Data collection was supported by grants from MINECO-Instituto de Salud Carlos III-FEDER [grant numbers: PS09/01153 (M Sala), PI12/00387 (M Sala), PI11/01296 (X Castells) and PI15/00098 (X Castells)]. Data analysis was partly supported by grants the Research Network on Health Services in Chronic Diseases (REDISSEC) (MINECO-Instituto de Salud Carlos III) [RD12/0001/0015 (M Sala); RD12/0001/0007 (M Baré); RD16/0001/0013 (M Sala)]. The funders had no role in study design, data collection, data analysis, data interpretation, or writing of the manuscript.

Background: We aimed to identify the risk factors associated with early, late and long-term readmissions in women diagnosed with breast cancer participating in screening programs. Methods: We performed a multicenter cohort study of 1055 women aged 50-69 years participating in Spanish screening programs, diagnosed with breast cancer between 2000 and 2009, and followed up to 2014. Readmission was defined as a hospital admission related to the disease and/or treatment complications, and was classified as early (< 30 days), late (30 days-1 year), or long-term readmission (> 1 year). We used logistic regression to estimate the adjusted odds ratios (aOR), and 95% confidence intervals (95% CI) to explore the factors associated with early, late and long-term readmissions, adjusting by women's and tumor characteristics, detection mode, treatments received, and surgical and medical complications. Results: Among the women included, early readmission occurred in 76 (7.2%), late readmission in 87 (8.2%), long-term readmission in 71 (6.7%), and no readmission in 821 (77.8%). Surgical complications were associated with an increased risk of early readmissions (aOR = 3.62; 95%CI: 1.27-10.29), and medical complications with late readmissions (aOR = 8.72; 95%CI: 2.83-26.86) and long-term readmissions (aOR = 4.79; 95%CI: 1.41-16.31). Conclusion: Our results suggest that the presence of surgical or medical complications increases readmission risk, taking into account the detection mode and treatments received. Identifying early complications related to an increased risk of readmission could be useful to adapt the management of patients and reduce further readmissions. Trial Registration: ClinicalTrials.govIdentifier: NCT03165006. Registration date: May 22, 2017 (Retrospectively registered).