PIK3CB, NAB2, SOX9 and FAT1 [p=0.08], TP53, and MAP2K4 [p=0.22]). Conversely, we also noted that 6/7 pts with GATA3 mutations had TK1- disease (p=0.23). Conclusions: Using a comprehensive “omics” approach, our data suggest that a secreted biomarker of proliferation (TK1) obtained prior to initiating CDK4/6i and ET for the first line treatment of HR+ MBC is associated with established and novel genes and pathways associated with prognosis of pts receiving ET and CDK 4/6i. Analysis of on-treatment (after 2 cycles) tumor RNA seq and its association with change in TK1 as well as data from the 2nd-line cohort will be presented at the meeting.

Citation Format: Ciara C O Sullivan, Krishna R Kalari, Vera J Suman, Peter T Vedell, Ann Moyer, Abraham D Eyman Casey, Jason Sinnwell, Xiaojia Tang, Kevin Thompson, Alvaro Moreno-Aspitia, Donald W Northfelt, Minetta C Liu, Tufia C Haddad, Saranya Chumsri, Prema Peethambaram, Kathryn J Ruddy, Karthik V Giridhar, Roberto A Leon-Ferre, Adrian Nordmark, Mattias Bergqvist, Brendan P McMenomy, Richard M Weinshilboum, Liewei Wang, Matthew P Goetz. Novel genomic variants and pathways associated with baseline serum thymidine kinase 1 levels in HR-positive HER2-negative MBC patients commencing palbociclib and letrozole [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS5-24.

The Landmark Series: Neoadjuvant Chemotherapy for Triple-Negative and HER2-Positive Breast Cancer

While historically breast cancer has been treated with primary surgery followed by adjuvant therapy, the delivery of systemic therapy in the neoadjuvant setting has become increasingly common, especially for triple-negative and HER2-positive breast cancer. The initial motivations for pursuing neoadjuvant chemotherapy (NAC) were decreasing the tumor burden in the breast and axilla to enable de-escalation of surgery, and use the strategy to advance drug development. While these remain of interest, recent trials have additionally demonstrated survival advantages from escalation of systemic treatment in patients with residual disease, and new studies are testing de-escalation of systemic therapy based on pathologic response. Thus, response information to NAC has become pivotal to guide adjuvant treatment recommendations, and has resulted in NAC being the preferred approach for most HER2-positive and triple-negative breast cancers. Herein, we review select landmark trials that have paved the way for the use of chemotherapy in the neoadjuvant setting for breast cancer.

Abstract P1-19-42: Evaluation of mean corpuscular volume (MCV) as a pharmacodynamic predictive biomarker in patients receiving CDK4/6 inhibitors for metastatic breast cancer (MBC)

Introduction: CDK 4/6 inhibitors (CDK4/6i) are FDA approved for treatment of hormone receptor (HR) positive, HER2 negative metastatic breast cancer (MBC). Recent work demonstrated that a rise in MCV was correlated with longer median progression free survival (Anampa et al, Haemoatologica 2018). We performed a single-institution retrospective analysis to evaluate whether palbociclib induced early changes in MCV serve as a pharmacodynamic biomarker to predict response to CDK4/6i.

Methods: We identified a retrospective cohort of 81 patients with HR+, HER2- MBC treated with CDK4/6i as first line metastatic treatment at Mayo Clinic, Rochester. Hematologic indices were abstracted pretreatment and at the start of each cycle through the start of cycle 4 (C4). Wilcoxon signed test was used to examine the changes in MCV (ΔMCV) comparing pretreatment up to C4 and ΔMCV between cycles. Optimal cut points for ΔMCV were determined using Cutoff finder (Budczies et al., PLOS One 2012). Cox proportional hazard regression analysis was performed to evaluate associations of MCV and time to treatment failure (TTF), which was defined as the time from the start of the analyzed cycle to treatment discontinuation for any reason(in months). As eight comparisons were made, a Bonferroni correction established p-value &lt;0.00625 as the adequate cutoff for statistical significance. Statistical analyses were performed using JMP (SAS Institute Inc, Cary, NC).

Results: 60/81 patients had pretreatment and at least one subsequent lab data point that included MCV. The pretreatment mean hemoglobin (Hgb) was 12.8 [standard deviation (SD) 1.37 g/dL] and 6/60 (10.2%) patients with Hgb &lt;11.0 g/dL. Mean pretreatment MCV was 89.0 femtoliters/cell [fl (SD 4.63)] and no macrocytosis (defined as MCV &gt;100 fl) was observed. At C4, the mean Hgb was 12.1 g/dL (SD 1.11) with 4/49 (8.2%) with Hgb &lt;11.0 g/dL. The C4 mean MCV was 96.6 fl (SD 5.23) and 8/29 (16.3%) developed macrocytosis. Wilcoxon signed analysis showed a significant increase in ΔMCV pretreatment to C2 [n=51, median 1.5 with interquartile range (IQR) -0.1-3.2, p&lt;0.0001], C2 to C3 (n=44, median 2.9, IQR 1.4-5.2, p&lt;0.0001), and C3 to C4 (n=41, median 3.4, IQR 1.9-4.9, p&lt;0.0001). A rise in MCV≥8.15 from pretreatment to C4 was associated with a non-statistically significant improvement in TTF [n=49, hazard ratio (HR) 0.38, p = 0.06]. Between C2 and C3, a rise in MCV ≥2.9 was associated favorably with TTF (n=44, HR 0.36, p = 0.029). The estimated probability of remaining on treatment at 30 months was higher in those with C2-C3 ΔMCV ≥2.9 [44.1%; 95% Confidence Interval (CI) 17.3-68.2%] compared to those with a C2-C3 ΔMCV &lt;2.9 (10.1%; 95%CI 1.5-28.7%).

Discussion: We observed an increase in MCV in all patients receiving CDK4/6i by start of C4. The rise in MCV during CDK4/6i treatment may reflect drug induced cell-cycle arrest in hematopoietic cells. Evaluation in larger studies is needed to validate dynamic changes in MCV as a predictive biomarker of response to CDK4/6i therapy.

