Reduced Risk Of Breast Cancer Research Articles

Breast Cancer Risk After Bariatric Surgery and Influence of Insulin Levels

Obesity and insulin are risk factors for breast cancer, and retrospective studies suggest bariatric surgery reduces breast cancer risk in women. However, long-term prospective data on breast cancer risk after bariatric surgery and the role of baseline insulin levels are lacking. To examine if bariatric surgery is associated with breast cancer incidence in women and if treatment benefit is modified by baseline insulin levels. The Swedish Obese Subjects (SOS) study was a nonrandomized intervention trial designed to investigate the long-term effects of bariatric surgery on obesity-related mortality and morbidity. Study recruitment took place between 1987 and 2001, and median (IQR) follow-up time was 23.9 years (20.1-27.1) years. The study was conducted at 25 public surgical departments and 480 primary health care centers in Sweden and included 2867 women aged 37 to 60 years and with body mass index 38 or greater (calculated as weight in kilograms divided by height in meters squared). In the surgery group (n = 1420), 260 women underwent gastric banding, 970 vertical banded gastroplasty, and 190 gastric bypass. The remaining contemporaneously matched control individuals (n = 1447) received usual obesity care. Breast cancer, the main outcome of this secondary report, was not a predefined outcome in the SOS study. Breast cancer events were identified in the Swedish National Cancer Registry. The study population comprised 2867 women with a mean (SD) age of 48.0 (6.2) years. During follow-up, there were 154 breast cancer events, 66 in the surgery group and 88 in the usual care group, and a decreased risk of breast cancer was observed in the bariatric surgery group (hazard ratio [HR], 0.68; 95% CI, 0.49-0.94; P = .019; adjusted HR, 0.72; 95% CI, 0.52-1.01; P = .06). The surgical treatment benefit on breast cancer risk was greater in women with baseline insulin levels above the median 15.8 μIU/L (HR, 0.48; 95% CI, 0.31-0.74; P = .001; adjusted HR, 0.55; 95% CI, 0.35-0.86; P = .008) compared to those below (HR, 0.95; 95% CI, 0.59-1.53; P = .84; adjusted HR, 1.01; 95% CI, 0.61-1.66; P = .97; interaction P = .02). This prospective clinical trial indicated a reduced risk of breast cancer after bariatric surgery in women with obesity. The surgical treatment benefit was predominantly seen in women with hyperinsulinemia. ClinicalTrials.gov Identifier: NCT01479452.

Mammographic density mediates the protective effect of early-life body size on breast cancer risk

The unexplained protective effect of childhood adiposity on breast cancer risk may be mediated via mammographic density (MD). Here, we investigate a complex relationship between adiposity in childhood and adulthood, puberty onset, MD phenotypes (dense area (DA), non-dense area (NDA), percent density (PD)), and their effects on breast cancer. We use Mendelian randomization (MR) and multivariable MR to estimate the total and direct effects of adiposity and age at menarche on MD phenotypes. Childhood adiposity has a decreasing effect on DA, while adulthood adiposity increases NDA. Later menarche increases DA/PD, but when accounting for childhood adiposity, this effect is attenuated. Next, we examine the effect of MD on breast cancer risk. DA/PD have a risk-increasing effect on breast cancer across all subtypes. The MD SNPs estimates are heterogeneous, and additional analyses suggest that different mechanisms may be linking MD and breast cancer. Finally, we evaluate the role of MD in the protective effect of childhood adiposity on breast cancer. Mediation MR analysis shows that 56% (95% CIs [32%–79%]) of this effect is mediated via DA. Our finding suggests that higher childhood adiposity decreases mammographic DA, subsequently reducing breast cancer risk. Understanding this mechanism is important for identifying potential intervention targets.

Making informed choices on incorporating chemoprevention into carE (MiCHOICE, SWOG 1904): Design and methods of a cluster randomized controlled trial

IntroductionWomen with atypical hyperplasia (AH) or lobular carcinoma in situ (LCIS) have a significantly increased risk of breast cancer, which can be substantially reduced with antiestrogen therapy for chemoprevention. However, antiestrogen therapy for breast cancer risk reduction remains underutilized. Improving knowledge about breast cancer risk and chemoprevention among high-risk patients and their healthcare providers may enhance informed decision-making about this critical breast cancer risk reduction strategy. Methods/designWe are conducting a cluster randomized controlled trial to evaluate the effectiveness and implementation of patient and provider decision support tools to improve informed choice about chemoprevention among women with AH or LCIS. We have cluster randomized 26 sites across the U.S. through the SWOG Cancer Research Network. A total of 415 patients and 200 healthcare providers are being recruited. They are assigned to standard educational materials alone or combined with the web-based decision support tools. Patient-reported and clinical outcomes are assessed at baseline, after a follow-up visit at 6 months, and yearly for 5 years. The primary outcome is chemoprevention informed choice after the follow-up visit. Secondary endpoints include other patient-reported outcomes, such as chemoprevention knowledge, decision conflict and regret, and self-reported chemoprevention usage. Barriers and facilitators to implementing decision support into clinic workflow are assessed through patient and provider interviews at baseline and mid-implementation. Results/discussionWith this hybrid effectiveness/implementation study, we seek to evaluate if a multi-level intervention effectively promotes informed decision-making about chemoprevention and provide valuable insights on how the intervention is implemented in U.S. clinical settings. Trial RegistrationNCT04496739

Abstract PO3-27-09: A Multidisciplinary Telehealth Approach to Breast Cancer Prevention in a Veteran Population

