Causes and consequences of delayed diagnosis in breast cancer screening with a focus on mammographic features and tumour characteristics

Purpose: To study the prevalence, causes and consequences of delayed breast cancer diagnosis in the screening population. Methods: This retrospective study was performed in women who underwent biennial screening mammography between January 1, 2009 and June 30, 2019. Patients were divided into 3 groups; screen-detected breast cancer (SDC) without a diagnostic delay, a primary diagnostic delay (i.e. missed cancer at previous screening round) and a delay in diagnostic work-up after recall. Women with a true interval cancer (IC; i.e. not visible on prior examinations) were excluded. Outcome parameters included mammographic and tumour characteristics, lymph node status and surgical treatment. Results: In our sample of 4491 women with breast cancer (4292 SDC and 199 'missed' IC), respectively, a total of 1112 women experienced a diagnostic delay of >= 4 months. Compared to women without a diagnostic delay (n = 2720), the 176 women with a delay in diagnostic work-up showed overall similar mammographic abnormalities (P = 0.052). These groups show similar distributions in invasive tumours, tumour stage and lymph node status (P = 0.25, P = 0.95 and P = 0.93, respectively). Women with a primary diagnostic delay (n = 936) showed less calcifications (P < 0.001), and more masses with calcifications and architectural distortions on mammography (P = 0.01 and P = 0.04, respectively). Moreover, this group comprised larger tumours (P < 0.001) and lymph node metastases (P < 0.001), and more often underwent mastectomy (P < 0.001). Conclusions: A primary diagnostic delay in breast cancer diagnosis results in less favourable tumour characteristics and relatively more mastectomies compared to no delay in breast cancer diagnosis and a delay in diagnostic work-up after recall.