Abstract P2-02-09: Obesity associated factors are inversely associated with circulating tumor cells in metastatic breast cancer

Background: Elevated levels of circulating tumor cells (CTCs) are associated with adverse outcomes in metastatic breast cancer (BC). However, relationships between CTCs and various patient-related factors that may impact outcome remain undefined. Consequently, associations of CTC counts with obesity and metabolic factors were evaluated in order to gain insight into potential interactions between patient physiology and disease burden. We hypothesized that obesity and associated metabolic factors would be associated with higher CTC counts.

Methods: Non-diabetic women with metastatic BC beginning a new line of treatment due to progressive disease were recruited from four Ontario cancer hospitals between February 2013 and April 2015. Patients provided blood for CTC analysis, which was completed within 72 hours of collection using the Janssen CellSearch platform. Fasting serum was also collected for assessment of metabolic factors including glucose (mmol/L), insulin (pmol/L), leptin (ng/mL) and adiponectin (ng/mL). Associations of CTC counts with these factors, as well as anthropometric measurements (height (cm), weight (kg), BMI (kg/m2)) were evaluated using Pearson correlation coefficients after transforming the variables involved to normality. For CTC counts, the log transformation with half integer correction was used.

Results: 96 patients with a median age of 60.5 years completed the study. Most were post-menopausal (87, 90.6%) and exhibited grade II/III tumors (75, 78.1%). The majority of patients had hormone receptor positive disease (83, 86.5%), but 16.7% (16) were HER2 positive and 10.4% (10) were triple negative. The number of CTCs observed ranged from 0 to 1238 (median 2, geometric mean 3.63). No CTCs were detected in 29 patients (30.2%), whereas 25 patients (26 %) exhibited counts of 1 to 4 CTCs and 42 (43.8%) had 5 or more CTCs. CTCs were not significantly associated with tumor characteristics including ER/PgR, HER2, grade, stage (T/N) or lymphovascular invasion. The number of CTCs inversely correlated with BMI (r=-0.26, p=0.01), leptin (r=-0.29, p=0.004), and leptin-adiponectin ratio (r=-0.3, p=0.004). A similar trend that approached significance was noted for body weight (r=-0.19, p=0.07), insulin (r=-0.19, p=0.06) and homeostatic model assessment (HOMA, an estimate of insulin resistance, r=-0.2, p=0.055). Conversely, adiponectin (r=0.18, p=0.07) and height (r=0.18, p=0.07) were positively associated with CTC counts in correlations that neared significance. No associations were observed for age (r=0.09, p=0.4) or glucose (r=-0.09, p=0.4).

Conclusions: Obesity associated metabolic factors including weight, BMI, insulin, HOMA and leptin were inversely associated (and adiponectin and height positively associated) with CTC counts. These patterns are consistent with weight loss and/or cachexia in women with elevated CTC counts who have higher disease burden. Additional analyses are underway to further characterize these associations and include assessment of serum albumin, free fatty acids, creatine kinase and hepcidin.

Citation Format: Dowling RJO, Chang MC, Lohmann AE, Ennis M, Amir E, Elser C, Brezden-Masley C, Vandenberg T, Lee E, Fazaee K, Stambolic V, Goodwin PJ. Obesity associated factors are inversely associated with circulating tumor cells in metastatic breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-02-09.

Abstract ES9-3: Targeted interventions: Metformin and lifestyle change

Obesity is associated with increased risk of premenopausal (triple negative) and postmenopausal [primarily estrogen receptor (ER) positive] breast cancer (BC). Higher Body Mass Index [BMI = weight (kg)/height (m)2] and lower physical activity have been associated with increased risk of distant recurrence and death in both pre- and postmenopausal BC, regardless of ER status; some recent studies nested in clinical trials have found an association only in ER+ BC. There is growing evidence that obese women may have less benefit from aromatase inhibitors (AIs) other than letrozole. Translational and preclinical research suggests that obesity associated alterations in systemic physiology (higher estrogens, insulin resistance leading to higher insulin and glucose, altered adipokines and inflammation) or changes in the tumor microenvironment (localized inflammation) may mediate effects of obesity on BC outcomes.