Abstract INTRODUCTION An estimated 13% of women will be diagnosed with breast cancer at some point in their lifetime. There are non-modifiable and modifiable risk factors including family history, genetics, obesity, and estrogen exposure. Interventions that reduce breast cancer risk and/or mortality include screening, chemoprevention, and lifestyle modification. A recent national survey shows that there are significant gaps in providing breast cancer prevention care for female Veterans. We describe the creation of a multi-disciplinary telehealth clinic aimed at reducing breast cancer risk in a high-risk female Veteran population. METHODS The breast cancer prevention clinic (BCPC) team consists of a medical oncologist, geneticist, genetic counselor, dietician, psychologist, and nurse navigator. High risk women are identified through a combination of screening questionnaires at annual mammography and genetics or primary care provider (PCP) evaluation, then referred to the clinic. Criteria for referral include age >=35, Gail 5 year risk >= 1.7%, Tyrer-Cuzick 10 year risk >= 5%, or history of thoracic radiation. At the BCPC telehealth visit, the medical oncologist makes individualized recommendations about chemoprevention by discussing the risks and possible complications of therapy. Use of screening magnetic resonance imaging (MRI) is also recommended to women with lifetime Tyrer-Cuzick score > 20%. Within the same visit, patients meet with a dietician to discuss nutrition modification, and a psychologist to address psychosocial barriers to lifestyle change. Those who start chemoprevention attend a 3 month follow-up with a nurse navigator to discuss tolerability and side effects. Subsequently, the patient’s PCP becomes responsible for management of chemoprevention and annual breast MRI. RESULTS Between January and December 2022, 33 patients were seen in BCPC. Patients had an average age of 52 years (range 42-70), Gail 5-year score of 2.53%, Tyrer-Cuzick 10-year score of 6.65%, and Tyrer-Cuzick lifetime score of 21.5%. Thirteen patients (39.4%) started chemoprevention, the majority of which were selective estrogen receptor modulators (SERM). Nine reported starting the medication at the 3 month follow-up appointment. The most reported side effect was hot flashes in 67%, although only the majority had mild symptoms. Three reported weight gain and one reported vaginal dryness. None reported worsening arthralgia or fatigue. Despite the low incidence of severe symptoms, only 3 continued to fill the medication at the time of chart review in August 2023. Twenty (60.6%) patients did not initiate chemoprevention. Four (20%) did not qualify due to cardiovascular or thrombotic risk factors, and three (15%) did not qualify due to concurrent use of hormone replacement therapy. Two (10%) elected not to start chemoprevention because they were planning for risk reducing mastectomies. Eleven (55%) did not initiate chemoprevention due to patient preferences and concern for side effects. Twenty-eight patients were recommended to obtain breast MRI in addition to mammogram for yearly screening. At time of chart review, 15 had at least one screening breast MRI ordered by PCP after BCPC visit, with 10 MRIs performed. CONCLUSIONS The unique interdisciplinary model of our breast cancer prevention clinic allows for a comprehensive and personalized evaluation for high-risk female Veterans on interventions to reduce their breast cancer risk. However, the current model does not ensure long-term compliance with these interventions. Studies have shown that more frequent/short-term follow up may improve compliance with endocrine therapies. Future directions include clinic expansion and providing additional follow-up with the multidisciplinary team to promote continued adherence to BCPC interventions. Citation Format: Hanqing Shang, Sarah Ansari, Shweta Dhar, Mahdieh Irranejadparizi, Stacey Edwards, Jessica Honkomp, Meagan Siehr, Bethany Aiena, Mary Nikityn, Diana Bearden, Deleene Menefee, Sita Bushan. A Multidisciplinary Telehealth Approach to Breast Cancer Prevention in a Veteran Population [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-27-09.

Abstract PO2-08-10: Effect of 6 months of bazedoxifene + conjugated estrogens on body composition and insulin resistance

Abstract Menopause transition is often marked by an acceleration of visceral fat accumulation. Excess visceral fat is associated with insulin resistance and increased risk for breast cancer as well as heart disease and diabetes. We measured change in body composition (via iDXA), fasting insulin and glucose as part of an ongoing, Phase IIB trial (NCT04821141) of 6 months of bazedoxifene (BZA) + conjugated estrogen (CE) vs control with primary endpoints of change in mammographic density and breast tissue Ki-67. Participants are women ages 45-60 with vasomotor symptoms at increased risk for development of breast cancer. Methods: Visceral and total fat, lean, and total mass, were measured with iDXA (GE CoreScan™). Fasting plasma was assayed same day as drawn for total insulin using a chemiluminescence assay and glucose using a hexokinase method. Values generated were used to calculate HOMA IR (as a measure of insulin resistance) using the formula insulin µl/ml x glucose mg/dl/405. HOMA %S was calculated as 1/HOMA IR X100 as a measure of insulin sensitivity. Optimal HOMA IR is considered as ≤1; HOMA IR >1.5 is considered abnormal with >2.0 as evidence of insulin resistance. Optimal HOMA %S is 100%. Results: 24 women (12 BZA+CE, 12 Control) have completed baseline and 6-month body composition and insulin resistance assessments. Women randomized to BZA+CE were more likely to experience reduction in insulin resistance and improved insulin sensitivity despite a small weight gain over the initial 6 months. 7/12 randomized to BZA+CE had ≥15% reduction in HOMA IR vs only 2/12 controls. Three participants had HOMA IR >2 at baseline. Of these, one was randomized to BZA+CE and had a normal HOMA IR value at 6 months. The remaining two women were in the control group and saw no improvement in HOMA IR at 6 months. In addition, one woman randomized to control with normal HOMA-IR at baseline had HOMA IR > 2 at 6 months. Next Steps: The improvements in insulin resistance parameters with BZA+CE are similar to those observed in our rodent studies, supporting this combination as promising for use in breast cancer risk reduction in women with vasomotor symptoms at high-risk for metabolic disease. Citation Format: Carol Fabian, Adrian Zelenchuk, Kandy Powers, Amy Kreutzjans, Krystal Pittman, Bill Hendry, Christy Altman, Erin Giles, Katherine L. Cook, Stephen Hursting, Bruce Kimler. Effect of 6 months of bazedoxifene + conjugated estrogens on body composition and insulin resistance [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-08-10.

Abstract PS07-08: Bazedoxifene plus conjugated estrogen reduces mammary proliferation markers and improves adipocyte size, gut microbiome, and metabolic health: Findings from a preclinical model of obesity and breast cancer risk

