“…To ensure each covariate was scientifically sound, the covariates should be identified based on clinical assumptions and biology ( 46 ). Therefore, based on the above literature ( 46 , 47 ) and previous related studies ( 48 – 78 ), we assumed that the heterogeneity might arise from the age, gender (male and female), sample size (<200 and ≥200), types of cancer (breast cancer group, mixed-type group, and other-type group), publication year, region (north and south), follow-up, random sampling, instruments used to measure FCR and SS, and source of SS. In this study, meta-regression was performed to explore whether the differences in categorical covariates such as SS measurement, FCR measurement, types of cancer, follow-up, and region, whereas sample size and publication year were used as continuous covariates, when covariates were statistically significant, with P ≤ 0.05.…”