Aromatase expression in atypical ductal hyperplasia in women.

PURPOSE: To determine the levels of aromatase in atypical ductal hyperplasia (ADH) lesions, tissue surrounding the ADH, and in dense and non-dense normal breast tissue. We postulated that excess aromatase in breast tissue might, through production of increased estrogen, drive the carcinogenic process. Estrogens and their metabolites are thought to contribute to the development of breast cancer through estrogen receptor-mediated mechanisms and genotoxic effects of estrogen metabolites. ADH is a benign lesion of the breast which is associated with substantially increased risk for subsequent development of breast cancer. After 25 years, approximately 30% of women with ADH develop breast cancer. In women with three or more separate ADH lesions at the same time, 47% will develop breast cancer over that time period. Another important risk factor for breast cancer is the presence of mammographically dense breast tissue. METHODS: We utilized quantitative immunochemical analysis of aromatase in biopsy tissue to test this possibility. Previously published results comparing dense with non-dense breast tissue in normal women (Vachon et al. Breast Cancer Res Treat 125:243-252, 2011) were used for comparisons with ADH. A well-characterized histochemical H-score was employed for quantitative assessment of aromatase in the various tissue studied. RESULTS: The H-score of aromatase staining was statistically significantly higher (p = 0.003) in the ADH epithelium than surrounding epithelial tissue. In order of H-score from highest to lowest were ADH, issue surrounding ADH, dense normal and non-dense normal breast tissues. The levels of aromatase in a subset of women with ADH who went on to develop breast cancer were not higher than in women who did not. CONCLUSIONS: We suggest from these studies that overexpression of aromatase in breast tissue and its resultant increase in estradiol levels may contribute to the later development of breast cancer in women with ADH.

Racial differences in primary cytogenetic abnormalities in multiple myeloma: a multi-center study.

We examined four clinically assessed cytogenetic subtypes (t(11;14), t(4;14), monosomy 13/del13q and monosomy 17/del17p in 292 black patients with newly diagnosed multiple myeloma (MM) from four medical centers, who had fluorescent in situ hybridization testing results available in their medical records. We then compared the prevalence of these abnormalities with a previously characterized Mayo Clinic cohort of 471 patients with MM. We found a significant difference in the prevalence of the t(11;14) immunoglobulin heavy chain (IgH) translocation between blacks and whites, 6.5% versus 17.6%, respectively, P<0.0001. Blacks also had lower rates of the t(4;14) IgH translocation, (5.5% versus 10%); monosomy 13/del13q (29.1 versus 49.3%); and monosomy 17/del17p (7.9% versus 13%). Consequently, 63.4% of blacks versus 34.6% of whites did not have any of the four abnormalities that we studied, P<0.001. As almost all MM is associated with either an IgH translocation or trisomies, we hypothesize that MM in blacks is associated with either excess prevalence of either the trisomic (hyperdiploid) form of MM or an IgH translocation besides t(11;14) or t(4;14). We conclude that there are significant differences in the cytogenetic subtypes of MM that occur in blacks and whites.

Disparities in the prevalence, pathogenesis and progression of monoclonal gammopathy of undetermined significance and multiple myeloma between blacks and whites.

There is marked racial disparity in the incidence of monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma, with a two to threefold increased risk in blacks compared with whites. The increased risk has been seen both in Africans and African Americans. Similarly, an increased risk of monoclonal gammopathies in blacks compared with whites has been noted after adjusting for socioeconomic and other risk factors, suggesting a genetic predisposition. The higher risk of multiple myeloma in blacks is likely a result of the higher prevalence of the premalignant MGUS stage; there are no data to suggest that blacks have a higher progression rate of MGUS to myeloma. Studies are emerging that suggest the baseline cytogenetic characteristics, and progression may differ by race. In contrast, to the increased risk noted in blacks, studies suggest that the risk may be lower in certain racial and ethnic groups, notably persons from Japan and Mexico. We review the literature on racial disparity in the prevalence, pathogenesis and progression of MGUS and multiple myeloma between blacks and whites. We also discuss future directions for research that could inform management of these conditions and positively influence patient outcomes.

