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Background Lower body negative pressure (LBNP) simulates hemorrhage, evoking compensatory cardiovascular mechanisms of increased heart rate (HR) while stroke volume (SV) and cardiac output (CO) progressively decline, ultimately leading to presyncope. Previous work has shown that circulating levels of plasma epinephrine are elevated during LBNP; however, the role of early administration of epinephrine in compensatory cardiovascular mechanisms to simulated hemorrhage is not well understood. Purpose We hypothesized that during simulated hemorrhage, a low‐dose exogenous infusion of epinephrine in humans would: 1) augment HR response, 2) attenuate the decline of SV and CO, and 3) prolong time to tolerance. Methods Nine healthy subjects (5M/4F, 35±9yrs, BMI 25±1 kg·m −2 ) participated in LBNP on two separate study days. Protocols on each day consisted of a 10‐minute pre‐infusion baseline, 15‐minute infusion period (randomized to saline or epinephrine, dose = 0.1 μg·kg −1 ·min −1 , delivered through a peripherally inserted central catheter), 10‐minute post‐infusion baseline, and 5 minute stages of progressive LBNP with stepwise increases of 10–15 mmHg negative pressure until tolerance (systolic blood pressure less than 80 mmHg, bradycardia, or voluntary termination due to presyncopal symptoms). Heart rate (HR; electrocardiogram) and blood pressure (BP; radial arterial catheter) were recorded continuously. Cardiovascular function (HR, SV, CO, and systemic vascular resistance (SVR)) was determined using arterial waveform analysis. Data were analyzed via percent tolerance using repeated measures ANOVA with student method for pairwise comparisons. Results Infusion of exogenous epinephrine lowered MAP (p<0.01) and diastolic blood pressure (DBP; p<0.001), but raised systolic blood pressure (SBP; p=0.019) throughout all stages of LBNP. Epinephrine compared to saline augmented mean HR, SV and CO to the penultimate stage of LBNP (p≤0.01 for all cardiac measures) and concurrently reduced SVR (p=0.002). However, time to tolerance was not significantly different between epinephrine and saline conditions (1415 ± 79 vs. 1475 ± 150s, respectively; p=0.69). Discussion Our findings suggest that during simulated hemorrhage exogenous epinephrine can augment cardiac function without increasing tolerance to progressive central hypovolemia. During the epinephrine infusion, benefits to cardiac function may have been limited by reduced vascular resistance. Support or Funding Information The United States Department of Defense W81XWH‐13‐2‐0038

Background Maintaining baroreflex sensitivity is integral to ensuring blood pressure maintenance and end‐organ perfusion during hemorrhage. This is especially true under conditions of hypoxemia, where decreased tolerance to central hypovolemia is commonly observed. Hypoxia activates peripheral chemoreceptors and reduces baroreceptor‐vascular resistance reflex sensitivity. However, a direct role for the peripheral chemoreceptors in the hemodynamic response to hemorrhage in hypoxia remains unclear. Objective We tested the hypothesis that attenuation of peripheral chemoreceptor activity (low‐dose dopamine; 1–2 μg/kg/min) during acute hypoxia would promote maintenance of mean arterial pressure, pulse pressure, and other hemodynamic markers [heart rate (HR), stroke volume (SV), cardiac output (CO), total peripheral resistance (TPR)] during simulated hemorrhage. Methods Ten healthy men (35±3 years, BMI 25±1 kg/m 2 ) participated in a randomized, double‐blind, placebo controlled study. Participants completed two experimental visits (saline and low‐dose dopamine) at which lower body negative pressure (LBNP) was conducted during hypoxia (SpO 2 ~85%; PaO2 ~52 mmHg) delivered via a non‐rebreather mask. Ventilation [V̇ (turbine transducer)], arterial blood pressure (brachial artery catheter), HR (ECG), and central venous pressure (peripherally inserted central catheter) were measured continuously and SV, CO, and TPR were calculated. Following a 5‐min rest, participants underwent LBNP for 5‐min at 3 intervals (−15, −30, and −45 mmHg). Outcome values were analyzed and compared using a mixed linear model (SAS PROC MIXED) with a direct