Citation Format: Grace Mei Yee Choong, Roberto A Leon-Ferre, Ciara C O'Sullivan, Kathyrn J Ruddy, Tufia C Haddad, Timothy J Hobday, Prema P Peethambaram, Charles L Loprinizi, Minetta C Liu, Vera J Suman, Matthew P Goetz, Karthik V Giridhar. Evaluation of mean corpuscular volume (MCV) as a pharmacodynamic predictive biomarker in patients receiving CDK4/6 inhibitors for metastatic breast cancer (MBC) [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-19-42.

Abstract P5-04-09: Deep phenotyping using CyTOF identifies peripheral blood immune signatures associated with clinical outcomes and molecular subtypes in patients with early-stage triple negative breast cancer (TNBC)

Background: Local antitumor immunity—as assessed by quantifying tumor-infiltrating immune cells—is increasingly recognized as a critical factor influencing prognosis and therapy response in TNBC. However, an understanding of systemic antitumor immune responses occurring in peripheral blood, and their influence on prognosis and chemotherapy response has not been rigorously studied.

Methods: Cytometry by time-of-flight (CyTOFTM, Fluidigm) was used to examine viably cryopreserved peripheral blood mononuclear cell (PBMC) suspensions prospectively collected from patients with early-stage TNBC prior to initiation of standard neoadjuvant paclitaxel followed by doxorubicin and cyclophosphamide (NACT) as part of the BEAUTY study [1]. Samples were stained using a panel of metal-tagged antibodies, recognizing 30 surface proteins optimized for immune monitoring of human peripheral blood. Differential abundance analysis of immune cell subsets was carried out to evaluate differences between patients who achieved pCR versus those with residual disease after NACT, and between patients with known luminal androgen receptor (LAR) versus basal TNBC subtypes defined by bulk tumor RNA sequencing.

Results: Viably cryopreserved PBMC samples from 40 treatment-naive TNBC patients were available for analysis. The median age was 52 years (range 32 - 73), with 6 (15%) patients having tumors classified as LAR TNBC, and the remaining 34 (85%) as basal TNBC. Overall, 21 (53%) patients achieved pCR after NACT. After acquisition on the mass cytometer, the median yield per sample was 626,815 single-cell events (range 42,786 - 1,035,575), with a median percent debris of 13.7% (range 14 - 58). Across the 40 PBMC samples, the total yield was 23,507,094 single-cell events. The median frequencies of major circulating immune cell subsets across the 40 TNBC patients were: T cells 53.9% (range 25.4 - 71.3), with 33.4% CD4+ T cells (range 11.4 - 46.7) and 10.3% CD8+ T cells (range 5.8 - 19.9); B cells 10.8% (3.3 - 32.6), NK cells 8.6% (1.7 - 17.0) and monocytes 10.6% (2.7 - 29.8). Examining pre-treatment blood samples, patients with residual disease after NACT exhibited a higher median frequency of baseline CD14+CD16- classical monocytes (7.5% vs. 4.1%, p=0.025) and a lower frequency of terminally-differentiated effector memory cytotoxic (CD8+) T cells (0.6% vs. 1.7%, p=0.038) compared to patients who achieved pCR. Patients with LAR TNBC also exhibited a higher frequency of CD14+CD16- classical monocytes (11.5% vs 4.3%, p=0.058), and in addition exhibited a lower frequency of central memory CD4+ T cells (10.4% vs 15.2%, p=0.048). No difference in CD8+ T cells was seen by LAR status. Additional associations of peripheral blood immune cell subsets and classic tumor pathological features will be presented at the meeting.

Conclusion: To our knowledge, this is the first study focused on TNBC to demonstrate variation in peripheral blood immune cell populations by molecular TNBC subtype (LAR vs. basal), and by chemotherapy response. A higher frequency of circulating classical monocytes—which can infiltrate into tissues and give rise to macrophages—appears to be detrimental; whereas a higher frequency of circulating antigen-experienced memory CD8+ T cells seems to be protective, suggesting a putative role of this cell subset in TNBC anti-tumoral immunity.

Reference: [1] Goetz MP et al. JNCI 2017, PMID:28376176

Citation Format: Roberto A Leon-Ferre, Kaitlyn McGrath, Jodi M Carter, Krishna R Kalari, Vera J Suman, Richard Weinshilboum, Liewei Wang, Keith L Knutson, Stephen M Ansell, Judy C Boughey, J C Villasboas, Matthew P Goetz. Deep phenotyping using CyTOF identifies peripheral blood immune signatures associated with clinical outcomes and molecular subtypes in patients with early-stage triple negative breast cancer (TNBC) [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-04-09.

Abstract P2-11-07: Comprehensive tumor sequencing to identify biomarkers of palbociclib response: First report of the PROMISE study