Immunophenotypic and gene expression analysis of monoclonal B-cell lymphocytosis shows biologic characteristics associated with good prognosis CLL.

Monoclonal B-cell lymphocytosis (MBL) is a hematologic condition wherein small B-cell clones can be detected in the blood of asymptomatic individuals. Most MBL have an immunophenotype similar to chronic lymphocytic leukemia (CLL), and 'CLL-like' MBL is a precursor to CLL. We used flow cytometry to identify MBL from unaffected members of CLL kindreds. We identified 101 MBL cases from 622 study subjects; of these, 82 individuals with MBL were further characterized. In all, 91 unique MBL clones were detected: 73 CLL-like MBL (CD5(+)CD20(dim)sIg(dim)), 11 atypical MBL (CD5(+)CD20(+)sIg(+)) and 7 CD5(neg) MBL (CD5(neg)CD20(+)sIg(neg)). Extended immunophenotypic characterization of these MBL subtypes was performed, and significant differences in cell surface expression of CD23, CD49d, CD79b and FMC-7 were observed among the groups. Markers of risk in CLL such as CD38, ZAP70 and CD49d were infrequently expressed in CLL-like MBL, but were expressed in the majority of atypical MBL. Interphase cytogenetics was performed in 35 MBL cases, and del 13q14 was most common (22/30 CLL-like MBL cases). Gene expression analysis using oligonucleotide arrays was performed on seven CLL-like MBL, and showed activation of B-cell receptor associated pathways. Our findings underscore the diversity of MBL subtypes and further clarify the relationship between MBL and other lymphoproliferative disorders.

Centrosome-related genes, genetic variation, and risk of breast cancer.

Centrosome amplification has been detected in premalignant lesions and in situ tumors in the breast and in over 70% of invasive breast tumors, and has been associated with aneuploidy and tumor development. Based on these observations, the contribution of commonly inherited genetic variation in candidate genes related to centrosome structure and function to breast cancer risk was evaluated in an association study. Seven-hundred and 82 single nucleotide polymorphisms (SNPs) from 101 centrosomal genes were analyzed in 798 breast cancer cases and 843 controls from the Mayo Clinic Breast Cancer Study to assess the association between these SNPs (both individually and combined) and risk of breast cancer in this population. Eleven SNPs out of 782 from six genes displayed associations with breast cancer risk (P < 0.01). Haplotypes in five genes also displayed significant associations with risk. A two SNP combination of rs10145182 in NIN and rs2134808 in the TUBG1 locus (P-interaction = 0.00001), suggested SNPs in mediators of microtubule nucleation from the centrosome contribute to breast cancer. Evaluation of the simultaneous significance of all SNPs in the centrosome pathway suggested that the centrosome pathway is highly enriched (P = 4.76 × 10(-50)) for SNPs that are associated with breast cancer risk. Collections of weakly associated genetic variants in the centrosome pathway, rather than individual highly significantly associated SNPs, may account for a putative role for the centrosome pathway in predisposition to breast cancer.

A novel and automatic mammographic texture resemblance marker is an independent risk factor for breast cancer.