product AR(1) covariance structure using indicator variables for saline vs. dopamine. Data from the mixed linear model are reported as an estimated change per 15 mmHg of LBNP. Results Dopamine had no effect on hypoxia P a O 2 , P a CO 2 , V̇ or respiratory rate (all P >0.05) and this relationship persisted throughout all LBNP stages. The mixed linear model showed no effect of dopamine vs. saline on changes in: central venous pressure (−1.1±0.4 vs −1.3±0.3 mmHg, P =0.15), mean arterial pressure (−4.7±2.3 vs −5.3±1.4 mmHg, P =0.25), pulse pressure (−6.7±1.5 vs −8.3±1.4 mmHg, P =0.50), HR (7.8±1.5 vs 6.1±1.5 bpm, P =0.41), SV (−10.9±1.9 vs −11.6±3.3 mL, P =0.41), CO (−0.3±0.2 vs −0.4±0.4 L · min −1 , P =0.31) or TPR (0.2±0.4 vs 0.7±0.6 mmHg · L · min −1 P =0.27). Discussion Intravenous infusion of low‐dose dopamine designed to attenuate peripheral chemoreflex activity during acute hypoxia did not alter the integrated hemodynamic response to simulated hemorrhage. Our data suggests that peripheral chemoreceptors have a limited role during hypoxic central hypovolemia. More research is needed to understand the sensitivity and cross‐talk between chemoreceptors and baroreceptors during hemorrhage. Support or Funding Information Funding: W81XWH‐13‐2‐0038 (DOD), DK90541 (NIH), UL1 TR000135 (NIH).

Abstract Introduction. The NCIC CTG is conducting phase II testing to establish the tolerability and estimate the efficacy of combining lenalidomide (L) + melphalan (M) over multiple cycles for previously untreated patients with multiple myeloma who are ineligible for stem cell transplantation. We report the data from the preliminary safety phase of this trial. Methods. The MY.11 trial was initially designed as a randomized phase II test of M 9 mg/m2 given on days 1–4 (M9) plus either L 10 mg (L10) or 20 mg given on days 1–21 of a 28 day cycle. Primary prophylaxis with G-CSF was not included, but use of G-CSF for established neutropenia was permitted; our intent was to determine dose levels that could be given independently of G-CSF. A dose attenuation schedule was developed for neutropenia and/or thrombocytopenia that was severe and occurred during the administration of L or was persistent and caused a delay in the next treatment cycle. A hematologic dose limiting toxicity (H-DLT) was defined as the need for 2 dose attenuations of L or 1 dose attenuation of M. Prior to the randomized phase of the trial, a safety run-in phase testing M9+L10 in 6 patients was planned; closure of this arm was to occur if, during the first 3 treatment cycles, there were ≥ 3 H-DLTs or any non-hematologic serious adverse event (SAE) judged to be treatment related. Four of the planned 6 patients were entered; during their first 3 treatment cycles, each experienced a H-DLT and one died from sepsis. The study was therefore amended with the intent to conduct a randomized phase II test of M 4 mg/m2 days 1–4 plus L 15 mg days 1–21 (M4L15) and M 6 mg/m2 days 1–4 plus L 10 mg days 1–21 (M6L10). Prior to the randomized phase of testing, each regimen was tested in non-randomized safety run-ins that included 6 patients per arm. The same parameters as above for study arm closure were applied. If the M6L10 arm was closed, the trial would proceed to test M 5 mg/m2 days 1–4 and L 10 mg days 1–21 (M5L10). Results. Six patients were enrolled to M4L15: during their first 3 treatment cycles, 4 patients experienced H-DLTs related to severe or persistent grade 3–4 neutropenia and one other patient experienced an SAE related to hallucinations and multiple constitutional complaints. This arm was therefore closed to accrual. Six patients were enrolled to M6L10: during their first 3 treatment cycles, 3 patients experienced H-DLTs related to severe or persistent grade 3–4 neutropenia. One of these patients was hospitalized with pulmonary edema and another with febrile neutropenia. This arm was therefore closed and the MY.11 trial amended to proceed as a single-arm phase II testing M5L10. Conclusion. Although M + L holds promise as an effective combination for previously untreated myeloma patients, the regimen is associated with considerable myelosuppression. The efficacy of the combination when given at tolerable doses remains to be established.

