Incident Breast Cancer Research Articles

Abstract PO3-08-07: Licochalcone A as a risk reducing agent against luminal and non-luminal breast cancers

Abstract Background: Breast cancer risk reducing drugs with proven efficacy have adverse side effects, significantly minimizing their uptake and impact. Further, they do not prevent ER- breast cancer. Effective alternative strategies with lower toxicity are needed. Previously, we have shown that licochalcone A (LicA) suppresses aromatase expression and activity, enhances the activity of detoxifying enzymes, and reduces estrogen genotoxic metabolism in cell lines and animal models. These data led us to hypothesize that LicA creates a tumor preventive environment in the breast by reprogramming metabolism and antioxidant/anti-inflammatory responses in the breast leading to decreased proliferation and tumor suppression. We now report on the breast tumor preventive effects of LicA in xenograft models, its oral bioavailability, and its biologic effects on human breast microstructures from women at increased risk of breast cancer. Methods: We prepared microstructures from the fresh tissue of contralateral unaffected mastectomy specimens of 6 postmenopausal women with incident unilateral breast cancer. After exposing them to DMSO (control) or LicA (5 µM), we performed total RNA sequencing. Differentially expressed genes were identified and analyzed by gene ontology and pathway membership. The RNA-seq data was also utilized to conduct metabolism flux analysis. Combined enrichment scores > 4 and FDR < 0.05 was considered significant. The NanoString metabolism panel was employed in 6 additional subjects. We performed live cell imaging to monitor proliferation of pre-malignant DCIS.COM, DCIS.COM/ER+ PR+; and malignant MDA-MB-231 (ER- PR-), MCF-7 (ER+ PR+), MCF-7aro, and BRCA1 defective HCC-1937, and HCC3153 cells. Xenograft models of MCF-7aro and MDA-MB-231 tumors were established in female nude mice and the animals treated for 28 days with vehicle or LicA (80 mg/kg.day, s.c.). We measured the rate of tumor growth. We also conducted a PK/PD study with oral LicA (100 mg/kg) in intact BALB/c female mice. Results: We observed significant (FDR < 0.05) upregulation of antioxidant genes (up to 8-fold), consistent with upregulation of NRF2 and the thioredoxin system, the major regulators of antioxidant pathways. This was accompanied by significant downregulation of RELA- and NF-kB1-dependent inflammatory pathways. In addition, we observed decreased expression of PI3K-AKT genes and the pro-adipogenic transcription factors SREBF1 and SREBF2, which may explain the downregulation (4 to 32-fold) of cholesterol biosynthesis and transport, and lipid metabolism genes. Metabolism studies confirmed these data and demonstrated a robust increase in the pentose phosphate shunt and NAD(P)H generation without enhancing ribose 5 phosphate formation, suggesting an antioxidant and anti-proliferative environment. LicA also suppressed proliferation of pre-malignant and malignant cells, with sustained effects on aggressive cells at doses < 10 µM. LicA significantly reduced tumor growth in luminal (P = 0.008) and triple negative (P = 0.001) in vivo models (unpaired t-test with Welch’s correction for unequal variances). Promising serum and breast bioavailability, equivalent to low micromolar concentrations sufficient to show efficacy was demonstrated as well. Conclusion: Our data suggest that LicA is a good candidate for breast cancer prevention in both ER+ and ER- breast cancers through reprogramming metabolism and antioxidant pathways leading to decreased proliferation. We will study LicA in intraductal models of ER+ and ER- precancer lesions in immunocompetent mice and will monitor their progression to invasive breast cancer to further establish its preventive efficacy. Citation Format: Atieh Hajirahimkhan, Elizabeth Bartom, Sriram Chandrasekaran, Susan Clare, Seema Khan. Licochalcone A as a risk reducing agent against luminal and non-luminal breast cancers [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 PO3-08-07.

Abstract PS07-03: Randomized trials of oestrogen-alone and breast cancer incidence: a meta-analysis

Abstract Background Findings from cohort studies compared with those from the Women's Health initiative (WHI) randomized, placebo-controlled clinical trial regarding estrogen-alone and breast cancer risk are discordant. The WHI randomized trial enrolled 10,729 postmenopausal women with prior hysterectomy, mean age 64 years (33.2% 50-59), no prior breast cancer and a non-suspicious baseline mammogram. After 7.2 years intervention and 16.2 years cumulative follow-up, conjugated equine estrogen (CEE)-alone (vs placebo) significantly reduced breast cancer incidence by 22% (P = 0.005) and significantly reduced breast cancer mortality by 40% (P = 0.04) (Chlebowski JAMA 2020). In contrast, cohort studies had opposite findings, estrogen-alone use was associated with significantly higher breast cancer incidence and significantly higher breast cancer mortality. Therefore, we identified all available estrogen-alone randomized clinical trials where breast cancer findings were reported to conduct a meta-analysis examining the totality of the randomized clinical trial evidence regarding estrogen-alone influence on breast cancer incidence. Methods We conducted PubMed and Google Scholar searches on randomized trials and: estrogen, hormone therapy, and breast cancer, and searches from a prior meta-analyses and reviews. In the current meta-analysis, for trials with published relative risks (RR) and 95% confidence intervals (CI), each log-RR was multiplied by weight = 1/V, where V = variance of the log-RR, and V was derived from the corresponding 95% CI. For smaller trials with only breast cancer numbers, a different method was used, the corresponding log-RR = (O – E)/weight, where O is the observed case number in the oestrogen-alone group and E the corresponding expected case number, E = nP. Findings Ten randomized trials, incorporating WHI findings, and findings from nine smaller trials included 14,272 randomized participants and 591 incident breast cancers. Of 9 smaller trials, 6 required negative baseline screening mammograms; mean entry age: 50 to 56 years in 5 trials and 62 to 71 years in 4 trials. In the nine smaller trials, 1.2% (24 of 2029) vs 2.2% (33 of 1514) randomized to estrogen-alone vs placebo (open label, one trial) were diagnosed with breast cancer, respectively (RR 0.65 95% CI 0.38-1.11, P = 0.12). For 5 trials evaluating estradiol formulations, RR = 0.63 95% CI 0.34-1.16, P = 0.15. In the WHI trial, 4.5% (238 of 5310) vs 5.5% (296 of 5429) randomized to estrogen-alone were diagnosed with breast cancer, respectively (RR 0.78 95% CI 0.65-0.93, P = 0.005)). Combining smaller trials and WHI results, 3.6% (262 of 7339) vs 4.7% (329 of 6943) randomized to estrogen-alone vs placebo were diagnosed with breast cancer, respectively (overall RR 0.77 95% CI 0.65-0.91, P = 0.002). Results from a sensitivity analysis for the smaller trials using exact conditional logistic regression were essentially unchanged (RR 0.64 95% CI 0.35-1.13). Interpretation The totality of randomized clinical trial evidence supports a conclusion that estrogen-alone use, among postmenopausal women with prior hysterectomy, significantly reduces breast cancer incidence. This consistent pattern seen in these randomized trials suggests the WHI CEE-alone findings are not “stand alone” outcomes or due to chance. Citation Format: Rowan Chlebowski, Aaron Aragaki, Kathay Pan, Joanne Mortimer, Karen Johnson, Jean Wactawski-Wende, Meryl LeBoff, Sayeh Lavasani, Dorothy Lane, Rebecca Nelson, JoAnn Manson. Randomized trials of oestrogen-alone and breast cancer incidence: a meta-analysis [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 PS07-03.