OBJECTIVE: We investigated whether breast cancer is predicted by a breast cancer risk mammographic texture resemblance (MTR) marker. METHODS: A previously published case-control study included 495 women of which 245 were diagnosed with breast cancer. In baseline mammograms, 2-4 years prior to diagnosis, the following mammographic parameters were analysed for relation to breast cancer risk: (C) categorical parenchymal pattern scores; (R) radiologist's percentage density, (P) computer-based percentage density; (H) computer-based breast cancer risk MTR marker; (E) computer-based hormone replacement treatment MTR marker; and (A) an aggregate of P and H. RESULTS: Density scores, C, R, and P correlated (tau=0.3-0.6); no other pair of scores showed large (tau>0.2) correlation. For the parameters, the odds ratios of future incidence of breast cancer comparing highest to lowest categories (146 and 106 subject respectively) were C: 2.4(1.4-4.2), R: 2.4(1.4-4.1), P: 2.5(1.5-4.2), E: non-significant, H: 4.2(2.4-7.2), and A: 5.6(3.2-9.8). The AUC analysis showed a similarly increasing pattern (C: 0.58±0.02, R: 0.57±0.03, P: 0.60±0.03, H: 0.63±0.02, A: 0.66±0.02). The AUC of the aggregate marker (A) surpasses others significantly except H. HRT-MTR (E) did not significantly identify future cancers or correlate with any other marker. CONCLUSIONS: Breast cancer risk MTR marker was independent of density scores and more predictive of risk. The hormone replacement treatment MTR marker did not identify patients at risk.

Intraoperative ventilator settings and acute lung injury after elective surgery: a nested case control study.

BACKGROUND: While acute lung injury (ALI) is among the most serious postoperative pulmonary complications, its incidence, risk factors and outcome have not been prospectively studied. OBJECTIVE: To determine the incidence and survival of ALI associated postoperative respiratory failure and its association with intraoperative ventilator settings, specifically tidal volume. DESIGN: Prospective, nested, case control study. SETTING: Single tertiary referral centre. PATIENTS: 4420 consecutive patients without ALI undergoing high risk elective surgeries for postoperative pulmonary complications. MEASUREMENTS: Incidence of ALI, survival and 2:1 matched case control comparison of intraoperative exposures. RESULTS: 238 (5.4%) patients developed postoperative respiratory failure. Causes included ALI in 83 (35%), hydrostatic pulmonary oedema in 74 (31%), shock in 27 (11.3%), pneumonia in nine (4%), carbon dioxide retention in eight (3.4%) and miscellaneous in 37 (15%). Compared with match controls (n = 166), ALI cases had lower 60 day and 1 year survival (99% vs 73% and 92% vs 56%; p<0.001). Cases were more likely to have a history of smoking, chronic obstructive pulmonary disease and diabetes, and to be exposed to longer duration of surgery, intraoperative hypotension and larger amount of fluid and transfusions. After adjustment for non-ventilator parameters, mean first hour peak airway pressure (OR 1.07; 95% CI 1.02 to 1.15 cm H(2)O) but not tidal volume (OR 1.03; 95% CI 0.84 to 1.26 ml/kg), positive end expiratory pressure (OR 0.89; 95% CI 0.77 to 1.04 cm H(2)O) or fraction of inspired oxygen (OR 1.0; 95% CI 0.98 to 1.03) were associated with ALI. CONCLUSION: ALI is the most common cause of postoperative respiratory failure and is associated with markedly lower postoperative survival. Intraoperative tidal volume was not associated with an increased risk for early postoperative ALI.

Association of childhood and adolescent anthropometric factors, physical activity, and diet with adult mammographic breast density.

Early-life exposures may influence the development of breast cancer. The authors examined the association of childhood and adolescent anthropometric factors, physical activity levels, and diet with adult mammographic breast density, a strong risk factor for breast cancer. Women in the Minnesota Breast Cancer Family Study cohort who had undergone mammograms but had not had breast cancer (n=1,893) formed the sample. Information on adolescent exposures, including relative height, weight, and physical activity at ages 7, 12, and 18 years and diet at age 12-13 years, was self-reported during two follow-up studies (1990-2003). Mammographic percent density was estimated using a computer-assisted thresholding program. Statistical analyses were performed using linear mixed-effects models with two-sided tests. Positive associations with height at ages 7 (p<0.001), 12 (p<0.001), and 18 (p<0.001) years and percent density were evident overall and within menopausal status categories. The minimum difference in percent density between the tallest and shortest girls was 3 percent, with a maximum of 7 percent. Weight at age 12 years (p=0.005) and adiposity at age 12 years (p=0.005) were both inversely associated with adult percent density. Adolescent physical activity and diet were unrelated to percent density. These results suggest that adolescent height, a known risk factor for breast cancer, is also associated with mammographic percent density.

