Breast density scales: the metric matters.

OBJECTIVE: Measures of percent mammographic density (PMD) are often categorized using various density scales. The purpose of this study was to examine information loss associated with the use of categorical density scales. METHODS: Baseline PMD was assessed at 1% precision for 2,374 females. The data were used to create 21-category, 4-category and 2-category density scales. R-squared and root mean square error were used to evaluate the effect of categorizing PMD. The area under the receiver operator characteristic curves were compared between cancer risk models employing solely categorical PMD scales and solely baseline PMD for a subset of females (424 cases, 848 controls). RESULTS: R-squared value decreased from 1.00 (1% PMD) to 0.56 (2-category scale), while root mean square error increased from 0.00 (1% PMD) to 10.83 (2-category scale). The area under the receiver operator characteristic curve decreased from 0.64 for a cancer risk model using 1% PMD to 0.58 for a risk model using a 21-category density scale (p < 0.0001), 0.55 for a 4-category Breast Imaging, Reporting and Data System-like scale (p < 0.0001) and 0.50 for a 2-category Breast Imaging, Reporting and Data System-like scale (high vs low) (p < 0.0001). CONCLUSION: Categorizing PMD measures into categorical density scales leads to a significant loss of information. Indeed, a simple high versus low split of PMD using a 50% cut point yields a cancer risk model with no discriminatory power. Advances in knowledge: Use of categorical mammographic density scales rather than continuous percent mammographic density measures leads to significant loss of information. Breast cancer risk models using categorical mammographic density scales perform more poorly than models using continuous PMD measures.

Utility of relative and absolute measures of mammographic density vs clinical risk factors in evaluating breast cancer risk at time of screening mammography.

OBJECTIVE: Various clinical risk factors, including high breast density, have been shown to be associated with breast cancer. The utility of using relative and absolute area-based breast density-related measures was evaluated as an alternative to clinical risk factors in cancer risk assessment at the time of screening mammography. METHODS: Contralateral mediolateral oblique digital mammography images from 392 females with unilateral breast cancer and 817 age-matched controls were analysed. Information on clinical risk factors was obtained from the provincial breast-imaging information system. Breast density-related measures were assessed using a fully automated breast density measurement software. Multivariable logistic regression was conducted, and area under the receiver-operating characteristic (AUROC) curve was used to evaluate the performance of three cancer risk models: the first using only clinical risk factors, the second using only density-related measures and the third using both clinical risk factors and density-related measures. RESULTS: The risk factor-based model generated an AUROC of 0.535, while the model including only breast density-related measures generated a significantly higher AUROC of 0.622 (p < 0.001). The third combined model generated an AUROC of 0.632 and performed significantly better than the risk factor model (p < 0.001) but not the density-related measures model (p = 0.097). CONCLUSION: Density-related measures from screening mammograms at the time of screen may be superior predictors of cancer compared with clinical risk factors. ADVANCES IN KNOWLEDGE: Breast cancer risk models based on density-related measures alone can outperform risk models based on clinical factors. Such models may support the development of personalized breast-screening protocols.

The burden of false-positive results in analog and digital screening mammography: experience of the Nova Scotia Breast Screening Program.

PURPOSE: The Canadian Task Force on Preventive Health Care released recommendations for breast cancer screening, in part, based on harms associated with screening. The purpose of this study was to describe the rate of false-positive (FP) screening mammograms and to describe the extent of the investigations after an FP. METHODS: A cohort was identified that consisted of all screening mammograms performed through the Screening Program (2000-2011) with patients ages 40-69 years at screening. Rates of FP screening mammograms were calculated as well as rates of further investigations required, including additional imaging, needle core biopsy, and surgery. Analyses were stratified by 10-year age group, screening status (first vs rescreen), and technology. RESULTS: A total of 608,088 screening mammograms were included. The FP rate varied by age group, and decreased with increasing age (digital, 40-49 years old, FP = 8.0%; 50-59 years old, FP = 6.3%; 60-69 years old, FP = 4.6%). The FP rate also varied by screening status (digital, first screen, FP = 12.0%; rescreen, FP = 5.6%), and this difference was consistent across age groups. The need for further investigation varied by age group, with invasive procedures being more heavily used as women age (digital, rescreen group, surgery: 40-49 years old, 1.1%; 50-59 years old 1.6%, 60-69 years old, 1.8%). CONCLUSIONS: Both the FP screening mammogram rate and the degree to which further investigation was required varied by age group and screening status. Reporting on these rates should form part of the evaluation of screening performance.

A review of interval breast cancers diagnosed among participants of the Nova Scotia Breast Screening Program.

PURPOSE: To conduct a radiologic review of interval breast cancer cases to determine rates of true interval and missed cancers in Nova Scotia, Canada. MATERIALS AND METHODS: This quality assurance project was exempt from institutional review board approval. Interval cancer cases were identified among women aged 40-69 years who were participants in the Nova Scotia Breast Screening Program from 1991 to 2004. For each case, the index negative screening mammogram was reviewed blindly by three radiologists from a pool of experienced radiologists. Cases were identified as those with normal or abnormal findings, the latter being a case that required further investigation. True interval cases were identified as cases in which a minimum of two radiologists reviewed the findings as normal. True interval and missed cancer rates were calculated separately for women according to age group and screening interval (for ages 40-49 years, a 1-year interval; for ages 50-69 years, a 1-year and a 2-year interval). RESULTS: The rate of missed cancers per 1000 women screened was one-half of the true interval rate among women screened annually (for ages 40-49 years, 0.45 vs 0.93; for ages 50-69 years, 1.08 vs 2.22). Among women aged 50-69 years who were screened biennially, the rate of missed cancers per 1000 women screened was one-third of the true interval rate (0.90 vs 3.15). Similarly, the rate of missed cancers per 10,000 screening examinations was one-half of the true interval rate among those 40-49 years old (1.95 vs 3.99) and one-third of the true interval rate among those 50-69 years old (3.34 vs 10.44). CONCLUSION: In screening programs, true interval cancer rates should be differentiated from missed cancer rates as part of ongoing quality assurance.

