Mammographic density and the risk of breast cancer recurrence after breast-conserving surgery.

BACKGROUND: Women with invasive breast cancer who are treated with breast-conserving surgery and radiotherapy face a cumulative risk of local disease recurrence of approximately 10% at 10 years. To the authors' knowledge, the role of mammographic density as a risk factor for the development of local recurrence has not been thoroughly evaluated to date. METHODS: Medical records were reviewed for 335 patients who underwent breast-conserving surgery for invasive breast cancer and for whom a pretreatment mammogram was available. Information was recorded concerning mammographic density as well as tumor features, patient characteristics, and adjuvant treatments received. Patients were categorized for mammographic density based on the Wolfe classification as either low (<25% density), intermediate (25-50% density), or high (>50% density). A multivariate survival analysis was conducted using the Cox proportional hazards model with local disease recurrence as the primary endpoint. RESULTS: Patients in the high mammographic density group experienced a much greater risk of local disease recurrence compared with women with the least dense breasts (10-year actuarial risks: 21% vs 5%; hazards ratio [HR], 5.7 [95% confidence interval, 1.6-20; P=.006]). The difference in the rates of disease recurrence at 10 years was pronounced for women who did not receive radiotherapy (40% vs 0% for patients with >50% density and <25% density, respectively; P<.0001). CONCLUSIONS: Mammographic breast density is an important risk factor for local breast cancer recurrence among women not receiving breast irradiation. Mammographic density should be taken into consideration when stratifying patients for clinical trials of partial breast radiotherapy. If confirmed, mammographic density might be used to help determine which patients might benefit from radiotherapy.

Mammographic density and the risk and detection of breast cancer.

BACKGROUND: Extensive mammographic density is associated with an increased risk of breast cancer and makes the detection of cancer by mammography difficult, but the influence of density on risk according to method of cancer detection is unknown. METHODS: We carried out three nested case-control studies in screened populations with 1112 matched case-control pairs. We examined the association of the measured percentage of density in the baseline mammogram with risk of breast cancer, according to method of cancer detection, time since the initiation of screening, and age. RESULTS: As compared with women with density in less than 10% of the mammogram, women with density in 75% or more had an increased risk of breast cancer (odds ratio, 4.7; 95% confidence interval [CI], 3.0 to 7.4), whether detected by screening (odds ratio, 3.5; 95% CI, 2.0 to 6.2) or less than 12 months after a negative screening examination (odds ratio, 17.8; 95% CI, 4.8 to 65.9). Increased risk of breast cancer, whether detected by screening or other means, persisted for at least 8 years after study entry and was greater in younger than in older women. For women younger than the median age of 56 years, 26% of all breast cancers and 50% of cancers detected less than 12 months after a negative screening test were attributable to density in 50% or more of the mammogram. CONCLUSIONS: Extensive mammographic density is strongly associated with the risk of breast cancer detected by screening or between screening tests. A substantial fraction of breast cancers can be attributed to this risk factor.

Influence of patterns of hormone replacement therapy use and mammographic density on breast cancer detection.

BACKGROUND: There is evidence that factors such as current hormone replacement therapy (HRT) use and mammographic density may each lower the sensitivity of mammography and are associated with a greater risk of developing an interval cancer. This study explores this relationship further by examining the influence of patterns of HRT use and the percentage of mammographic density on the detection of breast cancer by classification of interval cancer. METHODS: This study uses a case-case design nested within a cohort of women screened by the Ontario Breast Screening Program between 1994 and 2002. Interval cancers, both those missed at screening but seen on retrospective review (n = 87) or true intervals without visible tumor signs at screening (n = 288) were matched to 450 screen-detected cancers. The association between the percentage of mammographic density, measured by radiologists and a computer-assisted method, and HRT use, ascertained from a mailed questionnaire, and the risk of being diagnosed with an interval cancer was estimated using conditional logistic regression. RESULTS: A monotonic gradient of increasing risk for interval cancers was found for each 25% increase in mammographic density [odds ratio (OR), 1.77; 95% confidence intervals (95% CI), 1.07-2.95 for missed intervals and OR, 2.16; 95% CI, 1.59-2.94 for true intervals]. After adjusting for mammographic density, a significantly increased risk for true-interval cancers remained for women taking estrogen alone (OR, 1.75; 95% CI, 1.11-2.83) as well as for missed- (OR, 2.84; 95% CI, 1.32-6.13) and true-interval cancers (OR, 1.79; 95% CI, 1.10-2.90) for women taking combined HRT. CONCLUSIONS: Information on mammographic density and HRT use should routinely be collected at the time of screening. Women at risk should be made aware of the lower sensitivity of mammography and offered alternative procedures for screening.

Risk factors for breast cancer associated with mammographic features in Singaporean chinese women.

BACKGROUND: Mammographic density has been found to be a strong risk factor for breast cancer and to be associated with age, body weight, parity, and menopausal status. Most studies to date have been carried out in Western populations. The purpose of the study described here was to determine in a cross-sectional study in a Singaporean Chinese population the demographic, menstrual, reproductive, and anthropometric factors that are associated with quantitative variations in age-adjusted percentage mammographic densities and to examine the association of these factors with the dense and nondense areas of the mammogram. METHOD: We used mammograms and questionnaire data collected from subjects in the Singapore Breast Screening Project. Women ages 45 to 69 years participated and 84% of those screened were Chinese. Mammograms were digitized and percentage density was measured and analyzed in relation to the questionnaire data. RESULTS: Percentage mammographic density was associated with several risk factors for breast cancer, most of them also associated, in opposite directions, with the dense and nondense components of the image. Percentage density was associated with age and weight (both negatively), height and age at first birth (both positively), and number of births and postmenopausal status (both negatively). Percentage density was weakly associated with a previous breast biopsy but was not associated with age at menarche or menopause, with use of hormones, or with a family history of breast cancer. CONCLUSION: Percentage mammographic density in Singaporean Chinese women has similar associations with risk factors for breast cancer to those seen in Caucasians.