Pilot study of the impact of letrozole vs. placebo on breast density in women completing 5 years of tamoxifen.

Breast density, a strong risk factor for breast cancer, is reduced by the anti-estrogen, tamoxifen (TAM). We examined whether aromatase inhibitor (AI) therapy results in further reductions in breast density among women completing 5 years of TAM. Among a sample of women with early-onset breast cancer who were randomized to letrozole (LET)(n=56) or placebo (PLAC)(n=48) after 5 years of TAM, we examine the change in percent density at 9-15 months as well as a per-year change in PD by treatment group. There was no difference in the adjusted mean change (-1.0%, LET; -0.3%, PLAC (P=0.58)) or the percentage change (-2.7%, LET; -3.0%, PLAC (P=0.96)) in PD between treatment groups at 9-15 months. Results were similar for longitudinal change (-0.68% per year, LET; -0.12% per year, PLAC (P=0.23)). Breast density does not appear to be a clinically relevant biomarker in women who already have low PD following 5 years of TAM.

Lung cancer risk reduction after smoking cessation: observations from a prospective cohort of women.

PURPOSE: We conducted this study because the duration of excess lung cancer risk among former smokers has been inconsistently reported, doubt has been raised regarding the population impact of smoking cessation, and differential risk reduction by histologic cell type after smoking cessation needs to be confirmed. METHODS: The Iowa Women's Health Study is a prospective cohort study of 41,836 Iowa women aged 55 to 69 years. In 1986, mailed questionnaires were used to collect detailed smoking history. Age-adjusted lung cancer incidence through 1999 was analyzed according to years of smoking abstinence. Relative risks were estimated using Cox regression analysis. RESULTS: There were 37,078 women in the analytic cohort. Compared with the never smokers, former smokers had an elevated lung cancer risk (relative risk, 6.6; 95% confidence interval, 5.0 to 8.7) up to 30 years after smoking cessation for all former smokers. However, a beneficial effect of smoking cessation was observed among recent and distant former smokers. The risk of adenocarcinoma remained elevated up to 30 years for both former heavier and former lighter smokers. CONCLUSION: The risk for lung cancer is increased for both current and former smokers compared with never smokers and declines for former smokers with increasing duration of abstinence. The decline in excess lung cancer risk among former smokers is prolonged compared with other studies, especially for adenocarcinoma and for heavy smokers, suggesting that more emphasis should be placed on smoking prevention and lung cancer chemoprevention.

Adenocarcinoma of the lung is strongly associated with cigarette smoking: further evidence from a prospective study of women.

In a prospective cohort of 41,836 Iowa women aged 55-69 years with 13 years of follow-up from 1986 through 1998, the authors examined the association between cigarette smoking history and three common histologic subtypes of lung cancer (123 small cell, 115 squamous cell, and 234 adenocarcinoma). Using Cox proportional hazards and additive Poisson regression analysis, they estimated four epidemiologic measures of effect: age-adjusted incidence rate, relative risk, excess risk (or risk difference), and population attributable risk. Of the three major lung cancer subtypes, the excess risk for heavy smokers compared with never smokers was higher for adenocarcinoma (excess risk = 206) than for squamous cell (excess risk = 122) and small cell (excess risk = 104) carcinomas. Adenocarcinoma of the lung is more strongly associated with tobacco smoke exposure than previously recognized.

Investigation of an interaction of alcohol intake and family history on breast cancer risk in the Minnesota Breast Cancer Family Study.

