Association of treatment delay and stage with mortality in breast cancer: a nationwide cohort study in Taiwan

Breast cancer is the fifth leading cause of cancer death globally. In this retrospective study, we investigated the effects of the diagnosis-to-first-treatment interval (DFTI) and other related factors on cancer-specific survival in patients with breast cancer. We included 49,426 patients newly diagnosed as having breast cancer during 2011–2017. The Cox proportional hazards model was used to analyze the hazard ratio (HR) for mortality with various DFTIs; the HRs of the 31–60-, 61–90-, and ≥ 91-day DFTI groups did not differ significantly compared with the reference group (DFTI ≤ 30 days). After stratifying the patients according to initial tumor stage and age, we found that patients aged 55–64 and ≥ 65 years with stage II breast cancer treated ≥ 91 days after diagnosis had a 3.34- and 2.93-fold higher mortality risk (95% confidence intervals [CIs] 1.29–8.69 and 1.06–8.10, respectively). Patients aged ≥ 65 years with stage IV breast cancer treated within 61–90 or ≥ 91 days after diagnosis had a 7.14- and 34.78-fold higher mortality risk (95% CIs 1.28–39.82 and 3.08–393.32, respectively). In conclusion, DFTI is associated with mortality in patients with stage II and IV breast cancer, especially at an older age.