Fig. 2

Standardized incidence ratios (SIRs) and 95% confidence intervals (CIs) for second primary cancer according to characteristics of the first breast cancer among 16,004 women diagnosed with a first primary unilateral invasive breast cancer between 1990 to 2016 and followed through 2017. Abbreviations: SIRs–Standardized incidence ratios, CI–Confidence interval, O–Observed, E–Expected, ER–Estrogen receptor. Note: Second primary cancer excludes second ipsilateral breast cancer. ^aP-values to test for heterogeneity between SIRs. ^bNo/unknown receipt of radiotherapy is combined due to potential under ascertainment of radiotherapy in registry data (no radiotherapy: n = 5,302; unknown radiotherapy: n = 64). ^cRestricted to women diagnosed with a first ER-positive breast cancer (n = 12,746)