The presence of an association of obesity with breast cancer outcomes is not necessarily causal (non-causal associations may reflect healthy person bias, under-treatment of obese patients, or presentation of BC at more advanced stage in obese women). Even if the association is causal it may not be reversible (ie: adverse effects may be reflected in the biology of the BC that develops and may not be amenable to change). Evidence that an association is both causal and reversible can be obtained from any intervention research. Potential interventions include weight loss and targeted drugs such as metformin.

Metformin, a biguanide commonly used to treat type 2 diabetes, may act (i) indirectly to improve obesity associated systemic physiology (e.g. by lowering circulating insulin leading to reduced insulin receptor mediated activation of PI3K and ras pathways), (ii) directly via an effect on the mitochondrium leading to an LKBI mediated AMPK activation and downstream mTOR inhibition or (iii) directly via other non-AMPK mediated direct effects. Metformin has been associated with lower BC risk and improved BC outcomes in observational studies that may be susceptible to survival biases. It has led to reduced proliferation and increased apoptosis in some neoadjuvant studies (similar to effects seen in preclinical studies). Despite this epidemiologic, clinical, translational and preclinical research, definitive evidence of benefits from Phase III trials is needed. A Phase III adjuvant trial (NCIC MA.32) testing metformin (vs placebo) in the adjuvant BC setting has completed accrual and is anticipated to report BC outcome data in 2017.

Lifestyle based weight loss interventions (involving calorie restriction and enhanced physical activity) have been shown to lead to 5-7% weight loss in BC populations (and to improvement in potential systemic mediators noted above). Most ongoing or completed studies of weight loss in have been underpowered for BC outcomes and have focused primarily on weight loss. An adequately powered US Intergroup study (led by the Alliance) using a telephone based intervention involving over 3000 subjects is in advanced stages of planning. Results of this trial, anticipated 6-8 years after initiation, should provide rigorous evidence regarding possible benefits of the degree of weight loss that can be achieved through lifestyle change on BC outcomes.

Citation Format: Goodwin PJ. Targeted interventions: Metformin and lifestyle change. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr ES9-3.

Recommendations for Obesity Clinical Trials in Cancer Survivors: American Society of Clinical Oncology Statement

Observational evidence has established a relationship between obesity and cancer risk and outcomes. Interventional studies have demonstrated the feasibility and benefits of lifestyle change after cancer diagnosis, and guidelines recommend weight management and regular physical activity in cancer survivors; however, lifestyle interventions are not a routine part of cancer care. The ASCO Research Summit on Advancing Obesity Clinical Trials in Cancer Survivors sought to identify the knowledge gaps that clinical trials addressing energy balance factors in cancer survivors have not answered and to develop a roadmap for the design and implementation of studies with the potential to generate data that could lead to the evidence-based incorporation of weight management and physical activity programs into standard oncology practice. Recommendations highlight the need for large-scale trials evaluating the impact of energy balance interventions on cancer outcomes, as well as the concurrent conduct of studies focused on dissemination and implementation of interventions in diverse populations of cancer survivors, including answering critical questions about the degree of benefit in key subgroups of survivors. Other considerations include the importance of incorporating economic metrics into energy balance intervention trials, the need to establish intermediate biomarkers, and the importance of integrating traditional and nontraditional funding sources. Establishing lifestyle change after cancer diagnosis as a routine part of cancer care will require a multipronged effort to overcome barriers related to study development, funding, and stakeholder engagement. Given the prevalence of obesity and inactivity in cancer survivors in the United States and elsewhere, energy balance interventions hold the potential to reduce cancer morbidity and mortality in millions of patients, and it is essential that we move forward in determining their role in cancer care with the same care and precision used to test pharmacologic and other interventions.