Objective Bronchopulmonary dysplasia (BPD) is a condition of neonatal chronic lung disease due to disruption or dysregulation of pulmonary development. It is associated with decreased septation, alveolar hypoplasia, and abnormal disruption of pulmonary alveolar capillaries resulting in increased pulmonary resistance. However, the pathophysiology of BPD in the large conducting airways is not fully understood. The objective of our study was to determine if the luminal area of the central airways, measured by imaging, are altered in patients with a history of BPD. We hypothesized that compared to age‐ and sex‐matched controls, BPD patients would have a decreased luminal area of the central conducting airways and lung volume. Methods Fourteen BPD patients (8M/6F; Age=5.7±5.5 yrs) who had undergone a chest computed tomography (CT) scan were retrospectively identified. Age and sex matched controls (8M/6F, Age=5.6±5.3 yrs) who had undergone a CT scan for trauma were used for comparison. Measurement and analysis were performed by a single investigator using commercially available software (Aquarius, TeraRecon Inc.) that reconstructs the airways into 3D. Measurements of luminal airway area were conducted at three points based on anatomic bifurcations (corresponding to the beginning, middle and end of the airway) for each of the following structures: trachea, left main bronchus, left upper lobe, left lower lobe, right main bronchus, intermediate bronchus, and right upper lobe. Each airway’s luminal area was calculated based on the averages of the three measures obtained for each anatomic airway structure. Independent Student’s t‐test was used for statistical analysis. Results Airway luminal area was not different between BPD patients and matched controls (trachea: 89.8±57.1 vs 87.4±58.6 mm 2 ; right main bronchus: 58.8±40.8 vs 64.0±44.5 mm 2 ; intermediate bronchus: 33.6±21.2 vs 41.0±28.9 mm 2 ; left main bronchus: 39.3±27.1 vs 46.6±36.5 mm 2 ; left lower lobe: 22.7±14.6 vs 29.9±18.9 mm 2 ; p>0.05 for all comparisons; BPD and controls, respectively). Total lung volume detected in the CT scans was not different between BPD patients and matched controls (3069±1073 vs 3215±984 cm 3 , p>0.05). Conclusions Our results suggest the luminal areas of the large conducting airways in patients with BPD are not different from matched controls. Given the degree of respiratory complications and sequelae associated with BPD, our findings suggest future research should focus on alveolar and vascular impaired physiological and anatomic developments versus the large conducting airways. Support or Funding Information National Institutes of Health Grants R35‐HL139854 (MJJ), F32 HL‐131151 (SEB), T32 DK‐007352‐39 (CCW) and Mayo Clinic Internal Funding and Natural Science and Engineering Council of Canada RGPIN‐2019‐04615 (PBD)

Background Despite improvements in military aircraft safety, many aviation incidents are attributed to hypoxia. The correlation between moderate hypoxia and cognitive function are well studied but results remain controversial. Comparatively, the effects of severe hypoxia are still not well understood. In the present study, we examined the executive cognitive function and physiological indices under both moderate and severe hypoxia conditions. Purpose To examine the relationship between executive function and physiological indices during acute hypoxia exposure. Methods Ten young healthy participants (4M/6F, 29±4 years) completed two different levels of hypoxia: 1) 10 minute moderate hypoxia (MH; F i O 2 = 0.118) and 2) 3 minute severe hypoxia (SH; F i O 2 = 0.077) following 3 minute baseline (BL; F i O 2 =0.209). Reaction time and errors of commission (defined as a response to a non‐target stimulus) were evaluated continuously using a custom Go/No‐go test at baseline and throughout hypoxia exposure. In this Go/No‐go test, participants were required to push a key when upper case “A” or “@” appeared but not when lower case “a” appeared on a computer monitor as quick