Background: The combination of cyclin dependent 4/6 kinase inhibitors (CDK4/6i) with endocrine therapy (ET) has resulted in clinically significant improvements in progression-free survival (PFS) and overall survival (OS) in hormone-receptor (HR)-positive metastatic breast cancer (MBC). However, most patients’ disease ultimately progresses on CDK4/6i and ET. Therefore, further research is necessary to understand the mechanisms driving primary and secondary resistance. PROMISE is a multicenter prospective cohort study enrolling women with HR-positive MBC commencing treatment with palbociclib + letrozole (1st line) or palbociclib + fulvestrant (2nd Line). The study provides a comprehensive “omic” assessment of blood, tumor, urine and the fecal microbiome to identify molecular or cellular features associated with primary endocrine resistance (e.g. disease progression ≤ 12 months on treatment) and acquired resistance to CDK 4/6i. Additionally, patient derived xenografts and organoids are created to test new drug strategies designed to overcome resistance to CDK 4/6i and ET. Here, we present initial sequencing results from pretreatment biospecimens collected from PROMISE study participants. Methods: On-study tumor biopsies and blood samples were collected for DNA/RNA sequencing (TempusTM). The analyzed biospecimens were all obtained prior to initiation of palbociclib and ET. We correlated patient clinical characteristics (phenotypes) with molecular data and responses to protocol treatment. The data were analyzed using a series of cutting-edge bioinformatics pipelines for somatic and germline mutations in addition to copy number alterations (CNAs). The study database was locked for analysis on 06/20/2019. Results: We analyzed the somatic single nucleotide variants/INDELs (sSNV/INDEL) profiles across the tumor samples to determine the genes that were least likely to occur as a result of background mutation processes. Twenty-six patients had somatic copy number alterations (sCNA) and/or sSNV/INDEL in at least one of 18 genes with the most significant sSNV/INDEL profiles (p &lt; 0.03) which included clinically and biologically relevant genes. The genes with the most statistically significant sSNV/INDEL mutation profiles were GATA3, PIK3CA, CDH1, and ESR1 (p &lt; 0.0009). We observed a high percentage of tumors with somatic alterations in GATA3 (23% sSNV/INDEL, 15% sCNA), PIK3CA (38%, 12%), CDH1 (19%, 50%) and ESR1 (19%, 58%). ESR1 mutations were more frequent in patients receiving 2nd line treatment. Other frequently altered genes included TP53 (15%, 46%), MAP2K4 (8%, 50%), DNAAF1 (8%, 50%), and CDKN1B (8%, 35%). Further, ZNF317 and F3 were altered in 9 and 7 patients, respectively. Twenty-four samples had alterations in at least one of the CDK4/6 pathway genes (RB1, CCNE2, CCND1, CDK6, ESR1, CDKN2A, CCND3, CDK4, CDK2 and CCNE1). Four patients progressed on therapy; three of the four patients had mutations in PIK3CA, and one had a mutation in ESR1. Results of the RNA sequencing data (N=26) will be presented at the SABCS meeting. Conclusions: This is the first report of a prospective study designed to characterize the genomic landscape of ER+/HER2- MBC prior to palbociclib treatment. We observed high frequencies of known targetable alterations in PIK3CA and ESR1, including in patients that progress, which is consistent with previous reports. RNA sequencing data will be presented at the meeting.

Citation Format: Ciara C O Sullivan, Krishna R Kalari, Vera J Suman, Peter T Vedell, Ann Moyer, Erin Carlson, Jason Sinnwell, Tejaswi Alaparthi, Xiaojia Tang, Kevin Thompson, Jaeyun Sung, Alvaro Moreno-Aspitia, Donald Northfelt, Minetta C Liu, Tufia C Haddad, Prema Peethambaram, Saranya Chumsri, Kathryn J Ruddy, Karthik V Giridhar, Roberto A Leon-Ferre, Paula Gill, Mohammad Ranginwala, Asad Javed, Sameer Batoo, Brendan P. McMenomy, Richard Weinshilboum, Liewei Wang, Matthew P Goetz. Comprehensive tumor sequencing to identify biomarkers of palbociclib response: First report of the PROMISE study [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-11-07.

Abstract P4-17-08: Surveillance mammography after treatment for male breast cancer

Background: The clinical utility of routine annual mammogram after curative-intent treatment for male breast cancer is uncertain. There is potentially greater value after lumpectomy (as surveillance for ipsilateral recurrence) than mastectomy (as screening for a new contralateral cancer). The goal of this study was to assess real world use of mammography in men during the first year after lumpectomy or mastectomy to treat breast cancer.

Methods: Administrative claims data from OptumLabs Data Warehouse (a large US database that includes privately insured patients and Medicare Advantage-insured enrollees from all 50 states and of all ages and ethnic and racial groups) were used to identify men treated with breast surgery for a new diagnosis of breast cancer between 2007 and 2017. We required continuous coverage starting at least 6 months prior to the non-metastatic breast cancer diagnosis and continuing until at least 13 months after the breast surgery. Our primary endpoint was the proportion of patients who had at least one mammogram during the year (13-month period, to allow for scheduling and other logistical delays) after lumpectomy or mastectomy. Univariate and multivariate testing were performed to identify predictors of mammography (with p&lt;0.05 used as the threshold for statistical significance for both). Our secondary endpoint was the proportion with at least one mammogram within 24 months of surgery, performed in a subset who maintained their insurance coverage for at least that duration.

Results: The 13-month analysis included 730 men with a median age at diagnosis of 62 years (Range: 25 to 87 years) and a median follow-up duration of 35 months (Range: 13 to 134 months). 209 (29%) of these men underwent mammography within 13 months after surgery. The characteristics of patients who underwent mammography and those who did not are shown in Table 1. Mammography was more likely after lumpectomy than mastectomy (41% vs. 27%) and after radiation therapy (41% vs. 32% in those who did not receive radiation). In a multivariate logistic regression model, more recent diagnosis (2015+) was associated with lower odds of undergoing mammography, while receipt of radiation was associated with higher odds of undergoing mammography. In the subset of patients with two or more years of post-surgery coverage (n=527), the proportion who had at least one mammogram during that 24-month period was 49% after lumpectomy and 40% after mastectomy.

Conclusions: In this insured cohort, 73% of men did not undergo mammography within a year after mastectomy, and 59% did not within a year after lumpectomy. Mammography was less likely in patients diagnosed more recently (perhaps due to acknowledgment of the unique aspects of male breast cancer including a relatively low risk of contralateral second primary tumors), and more likely in those who received radiation. These variations in practice likely result from the paucity of evidence-based guidelines for male breast cancer survivorship care. More research is needed pertaining to whether or not mammograms improve clinical outcomes after curative intent treatment for male breast cancer.