Abstract P1-09-02: BMI and metabolic factors in long-term breast cancer survivors: Changes from diagnosis and comparison to non-breast cancer controls

Background: The metabolic syndrome is associated with poor breast cancer (BC) outcome. We evaluated changes from diagnosis in metabolic factors and BMI in long-term survivors and compared their status at long-term follow-up (LTFU) to that of age-matched women with no history of BC.

Methods: A total of 535 women with early breast cancer were enrolled between 1989 and 1996 and followed prospectively. From 2005 to 2007, those alive without distant recurrence were re-contacted to participate in a long-term followed-up study and 285 agreed. A control group of 167 age-matched women without cancer history was recruited from women presenting for screening mammograms. Mean changes in metabolic factors from diagnosis to long-term follow-up were assessed with paired t-tests. In spite of matching, controls were younger and had higher income than survivors and the comparison to controls was made using age-adjusted regression models. Variables were transformed to normality before statistical testing.

Results: With a median follow-up of 12.5 years, BC survivors gained on average 2.35 kg and BMI, waist and hip circumference, waist-hip ratio, glucose, insulin, HOMA, total cholesterol and its components (but not triglycerides) increased significantly. After age adjustment, waist circumference, glucose, HOMA and total triglycerides were significantly higher in BC survivors compared to controls

Comparison of LTFU BC survivors to non-cancer controls Unadjusted mean ± standard deviationUnadjusted mean ± standard deviation  BC patientscontrolsP-value for age-adjusted differencewaist circumference (cm)85 ± 1281 ± 10.01Glucose (mmol/L)5.5 ± 1.05.2 ± 0.9.01Insulin (pmol/L)60.9 ± 50.547.1 ± 28.3.06HOMA2.25 ± 2.241.64 ± 1.24.03Triglycerides (mmol/L)1.28 ± 0.641.10 ± 0.57.01BMI (kg/m2)26.3 ± 4.925.4 ± 4.5.26

Despite exclusion of BC patients with diabetes at study entry, 24.9% of BC survivors self reported diabetes or pre-diabetes (1.99%/year) versus 12.6% in controls (OR 2.3, p= .0017).

Conclusion: The metabolic status of long-term BC survivors deteriorated over time and age-adjusted at LTFU were worse with respect to a number of factors compared to the control group.

Citation Format: Ana Elisa Lohmann, Marguerite Ennis, Pamela J Goodwin. BMI and metabolic factors in long-term breast cancer survivors: Changes from diagnosis and comparison to non-breast cancer controls [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-09-02.

Effect of metformin vs placebo on and metabolic factors in NCIC CTG MA.32

BACKGROUND

Metformin may improve metabolic factors (insulin, glucose, leptin, highly sensitive C-reactive protein [hs-CRP]) associated with poor breast cancer outcomes. The NCIC Clinical Trials Group (NCIC CTG) MA.32 investigates effects of metformin vs placebo on invasive disease-free survival and other outcomes in early breast cancer. Maintaining blinding of investigators to outcomes, we conducted a planned, Data Safety Monitoring Committee-approved, analysis of the effect of metformin vs placebo on weight and metabolic factors at six months, including examination of interactions with baseline body mass index (BMI) and insulin, in the first 492 patients with paired blood samples.

METHODS

Eligible nondiabetic subjects with T1-3, N0-3, M0 breast cancer who had completed surgery and (neo)adjuvant chemotherapy (if given) provided fasting plasma samples at random assignment and at six months. Glucose was measured locally; blood was aliquoted, frozen, and stored at -80°C. Paired plasma aliquots were analyzed for insulin, hs-CRP, and leptin. Spearman correlation coefficients were calculated and comparisons analyzed using Wilcoxon signed rank test. All statistical tests were two-sided.

RESULTS

Mean age was 52.1±9.5 years in the metformin group and 52.6 ± 9.8 years in the placebo group. Arms were balanced for estrogen/progesterone receptor, BMI, prior (neo)adjuvant chemotherapy, and stage. At six months, decreases in weight and blood variables were statistically significantly greater in the metformin arm (vs placebo) in univariate analyses: weight -3.0%, glucose -3.8%, insulin -11.1%, homeostasis model assessment -17.1%, leptin -20.2%, hs-CRP -6.7%; all P values were less than or equal to .03. There was no statistically significant interaction of change in these variables with baseline BMI or insulin.