Ten years of breast screening in the Nova Scotia Breast Screening Program, 1991-2001. experience: use of an adaptable stereotactic device in the diagnosis of screening-detected abnormalities.

OBJECTIVE: To evaluate and present 10-year outcomes of the Nova Scotia Breast Screening Program (NSBSP), a population-based screening program in the province of Nova Scotia, Canada, total population 900 000. SETTING: Organized Breast Screening Program in Nova Scotia, Canada. METHODS: Rates of participation, abnormal referrals, cancer detection rates, and benign:malignant (B:M) rates for core biopsy and surgical biopsy were calculated for asymptomatic women receiving a mammogram through the NSBSP 1991-2001. RESULTS: Of 192 454 mammograms performed on 71 317 women, 33% were aged 40 to 49 years, 39% aged 50 to 59 years, 23% aged 60 to 69 years, and 5% aged 70 years and over. Cancer detection rate increased in each age group respectively: 3.7, 5.8, 9.7, and 13.5 per 1000 population on first-time screens. The positive predictive value of an abnormal screen increased with increasing age groups. Benign breast surgery decreased with increased use of needle core breast biopsy (NCBB). Open surgery decreased from 25 to 6 surgeries per 1000 screens. Of 1519 open surgical procedures (1328 women), 878 cancers were removed, with 37% 10 mm or less, and 61% 15 mm or less. In 613 women in whom the node status was assessed, 79% were negative. CONCLUSION: A quality screening program incorporating NCBB in the diagnostic work-up is effective in the early detection of breast cancer and results in less open surgery, particularly in younger women.

Ductal carcinoma in situ in core biopsies containing invasive breast cancer: correlation with extensive intraductal component and lumpectomy margins.

BACKGROUND AND OBJECTIVES: The diagnosis of invasive breast cancer is most commonly made on image-guided core biopsy (CB). The presence of extensive intraductal component (EIC), as identified on subsequent lumpectomy, is associated with an increased risk of positive margins and need for further surgery. CBs demonstrating invasive breast cancer may also contain ductal carcinoma in situ (DCIS), although the significance of this finding is unclear. The objective of this study was to examine the implications of DCIS found in the original CB, specifically related to the risk of EIC and/or positive lumpectomy margins. METHODS: All patients at a single academic institution who underwent initial breast conserving surgery for invasive breast cancer diagnosed on image-guided CB between 05/00 and 04/02 were included in the study. A systematic, blinded review of all CB and lumpectomy specimens was performed using standardized criteria for DCIS, EIC, and margins. RESULTS: A total of 95 patients were included in the study, with a mean of 5 (median 5) CB/patient. Of these, 43 (45%) patients had DCIS identified in their CB; in 34 (79%) of these patients, the DCIS was mixed with the invasive cancer. No differences in tumor size or lumpectomy volume were identified between patients with or without DCIS on CB. However, patients with DCIS were noted to be significantly younger. Overall, EIC was identified in 13 (14%) patients; the risk of EIC was significantly higher in patients with DCIS identified in CB than in those with invasive carcinoma alone (30% vs. 0%, respectively; P < 0.0001). Expectedly, the incidence of positive margins on lumpectomy was higher in patients with EIC (38% vs. 16%; P = 0.05). A trend, although not statistically significant, towards positive margins was also noted in patients with DCIS on CB compared to those with invasive carcinoma alone (24% vs. 15%, P = 0.3). CONCLUSIONS: The identification of DCIS in conjunction with invasive cancer on CB appears important; the absence of DCIS in a CB sample excludes the possibility of eventually identifying EIC. Knowledge of DCIS in CBs with invasive carcinoma may be helpful for surgeons in planning gross resection margins at lumpectomy.

Patient navigation: improving timeliness in the diagnosis of breast abnormalities.

OBJECTIVE: Patient navigation is a process that provides assistance to referring physicians in arranging further investigations and consultation for defined patient groups. This can facilitate timely investigations and potentially minimize delays. The purpose of this study was to determine the impact of patient navigation on timeliness in the diagnosis of breast abnormalities. METHODS: We retrospectively studied a cohort of 536 women who underwent breast core biopsy at our institution during comparable 6-month periods in 1999 and 2000 to determine the effects of patient navigation, age, and biopsy result on the wait for a biopsy after diagnostic imaging. Patient navigation was used for all women referred through the provincial breast cancer screening program. Navigation was unavailable to patients directly referred by physicians in 1999. In 2000, the program was expanded to encompass all patients. RESULTS: From 1999 to 2000, the median wait for a biopsy remained relatively stable for "navigated" screening patients at 12 days (n = 97) and 13 days (n = 133), respectively. The introduction of patient navigation for directly referred patients resulted in a statistically significant decrease in waiting times, from 20 days (n = 144) in 1999 to 14 days (n = 162) in 2000. Age and biopsy results were statistically significant variables, but their effect on the group data was negligible relative to that of navigation. CONCLUSIONS: Patient navigation significantly improves timeliness in the diagnosis of breast abnormalities and can potentially improve quality of life with more timely reassurance for women with benign conditions and earlier treatment for those with malignancy.