Table 1: Patient characteristics associated with receipt of mammogram within first 13 months after male breast cancer surgeryUnivariate AnalysisMultivariate AnalysisNo Mammogram (N=521)Mammogram (N=209)P-value, chi-square testOdds Ratio (OR) and 95% CIP-value for ORAge Group:0.1225-4966 (12.7%)32 (15.3%)Reference50-64216 (41.5%)98 (46.9%)0.99 (0.60, 1.63)0.9665-74112 (21.5%)44 (21.1%)0.87 (0.48, 1.57)0.6575+127 (24.4%)35 (16.7%)0.57 (0.30, 1.07)0.08Census Region:0.52Midwest138 (26.5%)59 (28.2%)ReferenceNortheast97 (18.6%)47 (22.5%)1.10 (0.68, 1.78)0.69South223 (42.8%)79 (37.8%)0.74 (0.49, 1.11)0.15West63 (12.1%)24 (11.5%)0.83 (0.47, 1.47)0.51Year of diagnosis:0.072007-2010126 (24.2%)65 (31.1%)Reference2011-2014199 (38.2%)82 (39.2%)0.80 (0.54, 1.20)0.292015+196 (37.6%)62 (29.7%)0.63 (0.41, 0.96)0.03Elixhauser Category:0.250148 (28.4%)69 (33.0%)Reference1-2218 (41.8%)74 (35.4%)0.85 (0.56, 1.28)0.433+155 (29.8%)66 (31.6%)1.18 (0.75, 1.87)0.47Surgery Type:0.005Lumpectomy55 (10.6%)38 (18.2%)ReferenceMastectomy466 (89.4%)171 (81.8%)1.57 (0.97, 2.55)0.07Chemotherapy:0.79No301 (57.8%)123 (58.9%)ReferenceYes220 (42.2%)86 (41.1%)0.79 (0.54, 1.16)0.23Radiation:0.02No355 (68.1%)124 (59.3%)ReferenceYes166 (31.9%)85 (40.7%)1.51 (1.03, 2.20)0.03

Citation Format: Siddhartha Yadav, Lindsey Sangaralingham, Stephanie R. Payne, Karthik V. Giridhar, Tina J. Hieken, Judy C. Boughey, Robert W. Mutter, John R. Hawse, Rafael E. Jimenez, Rachel A. Freedman, Sadia Choudhery, Fergus J. Couch, Celine M. Vachon, Nilay Shah, Roberto A. Leon-Ferre, Kathryn J. Ruddy. Surveillance mammography after treatment for male breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-17-08.

Folate receptor alpha expression associates with improved disease-free survival in triple negative breast cancer patients

Triple negative breast cancer (TNBC) comprises 15-20% of all invasive breast cancer and is associated with a poor prognosis. As therapy options are limited for this subtype, there is a significant need to identify new targeted approaches for TNBC patient management. The expression of the folate receptor alpha (FRα) is significantly increased in patients with TNBC and is therefore a potential biomarker and therapeutic target. We optimized and validated a FRα immunohistochemistry method, specific to TNBC, to measure FRα expression in a centrally confirmed cohort of 384 patients with TNBC in order to determine if expression of the protein is associated with invasive disease-free survival (IDFS) and overall survival (OS). The FRα IHC demonstrated exceptional performance characteristics with low intra- and interassay variability as well as minimal lot-to-lot variation. FRα expression, which varied widely from sample to sample, was detected in 274 (71%) of the TNBC lesions. In a multivariable model adjusted for baseline characteristics, FRα expression was associated with improved IDFS (HR = 0.63, p = 0.01) but not with OS. The results demonstrate the potential of targeting the FRα in the majority of TNBC patients and suggest that variable expression may point to a need to stratify on FRα expression in clinical studies.

Oxybutynin vs Placebo for Hot Flashes in Women With or Without Breast Cancer: A Randomized, Double-Blind Clinical Trial (ACCRU SC-1603)

BACKGROUND

Hot flashes (HFs) negatively affect quality of life among perimenopausal and postmenopausal women. This study investigated the efficacy of oxybutynin vs placebo in decreasing HFs.

METHODS

In this randomized, multicenter, double-blind study, women with and without breast cancer with 28 or more HFs per week, lasting longer than 30 days, who were not candidates for estrogen-based therapy, were assigned to oral oxybutynin (2.5 mg twice a day or 5 mg twice a day) or placebo for 6 weeks. The primary endpoint was the intrapatient change from baseline in weekly HF score between each oxybutynin dose and placebo using a repeated-measures mixed model. Secondary endpoints included changes in weekly HF frequency, HF-related daily interference scale questionnaires, and self-reported symptoms.

RESULTS

We enrolled 150 women. Baseline characteristics were well balanced. Mean (SD) age was 57 (8.2) years. Two-thirds (65%) were taking tamoxifen or an aromatase inhibitor. Patients on both oxybutynin doses reported greater reductions in the weekly HF score (5 mg twice a day: -16.9 [SD 15.6], 2.5 mg twice a day: -10.6 [SD 7.7]), placebo -5.7 (SD 10.2); P < .005 for both oxybutynin doses vs placebo), HF frequency (5 mg twice a day: -7.5 [SD 6.6], 2.5 mg twice a day: -4.8 [SD 3.2], placebo: -2.6 [SD 4.3]; P < .003 for both oxybutynin doses vs placebo), and improvement in most HF-related daily interference scale measures and in overall quality of life. Patients on both oxybutynin arms reported more side effects than patients on placebo, particularly dry mouth, difficulty urinating, and abdominal pain. Most side effects were grade 1 or 2. There were no differences in study discontinuation because of adverse effects.

CONCLUSION

Oxybutynin is an effective and relatively well-tolerated treatment option for women with HFs.

Abstract P6-19-05: Clinical characteristics and survival of patients with male breast cancer: The Mayo Clinic experience

Background:

Male breast cancer (MBC) is rare, and usually managed by extrapolation from female breast cancer. We report on the characteristics and survival outcomes of MBC patients from Mayo Clinic Rochester (MCR).

Methods:

Medical records of MBC patients treated at MCR during a 25-year period (1990-2015) were reviewed. Demographic variables, tumor characteristics, recurrences, and overall survival (OS) were collected. Progression free survival (PFS) and OS were estimated by the Kaplan-Meier method. Multivariate Cox-proportional hazard regression was used to identify predictors of OS.