CONCLUSIONS

Metformin statistically significantly improved weight, insulin, glucose, leptin, and CRP at six months. Effects did not vary by baseline BMI or fasting insulin.

Changes in insulin receptor signaling underlie neoadjuvant metformin administration in breast cancer: a prospective window of opportunity neoadjuvant study

INTRODUCTION

The antidiabetic drug metformin exhibits potential anticancer properties that are believed to involve both direct (insulin-independent) and indirect (insulin-dependent) actions. Direct effects are linked to activation of AMP-activated protein kinase (AMPK) and an inhibition of mammalian target of rapamycin mTOR signaling, and indirect effects are mediated by reductions in circulating insulin, leading to reduced insulin receptor (IR)-mediated signaling. However, the in vivo impact of metformin on cancer cell signaling and the factors governing sensitivity in patients remain unknown.

METHODS

We conducted a neoadjuvant, single-arm, "window of opportunity" trial to examine the clinical and biological effects of metformin on patients with breast cancer. Women with untreated breast cancer who did not have diabetes were given 500 mg of metformin three times daily for ≥2 weeks after diagnostic biopsy until surgery. Fasting blood and tumor samples were collected at diagnosis and surgery. Blood glucose and insulin were assayed to assess the physiologic effects of metformin, and immunohistochemical analysis of tumors was used to characterize cellular markers before and after treatment.

RESULTS

Levels of IR expression decreased significantly in tumors (P = 0.04), as did the phosphorylation status of protein kinase B (PKB)/Akt (S473), extracellular signal-regulated kinase 1/2 (ERK1/2, T202/Y204), AMPK (T172) and acetyl coenzyme A carboxylase (S79) (P = 0.0001, P < 0.0001, P < 0.005 and P = 0.02, respectively). All tumors expressed organic cation transporter 1, with 90% (35 of 39) exhibiting an Allred score of 5 or higher.

CONCLUSIONS

Reduced PKB/Akt and ERK1/2 phosphorylation, coupled with decreased insulin and IR levels, suggest insulin-dependent effects are important in the clinical setting. These results are consistent with beneficial anticancer effects of metformin and highlight key factors involved in sensitivity, which could be used to identify patients with breast cancer who may be responsive to metformin-based therapies.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00897884. Registered 8 May 2009.

Impact of the obesity epidemic on cancer

There is growing appreciation that the current obesity epidemic is associated with increases in cancer incidence at a population level and may lead to poor cancer outcomes; concurrent decreases in cancer mortality at a population level may represent a paradox, i.e., they may also reflect improvements in the diagnosis and treatment of cancer that mask obesity effects. An association of obesity with cancer is biologically plausible because adipose tissue is biologically active, secreting estrogens, adipokines, and cytokines. In obesity, adipose tissue reprogramming may lead to insulin resistance, with or without diabetes, and it may contribute to cancer growth and progression locally or through systemic effects. Obesity-associated changes impact cancer in a complex fashion, potentially acting directly on cells through pathways, such as the phosphoinositide 3-kinase (PI3K) and Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathways, or indirectly via changes in the tumor microenvironment. Approaches to obesity management are discussed, and the potential for pharmacologic interventions that target the obesity-cancer link is addressed.

Randomized trial of a telephone-based weight loss intervention in postmenopausal women with breast cancer receiving letrozole: the LISA trial

PURPOSE

Obesity is associated with poor outcomes in women with operable breast cancer. Lifestyle interventions (LIs) that help women reduce their weight may improve outcomes.