BACKGROUND: One explanation for the variability in results in studies of alcohol consumption and breast cancer could be the presence of effect modifiers, such as genetic susceptibility. The authors examined the interaction of alcohol and family history of breast cancer on breast cancer risk in a population-based family study of 426 multigenerational breast cancer families. The authors evaluated whether alcohol use was a stronger risk factor for breast cancer among sisters, daughters, nieces, and granddaughters of breast cancer probands than among women who married into these families. METHODS: Analyses were performed on surrogate and self-reported data combined and on self-reported data alone. To evaluate the interaction of alcohol and breast cancer risk among women with a family history of breast cancer, the authors performed analyses on all 426 families and on a subset of 132 families that had 3 or more breast and/or ovarian cancers in their family. RESULTS: A total of 9032 blood relatives and marry-ins and 558 breast cancer cases were available for analysis. In the entire 426 families, there was a suggestion of an interaction of relationship to the proband and frequency of alcohol consumption on breast cancer risk (P(interaction) = 0.14) for surrogate and self-reported information combined. Among first-degree relatives of the proband, daily drinkers had a significantly increased risk of breast cancer compared with never drinkers (RR = 2.45 [1.20, 5.02]), but this increase was less evident among second-degree relatives who reported daily alcohol intake (RR = 1.27 [0.73, 2.22]) and was not evident in marry-ins who reported daily use of alcohol (RR = 0.90 [0.42, 1.90]). The findings based on the subset of 132 high-risk families with 3 or more breast and/or ovarian cancers were similar to findings based on all 426 families (P(interaction) = 0.07). An interaction of family history with alcohol use was also suggested when the analyses were restricted to self-respondents, although the interaction test P-value was no longer of borderline significance. CONCLUSION: An increased risk of breast cancer due to an increased frequency of alcohol consumption may be limited to women with a family history of breast cancer.

Dietary folate intake, alcohol, and risk of breast cancer in a prospective study of postmenopausal women.

Low B-vitamin intake may increase risk of breast cancer through decreased DNA repair capacity. Alcohol intake increases risk for breast cancer, with evidence from prospective studies of an interaction between alcohol and folate. We explored dietary intake of folate and other B vitamins with risk of breast cancer in a cohort study of 34,387 postmenopausal women. To measure diet, we mailed a food frequency questionnaire; we estimated nutrient intakes and categorized them into four levels: <10th, 11th-30th, 31st-50th, and >50th percentiles. Through 12 years of follow-up, we identified 1,586 cases of breast cancer in the cohort at risk. We estimated relative risks (RRs) and 95% confidence intervals (CIs) through Cox regression models adjusted for age, energy, and other risk factors. Women in the lowest 10th percentile of folate intake from diet alone were at modestly increased risk of breast cancer relative to those above the 50th percentile: RR = 1.21 (95% CI = 0.91--1.61). We examined the joint association of folate intake and alcohol use on risk of breast cancer, with the reference group defined as women with high folate (>50th percentile) and no alcohol use. The RRs of breast cancer associated with low dietary folate intake were 1.08 (95% CI = 0.78--1.49) among nondrinkers, 1.33 (95% CI = 0.86--2.05) among drinkers of < or = 4 gm per day, and 1.59 (95% CI = 1.05--2.41) among drinkers of > 4 gm per day. These results suggest that the risks of postmenopausal breast cancer may be increased among women with low intakes of folate if they consume alcohol-containing beverages.

Cigarette smoking increases risk for breast cancer in high-risk breast cancer families.

