Effect of Metformin Versus Placebo on New Primary Cancers in Canadian Cancer Trials Group MA.32: A Secondary Analysis of a Phase III Randomized Double-Blind Trial in Early Breast Cancer

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned coprimary or secondary analyses are not yet available. Clinical trial updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.Metformin has been associated with lower cancer risk in epidemiologic and preclinical research. In the MA.32 randomized adjuvant breast cancer trial, metformin (v placebo) did not affect invasive disease-free or overall survival. Here, we report metformin effects on the risk of new cancer. Between 2010 and 2013, 3,649 patients with breast cancer younger than 75 years without diabetes with high-risk T1-3, N0-3 M0 breast cancer (any estrogen receptor, progesterone receptor, human epidermal growth factor receptor 2) were randomly assigned to metformin 850 mg orally twice a day or placebo twice a day for 5 years. New primary invasive cancers (outside the ipsilateral breast) developing as a first event were identified. Time to events was described by the competing risks method; two-sided likelihood ratio tests adjusting for age, BMI, smoking, and alcohol intake were used to compare metformin versus placebo arms. A total of 184 patients developed new invasive cancers: 102 metformin and 82 placebo, hazard ratio (HR), 1.25; 95% CI, 0.94 to 1.68; P = .13. These included 48 contralateral invasive breast cancers (27 metformin v 21 placebo), HR, 1.29; 95% CI, 0.72 to 2.27; P = .40 and 136 new nonbreast primary cancers (75 metformin v 61 placebo), HR, 1.24; 95% CI, 0.88 to 1.74; P = .21. Metformin did not reduce the risk of new cancer development in these nondiabetic patients with breast cancer.

Metformin, placebo, and endocrine therapy discontinuation among participants in a randomized double-blind trial of metformin vs placebo in hormone receptor-positive early-stage breast cancer (CCTG MA32)

BACKGROUND

The MA32 study investigated whether 5 years of metformin (versus placebo) improves invasive disease-free survival in early-stage breast cancer (BC). Non-adherence to endocrine therapy (ET) and medications for chronic conditions is common and increases with drug toxicity and polypharmacy. This secondary analysis evaluates rates and predictors of early discontinuation of metformin, placebo, and ET among participants with HR-positive BC.

METHODS

Patients with high-risk non-metastatic BC were randomized to 60 months of metformin (850 mg BID) or placebo BID. Patients were administered bottles of metformin/placebo every 180 days. Metformin/placebo adherence was defined as a bottle dispensed at month 48 or later. The ET adherence analysis included patients with HR-positive BC who received ET with start and stop date reported, with adherence defined as > 48 months of use. Associations of covariates with study drug and ET adherence were examined using multivariable models.

RESULTS

Among the 2521 HR-positive BC patients, 32.9% were non-adherent to study drug. Non-adherence was higher among patients on metformin vs placebo (37.1% vs 28.7%, p < 0.001). Reassuringly, ET discontinuation rates were similar between treatment arms (28.4% vs 28.0%, p = 0.86). Patients who were non-adherent to ET were more likely to discontinue study therapy (38.8% vs 30.1%, p < 0.0001). In a multivariable analysis, study drug non-adherence was increased with metformin vs placebo (OR: 1.50, 95% CI 1.25-1.80; p < 0.0001); non-adherence to ET (OR: 1.47, 95% CI 1.20-1.79, p < 0.0001); grade 1 or greater GI toxicity during the first 2 years; lower age; and higher body mass index.

CONCLUSION

While non-adherence was higher among patients on metformin, it was still considerable among patients on placebo. Reassuringly, treatment arm allocation did not impact ET adherence. Attention to global medication adherence is needed to improve BC and non-oncological outcomes in cancer survivors.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01.

Effect of Metformin vs Placebo on Invasive Disease-Free Survival in Patients With Breast Cancer: The MA.32 Randomized Clinical Trial

Importance

Metformin, a biguanide commonly used to treat type 2 diabetes, has been associated with potential beneficial effects across breast cancer subtypes in observational and preclinical studies.

Objective

To determine whether the administration of adjuvant metformin (vs placebo) to patients with breast cancer without diabetes improves outcomes.

Design, Setting, and Participants

MA.32, a phase 3 randomized, placebo-controlled, double-blind trial, conducted in Canada, Switzerland, US, and UK, enrolled 3649 patients with high-risk nonmetastatic breast cancer receiving standard therapy between August 2010 and March 2013, with follow-up to October 2020.

Interventions

Patients were randomized (stratified for hormone receptor [estrogen receptor and/or progesterone receptor {ER/PgR}] status, positive vs negative; body mass index, ≤30 vs >30; human epidermal growth factor receptor 2 [ERBB2, formerly HER2 or HER2/neu], positive vs negative; and any vs no chemotherapy) to 850 mg of oral metformin twice a day (n = 1824) or oral placebo twice a day (n = 1825) for 5 years.

Main Outcomes and Measures

The primary outcome was invasive disease-free survival in hormone receptor-positive breast cancer. Of the 8 secondary outcomes, overall survival, distant relapse-free survival, and breast cancer-free interval were analyzed.