PATIENTS AND METHODS

We conducted a multicenter randomized trial comparing mail-based delivery of general health information alone or combined with a 24-month standardized, telephone-based LI that included diet (500 to 1,000 kcal per day deficit) and physical activity (150 to 200 minutes of moderate-intensity physical activity per week) goals to achieve weight loss (up to 10%). Women receiving adjuvant letrozole for T1-3N0-3M0 breast cancer with a body mass index (BMI) ≥ 24 kg/m(2) were eligible. Weight was measured in the clinic, and self-report physical activity, quality-of-life (QOL), and diet questionnaires were completed. The primary outcome was disease-free survival. Accrual was terminated at 338 of 2,150 planned patients because of loss of funding.

RESULTS

Mean weight loss was significantly (P < .001) greater in the LI arm versus the comparison arm (4.3 v 0.6 kg or 5.3% v 0.7% at 6 months and 3.1 v 0.3 kg or 3.6% v 0.4% at 24 months) and occurred consistently across strata (BMI 24 to < 30 v ≥ 30 kg/m(2); prior v no prior adjuvant chemotherapy). Weight loss was greatest in those with higher baseline levels of moderate-intensity physical activity or improvement in QOL. Hospitalization rates and medical events were similar.

CONCLUSION

A telephone-based LI led to significant weight loss that was still evident at 24 months, without adverse effects on QOL, hospitalizations, or medical events. Adequately powered randomized trials with cancer end points are needed.

Obesity and endocrine therapy: host factors and breast cancer outcome

Obesity is becoming increasingly prevalent and it has been linked to poor breast cancer outcomes. Because obesity is associated with increased adipose tissue mass and aromatase activity [the target of aromatase inhibitors (AIs)], there is concern that these agents may be less effective in women who are overweight or obese. Four of the randomized trials of AIs vs. tamoxifen conducted in the adjuvant breast cancer setting (ATAC, BIG 1-98 and TEAM in the postmenopausal setting and ABCSG-12 in the premenopausal setting) have reported effects of body mass index (BMI) on the relative effectiveness of an AI vs. tamoxifen. Obesity was confirmed as an adverse prognostic factor in ATAC and BIG 1-98 but not the TEAM study; in ABSCG-12, obesity was associated with poor outcomes in the anastrozole arm only. In the three postmenopausal trials, the use of an AI vs. tamoxifen was associated with better outcomes at all levels of BMI [all hazard ratios for recurrence <1, although 95% confidence intervals often included 1 due to lower power and smaller reductions in risk]. Of note, there was no significant interaction of BMI with letrozole (vs. tamoxifen) in the BIG 1-98 trial; while ATAC investigators concluded that the relative benefit of anastrozole (vs. tamoxifen) might be better in thinner (vs. heavier) women. In ABCSG-12, the use of anastrozole (vs. tamoxifen) was associated with significantly worse outcomes in women with BMI ≥25 kg/m(2) (similar to the detrimental effect of anastrozole on overall survival seen in the parent trial). These findings do not support the use of BMI as a predictor of AI (vs. tamoxifen) benefit in the adjuvant setting in postmenopausal breast cancer.

Hype versus hope: metformin and vitamin D as anticancer agents

There has been increasing interest in the use of metformin and vitamin D to reduce cancer risk and improve outcomes. Metformin, an oral antidiabetic drug, improves insulin resistance and has been associated with reduced cancer incidence and cancer mortality. Low levels of vitamin D have also been associated with increased cancer risk, mainly in retrospective studies, and it has been suggested that vitamin D supplementation might play a role in cancer prevention. Preclinical data provide a biologic rationale for these associations; however, the human data arise predominantly from observational studies and caution is needed in their translation into clinical practice. This is because of the recognized limitations of observational studies, such as time-related survival biases, selection and referral biases, short follow-up, and the presence of confounding factors that can lead to spurious or inaccurate findings. Combined examination of associations with cancer risk and outcome (occurring when exposure in a population that does not yet have cancer is analyzed in relation to cancer death) may yield results that are difficult to interpret. Finally, associations across all cancers may differ from those in specific cancer types. These shortcomings can be overcome in properly designed and adequately powered prospective randomized trials; however, such trials are both expensive and time consuming. We review the literature examining the associations of metformin and vitamin D with cancer, discussing weakness and strengths and making recommendations for further research and clinical practice.