Abstract Background: Many women at high risk for breast cancer will not take tamoxifen or aromatase inhibitors for cancer prevention due to concern of side effects including hot flashes. Further, tamoxifen has detrimental metabolic effects in some overweight/obese women. Duavee®, a tissue-selective complex of bazedoxifene + conjugated estrogen, is FDA-approved for relief of hot-flashes and prevention of osteoporosis. Preclinical studies suggest favorable metabolic effects and potential for breast cancer risk reduction. In a single arm clinical trial, BZA+CE reduced Ki-67 and mammographic density (PMID: 31420361), and this combination is currently being assessed further in a Phase IIB trial of postmenopausal high risk women with vasomotor symptoms. Here, we examined the modifying effects of obesity on response to BZA+CE in a rodent model of obesity and breast cancer risk. Methods: Rats received carcinogen at 7-weeks of age to induce mammary tumors and were fed a high-fat diet (46% kcal fat) to promote obesity. Lean and obese rat were selected based on adiposity at 16 weeks. Separate cohorts of lean and obese ovary-intact or ovariectomized (OVX) rats were randomized to a daily dose of BZA+CE or placebo control for 8 weeks. We assessed tumor development throughout the study and end of study RNA from mammary glands was analysed by gene expression microarray (Affymetrix). We also analyzed body weight/composition, markers of metabolic health (circulating glucose, insulin, adiponectin), as well as changes in the gut microbiome (metagenomic sequencing on DNA isolated from baseline and end-of-study fecal samples) in response to BZA+CE. Results: BZA+CE improved metabolic health in both ovary intact and OVX rats, including reduced body weight and % body fat, particularly in the visceral regions. These effects were greater in obese rats compared to lean. BZA+CE reduced the number of large adipocytes and increased small (insulin sensitive) adipocytes in the mammary adipose, indicating benefical changes in local tumor microenvironment. We found no evidence that Duavee® promoted tumor development or growth in ovary-intact or OVX’d rats. Gene set enrichment analysis (GSEA) of microarray data showed enrichment of cell proliferation pathways in MG from obese rats and these same pathways were downregulated with BZA+CE, consistent with anti-cancer effects. Analysis of the microbiome found that BZA+CE increased proportional abudance of Odoribacter laneus in the gut, regardless of lean/obese or intact/OVX status. Previous studies have demonstrated that this bacterim improves glucose control and reduces inflammatory cytokines when administered to obese mice, suggesting a possible mechanistic link in this study. Conclusions: Unlike traditional SERMs that can have negative metabolic effects, BZA+CE improved whole body and mammary gland metabolic health and reduced expression of cell proliferation pathways, particularly in obese rats. Prelminary data suggest that changes in the gut microbiome could contribute, at least in part, to these effects. Together this supports BZA+CE (Duavee) as an agent with potential beneficial effects on breast cancer risk reduction and improvements in metabolic health in women with obesity. Further analyses will guide assessment of outcomes in an ongoing parallel clinical study in postmenopausal women at high risk for breast cancer. Citation Format: Katherine L. Cook, Ramsey Jenshcke, Karen Corleto, Carol Fabian, Stephen Hursting, Bruce Kimler, Danilo Landrock, Erin Giles. Bazedoxifene plus conjugated estrogen reduces mammary proliferation markers and improves adipocyte size, gut microbiome, and metabolic health: Findings from a preclinical model of obesity and breast cancer risk [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS07-08.

Abstract PO4-01-11: Ovarian function suppression (OFS) use beyond five years?: Young breast cancer patient preferences

Abstract Background. Breast cancer (BC) is the leading cause of cancer-related death in young women worldwide, and late recurrence of hormone receptor-positive disease plays a substantial role. Adjuvant endocrine therapy with 5 years of ovarian function suppression (OFS) and an aromatase inhibitor or tamoxifen is recommended for many young patients with high risk hormone receptor-positive BC. Data are limited regarding extended endocrine therapy among premenopausal BC survivors, and non-existent to inform treatment decisions regarding extending OFS beyond 5 years. We sought to evaluate young BC survivors’ perceptions and preferences regarding extending OFS beyond 5 years, and consideration of a potential future study to assess the role of extended OFS. Methods. From January-April 2023, email invites were sent to the Young Survival Coalition (YSC) listserv (N=14,291) specifically asking members with a history of invasive BC (≤45 years at diagnosis; stage I-III without metastatic recurrence) receiving OFS injections for adjuvant endocrine treatment to complete a one-time anonymous online survey. The survey was designed to capture information regarding current endocrine therapy use, patient-provider communication regarding extended endocrine therapy including OFS, OFS-related concerns (rating 0-5 [low: 0-1, moderate: 2-3, severe: 4-5]), and interest in a potential future clinical trial utilizing OFS beyond 5 years. Descriptive statistics were utilized to summarize responses, and two-sided Fishers exact tests and chi-square analyses were used for comparisons. Results. A total of 1,030 YSC members completed the survey, and 615 were analyzed due to eligibility and completeness of data. The majority were from the United States (n=579, 94.1%) or Canada (n=8, 1.3%), were non-Hispanic white (n=452, 73.5%), non-Hispanic Black (n=46, 7.5%), or Hispanic (n=43, 7.0%), and had been diagnosed with stage II BC (n=316, 51.4%). The average age at survey was 38.1 years (SD=5.15, range=22-54) and at initial BC diagnosis was 34.6 years (SD=4.96, range=20-49). Most (n=510, 83.0%) were within their first 5 years of OFS treatment while 14.5% (n=89) had already been receiving OFS for more than 5 years. Many respondents (n=344, 55.9%) reported discussing OFS use beyond 5 years with their provider, of whom 39.8% (n=245) reported their provider recommending they continue OFS for more than 5 years. Despite reporting moderate and severe concerns regarding OFS side effects (n=476, 77.4%), inconvenience of injection visits (n=272, 44.2%), and high cost of medication (n=223, 36.3%), most respondents (n=396, 64.4%) would consider continuing OFS beyond 5 years if it would reduce risk of BC recurrence. For nearly half of respondents (n=289, 47.0%) a risk reduction of at least 5% would be required for extended OFS to be worthwhile compared to the remaining 46.3% (n=285) who indicated interest for < 5% risk reduction. When asked hypothetically if they would take part in a clinical trial to determine efficacy of OFS use beyond 5 years, the majority were interested (n=357, 58.0%). Respondents who were interested were less likely to be concerned about the high cost of medication (p=0.003) however they were also less likely to take OFS beyond 5 years if it only led to 1-2% BC risk reduction (p=0.006) compared to those who were not interested. There were no other proportional differences on any other outcome. Conclusion. Many BC survivors and providers are already considering incorporation of OFS beyond 5 years into adjuvant endocrine therapy despite harboring concerns and lack of data. Efforts to determine the efficacy and benefits of extended OFS are necessary given the risk of late recurrence in this population as well as the potential for significant short- and long-term toxicities. The results from this survey study suggest that future clinical trials evaluating potential benefits and risks of long-term OFS use among young BC survivors are needed and likely feasible. Citation Format: Kate Dibble, Tal Sella, Kathryn Ruddy, Craig Snow, Amanda Nixon, Patricia Spears, Karla Ballman, Lisa Carey, Ann Partridge. Ovarian function suppression (OFS) use beyond five years?: Young breast cancer patient preferences [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-01-11.