Results

Of the 3649 randomized patients (mean age, 52.4 years; 3643 women [99.8%]), all (100%) were included in analyses. After a second interim analysis, futility was declared for patients who were ER/PgR-, so the primary analysis was conducted for 2533 patients who were ER/PgR+. The median duration of follow-up in the ER/PgR+ group was 96.2 months (range, 0.2-121 months). Invasive disease-free survival events occurred in 465 patients who were ER/PgR+. The incidence rates for invasive disease-free survival events were 2.78 per 100 patient-years in the metformin group vs 2.74 per 100 patient-years in the placebo group (hazard ratio [HR], 1.01; 95% CI, 0.84-1.21; P = .93), and the incidence rates for death were 1.46 per 100 patient-years in the metformin group vs 1.32 per 100 patient-years in the placebo group (HR, 1.10; 95% CI, 0.86-1.41; P = .47). Among patients who were ER/PgR-, followed up for a median of 94.1 months, incidence of invasive disease-free survival events was 3.58 vs 3.60 per 100 patient-years, respectively (HR, 1.01; 95% CI, 0.79-1.30; P = .92). None of the 3 secondary outcomes analyzed in the ER/PgR+ group had statistically significant differences. Grade 3 nonhematological toxic events occurred more frequently in patients taking metformin than in patients taking placebo (21.5% vs 17.5%, respectively, P = .003). The most common grade 3 or higher adverse events in the metformin vs placebo groups were hypertension (2.4% vs 1.9%), irregular menses (1.5% vs 1.4%), and diarrhea (1.9% vs 7.0%).

Conclusions and Relevance

Among patients with high-risk operable breast cancer without diabetes, the addition of metformin vs placebo to standard breast cancer treatment did not significantly improve invasive disease-free survival.

Trial Registration

ClinicalTrials.gov Identifier: NCT01101438.

The Futility of Futility Analyses in Adjuvant Trials in Hormone Receptor Positive Breast Cancer

An interim analysis is commonly used in phase III superiority trials to compare treatment arms, with the goal of terminating exposure of patients to ineffective or unsafe drugs, or to identify highly effective therapies for earlier public disclosure. Traditionally, interim analyses have been designed to identify early evidence of extremely large benefit of the experimental approach, potentially leading to early dissemination of effective treatments. Increasingly, interim analysis has also involved analysis of futility which may lead to early termination of a trial that will not yield additional useful information This presents an important challenge in early-stage hormone receptor positive breast cancer, where recurrence often occurs late, with a steady annual event rate up to 20 years. Early analysis of events may miss late treatment effects that can be observed only with longer follow-up. We discuss approaches to futility analysis in adjuvant clinical trials in hormone receptor positive breast cancer, the role of the Data Safety Monitoring Committee in such analyses, considerations of the potential harms versus benefits of treatment, and the risks of continuing versus early stopping of a trial.

A scalable serology solution for profiling humoral immune responses to SARS-CoV-2 infection and vaccination

Objectives

Antibody testing against severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) has been instrumental in detecting previous exposures and analyzing vaccine‐elicited immune responses. Here, we describe a scalable solution to detect and quantify SARS‐CoV‐2 antibodies, discriminate between natural infection‐ and vaccination‐induced responses, and assess antibody‐mediated inhibition of the spike‐angiotensin converting enzyme 2 (ACE2) interaction.

Methods

We developed methods and reagents to detect SARS‐CoV‐2 antibodies by enzyme‐linked immunosorbent assay (ELISA). The main assays focus on the parallel detection of immunoglobulin (Ig)Gs against the spike trimer, its receptor binding domain (RBD) and nucleocapsid (N). We automated a surrogate neutralisation (sn)ELISA that measures inhibition of ACE2‐spike or ‐RBD interactions by antibodies. The assays were calibrated to a World Health Organization reference standard.

Results

Our single‐point IgG‐based ELISAs accurately distinguished non‐infected and infected individuals. For seroprevalence assessment (in a non‐vaccinated cohort), classifying a sample as positive if antibodies were detected for ≥ 2 of the 3 antigens provided the highest specificity. In vaccinated cohorts, increases in anti‐spike and ‐RBD (but not ‐N) antibodies are observed. We present detailed protocols for serum/plasma or dried blood spots analysis performed manually and on automated platforms. The snELISA can be performed automatically at single points, increasing its scalability.

Conclusions

Measuring antibodies to three viral antigens and identify neutralising antibodies capable of disrupting spike‐ACE2 interactions in high‐throughput enables large‐scale analyses of humoral immune responses to SARS‐CoV‐2 infection and vaccination. The reagents are available to enable scaling up of standardised serological assays, permitting inter‐laboratory data comparison and aggregation.

Abstract GS1-08: CCTGMA.32, a phase III randomized double-blind placebo controlled adjuvant trial of metformin (MET) vs placebo (PLAC) in early breast cancer (BC): Results of the primary efficacy analysis (clinical trials.gov NCT01101438)