Quality of Life in Long-Term Breast Cancer Survivors

Purpose

There is considerable interest in the quality of life (QOL) of long-term breast cancer (BC) survivors. We studied changes in QOL from time of BC diagnosis to long-term survivorship and compared QOL in long-term survivors to that of age-matched women with no history of BC.

Patients and Methods

In all, 535 women with localized BC (T1-3N0-1M0) were recruited from 1989 to 1996 and followed prospectively, completing QOL questionnaires at diagnosis and 1 year postdiagnosis. Between 2005 and 2007, those alive without distant recurrence were recontacted to participate in a long-term follow-up (LTFU) study. A control group was recruited from women presenting for screening mammograms, and both groups completed LTFU QOL questionnaires. Longitudinal change in BC survivors and differences between BC survivors and controls were assessed in eight broad categories with clinically significant differences set at 5% and 10% of the breadth of each QOL scale.

Results

A total of 285 patients with BC were included in the study, on average 12.5 years postdiagnosis. Longitudinally, clinically significant improvements were observed in overall QOL by 1 year postdiagnosis with further improvements by LTFU. Some clinically significant improvements over time were seen in all categories. A total of 167 controls were recruited. Deficits were observed in self-reported cognitive functioning (5.3% difference) and financial impact (6.3% difference) in BC survivors at LTFU compared with controls.

Conclusion

Long-term BC survivors show improvement in many domains of QOL over time, and they appear to have similar QOL in most respects to age-matched noncancer controls, although small deficits in cognition and finances were identified.

Association between metformin therapy and mortality after breast cancer: a population-based study

OBJECTIVE

Metformin has been associated with a reduction in breast cancer risk and may improve survival after cancer through direct and indirect tumor-suppressing mechanisms. The purpose of this study was to evaluate the effect of metformin therapy on survival in women with breast cancer using methods that accounted for the duration of treatment with glucose-lowering therapies.

RESEARCH DESIGN AND METHODS

This population-based study, using Ontario health care databases, recruited women aged 66 years or older diagnosed with diabetes and breast cancer between 1 April 1997 and 31 March 2008. Using Cox regression analyses, we explored the association between cumulative duration of past metformin use and all-cause and breast cancer-specific mortality. We modeled cumulative duration of past metformin use as a time-varying exposure.

RESULTS

Of 2,361 breast cancer patients identified, mean (±SD) age at cancer diagnosis was 77.4±6.3 years, and mean follow-up was 4.5±3.0 years. There were 1,101 deaths (46.6%), among which 386 (16.3%) were breast cancer-specific deaths. No significant association was found between cumulative duration of past metformin use and all-cause mortality (adjusted hazard ratio 0.97 [95% CI 0.92-1.02]) or breast cancer-specific mortality (0.91 [0.81-1.03]) per additional year of cumulative use.

CONCLUSIONS

Our findings failed to show an association between improved survival and increased cumulative metformin duration in older breast cancer patients who had recent-onset diabetes. Further research is needed to clarify this association, accounting for effects of cancer stage and BMI in younger populations or those with differing stages of diabetes as well as in nondiabetic populations.

Abstract PD03-05: Analysis of tumour cell signaling in response to neoadjuvant metformin in women with early stage breast cancer

Background: The anti-diabetic drug metformin, commonly used to treat type 2 diabetes due to its ability to reduce circulating glucose and insulin, has emerged as a potential anti-cancer agent. Observational studies have reported decreased cancer incidence and mortality in diabetics receiving metformin. Metformin's ability to reduce insulin may be particularly important for breast cancer (BC) because hyperinsulinemia is an adverse prognostic factor and most cells express the insulin receptor (IR). The anti-cancer effects of metformin are associated with both direct (insulin-independent) and indirect (insulin-dependent) actions. Direct effects are linked to activation of AMPK and an inhibition of mTOR signalling, while indirect effects are mediated by reductions in circulating insulin levels, leading to reduced IR-activated PI3K signalling. We conducted a neoadjuvant, single arm, “window of opportunity” trial examining the clinical and biological effects of metformin on thirty-nine locoregional BC patients awaiting definitive surgery.