Abstract PS10-01: Hormonal Contraception and Breast Cancer Risk for Carriers of Germline Pathogenic Variants in BRCA1 and BRCA2

Abstract BACKGROUND: Current use of hormonal contraception is associated with a 20-30% relative increase in the risk of breast cancer (BC) for women in the general population compared with never using. Longer duration of use is associated with higher risk, and the risk remains elevated above that of never users for at least 5 years after cessation. Most published data are for various formulations of the combined oral contraceptive pill, but associations are similar for progestogen-only contraceptives, including intrauterine devices. For women in the general population who use hormonal contraceptives in their 20s and 30s, when baseline BC risk for most women is low, these increased relative risks translate into only small increases in absolute risk. It is unclear whether use of hormonal contraceptives increases BC risk for women carrying a germline BRCA1 or BRCA2 pathogenic variant (PV). These women are at markedly higher risk of early-onset BC, so even slightly increased relative risks could translate to important increases in their absolute risk of BC. This study assessed the association between use of any hormonal contraception and BC risk for BRCA1 and BRCA2 PV carriers using individual participant data from four prospective cohorts. METHODS: Data from females born after 1920 with a PV in BRCA1 or BRCA2 and no history of cancer or bilateral mastectomy at cohort entry were analyzed. Cox regression models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for BC (invasive disease or ductal carcinoma in situ) associated with use of hormonal contraceptives for at least 1 year, with age as the timescale, entry at cohort enrolment, and censoring at the earlier of bilateral mastectomy, death, diagnosis of another cancer or last follow-up. Analyses were adjusted for study, birth cohort, first-degree family history of BC, parity, premenopausal bilateral oophorectomy and menopausal status. Current use of hormonal contraceptives was defined as use within the previous year, to account for cessation of use due to BC symptoms or clinical investigation. RESULTS: Of 3,882 BRCA1 and 1,509 BRCA2 PV carriers, 53% and 71%, respectively had ever used hormonal contraceptives (for at least one year). The median cumulative duration of hormonal contraceptive use was 4.8 and 5.7 years, respectively. Overall, 488 BRCA1 and 191 BRCA2 PV carriers developed incident BC during a median of 5.9 and 5.6 years of follow-up, respectively. For BRCA1 PV carriers, use of hormonal contraceptives for at least 1 year was associated with increased BC risk (HR [95% CI]: 1.29 [1.04-1.60] p=0.019). BC risk increased with longer cumulative duration of hormonal contraceptive use (HR [95% CI]: 1.13 [0.88-1.45] p=0.35, 1.48 [1.11-1.96] p=0.007 and 1.56 [1.13-2.17] p=0.007 for 1-5, 6-10 and >10 years of use, respectively), with an estimated proportional increase in risk of 3% (1%-5%, p=0.002) for each additional year of use. For BRCA2 PV carriers, there was no evidence that current or past use, or cumulative duration of use, were associated with increased risk of BC, but confidence intervals on the HRs were wide. CONCLUSION: Hormonal contraceptive use is associated with an increased risk of BC for women carrying PVs in BRCA1 and risk increases with cumulative duration of use. Hormonal contraceptives are an important healthcare option for women; they provide excellent contraceptive efficacy and reduce risks of ovarian and endometrial cancer. Decisions about use of hormonal contraceptives in women at increased risk for BC due to BRCA1 PVs need to carefully weigh the risks and benefits; while shorter-term use may result in only small increases, prolonged cumulative use may result in larger increases in absolute BC risk that may not be acceptable to some women. Citation Format: Kelly-Anne Phillips, Joanne Kotsopoulos, Susan Domchek, James Chamberlain, Julie Bassett, Amber Aeilts, Irene Andrulis, Saundra Buys, Wanda Cui, Mary Daly, Andrea Eisen, William Foulkes, Michael Friedlander, Jacek Gronwald, John Hopper, Esther John, Beth Karlan, Raymond Kim, Jan Lubiński, Kelly Metcalfe, Katherine Nathanson, Christian F. Singer, Heather Symecko, Nadine Tung, Steven Narod, Mary Beth Terry, Roger Milne. Hormonal Contraception and Breast Cancer Risk for Carriers of Germline Pathogenic Variants in BRCA1 and BRCA2 [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 PS10-01.

Application of multiple validated algorithms for identifying incident breast cancer among individuals with atopic dermatitis.

