Background: The aim of this study was to examine breast density in relation to breast cancer specific survival and\r\nto assess if this potential association was modified by mode of detection. An additional aim was to study whether\r\nthe established association between mode of detection and survival is modified by breast density.\r\nMethods: The study included 619 cases from a prospective cohort, The Malm�¶ Diet and Cancer Study. Breast density\r\nestimated qualitatively, was analyzed in relation to breast cancer death, in non-symptomatic and symptomatic women,\r\nusing Cox regression calculating hazard ratios (HR) with 95% confidence intervals. Adjustments were made in\r\nseveral steps for; diagnostic age, tumour size, axillary lymph node involvement, grade, hormone receptor status,\r\nbody mass index (baseline), diagnostic period, use of hormone replacement therapy at diagnosis and mode of\r\ndetection. Detection mode in relation to survival was analyzed stratified for breast density. Differences in HR\r\nfollowing different adjustments were analyzed by Freedmans%.\r\nResults: After adjustment for age and other prognostic factors, women with dense, as compared to fatty\r\nbreasts, had an increased risk of breast cancer death, HR 2.56:1.07-6.11, with a statistically significant trend over\r\ndensity categories, p = 0.04. In the stratified analysis, the effect was less pronounced in non-symptomatic women, HR\r\n2.04:0.49-8.49 as compared to symptomatic, HR 3.40:1.06-10.90. In the unadjusted model, symptomatic women had a\r\nhigher risk of breast cancer death, regardless of breast density. Analyzed by Freedmans%, age, tumour size, lymph\r\nnodes, grade, diagnostic period, ER and PgR explained 55.5% of the observed differences in mortality between\r\nnon-symptomatic and symptomatic cases. Additional adjustment for breast density caused only a minor change.\r\nConclusions: High breast density at diagnosis may be associated with decreased breast cancer survival. This\r\nassociation appears to be stronger in women with symptomatic cancers but breast density could not explain\r\ndifferences in survival according to detection mode
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