Abstract SS02-02: Hormone Replacement and Alternatives for Relief of Vasomotor Symptoms in Women at Increased Risk for Breast Cancer

Abstract 70% of women will experience vasomotor symptoms sufficient to impact their quality of life during menopause transition and the early menopause. These symptoms are thought result from neurotransmitter imbalances resulting from ovarian hormone reductions and hypersecretion of gonadotropins. Increases in gonadotropins result in neurotransmitter triggered stimulation of the neurokinin 3 (NK3) receptor and thermoregulatory imbalance. Estrogen deficiency also reduces serotonin which can also trigger increases in hot flashes, and sleep disturbances. Vasomotor symptoms last on the average for 7 years until acclimation to persistent low estrogen levels occurs. Estrogen +/- progestin replacement therapy is associated with the greatest likelihood of vasomotor symptom relief as it reduces gonadotropin and NK3 receptor signaling and increases serotonin. Progestins also increase the neuroinhibitory transmitter gamma-aminobutyric acid (GABA) which improves sleep quality. There continues to be confusion on the part of providers and patients regarding the excess risk of breast cancer and thromboembolic events as these risks are affected by type of agent, route of delivery, age, duration of treatment, and presence of obesity. The majority of placebo controlled randomized clinical trial data on hormone replacement with estrogen or estrogen + a progestin comes from the Women’s Health Initiative (WHI) for women 50-79 in which oral conjugated estrogen (CE) 0.625 mg was used as the estrogen for women without a uterus and medroxyprogesterone acetate (MPA) was added to CE for women with a uterus to protect against endometrial hyperplasia and cancer. The median age at entry to WHI that trial was 63 and a substantial proportion had previously taken hormones. Large longitudinal cohort studies have been helpful in assessing risks in women starting hormones at a more clinically relevant age (45-55) and with hormonal preparations other than oral CE and MPA. Five to seven years of estrogen alone results in minimal if any increased risk for breast cancer. However, combined estrogen+ progestin replacement for women over 50, necessary for women with a uterus, results in an ~ 30 % relative increased risk for breast cancer if taken for up to 5 years and a doubling of risk with 10 years of treatment. So called bioidentical hormones often compounded as oral troches of estradiol, progesterone, and testosterone, are also associated with increased breast cancer risk. Vaginal hormones have not been found to increase risk for breast cancer. Increased risk of thromboembolism is predominately observed in women over 50 using oral as opposed to transdermal preparations. Increased risk for stroke and dementia was observed in the WHI again with oral hormones in women over 65. In the WHI there was no increase in cancer related, cardiovascular or overall mortality with estrogen or estrogen and progestin. For high-risk peri and post-menopausal women with who would like to reduce/alleviate their vasomotor symptoms with no increase in risk for breast cancer there are several options: 1) the tissue selective estrogen complex bazedoxifene (BZA) combined with conjugated estrogen (CE) 2) the non-hormonal option of NK3 receptor antagonists such as fezolinetant ( 3) non-hormonal options of gabapentin, selective serotonin reuptake inhibitors (SSRI) and serotonin and norepinephrine uptake inhibitors (SNRI). BZA and CE and fezolinetant are reported to reduce hot flashes in 70% or more of individuals with paroxetine effectiveness reported as 50%. All three are FDA approved for reduction of vasomotor symptoms. The combination of BZA and CE is also being investigated for breast cancer risk reduction. These agents differ with respect to side effects with increased risk of blood clots for bazedoxifene and conjugated estrogen, increased risk of nausea, diarrhea, and liver dysfunction for fezolinetant and drowsiness and dry mouth for SSRIs. Drug costs may also dramatically affect insurance coverage and patient uptake of a particular strategy. A recent online perusal of a popular site for finding the lowest drug price suggested substantial differences in the cost of drugs for relief of vasomotor symptoms. The approximate cost for a 30- day supply of oral estradiol was $30, estradiol transdermal patches $35, oral progesterone $15, combined estradiol and levonorgestrel transdermal patches $240, oral CE $200, oral CE + medoxyprogesterone acetate $240, and for BZA+ CE $200. For non-hormonal therapies the cost of 30 days of gabapentin was $11, paroxetine $30 and fezolinetant $550. Crandall, Mehta, and Manson JAMA 2023 329:405-420 Collaborative Group on Hormonal Factors in Breast Cancer Lancet 2019 394: 1159-1168 Fabian et al Ca Prev Res 2019 10:711-720 Modi and Dhillo Neuroendocrinology 2019 109:242–248 Citation Format: C. Fabian. Hormone Replacement and Alternatives for Relief of Vasomotor Symptoms in Women at Increased Risk for Breast Cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr SS02-02.

Abstract PS07-01: Exemestane and breast cancer prevention: how low can we go? Drug and biomarker tissue levels in a randomized presurgical trial on exemestane alternative dosing regimen

Abstract Exemestane is an effective drug to reduce breast cancer risk reaching an overall 65% reduction in breast cancer in the placebo–controlled phase III MAP.3 trial. To improve its acceptability in primary prevention programs, we are seeking the minimal effective dose. In a 3-arm presurgical trial of 4-6 weeks before breast surgery in 180 postmenopausal women with ER-positive breast cancer, we investigated the activity of alternative exemestane schedules: 25 mg per day (QD), 25 mg three times/week (TIW) or 25 mg per week (QW) and showed that in adherent participants TIW was not inferior to QD in reducing circulating estradiol (Serrano et al JAMA Oncol. doi:10.1001/jamaoncol.2023.0089). Moreover, Ki67 reduction was seen in all arms with no significant difference among arms. Here, we analyzed the concentration of sex steroids, exemestane, and its main metabolite in the cancer and adjacent non-cancerous breast tissue. Tissues samples were homogenized before liquid-liquid extraction. After reconstitution, samples were analyzed by coupling liquid chromatography with tandem mass spectrometry (Sciex QTRAP 6500, Nexera system, Shimadzu). We obtained breast cancer tissue from 93 and non-cancerous breast tissue from 117 participants to measure exemestane, 17-OH-exemestane, and sex steroids. Exemestane and 17-OH-exemestane concentrations were detectable only in the QD arm, while in TIW and QW arms levels were below the Lower Limit of Detection (< LLD). Median exemestane level was 3807 fmol/g and 17485 fmol/g and median 17-OH-exemestane level was 338 fmol/g and 1343 fmol/g in cancer and non-cancerous tissue, respectively. Interestingly, drug and its metabolite accumulated 4-5-fold in non-cancerous tissue compared to cancer tissue in the QD arm. Despite the between-arm drug concentration difference, estradiol was almost completely suppressed in all arms in the non-cancerous tissue, attaining level < LLD in QD and TIW arms, and barely detectable in QW arm. The median in the QW arm was < LLD (< LLD, interquartile range < LLD, 25.5 fmol/g) showing no differences in QD vs TIW and QD vs QW (p = 0.364 and p = 0.693 respectively). While a dose-response trend was observed in cancer tissue, estradiol level was < LLD (< LLD,52.2 fmol/g) on QD, 17.1 (< LLD, 125.3) on TIW, and 128 (< LLD, 224.8) on QW (p=0.046 QD vs TIW arms). Estrone showed a clear dose response trend among arms, whereas no differences were observed for testosterone and androstenedione for both cancer and non-cancerous tissue in all arms. The Ki-67 change was analyzed in the previous paper; here we report the data for those patients who had drug and hormones tissue concentration measured, where Ki-67 decreased in all arms: median Ki67 change from baseline was QD -8 (-10, -3), TIW -6 (-11, -2), QW -4 (-8, -1). Conclusions: Exemestane 25 mg three times a week maintains comparable activity to the standard dose on tissue estradiol suppression and Ki67 decrease. Considering the estradiol suppression in non-cancerous tissue of the lowest exemestane dose, QW might even be considered for breast cancer risk reduction in primary prevention. Further analyses are ongoing to investigate the correlation with other biomarkers including the role of polymorphic UGT2B17 genotype that could identify candidates to lower exemestane dosage. Citation Format: Davide Serrano, Harriet Johansson, Bjørn-Erik Bertelsen, Gunnar Mellgren, Parijatham Thomas, Katherine Crew, Nagi B Kumar, Debora Macis, Valentina Aristarco, Aliana Guerrieri Gonzaga, Sara Gandini, Mauro D’Amico, Tania Buttiron Webber, Irene Maria Briata, Stefano Spinaci, Viviana Galimberti, Giuseppe Viale, Lana A. Vornik, Eduardo Villar-Sanchez, Powel Brown, Brandy M Heckman-Stoddard, Eva Szabo, Bernardo Bonanni, Andrea De Censi. Exemestane and breast cancer prevention: how low can we go? Drug and biomarker tissue levels in a randomized presurgical trial on exemestane alternative dosing regimen [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS07-01.