Validated algorithms (VAs) in insurance claims databases are often used to estimate the prevalence and incidence of comorbidities and evaluate safety signals. However, although they are then used in different data sources or subpopulations from those in which they were developed the replicability of these VAs are rarely tested, making their application and performance in these settings potentially unknown. This paper describes testing multiple VAs used to identify incident breast cancer cases in a general population and in an indication-specific population, patients with atopic dermatitis (AD). Two algorithms were tested in multiple insurance claims databases and four cohorts were created. Modifications were made to account for the US insurance setting. The resulting incidence rates (IRs) were then compared across algorithms and against surveillance, epidemiology, and end results (SEER) estimates to assess reliability. Algorithm 1 produced low IRs compared to Algorithm 2. Algorithm 2 provided similar estimates to those of SEER. Individuals in the AD cohorts experienced lower incident breast cancer cases than those in the general population cohorts. Regardless of an algorithm's reported accuracy, the original study setting and targeted population for the VAs may matter when attempting to replicate the algorithm in an indication-specific subpopulation or varying data sources. Investigators should use caution and conduct sensitivity analyses or use multiple algorithms when attempting to calculate incidence or prevalence estimates using VAs.

Racial Differences in Germline Genetic Testing Completion Among Males With Pancreatic, Breast, or Metastatic Prostate Cancers.

Germline genetic testing is a vital component of guideline-recommended cancer care for males with pancreatic, breast, or metastatic prostate cancers. We sought to determine whether there were racial disparities in germline genetic testing completion in this population. This retrospective cohort study included non-Hispanic White and Black males with incident pancreatic, breast, or metastatic prostate cancers between January 1, 2019, and September 30, 2021. Two nationwide cohorts were examined: (1) commercially insured individuals in an administrative claims database, and (2) Veterans receiving care in the Veterans Health Administration. One-year germline genetic testing rates were estimated by using Kaplan-Meier methods. Cox proportional hazards regression was used to test the association between race and genetic testing completion. Causal mediation analyses were performed to investigate whether socioeconomic variables contributed to associations between race and germline testing. Our cohort consisted of 7,894 males (5,142 commercially insured; 2,752 Veterans). One-year testing rates were 18.0% (95% CI, 16.8%-19.2%) in commercially insured individuals and 14.2% (95% CI, 11.5%-15.0%) in Veterans. Black race was associated with a lower hazard of testing among commercially insured individuals (adjusted hazard ratio [aHR], 0.73; 95% CI, 0.58-0.91; P=.005) but not among Veterans (aHR, 0.99; 95% CI, 0.75-1.32; P=.960). In commercially insured individuals, income (aHR, 0.90; 95% CI, 0.86-0.96) and net worth (aHR, 0.92; 95% CI, 0.86-0.98) mediated racial disparities, whereas education (aHR, 0.98; 95% CI, 0.94-1.01) did not. Overall rates of guideline-recommended genetic testing are low in males with pancreatic, breast, or metastatic prostate cancers. Racial disparities in genetic testing among males exist in a commercially insured population, mediated by net worth and household income; these disparities are not seen in the equal-access Veterans Health Administration. Alleviating financial and access barriers may mitigate racial disparities in genetic testing.

Randomized trials of estrogen-alone and breast cancer incidence: a meta-analysis.

In the Women's Health initiative (WHI) randomized clinical trial, conjugated equine estrogen (CEE)-alone significantly reduced breast cancer incidence (P = 0.005). As cohort studies had opposite findings, other randomized clinical trials were identified to conduct a meta-analysis of estrogen-alone influence on breast cancer incidence. We conducted literature searches on randomized trials and: estrogen, hormone therapy, and breast cancer, and searches from a prior meta-analysis and reviews. In the meta-analysis, for trials with published relative risks (RR) and 95% confidence intervals (CI), each log-RR was multiplied by weight = 1/V, where V = variance of the log-RR, and V was derived from the corresponding 95% CI. For smaller trials with only breast cancer numbers, the corresponding log-RR = (O - E)/weight, where O is the observed case number in the oestrogen-alone group and E the corresponding expected case number, E = nP. Findings from 10 randomized trials included 14,282 participants and 591 incident breast cancers. In 9 smaller trials, with 1.2% (24 of 2029) vs 2.2% (33 of 1514) randomized to estrogen-alone vs placebo (open label, one trial) (RR 0.65 95% CI 0.38-1.11, P = 0.12). For 5 trials evaluating estradiol formulations, RR = 0.63 95% CI 0.34-1.16, P = 0.15. Combining the 10 trials, 3.6% (262 of 7339) vs 4.7% (329 of 6943) randomized to estrogen-alone vs placebo (overall RR 0.77 95% CI 0.65-0.91, P = 0.002). The totality of randomized clinical trial evidence supports a conclusion that estrogen-alone use significantly reduces breast cancer incidence.

Nano-inducer of ferroptosis for targeted chemotherapy of human triple negative breast carcinoma

Triple negative breast carcinoma (TNBC) accounts for 15–20 % of all incident breast cancers (BC) and is known to be highly invasive, has fewer treatment options, and tends to have a worse prognosis. However, due to its biological heterogeneity and diverse clinical and epidemiological behaviors, TNBC lacks a tumor-specific targeted therapy. In the present work we have developed a TNBC-specific targeted nano-delivery agent comprising of a cRGD labeled magneto-liposome (T-LMD) co-encapsulated with oleic acid coated iron oxide nanoparticles (MN-OA) and doxorubicin (Dox) in the liposome bilayer and core, respectively. T-LMD was found to show enhanced uptake and induction of ferroptotic cell death in MDA-MB-231, a TNBC model cell line. Additionally, T-LMD induced ferroptosis was found to be accompanied by release of HMGB1, an immunogenic cell death marker, suggesting its immunogenicity for augmenting the activation of anti-tumor immunity in TNBC. The strategic placement of IONPs in the liposome bilayer of T-LMD facilitates the sensitization of MDA-MB-231 cells to undergo ferroptosis; predominantly via the activation of the iron/lipid metabolism pathway, as validated by use of small molecule ferroptosis inhibitor (ferrostatin-1) and iron chelator (deferoxamine). Activation of ferroptotic cell death was also corroborated by ferroptosis specific-ultrastructural alterations in the shape/size of cellular mitochondria and cell ballooning as observed by transmission electron microscopy and bright field imaging, respectively. Thus, our ferroptosis nano-inducer (T-LMD) can efficiently kill TNBC cells via enhanced LPO and ROS generation leading to membrane damage and consequent release of LDH and HMGB1, induce mitochondrial alterations and enhanced DNA double strand breaks. Altogether, our results suggest significant implications of T-LMD for treatment of TNBC.

