Interval cancer in the Córdoba Breast Tomosynthesis Screening Trial (CBTST): comparison of digital breast tomosynthesis plus digital mammography to digital mammography alone

Abstract

Purpose: This work aims to compare the interval cancer rate and interval cancer characteristics between women screened with digital breast tomosynthesis (DBT) + digital mammography (DM) and those screened with DM alone.

Methods: The interval cancer rate and interval cancer characteristics of the study population included in the Córdoba Breast Tomosynthesis Screening Trial (CBTST) were compared to a contemporary control population screened with DM. The tumour characteristics of screen-detected and interval cancers were also compared. Contingency tables were used to compare interval cancer rates. The chi-square test and Fisher's exact test were used to compare the qualitative characteristics of the cancers whereas Student's t test and the Mann-Whitney U test were used to analyse quantitative features.

Results: A total of 16,068 screening exams with DBT + DM were conducted within the CBTST (mean age 57.59 ± 5.9 [SD]) between January 2015 and December 2016 (study population). In parallel, 23,787 women (mean age 58.89 ± 5.9 standard deviation [SD]) were screened with DM (control population). The interval cancer rate was lower in the study population than in the control population (15 [0.93‰; 95% confidence interval (CI): 0.73, 1.14] vs 43 [1.8‰; 95% CI: 1.58, 2.04] respectively; p = 0.045). The difference in rate was more marked in women with dense breasts (0.95‰ in the study population vs 3.17‰ in the control population; p = 0.031). Interval cancers were smaller in the study population than in the control population (p = 0.031).

Conclusions: The interval cancer rate was lower in women screened with DBT + DM compared to those screened with DM alone. These differences were more pronounced in women with dense breasts.

Clinical relevance statement: Women screened using tomosynthesis and digital mammography had a lower rate of interval cancer than women screened with digital mammography, with the greatest difference in the interval cancer rate observed in women with dense breasts.

Key points: • The interval cancer rate was lower in the study population (digital breast tomosynthesis [DBT] + digital mammography [DM]) than in the control population (DM). • The difference in interval cancer rates was more pronounced in women with dense breasts. • Interval cancers were smaller in the study population (DBT + DM) than in the control population (DM).

Keywords: Breast neoplasms; Digital breast tomosynthesis; Mammography; Mass screening.

Fig. 1

Flowchart of data selection and collection in the study. In total, 39,855 women were included: 23,787 in the control population and 16,067 in the study population. *One woman in the study population had bilateral cancer; thus, 16,068 screening exams were ultimately included. CBTST, Córdoba Breast Tomosynthesis Screening Trial; DBT, digital breast tomosynthesis; DM, digital mammography

Fig. 2

DM interval carcinoma. A 59-year-old woman with a palpable lump on the upper outer quadrant of the right breast 20 months after the last screening mammography, which was interpreted as normal. Craniocaudal (a) and right mediolateral oblique (b) projections of the screening mammography in which no suspicious findings were identified. Craniocaudal (c) and right mediolateral oblique (d) projections of diagnostic mammography, in which a spiculated mass (arrow) is seen in the symptomatic area. A percutaneous biopsy revealed a luminal B grade 2 invasive lobular carcinoma

Fig. 3

DM interval carcinoma. A 57-year-old woman with a palpable lump on the upper outer quadrant of the left breast 15 months after the last screening mammography, which was interpreted as normal. Craniocaudal (a) and left mediolateral oblique (b) projections of screening mammography without notable findings. Craniocaudal (c) and left mediolateral oblique (d) projections of diagnostic mammography, in which a spiculated mass (arrow) is identified in the symptomatic area. A triple-negative invasive ductal carcinoma with axillary involvement was confirmed

Fig. 4

DBT interval carcinoma. A 60-year-old asymptomatic patient who underwent a repeat mammographic study 20 months after the screening study interpreted as normal due to the diagnosis of breast cancer in a first-degree relative. Craniocaudal (a) and mediolateral oblique (b) projections, respectively, of the tomosynthesis of the right breast performed in the screening program, in which a small spiculated mass is identified in the upper inner quadrant of the right breast (arrow) that was not noticed at the time. Craniocaudal (c) and mediolateral oblique (d) projections, respectively, of the diagnostic mammogram showing that the mass had increased in size. e Breast ultrasound, in which the mass is visible. f Breast MRI. MIP T1 reconstruction with IV contrast and fat suppression in which it is verified that the lesion is unique (arrow). Pathological result: luminal A grade 2 invasive ductal carcinoma