***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background : A better underst and ing of factors that affect breast density , one of the strongest breast cancer risk indicators , may provide important clues about breast cancer etiology and prevention . This study evaluates the association of vitamin D and calcium , from food and /or supplements , to breast density in premenopausal and postmenopausal women separately . Methods : A total of 777 premenopausal and 783 post-menopausal women recruited at two radiology clinics in Quebec City , Canada , in 2001 to 2002 , completed a food frequency question naire to assess vitamin D and calcium .  Breast density from screening mammograms was assessed using a computer-assisted method . Associations between vitamin D or calcium and breast density were evaluated using linear regression models . Adjusted means in breast density were assessed according to the combined daily intakes of the two nutrients using generalized linear models . Results : In premenopausal women , total intakes of vitamin D and calcium were inversely related to breast density ( β = −1.4 ; P = 0.004 for vitamin D ; β = −0.8 ; P = 0.0004 for calcium ) . In multivariate linear regression , simultaneous increments in daily total intakes of 400 IU vitamin D and 1,000 mg calcium were associated with an 8.5 % ( 95 % confidence interval , 1.8 - 15.1 ) lower mean breast density . The negative association between  dietary vitamin D intake and breast density tended to be stronger at higher levels of calcium intake and vice versa . Among postmenopausal women , intakes of vitamin D and calcium were not associated with breast density . Conclusion : These findings show that higher intakes of vitamin D and calcium from food and supplements are related to lower levels of breast density among premenopausal women . They suggest that increasing intakes of vitamin D and calcium may represent a safe and inexpensive strategy for breast cancer prevention BACKGROUND Whether a change over time in clinical ly measured mammographic breast density influences breast cancer risk is unknown . METHODS From January 1993 to December 2003 , data that included American College of Radiology Breast Imaging Reporting and Data System ( BI-RADS ) breast density categories ( 1 - 4 in order of increasing density ) were collected prospect ively on 301,955 women aged 30 and older who were not using postmenopausal hormone replacement therapy and underwent at least two screening mammography examinations ; 2639 of the women were diagnosed with breast cancer within 1 year of the last examination . Women 's first and last BI-RADS breast density ( average 3.2 years apart ) and logistic regression were used to model the odds of having invasive breast cancer or ductal carcinoma in situ diagnosed within 12 months of the last examination by change in BI-RADS category . Rates of breast cancer adjusted for age , mammography registry , and time between screening examinations were estimated from this model . All statistical tests were two-sided . RESULTS The rate ( breast cancers per 1000 women ) of breast cancer was higher if BI-RADS breast density category increased from 1 to 2 ( 5.6 , 95 % confidence interval [ CI ] = 4.7 to 6.9 ) or 1 to 3 ( 9.9 , 95 % CI = 6.4 to 15.5 ) compared to when it remained at BI-RADS density of 1 ( 3.0 , 95 % CI = 2.3 to 3.9 ; P<.001 for trend ) . Similar and statistically significant trends between increased or decreased density and increased or decreased risk of breast cancer , respectively , were observed for women whose breast density category was initially 2 or 3 and changed categories . BI-RADS density of 4 on the first examination was associated with a high rate of breast cancer ( range 9.1 - 13.4 ) that remained high even if breast density decreased . CONCLUSION An increase in BI-RADS breast density category within 3 years may be associated with an increase in breast cancer risk and a decrease in density category with a decrease in risk compared to breast cancer risk in women in whom breast density category remains unchanged . Two longitudinal measures of BI-RADS breast density may better predict a woman 's risk of breast cancer than a single measure BACKGROUND Mammographic breast density is a strong risk factor for breast cancer .  