Peptide-drug conjugate designated for targeted delivery to HER2-expressing cancer cells.

Targeted therapy of the highest globally incident breast cancer shall resolve the issue of off-target toxicity concurring with augmented killing of specific diseased cells. Thus, the goal of this study was to prepare a peptide-drug conjugate targeting elevated expression of HER2 receptors in breast cancer. Towards this, the rL-A9 peptide was conjugated with the chemotherapeutic drug doxorubicin (DOX) through a N-succinimidyl-4-(N-maleimidomethyl) cyclohexane-1-carboxylate (SMCC) linker. The synthesized peptide-drug conjugate, rL-A9-DOX, was characterized by mass spectrometry. Molecular docking studies, based on binding energy data, suggested a stronger interaction of rL-A9-DOX with the HER2 receptor in comparison to the unconjugated peptide, rL-A9. The cytotoxic effect of the rL-A9-DOX conjugate was observed to be higher in HER2-positive SKOV3 cells compared to HER2-negative MDA-MB-231 cells, indicating selective cell killing. Cellular internalization of the rL-A9-DOX conjugate was evident from the flow cytometry analysis, where a noticeable shift in mean fluorescent intensity (MFI) was observed for the conjugate compared to the control group. This data was further validated by confocal microscopy, where the fluorescent signal ascertained nuclear accumulation of rL-A9-DOX. The present studies highlight the promising potential of rL-A9-DOX for targeted delivery of the drug into a defined group of cancer cells.

The Association Between Oncology Outreach and Timely Treatment for Rural Patients with Breast Cancer: A Claims-Based Approach.

Oncology outreach is a common strategy for increasing rural access to cancer care, where traveling oncologists commute across healthcare settings to extend specialized care. Examining the extent to which physician outreach is associated with timely treatment for rural patients is critical for informing outreach strategies. We identified a 100% fee-for-service sample of incident breast cancer patients from 2015 to 2020 Medicare claims and apportioned them into surgery and adjuvant therapy cohorts based on treatment history. We defined an outreach visit as the provision of care by a traveling oncologist at a clinic outside of their primary hospital service area. We used hierarchical logistic regression to examine the associations between patient receipt of preoperative care at an outreach visit (preoperative outreach) and >60-day surgical delay, and patient receipt of postoperative care at an outreach visit (postoperative outreach) and >60-day adjuvant delay. We identified 30,337 rural-residing patients who received breast cancer surgery, of whom 4071 (13.4%) experienced surgical delay. Among surgical patients, 14,501 received adjuvant therapy, of whom 2943 (20.3%) experienced adjuvant delay. In adjusted analysis, we found that patient receipt of preoperative outreach was associated with reduced odds of surgical delay (odds ratio [OR] 0.75, 95% confidence interval [CI] 0.61-0.91); however, we found no association between patient receipt of postoperative outreach and adjuvant delay (OR 1.04, 95% CI 0.85-1.25). Our findings indicate that preoperative outreach is protective against surgical delay. The traveling oncologists who enable such outreach may play an integral role in catalyzing the coordination and timeliness of patient-centered care.

Association between prolactin increasing antipsychotic use and the risk of breast cancer: a retrospective observational cohort study in a United States Medicaid population.

Results of retrospective studies examining the relationship between prolactin increasing antipsychotics and incident breast cancer have been inconsistent. This study assessed the association between use of high prolactin increasing antipsychotics (HPD) and the incidence of breast cancer using best practices in pharmacoepidemiology. Using administrative claims data from the MarketScan Medicaid database, schizophrenia patients initiating antipsychotics were identified. Those initiating HPD were compared with new users of non/low prolactin increasing drugs (NPD). Two definitions of breast cancer, two at-risk periods, and two large-scale propensity score (PS) adjustment methods were used in separate analyses. PS models included all previously diagnosed conditions, medication use, demographics, and other available medical history. Negative control outcomes were used for empirical calibration. Five analysis variants passed all diagnostics for sufficient statistical power and balance across all covariates. Four of the five variants used an intent-to-treat (ITT) approach. Between 4,256 and 6,341 patients were included in each group for the ITT analyses, and patients contributed approximately four years of follow-up time on average. There was no statistically significant association between exposure to HPD and risk of incident breast cancer in any analysis, and hazard ratios remained close to 1.0, ranging from 0.96 (95% confidence interval 0.62 - 1.48) to 1.28 (0.40 - 4.07). Using multiple PS methods, outcome definitions and at-risk periods provided robust and consistent results which found no evidence of an association between use of HPD and risk of breast cancer.

