Literature Search
Figure 1 illustrates the flow chart for the selection of eligible studies. 720 studies were identified by searching PubMed, Cochrane, and EMBASE databases. 469 studies remained after removing duplicate files. After scanning the titles and abstracts, 50 studies were selected for full-text review. Finally, we included 17 studies that met the inclusion criteria for our meta-analysis [7, 8, 11, 13–19, 21–27].
Study Characteristics
Table 1 shows the characteristics of the 17 studies included. Of these studies, 7 studies were conducted in Europe (Spain, Italy, Norway, and the European region) [8, 11, 13, 15, 21, 22, 24], and 9 studies were conducted in the Americas (United States, Canada and North American region) [7, 14, 16–19, 23, 24, 27]. 1 study was conducted in Asia (Korea) [25], and 1 study was conducted in Oceania (Australia) [26]. 15 studies were retrospective cohort studies [8, 11, 13–19, 21, 23–27], and 2 studies were clinical trials [7, 22]. 8 studies assessed MSI using quasimonomorphic mononucleotide markers [7, 8, 15–19, 21], and 9 studies assessed MSI using immunohistochemistry [11, 13, 14, 22–27].
Table 1
Characteristics of studies included in the meta-analysis
author
|
Year
|
Country or region
|
Number of patients
|
MSI, n
|
MSS, n
|
Stage distribution
|
histology
|
Microsatellite markers
|
Microsatellte instability definition
|
Outcome assessment
|
Study design
|
Follow-up time
|
Fiumicino et al.
|
2001
|
Italy
|
65
|
11
|
54
|
I-II
|
EEC
|
D2S123, D2S119, D9S171, D9S157, D10S216, BAT26
|
≥ 2 of 6 markers with mutant alleles
|
DFS
|
Retrospective cohort study
|
76ms
(12ms-139ms)
|
Maxwell et al.
|
2001
|
United States
|
131
|
29
|
102
|
I-IV
|
EEC
|
BAT26, D14S65, D14S197
|
≥ 2 of 3 markers with mutant alleles
|
OS
|
Retrospective cohort study
|
75.6ms
(least 3 years)
|
Zighelboim et al.
|
2007
|
United States
|
446
|
147
|
299
|
I-IV
|
EEC
|
BAT26, BAT25, D2S123, D5S346, D17S250
|
≥ 2 of 5 markers with mutant alleles
|
OS/DFS
|
Retrospective cohort study
|
54.8ms
(0.7ms-176ms)
|
Bilbao et al.
|
2010
|
United States
|
93
|
20
|
73
|
I-III
|
EEC
|
BAT26, BAT25, NR-21, NR-24, NR-27
|
≥ 2 of 5 markers with mutant alleles
|
DFS
|
Retrospective cohort study
|
138ms
(16-232ms)
|
Bilbao et al.
(early-stage)
|
2010
|
United States
|
79
|
14
|
65
|
I-II
|
EEC
|
BAT26, BAT25, NR-21, NR-24, NR-27
|
≥ 2 of 5 markers with mutant alleles
|
DFS
|
Retrospective cohort study
|
138ms
(16-232ms)
|
Mackey et al.
|
2010
|
Canada
|
84
|
23
|
61
|
I-II
|
EEC
|
BAT26, BAT25
|
≥ 1 of 2 markers with mutant alleles
|
DFS
|
Clinical trials
|
NR
|
Steinbakk et al.
|
2011
|
Norway
|
171
|
27
|
144
|
I
|
EEC
|
BAT26, BAT25, NR-21, NR-24, NR-27
|
≥ 2 of 5 markers withmutant alleles
|
OS
|
Retrospective cohort study
|
1-209ms
|
Nout et al.
|
2012
|
Italy
|
64
|
22
|
42
|
I
|
EEC
|
MLH1, MSH2, MSH6, PMS2
|
≥ 1 of 4 MMR protein was lost
|
DFS
|
Retrospective cohort study
|
88ms
(4-106ms)
|
Ruiz et al.
|
2014
|
Spain
|
163
|
50
|
113
|
I-II
|
EEC
|
MLH1, MSH2, MSH6, PMS2
|
≥ 1 of 4 MMR protein was lost
|
OS/DFS
|
Clinical trials
|
NR
|
Bilbao-Sieyro et al.
|
2014
|
Spain
|
155
|
32
|
123
|
I-III
|
EEC
|
BAT26, BAT25, NR21, NR24, NR27
|
≥ 2 of 5 markers with mutant alleles
|
DFS/ESS
|
Retrospective cohort study
|
112ms
(6-227ms)
|
Zighelboim et al.
|
2015
|
United States
|
475
|
368
|
107
|
I-IV
|
EEC
|
BAT26, BAT25, D2S123, D5S346, D17S250
|
≥ 2 of 5 markers with mutant alleles
|
OS/DFS
|
Retrospective cohort study
|
79ms
(0.2ms-122.5ms)
|
McMeekin et al.