A novel preclinical model of the normal human breast

Improved screening and treatment have decreased breast cancer mortality, although incidence continues to rise. Women at increased risk of breast cancer can be offered risk reducing treatments, such as tamoxifen, but this has not been shown to reduce breast cancer mortality. New, more efficacious, risk-reducing agents are needed. The identification of novel candidates for prevention is hampered by a lack of good preclinical models. Current patient derived in vitro and in vivo models cannot fully recapitulate the complexities of the human tissue, lacking human extracellular matrix, stroma, and immune cells, all of which are known to influence therapy response. Here we describe a normal breast explant model utilising a tuneable hydrogel which maintains epithelial proliferation, hormone receptor expression, and residency of T cells and macrophages over 7 days. Unlike other organotypic tissue cultures which are often limited by hyper-proliferation, loss of hormone signalling, and short treatment windows (< 48h), our model shows that tissue remains viable over 7 days with none of these early changes. This offers a powerful and unique opportunity to model the normal breast and study changes in response to various risk factors, such as breast density and hormone exposure. Further validation of the model, using samples from patients undergoing preventive therapies, will hopefully confirm this to be a valuable tool, allowing us to test novel agents for breast cancer risk reduction preclinically.

Abstract PO4-19-02: Genetic risk estimation in breast cancer and assessing health disparities

Abstract Background: Breast Cancer (BC) incidence and the distribution of BC risk factors vary between racial and ethnic groups within the United States. It has been demonstrated that providing education on individualized breast cancer risk will improve patient uptake to recommended BC screening and prevention strategies. Most clinical risk assessment tools, including the validated IBIS model were derived from data using non-Hispanic white women. Consortia have also now identified over 300 common genetic susceptibility loci for BC, summarized by the polygenic risk score (PRS). When combined with clinical risk assessment tools, such as the IBIS or BCRAT models, the PRS can further refine risk estimation for patients. To date, most studies on the use of PRS have been done in non-Hispanic white women. While these PRS still perform well in racial minorities, there has been a recognized need to improve racial and ethnic diversity in genomic research cohorts. Herein, we aim to combine clinical risk assessment models that are already used in routine clinical practice with information derived from PRS testing in women of racial minorities to determine if this can improve risk estimation, patient understanding, and uptake to recommended breast cancer screening and prevention strategies. Design: This is a minimal risk prospective study with a single arm incorporating the PRS into a standard breast cancer risk reduction consultation, followed by annual surveys over 10 years to determine if and how the information provided by the PRS influenced patient decisions regarding recommended BC screening and prevention. Patients will have IBIS and BCRAT risks calculated at baseline visit. A survey of patient perceptions/understanding of risk, intention to undergo screening, and use of preventive medicine is completed after baseline visit prior to receiving the PRS results. Blood sample is obtained at baseline and DNA samples are analyzed for approximately 300 SNPs on a custom-designed, targeted SNP panel from ThermoFisher Scientific by the Mayo Clinic Genomics Laboratory. This PRS result is then combined with the clinical risk assessments (IBIS and BCRAT scores) using the R package Individualized Coherent Absolute Risk Estimators (iCare) tool to provide a new estimate of breast cancer risk for 5year, 10year, and lifetime risk. Patients are seen for follow-up to review results and then complete a second survey to assess their understanding of the results, BC risk, and how the PRS impacted their decision to undergo screening/prevention strategies. Eligibility Criteria: Women who self-identify as African American/Black or Hispanic/Latinx between 30-75 years old with any of the following: 1.)IBIS score of ≥5% for the 10 year risk OR BCRAT score of ≥ 3 % for the 5 year risk. 2.) History of biopsy proven atypical hyperplasia 3.) History of biopsy proven lobular carcinoma in situ. Specific Aims: Aim 1: The primary aim of this study is to explore if the addition of PRS to the BCRAT and IBIS score will improve intentions to undergo recommended breast cancer screening strategies such as mammography, MRI, or molecular breast imaging in women of underserved racial minorities Aim 2: To explore if the addition of the PRS to the BCRAT and IBIS risk score will aid women of racial minorities in deciding whether to take preventative endocrine therapy. Aim 3: To understand how individualized risk assessment and information on PRS may alter perceived risk of breast cancer. Statistical Methods Analysis will be mostly descriptive. Continuous variables will be summarized as mean (standard deviation) or median (range) and categorical variables will be reported as frequency (percentage). Kaplan-Meier method will be used to estimate the long-term cumulative risk of cancer. Current Accrual: 3. Target Accrual: 50 Citation Format: Lauren Cornell, Sandhya Pruthi, Linda Hasadsri, Sarah McLaughlin. Genetic risk estimation in breast cancer and assessing health disparities [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-19-02.