Abstract 3458: DNA methylation-predicted blood protein levels and breast cancer risk

Abstract Background: Blood DNA methylation (DNAm) profiles can be used to predict a variety of human physiologic traits that are associated with breast cancer incidence and plasma concentrations of over 100 proteins, including those involved in inflammation, coagulation, metabolism, and growth. DNAm predictions of circulating proteins, here referred to as “DNAm proteins,” may be useful in providing molecular insights into breast cancer etiology and could be a valuable resource for personalizing breast cancer risk prediction. Methods: The Sister Study is a nationwide, prospective cohort of 50,884 women with a family history of breast cancer designed to identify novel environmental and biological risk factors for breast cancer. Epigenome-wide DNAm data were previously generated using the HumanMethylation450 or MethylationEPIC arrays on baseline blood samples collected from two case-cohort samples, for a combined sample of 4,479 women. This sample included 2,151 (48%) women who were selected because they were diagnosed with breast cancer (1,673 invasive cancer and 478 ductal carcinomas in situ) in the 15 years (mean: 7.9 years) following blood draw. Blood levels of 109 DNAm proteins were estimated from DNAm profiles using the method developed by Gadd et al. (eLife, 2022). Weighted Cox regression models were used to estimate associations between these DNAm proteins and incident breast cancer; associations were considered statistically significant at a False Discovery Rate (q) ≤ 0.10. Results: In age and platform adjusted models, higher breast cancer rates were associated with higher DNAm-predicted blood concentrations of RARRES2, IGFBP4, and CCL21 and lower predicted concentrations of F7, SELL, CXCL9, CD48, and IL19. The strongest associations were observed for RARRES2 (per 1-SD increase, HR: 1.24, 95% CI: 1.10, 1.40, P= 6 × 10−4, q= 0.03) and F7 (per 1-SD increase, HR: 0.82, 95% CI: 0.74, 0.91, P= 3 × 10−4, q= 0.03). Estimates were similar after adjustment for known breast cancer risk factors and excluding those diagnosed within two years of their blood draw. Associations appeared stronger for invasive breast cancer. Conclusions: Using novel DNAm-based estimates of blood proteins, we identified associations between circulating proteins and breast cancer incidence. IGFBP4 and RARRES2 have previously been reported to be higher in newly-diagnosed breast cancer patients. We also identify new potential protein biomarkers related to immune response (CCL21, SELL, CXCL9, CD48, and IL19). Citation Format: Jacob K. Kresovich, Brett Reid, Doratha A. Byrd, Katie M. O'Brien, Zongli Xu, Clarice R. Weinberg, Dale P. Sandler, Jack A. Taylor. DNA methylation-predicted blood protein levels and breast cancer risk [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 3458.

Abstract 2202: Association of multi-morbidity with incident cancer diagnoses

Abstract Background: Multi-morbidity (MM), which is usually defined as a simple count of the number of different diseases an individual has, has previously been identified as a risk factor for some incident cancer diagnoses. This study aimed to use more sophisticated machine learning techniques to classify MM into disease clusters and to investigate their association with incident colorectal (CRC), breast (BC), lung (LC) and prostate (PrC) cancer diagnoses. Methods: Participants in UK Biobank with a hospital (HES) record and no prevalent cancer were included in the study. Self-reported (SR), HES and primary-care (GP) recorded diseases were converted to phecodes. Sex-stratified latent class analyses (LCA) was used to identify disease clusters in the SR data. Associations between clusters and selected cancer diagnoses was undertaken using Cox proportional hazards modelling, adjusting for age, ethnicity, socio-economic status, year and region of recruitment, body mass index, smoking history, alcohol consumption and menopausal hormone therapy use (women only). The analyses were validated using HES and GP data. Results: The analysis included 158,951 women and 127,406 men. Just over 30% (49,061) of women and 37% (48,110) of men had MM (≥2 diseases) at recruitment. LCA identified 10 disease clusters in women, the most common of which was related to respiratory disease, largely comprising asthma (9344; 19.1%). Nine disease clusters were identified in men, the most common of which was related to heart disease (9358; 19.5%), and largely comprising ischemic heart disease and hypertension. No association between disease cluster and incident CRC or BC was identified. In women, LC risk was associated with several disease clusters: respiratory (Hazard Ratio 1.57 (95% confidence interval 1.28 - 1.91) p<0.001), arthritis/gut (1.46 (1.15 - 1.85) p=0.002), hyperlipidemia (1.51 (1.19 - 1.92) p=0.001, cardiac (1.74 (1.40 - 2.17) p<0.001) and type 2 diabetes (T2DM) (1.56 (1.16 - 2.09) p=0.003). In men, LC was associated with disease clusters of hyperlipidemia/hypertension (1.23 (1.02 - 1.48) p=0.03), cardiac (1.40 (1.18 - 1.66) p<0.001), T2DM (1.26 (1.02 - 1.56) p=0.03), respiratory (2.74 (2.21 - 3.39) p<0.001) and cardiometabolic/arthritis (1.81 (1.08 - 3.03) p=0.02). T2DM (0.80 (0.68 - 0.87) p<0.001) was associated with an inverse risk of PrC. Cluster distribution was similar in HES and GP data, with the association between the cardiac and the arthritis clusters replicated for LC in women, and the respiratory cluster for LC and T2DM cluster for PrC in men. Conclusion: Clusters of MM were identified in a large cancer-free population, which were replicated using different sources of healthcare data. Several disease clusters were associated with incident LC and, to a lesser extent, PrC. Further work to understand the potential causal nature of these associations is needed. Citation Format: Megan C. Conroy, Gillian K. Reeves, Naomi E. Allen. Association of multi-morbidity with incident cancer diagnoses [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 2202.

Abstract 828: Associations of perfluoroalkyl substances with breast cancer incidence risk and mediation role of mitochondrial DNA copy number: A prospective case-cohort study