Background: MET has been associated with beneficial anti-cancer effects in epidemiologic and preclinical research. It may act indirectly by reversing obesity associated physiologic changes or directly via mitochondrial mediated effects on LKB1/AMPK/mTOR and other mechanisms. MA.32 investigated the effect of MET vs PLAC (in addition to standard therapy) on adjuvant BC outcomes. Design: Randomized, placebo-controlled double-blind Phase III clinical trial conducted within the NCI US National Clinical Trials Network, NCRI (UK) BG, IBCSG. Methods: Between 2010-2013 BC patients &lt; 75 yo without diabetes (DM) with high risk T1-3, N0-3 M0 BC regardless of ER, PgR, HER2 and with adequate cardiac, renal and hepatic function were randomized (stratified for ER/PgR + vs -, BMI &lt; vs &gt; 30 kg/m2, HER2 +ve vs -ve, any vs no chemo) within 1 year of BC diagnosis to MET 850 mg po bid or PLAC bid for 5 years. Dose was reduced for toxicity with re-escalation when possible. Subjects were followed for Invasive Disease-Free Survival (IDFS primary outcome; events included invasive local/regional recurrences, distant recurrences, new ipsilateral/contralateral invasive BCs, new non-breast primary cancers, any death), Overall Survival (OS), Distant Relapse Free Survival (DRFS), BC Specific Survival (BCSS), BC Free Interval (BCFI), contralateral BC and cardiovascular (CV) events/new DM. 3582 subjects were required for 80% power to detect HR 0.76 (431 events). In 2011, entry was restricted to higher risk BC, leading to 80% power to detect HR 0.785 (544 events). In 2016, after the 2nd interim analysis at 29.5 months median F/U, the DSMB recommended (i) the intervention be continued with primary analysis triggered at 544 events be conducted in ER/PgR +ve (any HER2) subjects only and (ii) ER/PgR -ve subjects stop study drug for futility but blinding and follow-up continue. In 2021, a time driven analysis in ER/PgR +ve BC was approved (465 events providing 80% power to detect the original HR 0.76). Time to event survival described by the Kaplan-Meier method. Two-sided log-rank tests adjusting for stratification factors were primarily used to compare IDFS between arms. Cox proportional hazards models were used to identify and adjust for factors significantly related to IDFS. Results: 3649 subjects were enrolled. In the 2533 ER/PgR +ve subjects included in the primary analysis, baseline mean (± SD) age was 52.7 (±9.9 yrs); mean BMI 28.8 (±6.4) kg/m2. Baseline tumor characteristics were balanced: T stage 1/2/3/4 = 832/1351/349/1; N stage 0/1/2/3 = 964/1097/449/23; HER2+ 429. 1901 (75%) received XRT. 2150 (84.9%) received (neo)adj chemo, 2223 (87.8%) (neo)adj hormones and 434 (17.1%) HER2 targeted therapy. Any Grade ≥ 3 toxicity was similar in MET and PLAC arms (21.7% and 18.7%, P = 0.06). Median follow-up was 96.2 (range 0.2-121.0) months with 465 IDFS events (234 MET, 231 PLAC, 76% due to BC). Efficacy results are shown below.

MET vs PLACMET vs PLACIDFSOSPopulation Included# subjectsHR (95% CI)HR (95% CI)PRIMARY ANALYSISER/PgR +ve (any HER2)*25331.01 (0.84-1.21). P=0.920.89 (0.64-1.23). P=0.46ER/PgR -ve (any HER211161.01 (0.79-1.30. P=0.92)0.89 (0.64-1.23). P=0.46Exploratory. AnalysisHER2 +ve (any ER/PgR)6200.64 (0.43-0.95. P=0.0260.53 (0.30-0.98. P=0.0398**in ER/PgR pos BC HRs were similar for BCFI, DRFS, BCSS (ranging from 0.98-1.09)Conclusions: MET did not improve IDFS or other BC outcomes in ER/PgR positive or ER/PgR negative BC and should not be used as adjuvant treatment. Exploratory findings suggesting benefit in HER2+ve BC should be further investigated. Funded by: CCSRI, NCI (US), CBCF, BCRF, CRUK, Hold’Em for Life Charity, Apotex (Canada)

Citation Format: Pamela J. Goodwin, Bingshu E Chen, Karen A Gelmon, Timothy J Whelan, Marguerite Ennis, Julie Lemieux, Jennifer A Ligibel, Dawn L Hershman, Ingrid A Mayer, Timothy J Hobday, Judith M Bliss, Priya Rastogi, Manuela Rabaglio-Poretti, Som D. Mukherjee, Robert R Mackey, Vandana G Abramson, Conrad Oja, Robert Wesolowski, Alastair M Thompson, Daniel W Rea, Paul M Stos, Lois E Shepherd, Vuk Stambolic, Wendy R Parulekar. CCTGMA.32, a phase III randomized double-blind placebo controlled adjuvant trial of metformin (MET) vs placebo (PLAC) in early breast cancer (BC): Results of the primary efficacy analysis (clinical trials.gov NCT01101438) [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 GS1-08.

The Breast Cancer Weight Loss trial (Alliance A011401): A description and evidence for the lifestyle intervention

The Breast Cancer Weight Loss (BWEL) trial is a randomized controlled trial designed to determine whether weight loss after a breast cancer diagnosis can reduce the risk of cancer recurrence in women with overweight or obesity. The BWEL trial will compare the efficacy of a telephone-based weight-loss intervention plus health education materials versus health education materials alone on invasive disease-free survival in 3,181 women with stage II or III breast cancer and BMI > 27 kg/m² . This report provides a detailed description of the goals and methods of the lifestyle intervention and the evidence supporting the intervention used in the BWEL trial. The intervention's primary goal for participants is to achieve and maintain a weight loss ≥ 10% of baseline weight through increased physical activity and caloric restriction. The evidence supporting the diet, physical activity, and behavioral components of this telephone-based weight-loss intervention, as well as strategies to promote participant engagement and retention, is described. The intervention is provided through 42 sessions delivered by trained health coaches over a 2-year period. If the BWEL lifestyle intervention is successful in improving cancer outcomes, then weight loss will be incorporated into the care of thousands of breast cancer patients.

