Table 2.

Assessment of methodological quality including proportion of secondary breast cancer patients included, quality rating, GRADE rating and overall study weighting (n = 19)

No	Author (year)	Sample size (% of SBC patients) included	Quality ratinga	GRADE ratingb	Overall study weightingc
1	Accordino et al. (2017) [26]	4251/4521 (100)	Moderate	Moderate	1
2	Alves et al. (2022) [33]	296/2525 (12%)	Low	Low	3
3	Cole et al. (2019) [34]	65,380/601,680 (11)	Moderate	Moderate	2
4	Falchook et al. (2017) [35]	5855/28,731 (20)	Moderate	Moderate	2
5	Ferreira et al. (2020) [36]	10,816/151,931 (7)	Low	Low	3
6	Giap et al. (2023) [27]	60,685/60,685 (100)	Moderate	Moderate	2
7	Ozmen et al. (2015) [37]	29/1031 (3)	Low	Low	3
8	Recondo et al. (2019) [38]	268/13 (5)	Low–moderate	Low–moderate	3
9	Sathe et al. (2023) [28]	6082/6082 (100)	Moderate	Moderate	1
10	Shih et al. (2009) [39]	42,804/207,581 (21)	Moderate	Moderate	2
11	Shiovitz et al. (2015) [40]	3583/76,259 (5)	Moderate	Moderate	2
12	Skinner et al. (2021) [32]	608/608 (100)	Moderate	Moderate	2
13	Small et al. (2012) [41]	57,148/773,233 (7)	Moderate	Moderate	1
14	Statler et al. (2019) [30]	6234/6234 (100)	Moderate	Moderate	1
15	Vas Luiz et al. (2015) [31]	4364/4364 (100)	Moderate	Moderate	2
16	Vyas et al. (2021) [5]	1089/1089 (100)	Moderate	Moderate	1
17	Wan & Jubelirer (2015) [35]	4533/4533 (100)	Moderate	Moderate	1
18	Wang & Du (2015) [42]	1100/25,128 (4)	Low–moderate	Low–moderate	3
19	Wolfson et al. (2015) [43]	1441/75,987 (4)	Low–moderate	Low–moderate	3

^aJoanna Briggs Institute assessment of methodological quality [24, 25]

^bGRADE quality rating [26]. Low, true effect might be markedly different from the estimated effect. Moderate, true effect is probably close to the estimated effect

^cOverall study weighting for contribution to narrative synthesis

1 = High

2 = Moderate

3 = Low