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

PurposeThis 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.MethodsThe interval cancer rate and interval cancer characteristics of the study population included in the Cordoba 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.ResultsA total of 16,068 screening exams with DBT+DM were conducted within the CBTST (mean age 57.595.9 [SD]) between January 2015 and December 2016 (study population). In parallel, 23,787 women (mean age 58.895.9 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 parts per thousand in the control population; p=0.031). Interval cancers were smaller in the study population than in the control population (p=0.031).ConclusionsThe 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.