Cancer Antigen 15-3/Mucin 1 Levels in CCTG MA.32: A Breast Cancer Randomized Trial of Metformin vs Placebo

Background

Circulating levels of cancer antigen (CA) 15-3, a tumor marker and regulator of cellular metabolism, were reduced by metformin in a nonrandomized neoadjuvant study. We examined the effects of metformin (vs placebo) on CA 15-3 in participants of MA.32, a phase III randomized trial in early-stage breast cancer.

Methods

A total of 3649 patients with T1-3, N0-3, M0 breast cancer were randomly assigned; pretreatment and 6-month on-treatment fasting plasma were centrally assayed for CA 15-3. Genomic DNA was analyzed for the rs11212617 single nucleotide polymorphism. Absolute and relative change of CA 15-3 (metformin vs placebo) were compared using Wilcoxon rank and t tests. Regression models adjusted for baseline differences and assessed key interactions. All statistical tests were 2-sided.

Results

Mean (SD) age was 52.4 (10.0) years. The majority of patients had T2/3, node-positive, hormone receptor-positive, HER2-negative breast cancer treated with (neo)adjuvant chemotherapy and hormone therapy. Mean (SD) baseline CA 15-3 was 17.7 (7.6) and 18.0 (8.1 U/mL). At 6 months, CA 15-3 was statistically significantly reduced in metformin vs placebo arms (absolute geometric mean reduction in CA 15-3 = 7.7% vs 2.0%, P < .001; relative metformin: placebo level of CA 15-3 [adjusted for age, baseline body mass index, and baseline CA 15-3] = 0.94, 95% confidence interval = 0.92 to 0.96). This reduction was independent of tumor characteristics, perioperative systemic therapy, baseline body mass index, insulin, and the single nucleotide polymorphism status (all Ps > .11).

Conclusions

Our observation that metformin reduces CA 15-3 by approximately 6% was corroborated in a large placebo-controlled randomized trial. The clinical implications of this reduction in CA 15-3 will be explored in upcoming efficacy analyses of breast cancer outcomes in MA.32.

Crown-like structures in breast adipose tissue of breast cancer patients: associations with CD68 expression, obesity, metabolic factors and prognosis

Crown-like structures of the breast (CLS-B), defined by the clustering of macrophages (identified using CD68 immunohistochemical staining) to surround a dying adipocyte, are a sign of adipose-tissue inflammation. In human cohorts, CLS-B positively correlates with older age, obesity, dyslipidemia and higher levels of glucose, insulin, C-reactive protein and IL-6. In an existing cohort of early-stage breast cancer patients, CLS-B were identified using H&E stained histologic sections (hCLS-B), and by CD68 immunohistochemistry (CD68 + CLS-B). We examined associations of H&E and CD68-detected CLS-B with clinicopathologic features using χ2 tests, with metabolic factors using Wilcoxon rank sum tests and with disease free and overall survival using Cox regression models. hCLS-B were detected in 59 of 163 patients with slides (36.2%) and CD68 + CLS-B in 37 of 119 patients with paraffin blocks (31.1%). hCLS-B were positively correlated with higher weight (p = 0.003), BMI (p = 0.0008) and C-reactive protein (p = 0.045). CD68 + CLS-B were positively correlated with higher weight (p = 0.006), BMI p = 0.001), leptin (p = 0.034), insulin (p = 0.008) and Homeostasis Model Assessment (p = 0.027). CD68 + CLS-B were associated with poor distant disease-free with a hazard ratio (HR) of 2.81, 95% confidence interval (CI) 1.20-6.57, and overall survival with HR 3.97 (1.66-9.48), while hCLS-B were not associated with either: HR for distant recurrence 0.59 (0.26-1.30); HR for death 1.04 (0.50-2.16). The presence of hCLS-B and of CD68 + CLS-B were associated with obesity; CD68 + CLS-B were associated with insulin resistance and adverse prognosis. Similar patterns were not seen for hCLS-B. Research is needed to understand the biologic basis for these differences.

Circulating tumor cell number and endocrine therapy index in ER positive metastatic breast cancer patients

Circulating tumor cells (CTC) are prognostic in metastatic breast cancer (MBC). The CTC-endocrine therapy index (CTC-ETI), consisting of CTC-ER (estrogen receptor), BCL2, human epidermal growth factor receptor (HER2), and Ki67 expression, might predict resistance to endocrine therapy (ET) in patients with ER-positive MBC. One hundred twenty-one patients with ER-positive/HER2-negative MBC initiating a new ET after ≥1 lines of ET were enrolled in a prospective, multi-institutional clinical trial. CTC-ETI and clinical/imaging follow-up were performed at baseline and serial time points. Progression-free survival (PFS) and rapid progression (RP; determined at the 3-month time point) were primary endpoints. Associations with clinical outcomes used logrank and Fisher’s exact tests. At baseline, 36% (38/107) of patients had ≥5 CTC/7.5 ml whole blood (WB). Patients with ≥5 vs. <5 CTC/7.5 ml WB had significantly worse PFS (median 3.3 vs. 5.9 months, P = 0.03). Elevated CTC at 1 month was associated with even worse PFS (1.9 vs. 5.0 months from the 1-month sample, P < 0.001). Low, intermediate, and high CTC-ETI were observed in 71 (66%), 8 (8%), and 28 (26%) patients, with median PFS of 6.9, 8.5, and 2.8 months, respectively (P = 0.008). Patients with high vs. low CTC and CTC-ETI more frequently experienced RP (CTC: 66% vs. 41%; P = 0.03; CTC-ETI: 79% vs. 40%; P = 0.002). In conclusion, CTC enumeration and the CTC-ETI assay are prognostic at baseline and follow-up in patients with ER-positive/HER2-negative MBC starting new ET. CTC at first follow-up might identify a group of patients with ER-positive MBC that could forego ET, but CTC-ETI did not contribute further.