Results:

One hundred sixty-seven patients were included in the final analysis, with a median follow-up of 58 months after diagnosis. Baseline characteristics are presented in Table 1. Eighty percent of patients with ER-positive tumors received endocrine therapy. Among men with stage I-III disease, approximately 90% underwent mastectomy, and 44% received adjuvant chemotherapy.

The 5-year locoregional and distant recurrence rates for patients with stage I-III disease were 4.4% and 21.5%, respectively. The 5-year PFS and OS for patients with stage I-III disease were 65.5% and 80.1%, respectively. In a multivariate analysis assessing predictors of OS in patients with stage I-III disease, older age (HR 1.05; 95% CI: 1.02 – 1.09), stage II (HR 11.06; 95% CI: 3.84 – 31.85) or stage III disease (HR 14.74; 95% CI (3.99 – 54.45), and omission of surgery (HR 45.33; 95% CI: 3.97 – 517.32) were associated with poorer OS, while endocrine therapy (HR 0.21, 95% CI: 0.09 – 0.51) was associated with better OS. ER, PR, HER2 and grade were not independently prognostic.

The median OS for stage IV patients was 10 months, though this 11-man cohort was too small to allow assessment of prognostic factors in advanced male breast cancer.

Conclusions:

MBC remains an understudied condition. Prognostic factors in this stage I-III disease are consistent with those identified in other MBC retrospective cohorts. Prospective studies are needed to better understand the unique clinical features of MBC, and to improve outcomes, particularly for advanced disease.

Table 1:Baseline characteristics N=167  Median age at diagnosis (Years)64.4  Ethnicity/Race: Caucasian131 (78.4%)African American4 (2.4%)Other or unknown32 (19.2%)  Overall AJCC 7th edition stage: Stage I39 (23.4%)Stage II80 (47.9%)Stage III32 (19.2%)Stage IV11 (6.6%)Unknown5 (3.0%)  Grade: 18 (4.8%)247 (28.1%)3101 (60.5%)Unknown12 (7.1%)  ER status: Negative8 (4.8%)Positive153 (91.6%)Unknown6 (3.6%)  PR status: Negative17 (10.2%)Positive141 (84.4%)Unknown9 (5.4%)  HER-2 status: Negative70 (41.9%)Positive12 (7.2%)Unknown85 (50.9%)

Citation Format: Yadav S, Leon-Ferre RA, Jimenez RE, Hawse JR, Hieken TJ, Couch FJ, Boughey JC, Ruddy KJ. Clinical characteristics and survival of patients with male breast cancer: The Mayo Clinic experience [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 P6-19-05.

Abstract P4-16-01: A randomized, double-blind, placebo-controlled trial of testosterone (T) for aromatase inhibitor-induced arthralgias (AIA) in postmenopausal women: Alliance A221102

Background: Aromatase inhibitors are a mainstay hormone receptor-positive breast cancer treatment. AIA occur in up to 50% of patients (pts), adversely affecting quality of life and treatment compliance. A small phase II clinical trial of oral testosterone unedeconate appeared to improve AIA over placebo (P), with no significant androgenic side effects. The current study was performed to confirm these findings.

Methods: This randomized P-controlled trial enrolled postmenopausal women on adjuvant anastrozole or letrozole and experiencing moderate-to-severe AIA (≥5 on 0-10 scale). Pts were initially randomized to receive a subcutaneous pellet containing T 120 mg + anastrozole 8 mg (T+AIpellet) or P at the end of the first week on study (after obtaining baseline hot flash data) and at 3 months (mo). Due to slow accrual, the protocol was amended to change the route of delivery to topical T or P applied to the skin once daily for 6 mo. Baseline and monthly questionnaires were administered, including: Modified Brief Pain Inventory for aromatase arthralgia (BPI-AIA), prolife of mood states (POMS), the menopause specific quality of life questionnaire (MENQOL), a hot flash diary, the hot flash related daily interference scale (HFRDIS) and a symptom experience questionnaire. The primary endpoint was intra-patient change in joint pain at 3 mo, compared using a two-sample t-test.

Results: 227 pts were accrued between 9/1/2013-11/29/2017. 55 pts were randomized prior to the protocol amendment and received T+AIpellet or P. Baseline characteristics were balanced between arms, with the exceptions of median weight, BMI, hemoglobin (all higher in T arm), and breast tenderness, dissatisfaction with personal life/depression, and skin changes (all higher in P arm). Compared to baseline, there were no significant differences between T and P in average pain or joint stiffness at 3 (p=0.483) or 6 mo (p=0.573). Average pain was significantly lower each month compared to baseline, irrespective of treatment arm. There were no significant differences in any other items evaluated by BPI-AIA, POMS, MENQOL, hot flash diary or HFRDIS. Similarly, there were no substantial differences in toxicity. A subset analysis of the 55 pts randomized to receive T+AIpellet or P identified significant reductions in average pain scores with T+AIpellet during the first month (p=0.038), but not thereafter. T+AIpellet pts had significantly more reduction in reported % of baseline hot flash frequency (p=0.034) and score (p=0.031), nausea (p=0.019), fatigue (p=0.042), mood swings (p=0.026), hand/feet swelling (p=0.009), stress urinary incontinence (p=0.039) and changes in appearance, texture or tone of their skin (p=0.0083), than pts on P.

Conclusions: Overall, T did not improve AIA or menopausal symptoms compared to P. While there was significant improvement in AIA over the study period, T did not facilitate this process. However, T+AIpellet was associated with improvement in short-term AIA and several menopausal symptoms compared to P, suggesting that subcutaneous T combined with anastrozole may be superior to transdermal T alone.

Support: UG1CA189823, U10CA180820, U10CA189809; ClinicalTrials.gov Identifier: NCT01573442

Citation Format: Leon-Ferre RA, Le-Rademacher J, Terstriep S, Glaser R, Novotni P, Giuliano A, Copur MS, Jones C, Page S, Mitchell W, Birrell SN, Loprinzi CL. A randomized, double-blind, placebo-controlled trial of testosterone (T) for aromatase inhibitor-induced arthralgias (AIA) in postmenopausal women: Alliance A221102 [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 P4-16-01.