and as accurately as possible. The stimuli were presented one at a time at any one of nine differing locations across the screen. Cerebral oxygenation (rSO 2 ) was continuously monitored with near‐infrared spectroscopy (NIRS) positioned above the left supraorbital ridge. Finger oxygen saturation (S p O 2 ) was continuously assessed using a pulse oximetry. Data were analyzed in every 30 seconds and are presented as mean±SE. Two‐way ANOVA and Bonferroni test for multiple comparisons was used to evaluate significant differences. Results Both S p O 2 and rSO 2 were reduced with SH (S p O 2 %, BL: 99.3±0.1% vs. SH: 70.7±1.5%, P<0.01; rSO 2 %, BL: 70±4% vs. SH: 58±4%, P<0.01). In SH, correlations of S p O 2 and rSO 2 were significant to the number of errors during the cognitive performance task (S p O 2 ; R= −0.65, rSO 2 ; R= −0.58, Both P<0.01). SH significantly increased errors of commission of the last 30 seconds in 3 minute hypoxic exposure. (BL: 0.6±0.2 errors vs. SH: 1.7±0.5 errors, P<0.01). SH significantly decreased reaction time over hypoxic exposure (BL: 0.43±0.01 sec vs. SH: 0.41±0.01 sec, P<0.01). Comparatively, MH did not elicit an increase in the number of errors of commission nor a decrease in reaction time (Both, P>0.05). Conclusion Executive function deteriorated during severe hypoxia. Oxygenation of the prefrontal lobe which controls inhibition may be related to the increase in commission errors. Devices that monitor physiological indices such as S p O 2 or rSO 2 might be beneficial for a model to predict executive deterioration. Support or Funding Information This project was funded by the Office of Naval Research (ONR), grant number N00014‐18‐D‐7001‐TO1.

Background In humans, exercise tolerance is determined by the balance of diffusive and convective elements of oxygen transport. Mathematical models have suggested that alterations in hemoglobin‐oxygen (Hb‐O 2 ) binding affinity (P 50 ) have minimal effects of on oxygen delivery. However, there is limited experimental data in humans to evaluate these models during exercise in humans. Purpose We sought to investigate skeletal muscle blood flow and vascular conductance (hyperemic response to exercise and hypoxia) during exercise in otherwise healthy participants with chronically high Hb‐O 2 affinity (HAH). We hypothesized that patients with HAH would have a blunted hyperemic response to both handgrip and hypoxia due to the marked polycythemia that is typical in participants with HAH compared to controls. Methods Participants with HAH (n=6, 3 men, age= 37±12 yr, P 50 =15±2 mmHg) and control participants matched for age, sex, and BMI (CTL, n=5, 3 men, age=41±8 yr, and P 50 =26±1 mmHg) completed two intensities (10% and 20% maximal voluntary contraction (MVC)) of rhythmic handgrip exercise with a duty cycle of 1s contraction and 2s relaxation (20 contractions·min −1 ). Each exercise intensity was performed breathing three different gas mixtures: 21%, 15%, and 10% oxygen. Brachial artery mean blood velocity was measured using Doppler ultrasound. Beat‐by‐beat blood pressure was measured via arterial catheterization. Forearm blood flow (FBF) was calculated as the product of mean blood velocity (cm·s −1 ) and brachial artery cross‐sectional area (cm 2 ) and expressed as milliliters per minute (mL·min −1 ), and forearm vascular conductance (FVC) was calculated as (FBF) × (mean arterial pressure) −1 × 100 and expressed as mL·min −1 ·mmHg −1 . Data were analyzed using a three‐way ANOVA (Inspirate [21%, 15%, 10% O 2 ], group [CTL, HAH], handgrip intensity [Rest, 10% and 20% MVC]). Results During normoxia (21% O 2 ), groups were not different in FBF (P>0.05), FVC (P>0.05) or arterial saturation (S a O 2 , P=0.54). Similarly, the moderate hypoxia condition (15% O 2 ), groups were not different in FBF (P>0.05), or FVC (P>0.05) despite a preservation in arterial saturation in HAH (S a O 2 , CTL: 89.0±0.7% vs. HAH: 95.1±1.7%, P<0.001). However, with more severe hypoxic exposure (10% O 2 ), FBF and FVC were higher