Effect of metformin versus placebo on metabolic factors in the MA.32 randomized breast cancer trial

Metformin may exert anticancer effects through indirect (mediated by metabolic changes) or direct mechanisms. The goal was to examine metformin impact on metabolic factors in non-diabetic subjects and determine whether this impact varies by baseline BMI, insulin, and rs11212617 SNP in CCTG MA.32, a double-blind placebo-controlled randomized adjuvant breast cancer (BC) trial. 3649 subjects with T1-3, N0-3, M0 BC were randomized; pretreatment and 6-month on-treatment fasting plasma was centrally assayed for insulin, leptin, highly sensitive C-reactive protein (hsCRP). Glucose was measured locally and homeostasis model assessment (HOMA) calculated. Genomic DNA was analyzed for the rs11212617 SNP. Absolute and relative change of metabolic factors (metformin versus placebo) were compared using Wilcoxon rank and t-tests. Regression models were adjusted for baseline differences and assessed interactions with baseline BMI, insulin, and the SNP. Mean age was 52 years. The majority had T2/3, node positive, hormone receptor positive, HER2 negative BC treated with (neo)adjuvant chemotherapy and hormone therapy. Median baseline body mass index (BMI) was 27.4 kg/m2 (metformin) and 27.3 kg/m2 (placebo). Median weight change was -1.4 kg (metformin) vs +0.5 kg (placebo). Significant improvements were seen in all metabolic factors, with 6 month standardized ratios (metformin/placebo) of 0.85 (insulin), 0.83 (HOMA), 0.80 (leptin), and 0.84 (hsCRP), with no qualitative interactions with baseline BMI or insulin. Changes did not differ by rs11212617 allele. Metformin (vs placebo) led to significant improvements in weight and metabolic factors; these changes did not differ by rs11212617 allele status.

Association of Obesity with Breast Cancer Outcome in Relation to Cancer Subtypes: A Meta-Analysis

Background

Obesity at breast cancer (BC) diagnosis has been associated with poor outcome, although the magnitude of effect in different BC subtypes is uncertain. We report on the association of obesity or overweight at diagnosis of nonmetastatic BC with disease-free (DFS) and overall survival (OS) in the following defined subtypes: hormone receptor positive/HER2 negative (HR+HER2−), HER2 positive (HER2+), and triple negative (TNBC).

Methods

We searched MEDLINE, EMBASE, and COCHRANE databases up to January 1, 2019. Study eligibility was performed independently by 2 authors. Studies reporting hazard ratios (HRs) of OS and/or DFS for obesity or overweight in BC subtypes were included. The pooled hazard ratio was computed and weighted using generic inverse variance and random effects models.

Results

Twenty-seven studies were included. Obese compared with nonobese women had worse DFS in all subtypes: the hazard ratios were 1.26 (95% confidence interval [CI] = 1.13 to 1.41, P < .001) for HR+HER2− BC, 1.16 (95% CI = 1.06 to 1.26, P < .001) for HER2+ BC, and 1.17 (95% CI = 1.06 to 1.29, P = .001) for TNBC. OS was also worse in obese vs nonobese women (HR+HER2− BC HR = 1.39, 95% CI = 1.20 to 1.62, P < .001; HER2+ BC HR = 1.18, 95% CI = 1.05 to 1.33, P = .006; and TNBC HR = 1.32, 95% CI = 1.13 to 1.53, P < .001). As opposed to obesity, overweight was not associated with either DFS or OS in HER2+ BC (HR = 1.02, 95% CI = 0.81 to 1.28, P = .85; and HR = 0.96, 95% CI = 0.76 to 1.21, P = .99, respectively) or TNBC (HR = 1.04, 95% CI = 0.93 to 1.18, P = .49; and HR = 1.08, 95% CI = 0.81 to 1.44, P = .17), respectively. In HR+HER2− BC, being overweight was associated with worse OS (HR = 1.14, 95% CI = 1.07 to 1.22, P < .001).

Conclusions

Obesity was associated with modestly worse DFS and OS in all BC subtypes.

Abstract PS18-25: Concordance of immunohistochemical assays between peri-operative and post-operative breast tumor specimens: A prospective observational study of 18 cases

Background and Rationale: Biomarker evaluation on breast tumor tissue is an important component of clinical research. There is a concern that tissues collected at different times (pre- vs intra-op) and with different techniques (core biopsy vs. surgical excision) produce different results that may confound comparisons of patient samples. Our objective is to address the difference between tumor tissue from the same patient collected pre- vs intra-op and by core biopsy (Core Bx) vs surgical excision, with an emphasis on ER/PgR/HER2/Ki-67 and biomarkers related to insulin metabolism.