Abstract Background: Perfluorinated carboxylic acids (PFCAs) and perfluorinated sulfonic acids (PFSAs), notable representatives of perfluoroalkyl substances (PFASs), are synthetic persistent chemicals widely accumulated and detected in humans. Short-chain PFASs [PFCAs with carbon number <8 and PFSAs <6, e.g. perfluoroheptanoic acid (PFHpA)] are considered less bioaccumulative and increasingly used in commercial products, yet their health impacts are rarely investigated. Perfluorooctanoic acid (PFOA) has been categorized as a possible human carcinogen (group 2B) and a potential mammary toxicant. However, few population studies explored the prospective associations of PFOA and other common PFASs with breast cancer risk nor the underlying mechanisms. Methods: Hence, we conducted a case-cohort study within the DongFeng-Tongji Cohort, compromising 226 incident breast cancer cases and a random sub-cohort of 990 individuals. Plasma concentrations of four PFCAs [PFOA, perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), and PFHpA] and two PFSAs [perfluorooctane sulfonic acid (PFOS) and perfluorohexane sulfonic acid (PFHxS)], as well as peripheral blood mitochondrial DNA copy number (mtDNAcn) levels, were measured at baseline. Results: Using Barlow-weighted Cox regression, we found 35% and 20% increased incident risk of breast cancer for each 1-unit ln-transformed increase in PFOA and PFHpA, respectively [HR (95% CI) = 1.35 (1.03, 1.78) and 1.20 (1.02, 1.40)]. Quantile g-computation analysis revealed a 19% increased incident risk of breast cancer along with each simultaneous quartile increase in all ln-transformed PFCA concentrations [HR (95% CI) = 1.19 (1.01, 1.41)], driven mainly by contributions from PFOA (56%), PFNA (24%), and PFHpA (20%). Besides, mtDNAcn was positively associated with PFHpA levels [β (95% CI) =0.027 (0.005, 0.048)], but not with PFOA or PFNA (P>0.05). We also found significantly higher breast cancer risk in participants with the highest mtDNAcn (Q4, ≥1.52) than those with the lowest (Q1, <0.87) [HR (95% CI) =2.92 (1.69, 5.04)], and that mtDNAcn mediated 12.77% of PFHpA-breast cancer association [Indirect effect, HR (95% CI) =1.02 (1.00, 1.04)]. No significant mediation effect of mtDNAcn was observed in associations of PFOA and PFNA with breast cancer (P>0.05). Conclusions: Our work unveiled the relationship of short-chain PFHpA with increased incident risk of breast cancer for the first time and highlighted the intermediate role of mtDNAcn in this association, providing a research clue for exploring the potential mechanisms of PFAS-induced breast cancer. Moreover, co-exposure to PFASs was observed as a risk factor for breast cancer, shedding light on breast cancer prevention by regulating PFASs as a chemical class. Citation Format: Yue Feng, Huan Guo. Associations of perfluoroalkyl substances with breast cancer incidence risk and mediation role of mitochondrial DNA copy number: A prospective case-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 828.

Abstract 3442: Factors modifying the association between hormonal contraception and risk of early-onset breast cancer

Abstract Breast cancer rates among women younger than 50 years-old have been steadily increasing since the mid-1990s. There is consistent evidence that use of combination estrogen and progesterone oral contraceptives (OCs)—including contemporary formulations with lower estrogen—increases breast cancer risk. It is unclear, however, if this risk varies by factors such as progestin type in the OC formulation, timing of OC use, histopathologic characteristics of the breast cancer, or individual patient characteristics. This study included premenopausal women aged <50 years and cancer-free when they enrolled in the U.S.-based American Cancer Society Cancer Prevention Study-3 cohort between 2006 and 2013 (n=101,838 women). At enrollment participants responded to a detailed life history questionnaire including questions about type, brand, duration, and recency of OC use. Incident breast cancers diagnosed between 2006-2018 were identified through cancer registry linkages (n=759). Participants were followed until the first of 1) breast cancer diagnosis, 2) age >50 years, or 3) December 31, 2018. Multivariable hazard ratios (HRs) and 95% confidence intervals (CIs) were used to estimate associations between OC use and breast cancer risk. On average, participants were 39.3 years at baseline and were followed for 5.7 years (up to 12.3 years). Current versus never use of OCs for 10+ years was associated with a higher risk of breast cancer (10-<20 years: HR=1.46, 95% CI: 1.03-2.07; 20-<30 years: HR=1.66, 95% CI: 1.14-2.41; 30+ years HR= 2.51, 95% CI: 0.77-8.16). Cessation of OC use progressively attenuated the association down to the null 15 years after discontinuation of use (HR=1.04, 95% CI: 0.73-1.49). Associations with current OC use varied by generation of progestin in the formulation (first generation: HR=1.37, 95% CI: 0.93-2.02; second: HR=1.79, 95% CI: 1.20-2.67; third: HR=1.65, 95% CI: 1.13-2.42; fourth: HR= 0.91, 95% CI: 0.49-1.67). The strongest associations were observed for use of formulations with norgestrel: HR=2.82, 95% CI: 1.54-5.19; norgestimate: HR=1.80, 95% CI: 1.19-2.72; and levonorgestrel: HR=1.56, 95% CI: 1.00-2.43. The OC-breast cancer associations were primarily limited to localized, grade 1 or 2, and ER+ disease. Race, income, body mass index, physical activity, alcohol use, cigarette smoking, parity, and breastfeeding did not appear to modify the associations. There were also no clear differences in the associations based on age at first or last OC use or timing relative to pregnancy. Current, long-term OC use was associated with increased risk of early-onset breast cancer. These data suggest that risks may vary with progestin content, and future studies are needed to define formulations that minimize breast cancer risk while still maximizing protection against other female cancers. Citation Format: Lauren R. Teras, Emily L. Deubler, Mark E. Sherman, Clara Bodelon, Lauren E. McCullough, James M. Hodge, Sicha Chantaprasopsuk, Alpa V. Patel. Factors modifying the association between hormonal contraception and risk of early-onset 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 3442.