Methods: Non-diabetic women with newly diagnosed, untreated BC were given metformin 500 mg tid for ≥2 weeks post diagnostic core biopsy until surgery. Fasting blood and tumour samples were collected at diagnosis and surgery. Blood glucose and insulin were assayed to assess the physiologic effects of metformin, while IHC analysis of tumours was used to characterize cellular markers before and after metformin. Specifically, IR levels and the phosphorylation status of proteins involved in AMPK and PI3K/AKT/mTOR signalling, including AMPK (T172) and AKT (S473), were examined.

Results: 39 patients with a mean age of 51 years received metformin for a median of 18 days (range 13–40) with minor GI toxicities. The clinical effects (previously reported) included significant (p &lt; 0.05) decreases in body mass index (−0.5 kg/m2), weight (−1.2 kg), glucose (−0.14 mM) and HOMA (an estimate of insulin resistance, −0.21), and a decrease in insulin (−4.7 pmol/L) that approached significance (p = 0.0686). Ki67 staining in tumour tissue decreased significantly and TUNEL increased significantly. Levels of IR expression decreased significantly (from 4.39 to 3.82, p = 0.0375) as did the phosphorylation status of AKT (S473) and AMPK (T172) (from 9.82 to 7.08, p = &lt;0.0001; from 6.2 to 5.1, p = 0.0034, respectively).

Conclusions: Metformin impact was consistent with beneficial anti-cancer effects. Reduced AKT phosphorylation, coupled with decreased insulin and IR levels, suggest insulin-dependent effects are important in the clinical setting. Assessment of additional factors in BC cells, including OCT1 expression (required for metformin uptake), and the phosphorylation of ACC (a marker of AMPK activation), is underway and will be reported. Integrated analysis of these factors combined with the physiological and molecular data described above will further enhance understanding of metformin action in the clinical setting.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr PD03-05.

Abstract PD03-02: Evidence for the anti-cancer action of metformin mediated via tumor AMPK, Akt and Ki67, in a preoperative window of opportunity trial

Background: Metformin reduces the overall risk of cancer incidence by 31%, improves cancer-related mortality and enhances response to neoadjuvant chemotherapy in type 2-diabetics receiving metformin. There is evidence that metformin works through activation of Adenosine Monophosphate Protein Kinase (AMPK), an energy-sensing kinase that maintains cellular energy homeostasis. In a pre-operative window-of-opportunity randomized trial we have demonstrated that metformin significantly reduces proliferation and blunts the insulin response in primary operable breast cancer. This study further analysed cancer tissue from the trial to dissect the molecular mechanisms involved.

Methodology: Non-diabetic women with operable invasive breast cancer were randomised to receive pre-operative metformin or no drug. Forty seven patients had core biopsy at diagnosis then were randomized to metformin (metformin 500mg o.d. for 1 week increased to 1g b.d for a further week continued to surgery) or no drug, and 2 weeks later had core biopsy at surgery. Insulin receptor, phospho-AMPK (pAMPK), phospho-Akt (pAkt) and Ki67 immunohistochemistry was performed on formalin-fixed paraffin-embedded cores and scored blinded to treatment. Paired t-test was used for analysis.

Results: Significant up-regulation of pAMPK (p = 0.04) and down-regulation of pAkt (p = 0.04) in metformin treated patients was demonstrated compared to the control group. No change in insulin receptor expression was identified but, as previously reported, there was a fall in ki67. Changes were independent of Body Mass Index. Seven patients (7/24) receiving metformin withdrew because of gastro-intestinal upset and were excluded from the immunohistochemical analyses.

Conclusion: These findings suggest that metformin works in vivo in breast cancer patients via up-regulation of tumor pAMPK and down-regulation of pAkt and proliferation. Since down-regulation of pAMPK is a feature of breast cancer, this suggests mechanistic evidence for the therapeutic effect of metformin.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr PD03-02.