Design: Following a protocol approved by the IRB, patients with Core Bx proven invasive breast cancer (BC) &gt;1.5 cm in size by imaging underwent a peri-operative Core Bx followed by surgical excision. No neoadjuvant therapy was administered. Formalin-fixed paraffin-embedded tumor sections of the diagnostic and peri-operative Core Bx and surgical excision were immunohistochemically (IHC) stained for ER, PgR, HER2, Ki-67, insulin receptor (IR), phospho-AKT (pAKT), and phospho-AMPK (pAMPK) using standardized protocols on the same platforms. A pathologist (MCC) scored all sections in blinded order to yield H-Scores (which combine percentage of stain-positive cells and staining intensity). The level of agreement for each assay between specimens was assessed by using pairwise models based on normal theory.

Results: 18 women (mean age = 66.8 years, 16/18 postmenopausal) provided all specimens. Mean (± SD) invasive tumor size was 2.7 (± 1.2) cm. 1 BC was Nottingham Grade 1 (6%), 9 Grade 2 (50%), and 8 Grade 3 (44%). An in situ component was present in 4/18 (22%) cases (all non-extensive). Lymphovascular invasion was present in 6/18 (33%) cases. 10/18 were node-negative (N0, 56%), 2/18 had isolated tumor cells (pN0[i+], 22%), 5/18 had 1 to 3 nodes (pN1, 28%), 1/18 had &gt;9 nodes involved (pN3, 6%).There was high concordance between diagnostic Core Bx, peri-op Core Bx, and excisions for the standard prognostic markers ER, PgR, and HER2. ER was concordant in all samples including 16/18 (89%) ER-positive and 2/19 (11%) ER-negative BCs. PgR was concordant in 16/18 (89%) of cases. In the 2 discordant cases, PgR was negative in 2 of 3 tissue samples with low expression in the 3rd sample (1 diagnostic Core Bx and 1 excision). HER2 was concordant in all samples in 16/18 (89%) HER2-negative cases and in 2/18 (11%) HER2-positive cases including 1/18 cases (6%) positive by IHC, and 1/18 cases (6%) positive by ISH.

Table 1 summarizes the agreement between samples for Ki-67, IR, pAKT, and pAMPK. Ki-67 scores were statistically similar between diagnostic and peri-op Core Bx and excision samples. The IR, pAKT, and pAMPK H-Scores were statistically similar between diagnostic and peri-op Core Bx, but significantly different between Core Bxs versus excisional specimens. There was a systematic tendency towards lower IHC H-Scores in the excisional specimen for IR, pAKT, and pAMPK.

Conclusion: Tissue from surgical excisions are susceptible to reduced IHC staining for metabolic markers such as IR, and phosphorylated kinases, when compared to core biopsies. When evaluating non-standard biomarkers for research, core biopsies should be used when possible.

Funding: This study was funded by the Hold'Em For Life Charity and the Breast Cancer Research Foundation

Table 1: Concordance Between IHC Scores for Ki-67, Insulin Receptor, pAKT, and pAMPKScore: Mean ± Standard DeviationPeri-Operative Core Bx versus Diagnostic Core BxExcision versus Diagnostic Core BxDiagnostic Core BxPeri-Operative Core BxExcisionDifferenceP-valueDifferenceP-valueKi-67 (% Positive)33.5 ± 28.235.9 ± 31.034.2 ± 29.1Mean ± SD: 2.4 ± 5.60.09Mean ± SD: 0.6 ± 6.30.68Range: -7.7 to 12.3Range: -11.5 to 12.2Insulin Receptor (H-Score**)136 ± 102124 ± 9986 ± 78Mean ± SD: -13 ± 530.32Mean ± SD: -51 ± 540.001*Range: -215 to 40Range: -150 to 5Phospho-AKT (H-Score**)102 ± 70100 ± 8641 ± 41Mean ± SD: -1 ± 750.95Mean ± SD: -61 ± 520.0001*Range: -170 to 170Range: -144 to 0Phospho-AMPK (H-Score**)201 ± 79185 ± 78157 ± 86Mean ± SD: -15 ± 760.41Mean ± SD: -44 ± 690.016*Range: -225 to 120Range: -215 to 70* Statistically significant difference in pairwise values based on t-test** H-Score is the percentage of stain-positive cells multiplied by the average intensity score (0 = absent, 1 = faint, 2 = moderate, 3 = strong)

Citation Format: Martin C. Chang, Marguerite Ennis, Jaime Escallon, Karina Bukhanov, Ryan JO Dowling, Vuk Stambolic, Pamela J Goodwin. Concordance of immunohistochemical assays between peri-operative and post-operative breast tumor specimens: A prospective observational study of 18 cases [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 PS18-25.

The Effect of Metformin vs Placebo on Sex Hormones in Canadian Cancer Trials Group MA.32

BACKGROUND

Metformin has been associated with lower breast cancer (BC) risk and improved outcomes in observational studies. Multiple biologic mechanisms have been proposed, including a recent report of altered sex hormones. We evaluated the effect of metformin on sex hormones in MA.32, a phase III trial of nondiabetic BC subjects who were randomly assigned to metformin or placebo.

METHODS

We studied the subgroup of postmenopausal hormone receptor-negative BC subjects not receiving endocrine treatment who provided fasting blood at baseline and at 6 months after being randomly assigned. Sex hormone-binding globulin, bioavailable testosterone, and estradiol levels were assayed using electrochemiluminescence immunoassay. Change from baseline to 6 months between study arms was compared using Wilcoxon sum rank tests and regression models.