Abstract 751: Gut microbiome and breast cancer: Report from a case-control study in Vietnam

Abstract The importance of gut microbiome on human health is being increasingly recognized. The gut microbiota may play a critical role in breast cancer etiology, likely through the roles of the gut microbiota in estrogen and nutrient metabolism as well as in immune regulation. However, evidence on associations between breast cancer and gut microbiota is limited and inconsistent. Using resources from the Vietnamese Breast Cancer Case-Control Study (VBCS), we evaluated differences in gut microbiome profiles between women with breast cancer and healthy women. Pre-treatment tool samples of 162 incident breast cancer cases (age: 50.0±9.5) and stool samples of 370 age-matched controls (age: 49.7±9.0) were included in the study. The gut microbiome was measured using shotgun metagenomic sequencing. Differences in gut microbiome α-diversity and β-diversity between breast cancer patients and healthy controls were evaluated via linear regression models and PERMANOVA testing, respectively. Case-control differences in gut microbial taxa abundance were assessed through the differential abundance analysis with adjustment for potential confounders, including age, income levels, residence, menopausal status, reproductive factors, body mass index, comorbidity, dietary intake, and physical activity. An association with a false discovery rate (FDR) <0.1 was considered statistically significant. No significant difference between breast cancer patients and healthy controls was observed for α- and β-diversities. A total of 2,905 gut microbial taxa were evaluated. Among them, significant case-control differences were found in the abundance of one phylum, two classes, four orders, three families, four gena, and 67 species (all p<0.05 and FDR <0.1). Compared to healthy controls, breast cancer patients had a decreased abundance of species Pauljensenia keddieii, Bifidobacterium bifidum (phylum Actinobacteriota), Clostridium Q symbiosum, Faecalicatena fissicatena, Massilioclostridium methylpentosum, Parvimonas micra (phylum Firmicutes A), Leptotrichia wadei (phylum Fusobacteriota), Enterococcus D gallinarum, Lactobacillus H fermentum, Gemella haemolysans B, genus Streptococcus and its 24 species such as S. anginosus C, S. constellatus, S. equinus, S. infantis I, S. mitis, S. oralis, S. pseudopneumoniae O (phylum Firmicutes) (all p<0.05 and FDR <0.1). The species Clostridium Q symbiosum showed the strongest association, with a log2 fold-change (SE) of -2.02 (0.45), p=7.35 × 10−6; FDR=0.006. Additionally, breast cancer patients had an increased abundance of three species belonging to the phylum Firmicutes A including MGYG-HGUT-03165, MGYG-HGUT-04111, and MGYG-HGUT-00903, compared to healthy controls (p<0.05 and FDR <0.1). These results suggest that the gut microbiome of breast cancer differs from that of control women. Additional analyses are ongoing to reveal the biological underpinning of the observed associations. Citation Format: Sang Minh Nguyen, Huong T. Tran, Jirong Long, Martha J. Shrubsole, Hui Cai, Yaohua Yang, Thuan V. Tran, Wei Zheng, Xiao-Ou Shu. Gut microbiome and breast cancer: Report from a case-control study in Vietnam [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 751.

Abstract 798: Increasing breast cancer incidence across generation status in Mexican American women: The Multiethnic Cohort

Abstract Background: Breast cancer (BC) is the most commonly diagnosed cancer among Latino women in the US. Compared to foreign-born Latino women, US-born Latino women have a higher incidence of BC. While prior studies have suggested this difference in incidence may be explained by risk factors such as unhealthy lifestyle behaviors, reproductive history, and neighborhood socioeconomic status, it is unclear how the risk of BC has changed over generations among Latinos women. In this study, we investigated the association between generational status and BC incidence among Mexican American women within the Multiethnic Cohort (MEC). Methods: The study population included 15,303 self-reported Mexican Americans from the MEC. Generational status was categorized as: 1st generation (Mexico-born, n = 6,347), 2nd generation (US-born with one or two parents born in Mexico, n = 6,390), or 3rd generation (US-born with both parents born in the US, n = 2,566). Multivariable Cox models were used to calculate the hazard ratios (HR) and 95% confidence intervals (CI) of BC incidence by generational status. All models were adjusted for relevant risk factors including age, physical activity, smoking, alcohol intake, education, body mass index, diet, family history of BC, menopausal status, age at menarche, parity, mammography history, hormone use, neighborhood socioeconomic status, and Hispanic ethnic enclave. Results: During an average 21.5-year follow-up, 815 incident BC cases were identified. The age-adjusted incidence rate (per 100,000) of BC increased by generation (1st: 191.9; 2nd: 265.3; 3rd: 284.0). Third (70.4%) and 2nd (66.5%) generations had a larger proportion of localized disease at diagnosis compared to 1st generation women (59.7%). Compared to 1st generation Mexican Americans, 2nd (HR = 1.24; 95% CI: 1.03-1.49) and 3rd generation (HR = 1.28; 95% CI: 1.02-1.60) had elevated risks of BC (p-trend: 0.02) The positive association with generational status remained significant when restricting to women who reported mammogram use (HR 2nd vs. 1st = 1.27, 95% CI: 1.04-1.55; HR 3rd vs. 1st = 1.34, 95% CI: 1.06-1.70) (p-trend: 0.01). Conclusions: Our findings suggest that generational status among Mexican American women is associated with risk of BC, after adjusting for sociodemographic, lifestyle, neighborhood, and reproductive risk factors. Further studies are warranted to discover the potential factors that contribute to this increased risk and elucidate the underlying etiology. Citation Format: Xinman Zhang, Iona Cheng, Adelynn Paik, Brian Huang, Veronica Wendy Setiawan. Increasing breast cancer incidence across generation status in Mexican American women: The Multiethnic Cohort [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 798.

Infertility and risk of postmenopausal breast cancer in the women's health initiative.

Although infertility (i.e., failure to conceive after ≥ 12months of trying) is strongly correlated with established breast cancer risk factors (e.g., nulliparity, number of pregnancies, and age at first pregnancy), its association with breast cancer incidence is not fully understood. Previous studies were primarily small clinic-based or registry studies with short follow-up and predominantly focused on premenopausal breast cancer. The objective of this study was to assess the relationship between infertility and postmenopausal breast cancer risk among participants in the Women's Health Initiative (analytic sample = 131,784; > 25years of follow-up). At study entry, participants were asked about their pregnancy history, infertility history, and diagnosed reasons for infertility. Incident breast cancers were self-reported with adjudication by trained physicians reviewing medical records. Cox proportional hazards models were used to estimate risk of incident postmenopausal breast cancer for women with infertility (overall and specific infertility diagnoses) compared to parous women with no history of infertility. We examined mediation of these associations by parity, age at first term pregnancy, postmenopausal hormone therapy use at baseline, age at menopause, breastfeeding, and oophorectomy. We observed a modest association between infertility (n = 23,406) and risk of postmenopausal breast cancer (HR = 1.07; 95% CI 1.02-1.13). The association was largely mediated by age at first term pregnancy (natural indirect effect: 46.4% mediated, CI 12.2-84.3%). These findings suggest that infertility may be modestly associated with future risk of postmenopausal breast cancer due to age at first pregnancy and highlight the importance of incorporating reproductive history across the life course into breast cancer analyses.

