Women with dense breasts have higher odds of screen-detected, interval breast cancers

Screening examinations using an automated software showed increased rates of recall and biopsy, as well as higher likelihood of screen-detected and interval breast cancers, among women with dense compared with nondense breasts, according to results of a retrospective study.

“The odds of screen-detected and interval breast cancer were substantially higher for women with mammographically dense vs. fatty breasts in BreastScreen Norway,” Solveig Hofvind, PhD, from the faculty of health science at Oslo Metropolitan University, Norway, said in a press release. “We also found substantially higher rates of recalls and biopsies among women with mammographically dense breast tissue.”

The results can inform how automated volumetric density categorization will impact population-based screening performance and outcomes using an objective breast density measurement paradigm, according to researchers.

Studies have reported women with mammographically dense breasts have increased risks for breast cancer and missed cancers than women with nondense breasts.

Mammographic density studies have focused on the association between subjective density assessments and breast cancer risk. However, few studies used objective density measures for risk estimation and few have evaluated quantitative breast density measurement with regard to screening performance.

Because no standard exists for breast density determination, the most common classification for mammographic density is based on subjective interpretation using the American College of Radiology’s Breast Imaging Reporting and Data System.

In various areas in the United States, legislation mandates women be informed about their breast density or that additional imaging could be beneficial; however, supplemental screening for women with dense breasts is not recommended by any major medical societies or organizations.

Hofvind and colleagues sought to determine recall and biopsy rates, cancer detection rates, positive predictive values, sensitivity, specificity, histopathologic tumor characteristics,

odds of breast cancer and predicted numbers of breast cancer cases based on volumetric breast density categories.

“We hypothesized that screening examinations of women with high volumetric breast density were associated with less favorable screening outcomes compared with those of women with low breast density,” researchers wrote in the study.

Investigators used automated software to classify mammographic density of 107,949 women aged 50 to 69 years (mean age, 58.7 years) enrolled in BreastScreen Norway — a national program that offers women breast screening every 2 years. Each woman underwent an average 2.8 screening examinations during the study period, which accounted for 307,015 examinations.

Researchers used Senographe DS or Senographe Essential (GE Medical Systems SCS) for full-field digital mammography and Volpara, version 1.5.1 (Volpara Solutions) to measure absolute density, breast volume and volumetric breast density.

Twenty-eight percent (n = 87,021) of examination classified breasts as dense.

A greater proportion of women with dense breasts had recalls (3.6% vs. 2.7%) and needle biopsies due to abnormal screening (1.4% vs. 1.1%; P < .0001 for both) than women with nondense breasts.

Researchers reported a screen-detected cancer rate of 5.5 per 1,000 examinations (n = 1,210) among women with nondense breasts and 6.7 per 1,000 examinations (n = 581) among women with dense breasts (P < .001).

The rate for interval breast cancer was 1.2 per 1,000 examinations (n = 199 of 165,324) among women with nondense breasts compared with 2.8 per 1,000 examinations (n = 185 of 66,674) among women with dense breasts (P < .001).

Researchers reported a sensitivity of 82% among nondense breasts and 71% among dense breasts, whereas specificity was 98% and 97% (P < .0001 for both).

Among screen-detected cancers, mean tumor diameter was larger among women with dense breasts (16.6 mm vs. 15.1 mm; P = .009). Also, a greater proportion of women with dense breasts had lymph node-positive disease (24% vs. 18%; P = .023) and luminal B-like HER-2-positive tumors (11% vs. 7%; P = .007).

Researchers did not observe significant differences in tumor characteristics of interval breast cancer among women with nondense vs. dense breasts regarding mean tumor diameter (25.3 mm vs. 24.1 mm), lymph node involvement (41% vs. 44%) and triple-negative status (17% vs. 15%).

Overall, women with dense breasts had a 1.37-times (95% CI, 1.19-1.59) higher likelihood of screen-detected breast cancer and 2.93-times (95% CI, 2.16-3.97) higher likelihood of an interval breast cancer.

“We need well-planned and high-quality studies that can give evidence about the cost-effectiveness of more frequent screening, other screening tools such as tomosynthesis, and/or use the use of additional screening tools like MRI and ultrasound for women with dense breasts,” Hofvind said. “Further, we need studies on automated measurement tools for mammographic density to ensure their validity.”

This study is important because it validates than an automated means of density classification can correctly identify women with dense tissue, and because it shows screening mammography has poorer performance for women with dense tissue, Liane E. Philpotts, MD, FACR, chief of breast imaging and professor of radiology and biomedical imaging at Yale School of Medicine, wrote in an accompanying editorial.

“Breast cancer density is here to stay, and it is in everyone’s best interest to embrace understanding and optimization of breast imaging practice to best address the needs of women with dense tissue,” Philpotts wrote. – by Melinda Stevens

Disclosure s : Hofvind is the head of BreastScreen Norway. Please see the full study for a list of all other authors’ relevant financial disclosures. HemOnc Today could not confirm Philpotts’s relevant financial disclosures at the time of publication.