Abstract PS07-07: The RXR agonist, IRX4204, delays the formation of Brca1 mutant mammary tumors via modulation of the anti-tumor immune response

Abstract Background: Women with germline BRCA1 mutations are at an increased risk for developing breast cancer in their lifetime, often at a young age with more aggressive tumors. At present, prophylactic bilateral mastectomy is the most effective strategy for reducing breast cancer risk. However, this invasive procedure is irreversible and associated with potential complications. We and others have found that PARP inhibitors can delay Brca1-mutant tumor formation in mice and could be beneficial for the prevention of breast cancer. However, currently available PARP inhibitors are associated with modest toxicities that may not be acceptable to women without cancer. Thus, there remains an urgent need for the development of safe and effective therapies for the prevention of breast cancer. Here, we present data demonstrating the activity of IRX4204, a minimally toxic and highly specific agonist of the nuclear retinoid X receptor (RXR), to delay the formation of mammary tumors in a Brca1-deficient mouse model. This inhibitory effect on tumor growth is due, in part, to the role of IRX4204 in stimulating the anti-tumor immune response. Methods: We used the established MMTV-Cre, conditional Brca1 gene knockout, p53 heterozygous loss mouse model (BRCA1co/co; MMTV-Cre+/+; p53+/-) and selected for mutant female pups using PCR genotyping. At 16 weeks of age, all mice were separated into 4 treatment groups (n=10 per group): (1) sesame oil control; (2) the novel RXR agonist, IRX-4204 (10mg/kg); (3) high-dose IRX4204 (20 mg/kg); and (4) the RXR agonist, 9-cis-UAB-30 (5 mg/kg). All treatments were given by oral gavage five days per week, and mice were observed daily for tumor formation and toxicity. At the study endpoint, tumors and normal mammary glands were collected for additional analyses. Immunohistochemical staining was used to quantify CD8a, Ki-67 and cleaved caspase 3 expression in Brca1-deficient tumors. Oil Red O staining was used to measure changes in lipid accumulation in Brca1-deficient cell lines treated with IRX4204. qPCR was used to quantify the changes in gene expression of lipid metabolism-associated genes upon treatment with IRX4204 in vitro. Results: Vehicle-treated Brca1-deficient mice had a median time-to-tumor formation (TTF) of 211 days, with 100% developing tumors by 330 days. Mice treated with UAB 5 mg/kg had an improved median TTF of 261 days, whereas mice treated with IRX4204 10mg/kg or 20mg/kg had a median TTF of 347 and 304 days, respectively (p &amp;lt; 0.01). In addition, 60% of mice treated with IRX4204 10 mg/kg remained tumor-free at 330 days. IRX4204-treated tumors showed an increased infiltration of CD8-positive T-cells over vehicle-treated tumors (p &amp;lt; 0.05). Treatment of Brca1-deficient cell lines with IRX4204 in vitro resulted in a significant increase in lipid accumulation accompanied by a 2-fold increase of Srebf1 expression (a key transcription factor that regulates lipid homeostasis) within 24 hours of treatment (p &amp;lt; 0.05). Conclusion: These data demonstrate a novel use of the RXR agonist, IRX4204, to delay the formation of Brca1-deficient mammary tumors. We have found that IRX4204 treatment modulates the tumor immune response through increased infiltration of cytotoxic CD8-positive T-cells in Brca1-deficient mammary tumors in vivo. We have also determined that IRX4204 modulates lipid metabolism in breast cancer cell lines in vitro. It is known that lipid-derived antigens can stimulate T-cell activity. Our findings suggest that RXR agonists may alter lipid antigen production to activate an anti-tumor response. Additional immune and lipidomic studies are on-going. This work was supported by NCI-PREVENT grant (to PB and AM HHSN26100008) and CFP Foundation (Odyssey Fellowship to CM). Citation Format: Cassandra Moyer, Darian Coleman, Jamal Hill, Lana A. Vornik, Michelle Savage, Martin Sanders, Sei Shizuko, Altaf Mohammed, Powel Brown, Abhijit Mazumdar. The RXR agonist, IRX4204, delays the formation of Brca1 mutant mammary tumors via modulation of the anti-tumor immune response [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS07-07.

Pilot of lifestyle intervention to reduce breast cancer risk (PIONEER): A randomised study

Pilot of lifestyle intervention to reduce breast cancer risk (PIONEER): A randomised study

Association Between Polymorphisms in DNA Damage Repair Pathway Genes and Female Breast Cancer Risk.

Breast cancer risk have been discussed to be associated with polymorphisms in genes as well as abnormal DNA damage repair function. This study aims to assess the relationship between genes single nucleotide polymorphisms (SNPs) related to DNA damage repair and female breast cancer risk in Chinese population. A case-control study containing 400 patients and 400 healthy controls was conducted. Genotype was identified using the sequence MassARRAY method and expression of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor-2 (HER-2) in tumor tissues was analyzed by immunohistochemistry assay. The results revealed that ATR rs13091637 decreased breast cancer risk influenced by ER, PR (CT/TT vs. CC: adjusted odds ratio [OR] = 1.54, 95% confidence interval [CI]: 1.04-2.27, p = 0.032; CT/TT vs. CC: adjusted OR = 1.63, 95%CI: 1.14-2.35, p = 0.008) expression. Stratified analysis revealed that PALB2 rs16940342 increased breast cancer risk in response to menstrual status (AG/GG vs. AA: adjusted OR = 1.72, 95%CI: 1.13-2.62, p = 0.011) and age of menarche (AG/GG vs. AA: adjusted OR = 1.54, 95%CI: 1.03-2.31, p = 0.037), whereas ATM rs611646 and Ku70 rs132793 were associated with reduced breast cancer risk influenced by menarche (GA/AA vs. GG: adjusted OR = 0.50, 95%CI: 0.30-0.95, p = 0.033). In a summary, PALB2 rs16940342, ATR rs13091637, ATM rs611646, and Ku70 rs132793 were associated with breast cancer risk.