Abstract P3-08-01: Characteristics, outcomes and prognostic factors of luminal androgen receptor (LAR) triple-negative breast cancer (TNBC)

Background: The LAR subtype is a genomically distinct subset of TNBC. Using a large cohort of non-metastatic TNBC patients (pts) with long term follow-up, we sought to further characterize the clinicopathologic features and outcomes of LAR vs non-LAR TNBC.

Methods: From a cohort of 9982 women with surgically-treated non-metastatic breast cancer, 605 met criteria for TNBC (ER/PR&lt;1% and HER2-negative) by central pathology. RNA extracted from 304 FFPE tumor specimens using the HighPure RNA extraction kit was subjected to TruSeq RNA Access library preparation and sequencing on a HiSeq2500. Adequate RNA was available for 283 pts. Tumors were classified as LAR or non-LAR using a shrunken centroid model, CABAL (Clustering Among BAsal and Luminal androgen receptor). In addition to previously described analyses [Leon-Ferre et al, Breast Cancer Res Treat 2017], immunohistochemical (IHC) androgen receptor (AR) staining was performed and the impact of various parameters on invasive disease-free survival (IDFS) and overall survival (OS) was assessed using Cox proportional hazards models.

Results: 58 (20%) tumors were classified as LAR and 225 (80%) as non-LAR. Compared to non-LAR, LAR pts were older (mean age 65 vs 54) and more often postmenopausal (79%vs53%), both p=0.01. Apocrine histology was more common among LAR tumors (21%vs0%), which were also lower grade (grade3: 69%vs95%) and had lower Ki-67 (Ki-67&gt;15%: 64%vs82%), all p&lt;0.01. Additionally, LAR tumors had lower median stromal tumor infiltrating lymphocytes (TILs, 20%vs25%) and were less frequently lymphocyte-predominant [≥50% stromal or intratumoral TILs (19%vs32%)], although neither reached statistical significance. AR IHC was available for 223 of 283 tumors. Median AR IHC score in LAR was 65% (range 0-100%) vs 0% (range 0-90%) in non-LAR. T/N stage, surgery type, and receipt of adjuvant chemotherapy (AdjCT) or radiotherapy were similar between LAR and non-LAR. LAR pts had shorter IDFS and OS compared to non-LAR (5.6 vs 11.8 yrs and 10.8 vs 20.8 yrs, respectively), although this did not reach statistical significance. Test of proportional hazard assumption was not significant for IDFS or OS (p = 0.30 and 0.09). IDFS estimates were numerically higher in LAR vs non-LAR (80.2%vs70.5%,p = 0.92) at 3yrs post-diagnosis; whereas the opposite was true (40.9%vs55.6%,p = 0.07) after 10yrs. OS estimates at 3 and 5yrs were similar between LAR and non-LAR, but at 10yrs OS was inferior in LAR (40.9%vs66.4%,p = 0.24). In a univariate analysis including both LAR and non-LAR, older age, higher N stage, lower TILs and absence of AdjCT were associated with poorer IDFS and OS. In a multivariate analysis, higher N stage and absence of AdjCT remained associated with both poorer IDFS and OS; while lower stromal TILs were associated with poorer IDFS (p=0.01), and with a trend towards poorer OS (p=0.07).

Conclusions: LAR TNBCs occurred in older women, were lower grade, and had lower TIL density than nonLAR tumors. While significant differences in IDFS or OS were not demonstrated, LAR pts exhibited a numerically lower risk of a disease event at 3yrs, but higher risk by 10yrs compared to nonLAR pts. In the entire cohort, higher N stage, absence of AdjCT and lower TILs were independently associated with poorer outcomes.

Citation Format: Leon-Ferre RA, Polley M-Y, Liu H, Kalari KR, Boughey JC, Liu MC, Cafourek V, Negron V, Ingle JN, Thompson KJ, Tang X, Barman P, Carlson E, Visscher DW, Carter JC, Couch FJ, Goetz MP. Characteristics, outcomes and prognostic factors of luminal androgen receptor (LAR) triple-negative breast cancer (TNBC) [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 P3-08-01.

Abstract GS6-02: A randomized, double-blind, placebo-controlled trial of oxybutynin (Oxy) for hot flashes (HF): ACCRU study SC-1603

Background: HF occur in about 75% of midlife women and are associated with quality of life disruption and premature endocrine therapy discontinuation among breast cancer survivors. Estrogen therapy, effective for HF, is contraindicated in hormone receptor-positive breast cancer (BC). Previous studies have suggested that Oxy could be effective in managing HF.

Methods: This randomized, placebo (P)-controlled trial enrolled women who had experienced HF ≥28 times per week over &gt;30 days and of sufficient severity to seek treatment. Patients (pts) were randomized to receive oral Oxy at two doses: 2.5mg BID for 6 weeks (Oxy2.5), 2.5mg BID for a week with subsequent increase to 5mg BID (Oxy5), or matching P, in equal ratios. Baseline and monthly questionnaires were administered including a HF diary, the HF related daily interference scale (HFRDIS) and a symptom experience questionnaire. The primary endpoint was intra-patient change in weekly HF score and frequency from baseline to end of study compared using Kruskal-Wallis tests.

