did not reach statistical significanceP = 0.0569
There were slight differences in the RR of developing SPBC after chemotherapy among different age groups, but these differences did not reach statistical significance (from 18 to 50 years old, RR: 2, 95% CI: 1.09–3.65, P = 0.0569; from 50 to 70 years old, RR: 1.12, 95% CI: 0.9–1.39, P = 0.387; over 70 years old, RR: 1.32, 95% CI: 0.97–1.8, P = 0.13) (Fig. 8 E).