Statin use as a moderator on the association between metformin and breast cancer risk in women with type 2 diabetes mellitus

IntroductionMetformin and statins are considered as potential agents for prevention of breast cancer, however, existing evidence does not uniformly substantiate this claim, and the data is scarce concerning their interaction in relation to breast cancer risk. This study aims to investigate whether the effect of metformin on breast cancer incidence varied by statin use among women with type 2 diabetes mellitus (T2DM).MethodsThis study included women with T2DM, without a history of cancers, and followed up for more than one year from the Zwolle Outpatient Diabetes project Integrating Available Care (ZODIAC) for the period 1998–2014. The dataset was structured using a person-time approach, where the cumulative medication usage was annually updated for each person. The extended Cox proportional hazards models were employed, reporting adjusted hazard ratios (HR) with 95% confidence intervals (CI).ResultsDuring a median follow-up of 5 years, 515 of 29,498 women received a breast cancer diagnosis. Each additional year of metformin or statins use corresponded to a decrease in breast cancer incidence, while the magnitude attenuated over time. Noteworthily, statin use modified the effect of metformin on breast cancer incidence. For instance, after 5 years of follow-up, one-year increase of metformin use among women who used statins for 3 years was linked to a substantially reduced breast cancer risk (HR, 95% CI: 0.88, 0.84–0.93), however, there was no significant decrease in risk for those non-statins users (HR, 95% CI: 0.96, 0.89–1.04).ConclusionsExtending metformin or statin usage by one year conferred breast cancer protection in women with T2DM. Enhanced protective effect of metformin was observed among those who also use statins. These results suggest the potential of combined metformin and statin therapy as promising breast cancer prevention strategies.

Recreational physical activity and breast cancer risk by menopausal status and tumor hormone receptor status: results from the Nurses' Health Studies.

Physical activity is associated with lower breast cancer risk, especially in postmenopausal women. Associations in premenopausal women are less well established. We evaluated recreational physical activity and breast cancer risk in the Nurses' Health Study (NHS) and NHSII (187,278 women; n = 12,785 breast cancers; follow-up: NHS = 1986-2016, NHSII = 1989-2017) by menopausal status and estrogen (ER) and progesterone (PR) receptor status. Physical activity was evaluated as updated cumulative average of metabolic equivalent of task (MET)-h/week. Cox proportional hazards models were used to estimate multivariable hazard ratios (HR) and 95% confidence intervals (CI). Recreational physical activity was inversely associated with breast cancer risk in pre- and postmenopausal women. Higher activity levels were associated with lower risk of ER+/PR + breast cancer in both pre- and postmenopausal women (e.g., total recreational activity, ≥ 27 vs < 3 MET-h/week, premenopausal HR = 0.83, 95%CI = (0.70-0.99), postmenopausal HR = 0.86 (0.78-0.95); pheterogeneity = 0.97). Results were attenuated with adjustment for current body mass index (BMI) among postmenopausal, but not premenopausal, women (e.g., ≥ 27 vs < 3 MET-h/week, premenopausal HR = 0.83 (0.69-0.98); postmenopausal HR = 0.95 (0.85-1.05); pheterogeneity = 0.99). In analyses of moderate-vigorous activity and breast cancer risk, no heterogeneity by menopausal status was observed (phet ≥ 0.53; e.g., ≥ 27 vs < 3 MET-h/week, ER+/PR+,premenopausal HR = 0.88 (0.69-1.11); postmenopausal HR = 0.71 (0.58-0.88). No associations were observed for ER-/PR- disease. Recreational physical activity was associated with lower breast cancer risk in both pre- and postmenopausal women, supporting recreational physical activity as an accessible, modifiable exposure associated with reduced breast cancer risk regardless of menopausal status.

Nutrition Knowledge, Attitudes, and Lifestyle Practices That May Lead to Breast Cancer Risk Reduction among Female University Students in Lebanon.

Research has identified both nonmodifiable and modifiable risk factors for breast cancer (BC), with accumulating evidence showing that adopting adequate dietary practices could decrease the risk of this disease. This study aimed to assess nutrition knowledge, attitudes, and lifestyle practices (KAP) that may lead to BC risk reduction among female university students in Lebanon and examine the determinants of their practices. A cross-sectional survey was conducted using a convenience sampling method, comprising 356 (response rate: 71.2%) female students at the American University of Beirut aged 18 to 25 years with no history of BC. Participants completed a pre-tested questionnaire addressing the objectives of the study. The modified Bloom's cut-off of 75% was used to categorize knowledge and practice scores as poor or good and attitudes as negative or positive. Large proportions of students had poor knowledge (68.3%), negative attitudes (65.4%), and poor practices (98.0%) scores. Pursuing a health-related major and having a higher GPA were associated with better knowledge and attitudes while being older and having a lower degree of stress were associated with positive attitudes only. Having a lower body mass index (BMI) was associated with better practice scores. Better knowledge significantly predicted higher intake of fruits and vegetables. Overall knowledge and attitudes were significantly correlated with each other, but neither was significantly correlated with overall practice. These findings underscore the importance of implementing public health programs geared towards improving nutrition KAP that may lead to BC risk reduction.

Abstract 3407: Physical activity and post-menopausal breast cancer in the Multiethnic Cohort Study

Abstract Much research has been conducted on the relationship between physical activity and breast cancer, with meta-analyses showing 10 – 21% reduction in breast cancer risk for postmenopausal women with high compared to low level of physical activity. However, few studies have explored this relationship in non-Caucasian women. We analyzed data from 74,177 post-menopausal African American, Caucasian, Japanese American, Latina, and Native Hawaiian women in the Multiethnic Cohort in Hawaii and California. Data on physical activity (hours and metabolic equivalents (METs)) was based on a self-administered questionnaire at baseline (1993–1996). Multivariate Cox proportional hazards models provided estimates of hazard ratios (HRs) and 95% confidence intervals (CIs) adjusted for risk factors. We observed no associations between breast cancer risk and hours of moderate/vigorous activity per week (HR=1.01, 95% CI: 0.91-1.10, Ptrend=0.71), MET-hours of moderate/vigorous activity per week (HR=1.03, 95% CI: 0.94-1.13, Ptrend=0.92), and total METs-measured as average MET level per day multiplied by 7 (HR=0.94, 95% CI: 0.86-1.03, Ptrend=0.37) when comparing the highest quartile to the lowest. When examining the data across race/ethnicity, we observed a reduction in risk of breast cancer for total METs (HR=0.75, 95% CI: 0.61-0.94, Ptrend=0.05) among Latina women. Analysis across strata of BMI showed no differences across subgroups. In this study, we did not observe any consistent protective association between physical activity and breast cancer risk. Citation Format: Jasmeet K. Gill, Gertraud Maskarinec, Song-Yi Park, Lynne Wilkens, Loic Le Marchand. Physical activity and post-menopausal breast cancer in the Multiethnic Cohort Study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3407.