Tamoxifen , which reduces the risk of breast cancer in women at high risk , also reduces mammographic breast density . However , it is not known if tamoxifen-induced reductions in breast density can be used to identify women who will benefit the most from prophylactic treatment with this drug . METHODS We conducted a nested case-control study within the first International Breast Cancer Intervention Study , a r and omized prevention trial of tamoxifen vs placebo .  Mammographic breast density was assessed visually and expressed as a percentage of the total breast area in 5 % increments . Case subjects were 123 women diagnosed with breast cancer at or after their first follow-up mammogram , which took place 12 - 18 months after trial entry , and control subjects were 942 women without breast cancer . Multivariable logistic regression was used to adjust for other risk factors . All statistical tests were two-sided . RESULTS In the tamoxifen arm , 46 % of women had a 10 % or greater reduction in breast density at their 12- to 18-month mammogram . Compared with all women in the placebo group , women in the tamoxifen group who experienced a 10 % or greater reduction in breast density had 63 % reduction in breast cancer risk ( odds ratio = 0.37 , 95 % confidence interval = 0.20 to 0.69 , P = .002 ) , whereas those who took tamoxifen but experienced less than a 10 % reduction in breast density had no risk reduction ( odds ratio = 1.13 , 95 % confidence interval = 0.72 to 1.77 , P = .60 ) . In the placebo arm , there was no statistically significant difference in breast cancer risk between subjects who experienced less than a 10 % reduction in mammographic density and subjects who experienced a greater reduction . CONCLUSION The 12- to 18-month change in mammographic breast density is an excellent predictor of response to tamoxifen in the preventive setting Background : Mammographic density is a risk factor for breast cancer .  Mammographic density and breast magnetic resonance imaging ( MRI ) volume ( MRIV ) assess the amount of fibrogl and ular tissue in the breast . Mammographic density and MRIV can be modulated with hormonal interventions , suggesting that these imaging modalities may be useful as surrogate endpoint biomarkers for breast cancer chemoprevention trials . We evaluated the effect of raloxifene on mammographic density and MRIV in premenopausal women at increased risk for breast cancer . Methods : Mammograms and MRI were obtained at baseline and after 1 and 2 years of 60 mg raloxifene by mouth daily for 27 premenopausal women .  Mammographic percent dense area was calculated using a semiquantitative thresholding technique . T1-weighted spoiled gradient-echo MRI with fat suppression was used to determine breast MRIV using a semiautomatic method . Mean change in mammographic density and median change in MRIV were assessed by the Wilcoxon signed-rank test . Results : No significant change in mammographic density was seen after treatment with raloxifene . Mean change after 1 year was 1 % [ 95 % confidence interval ( 95 % CI ) , −3 to + 5 ] and after 2 years was 1 % ( 95 % CI , −2 to + 5 ) . MRIV decreased on raloxifene . Median relative change in MRIV after 1 year was -17 % ( 95 % CI , -28 to -9 ; P = 0.0017 ) and after 2 years was -16 % ( 95 % CI , -31 to -4 ; P = 0.0004 ) . Conclusions : In high-risk premenopausal women , mammographic density did not change on raloxifene , whereas MRIV significantly declined . Our findings suggest that MRIV is a promising surrogate biomarker in premenopausal women at increased risk for breast cancer and should be investigated further in breast cancer prevention trials . ( Cancer Epidemiol Biomarkers Prev 2008;17(7):1696–701 Background : Calcium and vitamin D may be inversely related to breast cancer risk , in part by affecting mammographic density . However , results from previous , mostly cross-sectional studies have been mixed , and there have been few r and omized clinical trials of the effect of calcium and vitamin D supplementation on change in mammographic density . Methods : We assessed the effect of one year of supplementation on mammographic density in 330 postmenopausal women enrolled in the Women 's Health Initiative hormone therapy ( HT ) and calcium and vitamin D ( CaD ) trials . Women were r and omized to receive 1,000 mg/d of elemental calcium carbonate plus 400 IU/d of vitamin D3 or placebo . Results : After approximately one year , mammographic density decreased 2 % in the CaD supplementation group and increased 1 % in the placebo group ( ratio of means = 0.97 ; 95 % CI = 0.81–1.17 ) . Results suggested potential interaction by HT use ( P = 0.08 ) . Among women r and omized to HT placebo , the ratio of mean density comparing CaD supplementation and placebo groups was 0.82 ( 95 % CI = 0.61–1.11 ) vs. 1.16 ( 95 % CI = 0.92–1.45 ) in women r and omized to active HT . In sensitivity analyses limited to women taking ≥80 % of study supplements , ratios were 0.67 ( 95 % CI = 0.41–1.07 ) in women not assigned to HT and 1.07 ( 95 % CI = 0.79–1.47 ) women assigned to HT . Conclusions : We observed no overall effect of vitamin D and calcium supplementation  on mammographic density after one year . Impact : Potential interaction between these nutrients and estrogen as related to mammographic density warrants further study . Cancer Epidemiol Biomarkers Prev ; 21(3 ) ; 462–73 . © 2012 AACR Mammographically detected breast density has been correlated with breast cancer risk . Breast density appears to be influenced by hormonal factors including increasing age , postmenopausal status , number of pregnancies , lower body weight , hormone replacement therapy , and tamoxifen therapy . The aromatase inhibitor letrozole profoundly reduces breast and circulating estrogen levels in postmenopausal women . We hypothesize that letrozole may reduce breast density and report here on its effects on mammographic breast density , bone mineral density ( BMD ) , bone biomarkers , plasma hormone , and serum lipid levels . MAP1 was a multicenter , r and omized , double-blind , placebo-controlled , feasibility trial in which postmenopausal women with or without prior invasive breast cancer were r and omized in a 2:1 ratio of letrozole ( 2.5 mg daily ) or placebo for 12 months and followed for a total of 24 months . Eligible women had an estimated > 25 % breast density on baseline mammogram . The primary endpoint was change in percent breast density ( PD ) between the baseline and 12-month mammograms as estimated by a computer-assisted thresholding program . Baseline and 12-month mammographic density was also assessed in a blinded manner by visual inspection . Secondary endpoints included changes in serum hormones , plasma lipid levels , bone biomarkers , and BMD . Data are available for 67 women ( 44 on letrozole and 23 on placebo ) . No significant changes in PD were noted between the treatment arms at either 12 or 24 months . No distinguishable difference in density measurements by visual inspection were noted between baseline and 12-month mammograms . A significant decrease in percentage change in T-score of the femoral neck at 12 months was noted in the letrozole arm without other significant changes in BMD parameters . Lipid values did not differ between treatment groups except for a borderline significant decrease in total cholesterol at 3 months among women treated with letrozole . Letrozole therapy was associated with a significant reduction in mean serum estradiol , estrone , and estrone sulfate levels at 12 months , but not at 24 months . A significant increase in serum IGF-1 levels was also noted in the letrozole group compared to the placebo group at both 12 and 24 months . To conclude , compared with placebo , 12 months of letrozole therapy does not appear to have a significant effect on mammographic PD . Twelve months of letrozole was associated with a decrease of uncertain clinical significance in the T-score of the femoral neck at 12 months which was reversible at 24 months with recovery of estrogen levels . Letrozole therapy was found to increase IGF-1 levels at 12 and 24 months Soy consumption may be related to lower  breast cancer  risk as assessed by breast density . The aims of this 2-y trial were to examine the effects of soy foods and lifetime soy intake on mammographic density . After 220 premenopausal women were r and omly assigned to the intervention or control group , the former group consumed 2 daily servings of soy foods equivalent to 50 mg of isoflavones and the latter consumed their regular diet . The respective dropout rates were 15.6 and 12.6 % ; adherence to the study regimen was high . We assessed lifetime soy intake with a question naire and measured breast density 
    Output:
    
TAM induces BD reduction ; however , the effect of RLX , tibolone , and AIs on BD is unclear .
Although data on association between diet and BD in adulthood are contradictory , intake of vegetables , vitamin D , and calcium appear to be associated with lower BD in premenopausal women