Results: 150 pts were accrued between 2/23/2017-3/5/2018. 4 pts cancelled before starting treatment and were excluded from analyses. This interim report includes the first 104 pts for which at least one post-baseline evaluation was available. Baseline characteristics were well-balanced between the arms. Sixty-two percent were on tamoxifen or an aromatase inhibitor for the duration of the study. Pts on both Oxy doses had a significantly greater reduction in HF score and frequency compared to P. Pts on Oxy2.5 had a mean change in HF score of -10 (SD 7.4) vs -5.1 (SD 9.7) with P, p=0.003; and a mean change in average weekly number of HF of -4.6 (SD 3.1) vs -2.3 (SD 3.9), p=0.002. Pts on Oxy5 had a mean change in HF score of -16.2 (SD 5.1) vs -5.1 (SD 9.7) with P, p&lt;0.001; and a mean change in average weekly number of HF of -7.0 (SD 4.0) vs -2.3 (SD 3.9), p&lt;0.001. Repeated measures mixed models confirmed that, after adjusting for baseline values, both Oxy arms had significantly lower HF scores and frequency compared to P (p&lt;0.001). HFRDIS revealed that pts in both Oxy arms experienced improvement in the following HF interference measures: work, social activities, leisure activities, sleep, relations, life enjoyment, and overall quality of life. Pts on Oxy5 also had improvement in HF interference with mood. Pts on Oxy2.5 experienced more stomach pain (p=0.031), diarrhea (p=0.007), nausea (p=0.04), headaches (0.032), episodes of confusion (0.012), dry mouth (p=0.003) and dry eyes (0.027) compared to P. Pts on Oxy5 experienced more constipation (0.004), dry mouth (0.001) and difficulty urinating (0.004) compared to P. There were no differences in study discontinuation due to adverse effects between either Oxy arm and P (Oxy2.5 vs P, p=0.653; Oxy5 vs P, p=0.483).

Conclusions: Oxy is superior to P for management of HF. Oxy2.5 and 5 were both associated with significant improvements in HF scores and frequency as well as improvement in HF interference with several quality of life measures. While pts on Oxy experienced more side effects than pts on P, rates of discontinuation due to adverse events were low.

This study was supported by the Breast Cancer Research Foundation.

Citation Format: Leon-Ferre RA, Novotny PJ, Faubion SS, Ruddy KJ, Flora D, Dakhil C, Rowland KM, Graham ML, Le-Lindqwister N, Loprinzi CL. A randomized, double-blind, placebo-controlled trial of oxybutynin (Oxy) for hot flashes (HF): ACCRU study SC-1603 [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 GS6-02.

Where Do We Stand on the Integration of PARP Inhibitors for the Treatment of Breast Cancer?

PURPOSE OF REVIEW

To provide an overview of the clinical development of poly(ADP-ribose) polymerase inhibitors (PARPi) in breast cancer to date and to review existing challenges and future research directions.

RECENT FINDINGS

We summarize the clinical development of PARPi in breast cancer from bench to bedside, and discuss the results of recent phase 3 trials in patients with metastatic breast cancer (MBC) and germline mutations in BRCA1/2 (gBRCAm). We will also provide an update regarding mechanisms of action and resistance to PARPi, and review clinical trials of PARPi as monotherapy or in combination regimens. PARPi are a novel treatment approach in persons with gBRCA1/2m-associated MBC. Going forward, the clinical applicability of these compounds outside the gBRCAm setting will be studied in greater detail. The identification of accurate predictive biomarkers of response is a research priority.

Association between the use of surveillance PET/CT and the detection of potentially salvageable occult recurrences among patients with resected high-risk melanoma

The optimal surveillance for patients with resected high-risk melanoma is controversial. Select locoregional or oligometastatic recurrences can be cured with salvage resection. Data on the ability of PET/CT to detect such recurrences are sparse. We evaluated whether surveillance PET/CT in patients with resected stage III-IV melanoma led to detection of clinically occult recurrences amenable to curative-intent salvage treatment. We retrospectively identified 1429 melanoma patients who underwent PET/CT between January 2008 and October 2012 at Mayo Clinic (Rochester, Minnesota). A total of 1130 were excluded because of stage I-II, ocular or mucosal melanoma, incomplete resection, PET/CT not performed for surveillance or performed at a different institution, and records not available. A total of 299 patients were eligible. Overall, 162 (52%) patients developed recurrence [locoregional: 77 (48%), distant: 85 (52%)]. The first recurrence was clinically occult in 98 (60%) and clinically evident in 64 (40%). Clinically evident recurrences were more often superficial (skin, subcutaneous, or nodal) or in the brain, whereas clinically occult recurrences more often visceral. Overall, 90% of all recurrences were detected by 2.8 years. In all, 70% of patients with recurrence underwent curative-intent salvage treatment (locoregional: 94%, distant: 48%), with similar rates for clinically occult versus clinically evident recurrences (66 vs. 75%, P=0.240). Overall survival was superior among those who underwent curative-intent salvage treatment [5.9 vs. 1.2 years; hazard ratio=4.27, 95% confidence interval (CI)=2.68-6.80; P<0.001], despite 79% developing recurrence again. PET/CT had high sensitivity (88%, 95% CI=79.94-93.31%), specificity (90%, 95% CI=88.56-91.56%), and negative predictive value (99%, 95% CI=98.46-99.52%). However, the positive predictive value was only 37% (95% CI=31.32-43.68%). In patients with resected stage III-IV melanoma, surveillance PET/CT detected a large proportion of clinically occult recurrences amenable to curative-intent salvage treatment. Despite a high rate of second relapse, curative-intent salvage treatment was associated with superior overall survival. Even though PET/CT had high sensitivity, specificity, and negative predictive value, positive predictive value was poor, highlighting the need for histologic confirmation of PET/CT-detected abnormalities.

Abstract P3-05-06: Prognostic value of the neutrophil-to-lymphocyte ratio (NLR) and its relation to stromal tumor infiltrating lymphocytes (sTILs) in triple negative breast cancer (TNBC)

Background: While TNBC remains the most aggressive type of breast cancer (BC), substantial heterogeneity in biology and outcomes exists among TNBC subtypes. Historically, risk stratification of TNBC has been based on anatomic factors such as tumor size, nodal involvement and presence of distant metastases. However, these features alone fail to accurately predict outcomes. Tumor immune infiltration (sTILs) and distribution of immune cell subsets in the perip heral blood (NLR) have emerged as variables reported to be associated with outcomes in TNBC. We sought to evaluate whether NLR and sTILs provided independent prognostic information in TNBC.