Abstract 778: Atorvastatin modulates serum biomarkers in women at increased risk for breast cancer

Abstract Background Tamoxifen and Aromatase inhibitors have been shown to be highly effective at reducing the incidence of ER-positive breast cancers in women at increased risk, but there are no approved agents for the risk reduction of ER-negative cancers. Evidence from observational and preclinical studies supports the study of statins for breast cancer risk reduction. Objective This study aimed to investigate the effects of Atorvastatin treatment on serum and tissue biomarkers in women at increased risk for breast cancer. Methods Women at increased risk for breast cancer were accrued prospectively at UTMDACC, Breast Medical Oncology High-Risk Clinic. The study was approved by the IRB and all participants signed informed consent. High risk was defined as having a previous history of DCIS, LCIS, or atypical hyperplasia, 5-year projected Gail risk &amp;gt;1.67 %, or lifetime risk &amp;gt;20 % calculated by clinical models. Patients were randomized to no treatment (n=15) or daily 10mg (n=15), 20mg (n=14), or 40mg (n=16) Atorvastatin for 3 months. Fasting blood and breast tissue samples via fine needle aspiration (FNA) were collected at baseline and at study completion. Serum biomarkers were analyzed with ELISA (R&amp;D Systems). The IGF1/IGFBP3 molar ratio was calculated using [IGF1 (ng/mL) x 0.13]/[IGFBP-3 (ng/mL) x 0.035]. The Wilcoxon matched-pairs signed rank test was used to determine significance. Results Tissue biomarker evaluation was previously reported. Serum biomarker levels of IGF1 and its main binding proteins IGFBP1 and IGFBP3 were compared in baseline and post-intervention samples by ELISA analysis. The average change in serum IGF1 (ng/mL) levels between pre- and post-treatment samples (represented as average difference with interquartile range) was +3.5 (-16.8 to 8.7) p=0.98, -0.6 (-23.6 to 15.4) p=0.64, -1.76 (-27.7 to 28.6) p=0.81, and +2.6 (-14.5 to 32.2) p=0.67 in the 0, 10, 20, and 40mg groups respectively. The average change in serum IGFBP1 (pg/mL) was -23.2 (-2372 to 4487) p=0.33, -480 (-4567 to 3008) p=0.72, 429 (-1259 to 3039) p=0.54, and -250 (-3581 to 2492) p=0.94 in the 0, 10, 20, and 40mg groups. The average change in serum IGFBP3 (ng/mL) was -24 (-193 to 98) p=0.72, -119 (-353 to 111) p=0.17, -190 (-433 to 14) p=0.07, and -234 (-369 to -79) p=0.002 in the 0, 10, 20, and 40mg groups. Serum IGF1/IGFBP3 molar ratio was +0.012 (-0.018 to 0.026) p=,0.76, +0.0065 (-0.013, to 0.047) p=0.53, +.0073 (-0.036 to 0.045) p=0.86, and +.027 (-.011 to .062) p=0.058 in the 0, 10, 20, and 40mg groups. Conclusions Serum IGFBP3, which has been associated with breast cancer risk, was decreased in a dose-dependent manner in patients treated with Atorvastatin. The IGF1/IGFBP3 molar ratio was increased in the 40mg group, although not statistically significant (p=.0577). This shows that treatment with Atorvastatin induced changes in circulating biomarkers and that Atorvastatin could be further studied in larger prospective breast cancer prevention trials. Citation Format: Amanda L. Lanier, Johannes Fahrmann, Fatma N. Mustafayev, Angelica Gutierrez Barrera, Powel H. Brown, Banu Arun. Atorvastatin modulates serum biomarkers in women at increased risk for breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 778.

Abstract 2189: Tirzepatide mitigates obesity-associated metabolic dysregulation and tumor progression in a mouse model of triple-negative breast cancer

Abstract Obesity is an established risk factor for breast cancer. Dietary and surgical weight loss interventions reduce breast cancer risk but have significant limitations to their widespread use as anticancer strategies. Incretin-based pharmaceuticals safely and effectively promote weight loss, but whether these drugs exert similar protective effects against cancer is unknown. Here we test whether weight loss induced by the glucagon-like peptide 1 (GLP-1)/glucose-dependent insulinotropic polypeptide (GIP) receptor agonist tirzepatide limits tumor growth in an orthotopic mouse model of triple-negative breast cancer. Ten-week-old female C57BL/6NCrl mice were randomized to either a 10 kcal% low-fat diet (control; n=14) or 60 kcal% high-fat diet to promote diet-induced obesity (DIO; n=43). After 18 weeks on diet, DIO mice were randomized by body weight to either i) remain on the high-fat diet (DIO; n=15); ii) lose weight with tirzepatide (TZP; n=13); or iii) lose weight with 30% daily calorie restriction relative to control mice (CR; n=15). All mice were subcutaneously injected with either TZP or vehicle every other day for 13 weeks with the following escalating dosing schedule: 3 nmol/kg TZP in week 1; 10 nmol/kg TZP in weeks 2-3; 20 nmol/kg TZP in weeks 4-7; 30 nmol/kg TZP in weeks 8-11; and 40 nmol/kg TZP in weeks 12-13. Fasting blood glucose and body composition was assessed after 9 weeks of weight loss, and 35,000 E0771 cells were orthotopically transplanted into the 4th mammary fat pad. Tumors growth was monitored for 4 weeks. TZP-treated mice lost on average &amp;gt;20% weight loss by week 4 and remained at or below 20% weight loss for the remainder of the study. Directly prior to E0771 tumor cell injections, TZP-treated mice had lost 23.6±8.9% body weight, versus 39.7±3.6% in CR mice. Relative to DIO mice, blood glucose control was restored in both weight loss groups (DIO: 149.5±18.5 mg/dl; TZP: 124.5±15.5 mg/dl; CR: 107.6±18.8 mg/dl) and &amp;gt;87.5% of the lost weight was attributed to fat mass, rather than lean mass, for TZP-treated and CR mice. Notably, tirzepatide suppressed tumor growth relative to DIO, but the CR group had a greater anticancer effect than TZP. Reduced tumor mass in both weight loss groups was accompanied by a significant reduction in circulating IGF-1, insulin, and leptin relative to DIO mice. These findings are timely and important because i) obesity is a highly prevalent metabolic disease that increases risk and progression of breast cancer and &amp;gt;13 other cancers; ii) incretin therapies, which show promise as highly effective weight loss drugs, are increasingly being prescribed; and iii) the tumor suppressive effects of tirzepatide described herein newly suggest incretin agonism as another propitious option for breaking the obesity-cancer link. Citation Format: Elaine M. Glenny, Alyssa N. Ho, Violet A. Kiesel, Fangxin Chen, Claire E. Gates, Evan M. Paules, Ruihan Xu, C. Alex Holt, Michael F. Coleman, Stephen D. Hursting. Tirzepatide mitigates obesity-associated metabolic dysregulation and tumor progression in a mouse model of triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2189.