RESULTS

312 women were eligible (141 metformin vs 171 placebo); the majority of subjects in each arm had T1/2, N0, HER2-negative BC and had received (neo)adjuvant chemotherapy. Mean age was 58.1 (SD=6.9) vs 57.5 (SD=7.9) years, mean body mass index (BMI) was 27.3 (SD=5.5) vs 28.9 (SD=6.4) kg/m2 for metformin vs placebo, respectively. Median estradiol decreased between baseline and 6 months on metformin vs placebo (-5.7 vs 0 pmol/L; P < .001) in univariable analysis and after controlling for baseline BMI and BMI change (P < .001). There was no change in sex hormone-binding globulin or bioavailable testosterone.

CONCLUSION

Metformin lowered estradiol levels, independent of BMI. This observation suggests a new metformin effect that has potential relevance to estrogen sensitive cancers.

Prognostic associations of plasma hepcidin in women with early breast cancer

PURPOSE

Iron is essential to energy metabolism, cell proliferation and DNA synthesis, and sufficient iron availability may be required for tumor growth. The hormone hepcidin is a systemic regulator of iron concentration in plasma. Intra-tumor RNA expression of hepcidin has been linked to shorter metastasis-free survival in women with early breast cancer, but the prognostic implications of this inflammatory marker and iron-regulating plasma peptide in the blood are unknown.

METHODS

Using an ELISA assay, hepcidin was measured in the banked blood of 518 women who were recruited from 1989 to 1996 for a prospective cohort study of diet and lifestyle factors in breast cancer. Blood samples were obtained 4-12 weeks post-operatively, prior to treatment with chemotherapy or tamoxifen.

RESULTS

Hepcidin was not associated with time to distant breast cancer recurrence (primary outcome) nor time to death from any cause. However, a pre-planned interaction test of body mass index (BMI) was statistically significant (p < 0.01). Among obese women (BMI > 30 kg/m²), higher hepcidin was associated with a shorter time to distant breast cancer recurrence in both uni- and multivariable analyses (adjusted HR 1.84; 95% CI 1.04-3.25). For overall survival, a similar pattern was seen in the univariable model but the effect was diminished in a multivariable analysis. Plasma hepcidin was not associated with high-sensitivity C-reactive protein, but it was significantly associated (r ≥ 0.32) with iron indices, including total iron (p < 0.01), transferrin (p < 0.01) and soluble transferrin receptor (p < 0.01).

CONCLUSIONS

Hepcidin may be associated with poor breast cancer outcome in obese women, however, replication is required. The biologic basis for this prognostic association requires further research.

Association between BMI, vitamin D, and estrogen levels in postmenopausal women using adjuvant letrozole: a prospective study

Studies have suggested that women with elevated BMI or 25-OH vitamin D levels may derive less benefit from AIs versus tamoxifen. We prospectively investigated whether high BMI or 25-OH vitamin D levels were associated with higher estrogen levels in post-menopausal women receiving standard adjuvant letrozole (2.5 mg/day). Furthermore, we evaluated whether an increased dose of letrozole resulted in lower serum estrogens in women with BMI > 25 kg/m2. Correlation between entry BMI and day 29 serum biomarkers (estrogens, 25-OH vitamin D, insulin, CRP, leptin) was assessed in all patients. On day 29, participants with BMI > 25 kg/m2 switched to letrozole 5 mg/day for 4-weeks and blood was drawn upon completion of the study. The change in serum estrogen levels was assessed in these patients (BMI > 25 kg/m2). 112 patients completed days 1-28. The Pearson correlations of estradiol and estrone with BMI or serum 25-OH vitamin D levels were near zero (-0.04 to 0.07, p = 0.48-0.69). Similar results were obtained for correlation with markers of obesity (insulin, CRP, and leptin) with estradiol and estrone (-0.15 to 0.12; p = 0.11-0.82). Thirty-one patients (BMI > 25 kg/m2) completed the interventional component; Increasing the dose of letrozole did not further reduce estradiol or estrone levels (change 0.1 and 0.4 pmol/L respectively; p = 0.74 and 0.36). There was no observed association between markers of obesity (BMI, insulin, leptin, and CRP), serum 25-OH vitamin D levels and estradiol or estrone levels. Additionally, an increased dose of letrozole did not further reduce estradiol or estrone levels compared to the standard dose.

The LISA randomized trial of a weight loss intervention in postmenopausal breast cancer

Obesity has been associated with poor breast cancer (BC) outcomes. We investigated whether a standardized, telephone-based weight loss lifestyle intervention in the adjuvant setting would impact BC outcomes. We conducted a multicenter trial randomizing women 1:1 to mail-based educational material alone (control) or combined with a standardized, telephone-based lifestyle intervention that focused on diet, physical activity, and behavior and involved 19 calls over 2 years to achieve up to 10% weight loss. In all, 338 (of 2150 planned) T1-3, N0-3, M0 hormone receptor positive BC patients with body mass index (BMI) ≥24 kg/m2 receiving adjuvant letrozole were randomized (enrolment ended due to funding loss). The primary outcome was disease-free survival (DFS); secondary outcome was Overall Survival (OS). At 8 years' median follow-up, in a planned analysis, DFS and OS were compared using the Kaplan-Meier method. Baseline BMI and other characteristics were similar between study arms. In all, 22 of 171 (12.9%) in the lifestyle intervention arm versus 30 of 167 (18.0%) in the education had DFS events; the hazard ratio (HR) was 0.71 (95% confidence interval [CI]: 0.41-1.24, p = 0.23). Although loss of funding reduced sample size, we view these hypothesis generating results as compatible with our hypothesis of a potential beneficial effect of a lifestyle intervention on DFS. They provide support for completion of ongoing randomized controlled trials of the effect of lifestyle interventions in BC outcomes.