Most epidemiological studies of cigarette smoking and breast cancer have failed to demonstrate a strong association. Only one study has been performed on women at high genetic risk, and smoking was reported to be a protective factor. To further explore this observation, we examined the association of cigarette smoking with the risk of breast cancer in a historical cohort study of high-risk breast cancer families. A total of 426 families ascertained through a consecutive series of breast cancer patients (probands) between 1944 and 1952 were followed through 1996. Occurrence of breast cancer and detailed smoking histories for sisters, daughters, granddaughters, nieces, and marry-ins were obtained through telephone interviews between 1991 and 1996. Cox proportional hazards regression, accounting for age, birth cohort, and other risk factors, was used to calculate relative risks and 95% confidence intervals (CIs) of breast cancer. All of the models were constructed within strata defined by relationship to the index case (proband), with nonsmokers designated as the referent group. Of the 426 families in the cohort, 132 had at least three incident breast and/or ovarian cancers in the biological relatives at the end of the follow-up period. Among sisters and daughters in these 132 high-risk families, those who ever smoked were at 2.4-fold increased risk of breast cancer (95% CI, 1.2-5.1) relative to never-smokers. No association between breast cancer and smoking was observed among nieces and granddaughters of probands or among marry-ins. When the analysis was restricted to 35 families at highest genetic risk (each containing five breast and/or ovarian cancers), smoking became an even stronger risk factor. Among sisters and daughters, ever-smokers were at 5.8-fold greater risk than nonsmokers (95% CI, 1.4-23.9). Among nieces and granddaughters, the risk of breast cancer associated with smoking was increased 60% (95% CI, 0.8-3.2). These results suggest that smoking may increase risk for breast cancer in families with multiple cases of breast or ovarian cancer, especially those with the strongest apparent familial predisposition.

Evidence for a major gene influence on abdominal fat distribution: the Minnesota Breast Cancer Family Study.

Abdominal fat has been shown to be an important risk factor for many chronic conditions, including diabetes, heart disease, and breast cancer. The objective of this study was to provide evidence for a major gene influence on the ratio of waist to hip circumference (WHR), a measurement commonly used in large scale studies to indicate the presence of abdominal fat. Segregation analysis was conducted on three subsets of families from the Minnesota Breast Cancer Family Study. One analysis was conducted among families with WHR measurements on all women. Two additional analyses were conducted on subsets of women stratified on menopausal status. Multiple regression analysis was used to identify factors associated with WHR expressed as a continuous trait. Complex segregation analyses were performed on the continuous trait of WHR and the covariates identified in the regression analysis. In the analysis of all women, all hypotheses were rejected. Among premenopausal women, the environmental hypothesis with no heterogeneity between generations fit the data best (P = 0.85). However, among postmenopausal women, the requirements for conclusion of the presence of a major gene were met. All non-Mendelian hypotheses were rejected (P < 0.0001), but the additive hypothesis was not rejected (P = 0.19) and provided the best fit to the data. The putative major gene identified by this model accounted for 42% of total phenotypic variance in WHR among these postmenopausal women. The allele for high WHR had a frequency of 27%. These findings support the hypothesis that the distribution of abdominal fat in postmenopausal women is under genetic control.

Risk of breast cancer with oral contraceptive use in women with a family history of breast cancer.

CONTEXT: Oral contraceptive (OC) use is weakly associated with breast cancer risk in the general population, but the association among women with a familial predisposition to breast cancer is less clear. OBJECTIVE: To determine whether the association between OC use and risk of breast cancer is influenced by family history of the disease. DESIGN AND SETTING: Historical cohort study of 426 families of breast cancer probands diagnosed between 1944 and 1952 at the Tumor Clinic of the University of Minnesota Hospital. Follow-up data on families were collected by telephone interview between 1991 and 1996. PARTICIPANTS: A total of 394 sisters and daughters of the probands, 3002 granddaughters and nieces, and 2754 women who married into the families. MAIN OUTCOME MEASURE: Relative risk (RR) of breast cancer associated with history of OC use by relationship to proband. RESULTS: After accounting for age and birth cohort, ever having used OCs was associated with significantly increased risk of breast cancer among sisters and daughters of the probands (RR, 3.3; 95% confidence interval [CI], 1.6-6.7), but not among granddaughters and nieces of the probands (RR, 1.2; 95% CI, 0.8-2.0) or among marry-ins (RR, 1.2; 95% CI, 0.8-1.9). Results were essentially unchanged after adjustment for parity, age at first birth, age at menarche, age at menopause, oophorectomy, smoking, and education. The elevated risk among women with a first-degree family history of breast cancer was most evident for OC use during or prior to 1975, when formulations were likely to contain higher dosages of estrogen and progestins (RR, 3.3; 95% CI, 1.5-7.2). A small number of breast cancer cases (n = 2) limited the statistical power to detect risk among women with a first-degree relative with breast cancer and OC use after 1975. CONCLUSIONS: These results suggest that women who have ever used earlier formulations of OCs and who also have a first-degree relative with breast cancer may be at particularly high risk for breast cancer. Further studies of women with a strong family history who have used more recent lower-dosage formulations of OCs are needed to determine how women with a familial predisposition to breast cancer should be advised regarding OC use today. JAMA. 2000;284:1791-1798.