Characterizing the Traveling Oncology Workforce and Its Influence on Patient Travel Burden: A Claims-Based Approach.

Oncology outreach is a common strategy for extending cancer care to rural patients. However, a nationwide characterization of the traveling workforce that enables this outreach is lacking, and the extent to which outreach reduces travel burden for rural patients is unknown. This cross-sectional study analyzed a rural (nonurban) subset of a 100% fee-for-service sample of 355,139 Medicare beneficiaries with incident breast, colorectal, and lung cancers. Surgical, medical, and radiation oncologists were linked to patients using Part B claims, and traveling oncologists were identified by observing hospital service area (HSA) transition patterns. We defined oncology outreach as the provision of cancer care by a traveling oncologist outside of their primary HSA. We used hierarchical gamma regression models to examine the separate associations between patient receipt of oncology outreach and one-way patient travel times to chemotherapy, radiotherapy, and surgery. On average, 9,935 of 39,960 oncologists conducted annual outreach, where 57.8% traveled with low frequency (0-1 outreach visits/mo), 21.1% with medium frequency (1-3 outreach visits/mo), and 21.1% with high frequency (>3 outreach visits/mo). Oncologists provided surgery, radiotherapy, and chemotherapy to 51,715, 27,120, and 5,874 rural beneficiaries, respectively, of whom 2.5%, 6.9%, and 3.6% received oncology outreach. Rural patients who received oncology outreach traveled 16% (95% CI, 11 to 21) and 11% (95% CI, 9 to 13) less minutes to chemotherapy and radiotherapy than those who did not receive oncology outreach, corresponding to expected one-way savings of 15.9 (95% CI, 15.5 to 16.4) and 11.9 (95% CI, 11.7 to 12.2) minutes, respectively. Our study introduces a novel claims-based approach for tracking the nationwide traveling oncology workforce and supports oncology outreach as an effective means for improving rural access to cancer care.

Machine learning algorithms to uncover risk factors of breast cancer: insights from a large case-control study.

This large case-control study explored the application of machine learning models to identify risk factors for primary invasive incident breast cancer (BC) in the Iranian population. This study serves as a bridge toward improved BC prevention, early detection, and management through the identification of modifiable and unmodifiable risk factors. The dataset includes 1,009 cases and 1,009 controls, with comprehensive data on lifestyle, health-behavior, reproductive and sociodemographic factors. Different machine learning models, namely Random Forest (RF), Neural Networks (NN), Bootstrap Aggregating Classification and Regression Trees (Bagged CART), and Extreme Gradient Boosting Tree (XGBoost), were employed to analyze the data. The findings highlight the significance of a chest X-ray history, deliberate weight loss, abortion history, and post-menopausal status as predictors. Factors such as second-hand smoking, lower education, menarche age (>14), occupation (employed), first delivery age (18-23), and breastfeeding duration (>42 months) were also identified as important predictors in multiple models. The RF model exhibited the highest Area Under the Curve (AUC) value of 0.9, as indicated by the Receiver Operating Characteristic (ROC) curve. Following closely was the Bagged CART model with an AUC of 0.89, while the XGBoost model achieved a slightly lower AUC of 0.78. In contrast, the NN model demonstrated the lowest AUC of 0.74. On the other hand, the RF model achieved an accuracy of 83.9% and a Kappa coefficient of 67.8% and the XGBoost, achieved a lower accuracy of 82.5% and a lower Kappa coefficient of 0.6. This study could be beneficial for targeted preventive measures according to the main risk factors for BC among high-risk women.

Personal Care Product Use during Puberty and Incident Breast Cancer among Black, Hispanic/Latina, and White Women in a Prospective US-Wide Cohort.

Some personal care products (PCPs) contain endocrine-disrupting chemicals that may affect breast cancer (BC) risk. Patterns of use vary by race and ethnicity. Use often starts in adolescence, when rapidly developing breast tissue may be more susceptible to environmental carcinogens. Few studies have examined associations of BC with PCP use during this susceptible window. We characterized race and ethnicity-specific patterns of PCP use at 10-13 years of age and estimated associations of use with incident BC. At enrollment (2003-2009), Sister Study participants ( Black, 2,104 Latina, and 39,312 White women) 35-74 years of age reported use of 37 "everyday" PCPs during the ages of 10-13 y (did not use, sometimes, or frequently used). We conducted race and ethnicity-specific latent class analyses to separately identify groups of women with similar patterns of beauty, hair, and skincare/hygiene product use. We estimated hazard ratios (HRs) and 95% confidence intervals (CIs) for associations of identified PCP classes and single products with incident BC using Cox proportional hazards regression. During a mean follow-up time of 10.8 y, 280 Black, 128 Latina, and 3,137 White women were diagnosed with BC. Classes of adolescent PCP use were not clearly associated with BC diagnosis among Black, Latina, or White women. HRs were elevated but imprecise for frequent nail product and perfume use in Black women (1.34; 95% CI: 0.85, 2.12) and greater hair product use in Black (1.28; 95% CI: 0.91, 1.80) and Latina (1.42; 95% CI: 0.81, 2.48) women compared with lighter use. In single-product models, we observed higher BC incidence associated with frequent use of lipstick, nail products, pomade, perfume, makeup remover, and acne/blemish products in at least one group. This work provides some support for the hypothesis that PCP use during puberty is associated with BC risk. More research is needed to confirm these novel findings. https://doi.org/10.1289/EHP13882.