in HAH than controls during the 20% MVC exercise (P<0.05). HAH also had higher FBF (P<0.05) and trended towards higher FVC in the 10% MVC exercise (P=0.08). Interestingly, arterial saturation was drastically higher for HAH at the end of handgrip exercise (20% MVC) in 10% O 2 (CTL: 69.2±4.5% vs. HAH: 89.1±1.4%, P<0.001). Conclusion As predicted in mathematical models, Hb‐O 2 binding affinity had little effect on skeletal muscle blood flow and forearm vascular conductance during light exercise under normoxic and moderate hypoxic conditions (21% and 15% O 2 ). However, with a greater physiological stress to skeletal muscle O 2 uptake in a more severe hypoxic condition (10% O 2 ), participants with HAH, contrary to our initial hypothesis, had preserved arterial O 2 saturation and a greater hyperemic response than controls. Support or Funding Information This work was supported by the NIH (5T32DK007352‐39 to CCW, R35HL139854 to MJJ) Rest 10% MVC 20% MVC FBF, mL·min − 1 21% O 2 CTL 87 ± 8 327 ± 25 589 ± 26 HAH 142 ± 19 420 ± 29 716 ± 68 15% O 2 CTL 173 ± 61 357 ± 63 707 ± 62 HAH 156 ± 66 539 ± 111 930 ± 143 10% O 2 CTL 154 ± 72 386 ± 81 668 ± 57 HAH 244 ± 133 703 ± 199 * 932 ± 118 * FVC, mL·min − 1 ·mmHg − 1 21% O 2 CTL 94 ± 9 356 ± 27 621 ± 24 HAH 130 ± 19 363 ± 25 617 ± 63 15% O 2 CTL 187 ± 63 384 ± 54 758 ± 53 HAH 137 ± 44 453 ± 79 764 ± 226 10% O 2 CTL 171 ± 71 431 ± 73 708 ± 67 HAH 221 ± 109 718 ± 136 917 ± 172 Abbreviations: FBF, forearm blood flow; FVC, forearm vascular conductance; MVC, maximal voluntary contraction; CTL, control group; HAH, high‐affinity Hb group. Values are presented as mean±SE. * indicates significant difference (P<0.05) from CTL group at same %MVC.

Abstract Background: Alcohol intake and breast density are established risk factors for breast cancer (BC). A few studies suggest breast density is on the causal pathway between alcohol and BC but the literature is not consistent. We examine the interrelationship between alcohol, volumetric breast density and BC risk, specifically whether there is a stronger alcohol and BC association among women with dense breasts and/or whether breast density mediates the alcohol and BC association. Methods: We conducted a nested case-control study within the San Francisco Mammography Registry consisting of four breast screening centers. From 2006-2013, through linkages with the California cancer registry, we identified 2572 women diagnosed with BC who had screening mammograms performed at least six months prior to diagnosis. Controls (5119) were matched to cases on age, date of earliest mammogram, race/ethnicity, facility, and mammography machine. We obtained the raw format of digital mammograms on average 3.1 (standard deviation (SD) =1.7) years prior to diagnosis or corresponding date for controls. We ascertained usual daily alcohol intake and other risk factors from a clinical questionnaire at time of mammography. We obtained BI-RADS density from clinical records and used VolparaTM to assess volumetric percent density, dense volume and non-dense volume from the mammogram. We examined the associations of daily alcohol intake (none, one or less, two or more drinks per day) and volumetric density phenotypes (per 1 SD) with BC risk using logistic regression (odds ratios, OR; 95% confidence intervals, CI; and trend tests). We examined deviation from multiplicative interaction using chi-squared tests. We evaluated mediation of the alcohol and BC association by volumetric density measures using logistic regression to estimate the association between alcohol use and BC with and without adjustment for density measures. Percent mediation was estimated using the differences in the log OR estimates from the two models. All models were adjusted for age, 1/BMI and menopause and matching factors. Analyses were also stratified by menopausal status. Results: Alcohol intake was available on 2233 cases and 4562 controls, 88% of those eligible. BC cases and controls had similar age (57.2 years (SD=11.5) vs. 57.1 years (SD=11.5)), BMI (25.3 kg/m2 (SD=5.3) vs. 24.9 kg/ m2 (SD=5.1)) and race (69.0% vs. 68.2% Caucasian). Cases were more likely to drink alcohol daily than controls (52.1% vs. 49.0%), in particular two or more drinks per day (14.8% vs. 13.2%). Alcohol was associated with increased BC risk (OR=1.14, 95% CI:1.02-1.27, for one or less drinks per day and OR=1.22, 95% CI:1.05-1.42 for 2 or more drinks per day) compared to non-drinkers (p-trend=0.004). Percent volumetric density (OR=1.45 per SD, 95%CI: 1.36-1.56,) and dense volume (OR=1.30, 95% CI: 1.24-1.37) were also positively associated with BC risk; non-dense volume was inversely associated (OR=0.93, 95%CI: 0.86-1.01). Associations were similar by menopausal subgroup. There was no evidence for a differential association of alcohol and breast cancer risk by dense breasts assessed using any of the density phenotypes examined (all P’s&gt;0.1). However, the association between alcohol and overall risk of BC was partially mediated by dense volume among all women (percent mediated=25%, P=0.01) and postmenopausal women (percent mediated=19%, P=0.03). Conclusions: The association of daily alcohol intake and breast cancer risk was similar among women with dense and non-dense breasts. However, dense volume partially mediated the association between alcohol and risk of breast cancer, particularly among postmenopausal women, suggesting that alcohol partially influences breast cancer risk through changes in breast tissue composition. Citation Format: Celine Marie Vachon, Christopher G. Scott, Stacey J Winham, John A Shepherd, Kathleen R Brandt, Matthew R Jensen, Carrie B Hruska, John J Heine, V. Shane Pankratz, Karla Kerlikowske. Association of daily alcohol intake, volumetric density and breast cancer risk [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-08-02.

1033 Background: MA.32 investigates effects of Metformin vs. Placebo, in addition to standard care, on invasive disease free survival and other outcomes. Metformin may improve obesity and metabolic factors [insulin, glucose, leptin, C-reactive protein (CRP)] that have been associated with poor BC outcomes. Maintaining blinding of investigators to outcomes, we conducted a planned, DSMB approved, analysis of the effect of Metformin vs. Placebo on weight and metabolic factors at 6 months, including examination of interactions with baseline body mass index (BMI), in the first 498 subjects with paired fasting plasma samples. Methods: 498 non-diabetic subjects with T1-3, N0-3, M0 BC meeting defined entry criteria who had completed surgery and adjuvant chemo (if given) provided fasting blood samples at randomization and 6 months (while on study drug). Glucose was measured locally; blood was aliquoted, frozen and stored at -80°C then shipped to NCIC CTG (Kingston, Canada). Paired plasma aliquots were shipped to Mount Sinai Hospital (Toronto, Canada) for analysis of Insulin (Dako), hsCRP (Roche Elecsys) and leptin (Luminex). Statistical analysis used the Wilcoxon signed rank test. Results: Mean age was 52.4 ±9.2 years. Arms were balanced for ER/PgR (63% pos), BMI, prior adjuvant chemo (89%), T and N status, grade, mastectomy/lumpectomy and radiation. Conclusions: Metformin significantly improved weight, insulin, glucose, leptin and CRP at 6 months. Effects did not vary by baseline BMI. Funded by: NIH, CCSRI, CBCF, BCRF, Apotex Canada (drug & placebo - in kind). Clinical trial information: NCT01101438. [Table: see text]