Association of mammographically defined percent breast density with epidemiologic risk factors for breast cancer (United States).

OBJECTIVE: Mammographically defined percent breast density is an important risk factor for breast cancer, but the epidemiology of this trait is poorly understood. Although several studies have investigated the associations between reproductive factors and density, few data are available on the associations of breast density and waist-to-hip ratio (WHR), physical activity, education, alcohol and smoking. METHODS: We investigated the associations of known and suspected breast cancer risk factors with breast density in a large breast cancer family study. Information was collected on members of 426 families through telephone interviews, mailed questionnaires and mammography. Mammographic films on 1900 women were digitized and breast density was estimated in discrete five-unit increments by one radiologist. Analysis of covariance techniques were used and all analyses were performed stratified by menopausal status. RESULTS: Similar to other reports, nulliparity, late age at first birth, younger age and lower body mass index were associated with increased percent density in both premenopausal and postmenopausal women, and hormone replacement therapy among postmenopausal women. Higher levels of alcohol consumption and low WHR were associated with increased percent density among both premenopausal and postmenopausal women (differences of 3-11% between high and low categories). However, smoking and education were inversely associated with percent density among premenopausal (p = 0.004 and p = 0.003, respectively) but not postmenopausal women (p = 0.52 and p = 0.90). Physical activity was not associated with percent density in either stratum (p values > 0.25). Combined, these factors explained approximately 37% of the variability in the percent density measure in premenopausal women and 19% in postmenopausal women. CONCLUSIONS: Many of these factors may potentially affect breast cancer risk through their effect on percent breast density.

An investigation of the effects of mammographic acquisition parameters on a semiautomated quantitative measure of breast cancer risk.

The aim of this work was to investigate the effect of mammographic acquisition parameter variations on the estimation of percent density (PD) produced by a particular semiautomated algorithm. The PD algorithm requires the user to specify a threshold pixel value segmenting breast tissue of greater and lesser density. A whole breast specimen was imaged using a variety of acquisition techniques, and the image data were processed as prescribed by the PD algorithm. PD estimates for all possible values of the user threshold were calculated for all the images. The image data were normalized so that PD varied between 30% and 80% over a fixed threshold range of 23, and a PD value of 50% was obtained for a threshold value of 195. PD differences between all the images and a baseline standard mammographic acquisition technique were calculated. We also estimated PD differences caused by small (3%) variations in operator selection of the threshold value. We found that the largest differences in PD involved changes in the density control of the mammography unit, and changes in the detector (either film type or computed radiography). The maximum PD differences due to technique were all less than 10%, with root-mean-square (RMS) variations less than 4%. PD differences due to operator variation were 24% (maximum) and 6.1% (RMS). These findings suggest that PD differences due to mammographic technique will be considerably less than those inherent to the technique, due to operator variation. All of these estimates are likely larger than differences seen in practice since optimization of the threshold by the operator was not considered in this analysis.