Abstract P3-02-02: CD68-positive crown-like structures of the breast are independently associated with adverse survival: A retrospective analysis of cases from a prospective cohort

Introduction: The association of breast cancer (BC) with obesity is complex and multifactorial, depending partly on diet and related metabolic imbalances. Previous reports have shown that local inflammation in adipocytes can be seen in tissue sections as rings of macrophages of macrophages around necrotic adipocytes (“Crown-Like Structures of the Breast”, CLS-B). We and others have shown that CLS-B have higher prevalence and density within the adipose tissue of obese patients. Our goal was to examine the association of CLS-B with survival in participants enrolled at one center (Mount Sinai Hospital, Toronto) of a multicenter prospective cohort study designed to investigate obesity-related prognostic factors in early stage BC.

Design: Archived H&E sections of breast adipose tissue were retrieved from Mount Sinai (Toronto) participants (N=163). All specimens were from breast excisions for invasive carcinoma. A CLS-B was defined as a ring of macrophages surrounding an adipocyte in otherwise normal breast tissue. In a subset (N=119), immunostains for CD68 were performed on a representative block to highlight macrophages. Sections containing tumor, fat necrosis, and mastitis were excluded. Slides were pathologist-reviewed, recording the number of CLS-B, slides containing CLS-B, and slides with normal tissue. Serologic markers of metabolism and inflammation were previously performed in a central laboratory. Correlations with clinical and serologic markers were examined using descriptive statistics and Wilcoxon tests. Survival analysis was performed with Cox proportional hazards models.

Results: CLS-B were identified in routine H&E sections of normal fat in 59 out of 163 cases (36%). In the representative subset stained for CD68 (N=119), 22 cases were identified as positive for CLS-B by both H&E and CD68, 15 cases by CD68 alone and 24 by H&E alone, giving a CLS-B prevalence of 39% as detected by H&E, 31% by CD68 and 51% when combining the two. Both i) CD68-positive and ii) H&E-positive CLS-B showed similar positive relationships with BMI (median BMI 27 versus 24 kg/m2, P&lt;0.01 for CLS-B present versus absent); however the relationship with insulin was stronger for CD68-positive CLS-B (median insulin 49 vs 35 pmol/L, P=0.009) than for H&E-positive CLS-B (insulin 39 vs 35 pmol/L, P=0.39).

Univariable Cox model hazard ratios (HRs) for CD68-positive CLS-B were 2.79 (95% confidence interval (CI) 1.31-5.95) and 3.74 (CI 1.73-8.07) for disease-free and overall survival respectively, and after adjustment for age, nodal status, tumour grade, stage, ER/PR status, adjuvant treatment and BMI, HRs were 2.43 (CI 1.01-5.81) and 3.19 (CI 1.3-7.79). In the same subset, H&E-positive CLS-B had univariable HRs of 0.66 (CI 0.29-1.52) and 1.18 (CI 0.55-2.54) respectively and adjusted HRs of 0.31 (CI 0.11-0.82) and 0.57 (CI 0.23-1.39). Combining H&E and CD68 did not improve prediction over using CD68 alone.

Conclusion: CLS-B visualized by the macrophage immunostain CD68 were associated with poor outcome, independent of patient BMI and tumour characteristics. Detection of CLS-B using H&E alone was not associated with poor outcome. Our results demonstrate that although CLS-B are a phenotype of obesity, they may also reflect a tissue-specific risk of adverse BC outcome. This risk may relate to localized tissue inflammation with higher prevalence in obese individuals. Although we do not advocate the clinical use of the CD68 stain, further work is warranted to clarify the connection between tissue inflammation and poor breast cancer outcome.

Acknowledgement: The authors wish to acknowledge the Hold'Em For Life Charity Challenge for Cancer Research for their generous support.

Citation Format: Martin C. Chang, Marguerite Ennis, Zohreh Eslami, Pamela J. Goodwin. CD68-positive crown-like structures of the breast are independently associated with adverse survival: A retrospective analysis of cases from a prospective cohort [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 P3-02-02.

Toronto Workshop on Late Recurrence in Estrogen Receptor-Positive Breast Cancer: Part 2: Approaches to Predict and Identify Late Recurrence, Research Directions

Late disease recurrence (more than 5 years after initial diagnosis) represents a clinical challenge in the treatment and management of estrogen receptor-positive breast cancer (BC). An international workshop was convened in Toronto, Canada, in February 2018 to review the current understanding of late recurrence and to identify critical issues that require future study. The underlying biological causes of late recurrence are complex, with the processes governing cancer cell dormancy, including immunosurveillance, cell proliferation, angiogenesis, and cellular stemness, being integral to disease progression. These critical processes are described herein as well as their role in influencing risk of recurrence. Moreover, observational and interventional clinical trials are proposed, with a focus on methods to identify patients at risk of recurrence and possible strategies to combat this in patients with estrogen receptor-positive BC. Because the problem of late BC recurrence of great importance, recent advances in disease detection and patient monitoring should be incorporated into novel clinical trials to evaluate approaches to enhance patient management. Indeed, future research on these issues is planned and will offer new options for effective late recurrence treatment and prevention strategies.