564 Background: Our group previously examined if baseline patient/tumor characteristics, or prior treatment affected cause of death in MA.17, a placebo controlled extended adjuvant trial of the aromatase inhibitor (AI) letrozole. We now examine factor effects on all cause mortality in MA.27. Methods: MA.27 was an adjuvant phase III superiority trial of 5 yrs of exemestane vs anastrozole, in ER+ postmenopausal breast cancer accrued between 2003 and 2008; event free survival was similar. We examined by intention-to-treat, the multivariate time-to-breast cancer-specific (BrCa), cardiovascular (Cardio), and other causes (OT) of death with log-normal survival analysis adjusted by treatment and stratification factors (lymph node status, adjuvant chemotherapy, celecoxib, aspirin, and trastuzumab). We tested whether factors were associated with 1) all cause mortality, and if so, 2) cause-specific mortality. We also fit step-wise forward cause-specific adjusted models. Results: 7,576 women (median age 64.1 years; 5417 (71.5%) <70 yrs and 2159 (28.5%) >70 yrs) were enrolled and followed for a median of 4.1 yrs. The 432 deaths comprised: 187 (43.3%) BrCa, 66 (15.3%) Cardiovascular, and 179 (41.4%) OT MA.27 therapy was not associated with mortality (p=0.84). Five baseline factors were differentially associated with cause of death. Older age was associated with greater BrCa (p=0.03), Cardio (p<0.001), and OT (p<0.001) mortality. Pre-existing cardiovascular history led to worse Cardio mortality (p<0.001). Worse ECOG performance status led to worse OT death (p<0.001). T1 tumors were associated with less BrCa mortality (p<0.001). PgR+ tumors were also associated with less BrCa mortality (p<0.001). There were fewer BrCa deaths with Node –ve disease (p<0.001), ER+ tumors (p=0.001) and without adjuvant chemotherapy (p=0.005); there was worse Cardio mortality (p=0.01) with receipt of trastuzumab; worse OT (p=0.03) for non-whites, and without adjuvant radiotherapy (p=0.003). Conclusions: 56.7% of deaths in MA.27 patients were non-breast cancer related. We showed baseline patient and tumor characteristics, and prior treatment differentially affected cause of death. Clinical trial information: NCT00066573.

6018 Background: Disease free survival was significantly improved in women receiving letrozole after standard adjuvant tamoxifen in the MA.17 trial. Based on the results of MA.17 and of other trials of aromatase inhibitors in early stage breast cancer, chronic aromatase inhibitor therapy, in postmenopausal women free of breast cancer recurrence, is now being widely employed. We analyzed the toxicity of letrozole according to ethnic status among women enrolled in MA.17. Methods: The chi-square test was used for comparison of rates of side effects between the two groups, Caucasian vs. ethnic minority (defined as all non-Caucasians). In a subset of women, quality of life (QOL) was assessed by the SF-36 Health Survey. Mean change scores in QOL from baseline were compared between groups for summary measures and domains using the Wilcoxon test. Results: 352 minority women and 4,708 Caucasians were enrolled in MA.17, of which 183 minority women and 2,339 Caucasians were randomized to receive letrozole. Caucasians were older than minority women and had a slightly longer duration of treatment with prior tamoxifen. Tumor size and nodal status were not significantly different between the two groups. In women who received letrozole, minority women had significantly lower incidence of hot flashes (49% vs. 58%; p = 0.02), fatigue (29% vs. 39%; p = 0.005), and arthritis (2% vs. 7%; p = 0.006) compared with Caucasians. Mean QOL change scores of SF-36 domains for women who received letrozole were not different but minority women had better mental health at 6 month assessment (p = 0.02) and worse bodily pain at 12 month assessment (p = 0.046). Conclusions: Minority women tolerated letrozole considerably better than Caucasians in the MA.17 trial. These preliminary findings suggest that minority women respond differently to letrozole in terms of toxicity. Recent demonstration of genotypic variations in the aromatase gene in different ethnic groups plus likely pharmacogenomic differences suggests that further research is needed to clarify the clinical outcomes of aromatase inhibition in women of diverse ethnicities. Future research strategies should focus on examining in vivo genotype-phenotype correlations to determine the effects of genetic variation on response to anticancer therapy and on toxicities and end-organ effects. [Table: see text]