Methods: From a cohort of 9,982 women who underwent BC surgery at Mayo Clinic, Rochester, MN between Jan 1985 and Dec 2012, we identified 605 centrally-confirmed TNBC tumors. Patients (pts) with prior BC, bilateral BC, non-invasive disease, stage IV, neoadjuvant therapy, endocrine therapy, or adenoid cystic histology were excluded. For eligible tumors, clinical and pathologic variables were evaluated, including peripheral blood NLR and central assessment of sTILs per the 2014 International TILs Working Group recommendations. We calculated the Pearson correlation coefficient (PCC) between NLR and sTILs and constructed Cox Proportional Hazards Models to evaluate their association with invasive-disease free (IDFS) and overall survival (OS). NLR and sTILs were both analyzed as continuous variables.

Results: Most pts had T1-2 (95%) and N0-1 disease (86%). Median OS follow-up was 10.6yrs. Median IDFS was 12yrs (95%CI 10.2-16.7) and median OS was 18.8yrs (95%CI 15.6-20.8). NLR and sTILs were available in 408 and 599 pts, respectively. The median NLR and sTIL content were 2.29 (0.14-10.50) and 20% (0-90%), respectively. NLR and sTILs were poorly correlated (PCC 0.0237). On univariate analysis (UVA), a higher NLR was associated with worse IDFS (HR 1.13; 95%CI 1.02-1.26, p=0.02) and OS (HR 1.17; 95%CI 1.04-1.31, p=0.01). Each 1% increment in sTILs was associated with improved IDFS (HR 0.99; 95%CI 0.98-0.99, p&lt;0.001) and OS (HR 0.99, 95%CI 0.98-1.00, p&lt;0.001). Among pts with high sTILs (≥20%), a higher NLR remained significantly associated with worse IDFS (HR 1.21; 95%CI 1.05-1.38, p=0.007) and OS (HR 1.25; 95%CI 1.09-1.44, p=0.001). In contrast, among pts with low sTILs (&lt;20%), NLR was not associated with IDFS (HR 1.07; 95%CI 0.89-1.28, p=0.49) or OS (HR 1.07; 95%CI 0.88-1.30, p=0.49). The interaction test between NLR and sTILs did not reach statistical significance. A multivariate analysis (MVA; including age, menopausal status, histologic subtype, grade, tumor size, nodal stage, Ki-67, NLR, sTILs, adjuvant chemotherapy, type of surgery and adjuvant radiation) showed that sTILs remained independently associated with IDFS (HR 0.99, 95%CI 0.97-1.0, p=0.019) and OS (HR 0.99, 95% CI 0.97-1.0, p=0.044), whereas NLR did not.

Conclusions: A lower NLR and a higher sTIL content were each associated with improved IDFS and OS among pts with nonmetastatic TNBC on UVA. However, when evaluated on a MVA, only sTILs remained independently associated with IDFS and OS. Our data suggest that the effect of sTILs on outcomes may not be modified by the NLR.

Citation Format: Leon-Ferre RA, Polley M-Y, Liu H, Gilbert J, Cafourek V, Hillman D, Negron V, Boughey JC, Liu MC, Ingle JN, Kalari K, Couch FJ, Visscher DW, Goetz MP. Prognostic value of the neutrophil-to-lymphocyte ratio (NLR) and its relation to stromal tumor infiltrating lymphocytes (sTILs) in triple negative breast cancer (TNBC) [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 P3-05-06.

Abstract P1-06-07: Mayo clinic TNBC outcome calculator: A clinical calculator to predict disease relapse and survival in women with triple-negative breast cancer

Purpose: Triple negative breast cancer (TNBC) is an aggressive breast cancer subtype with substantial risks of disease recurrence. While cytotoxic chemotherapy is commonly administered and reduces recurrence, disease outcomes vary considerably and few prognostic tools are available for risk stratification for TNBC patients. We constructed and validated clinical calculators for invasive-disease free survival (IDFS) and overall survival (OS) for TNBC and compared their performance against AJCC-based models which include only tumor size and nodal status.

Methods: From a surgical cohort of 9,982 patients who underwent breast cancer surgery at Mayo Clinic between January 1985 and December 2012, 605 centrally reviewed TNBC patients were identified and used to construct Cox models for IDFS and OS. Patients treated with neoadjuvant chemotherapy were excluded. Variables considered included age, menopausal status, tumor size, nodal status, Nottingham grade, type of breast surgery (mastectomy vs. lumpectomy), adjuvant radiation therapy, adjuvant chemotherapy, Ki67, stromal tumor infiltrating lymphocytes (sTILs), and neutrophil-to-lymphocyte ratio (NLR). Missing values were imputed using single imputation with all variables (including outcomes) included in the imputation model. Backward step-down procedure was used for model selections. The final models were internally validated for calibration and discrimination using bootstrapping methods and compared with AJCC-based models.

Results: For both IDFS and OS, higher sTIL's, less extensive nodal involvement, use of adjuvant chemotherapy, and lower NLR were significant predictors of improved clinical outcomes. Premenopausal status and younger age were additionally predictive of improved IDFS and OS, respectively. Models for IDFS and OS have good calibration and are associated with bias-corrected C-indices of 0.68 and 0.71, respectively, as compared with C-indices of 0.59 and 0.62 for AJCC-based models.

Conclusions: Our data indicate that a clinical calculator that includes sTIL's, NLR, menopausal status, age, nodal involvement as well as chemotherapy use can provide significantly greater prediction of clinical risk than tumor size and nodal status alone. These tools may be used to identify TNBC patients at elevated risk of disease relapse and to aid physician's communication with patients regarding their long-term disease outlook and planning treatment strategies. External validation is required to further evaluate broader applicability of this tool, which was developed utilizing a single-institutional experience.

Citation Format: Polley M-YC, Leon-Ferre RA, Liu H, Gilbert J, Cafourek V, Hillman DW, Negron V, Boughey JC, Liu MC, Ingle JN, Kalari K, Couch F, Visscher DW, Goetz MP. Mayo clinic TNBC outcome calculator: A clinical calculator to predict disease relapse and survival in women with triple-negative breast cancer [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 P1-06-07.