|
2016
|
United States
|
1024
|
639
|
385
|
I-IV
|
EEC
|
MLH1, MSH2, MSH6, PMS2
|
≥ 1 of 4 MMR protein was lost
|
PFS
|
Retrospective cohort study
|
NR
|
Kim et al.
|
2018
|
Korea
|
151
|
34
|
117
|
I-II
|
EEC
|
MLH1, MSH2, MSH6, PMS2
|
≥ 1 of 4 MMR protein was lost
|
OS/PFS
|
Retrospective cohort study
|
27ms
(1-123ms)
|
Nagle et al.
|
2018
|
Australia
|
581
|
458
|
123
|
I-IV
|
EEC
|
MLH1, MSH2, MSH6, PMS2
|
≥ 1 of 4 MMR protein was lost
|
OS/ESS
|
Retrospective cohort study
|
36-102ms
|
Bosse et al.
|
2018
|
Europe and North America
|
249
|
136
|
113
|
I-IV
|
EEC
|
MLH1, MSH2, MSH6, PMS2
|
≥ 1 of 4 MMR protein was lost
|
OS/RFS/Recurrence
|
Retrospective cohort study
|
73.2ms
(2.4-204ms)
|
Backes et al.
|
2018
|
United States
|
197
|
64
|
133
|
I-II
|
EEC
|
MLH1, MSH2, MSH6, PMS2
|
≥ 1 of 4 MMR protein was lost
|
RFS/Recurrence
|
Retrospective cohort study
|
54ms
(0-120ms)
|
Ruz-Caracuel et al.
|
2019
|
Spain
|
199
|
31
|
168
|
I-II
|
EEC
|
MLH1, MSH2, MSH6, PMS2
|
≥ 1 of 4 MMR protein was lost
|
OS/DFS
|
Retrospective cohort study
|
83.96ms
(0-174ms)
|
Kim et al.
|
2020
|
Canada
|
475
|
131
|
344
|
IA
|
EEC
|
MLH1, MSH2, MSH6, PMS2
|
≥ 1 of 4 MMR protein was lost
|
OS/PFS
|
Retrospective cohort study
|
23.4ms
(14-39ms)
|
EEC: endometrioid endometrial cancers; MMR: mismatch repair; OS: overall survival; PFS: progression-free survival; DFS: disease-free survival; ESS: EEC-specific survival; ms: months; NR: not reported
|
As shown in Table 2, all studies scored 7 or higher and were high-quality studies.
Table 2
Methodological quality of cohort studies included in the meta-analysis.
Authors
|
Year
|
Representativeness of the exposed cohort
|
Selection of the unexposed cohort
|
Ascertainment of exposure
|
Outcome of interest not present at start of study
|
Control for important factor or additional factor
|
Outcome assessment
|
Follow up long enough for outcomes to occur
|
Adequacy of follow up of cohorts
|
Total quality scores
|
Fiumicino et al.
|
2001
|
+*
|
+
|
+
|
+
|
+
|
+
|
+
|
+
|
9
|
Maxwell et al.
|
2001
|
+
|
+
|
+
|
+
|
++
|
+
|
+
|
+
|
9
|
Zighelboim et al.
|
2007
|
+
|
+
|
+
|
+
|
++
|
+
|
+
|
+
|
9
|
Bilbao et al.
|
2010
|
+
|
+
|
+
|
+
|
++
|
+
|
-**
|
+
|
8
|
Mackey et al.
|
2010
|
+
|
+
|
+
|
+
|
++
|
+
|
-
|
-
|
7
|
Steinbakk et al.
|
2011
|
+
|
+
|
+
|
+
|
-
|
+
|
+
|
+
|
7
|
Nout et al.
|
2012
|
-
|
-
|
+
|
+
|
++
|
+
|
+
|
+
|
7
|
Ruiz et al.
|
2014
|
+
|
+
|
+
|
+
|
++
|
+
|
-
|
+
|
8
|
Bilbao-Sieyro et al.
|
2014
|
-
|
-
|
+
|
+
|
++
|
+
|
+
|
+
|
7
|
Zighelboim et al.
|
2015
|
+
|
+
|
+
|
+
|
+
|
+
|
-
|
-
|
7
|
McMeekin et al.
|
2016
|
-
|
-
|
+
|
+
|
++
|
+
|
+
|
+
|
7
|
Kim et al.
|
2018
|
+
|
+
|
+
|
+
|
++
|
+
|
+
|
+
|
9
|
Nagle et al.
|
2018
|
+
|
+
|
+
|
+
|
++
|
+
|
+
|
+
|
9
|
Bosse et al.
|
2018
|
+
|
+
|
+
|
+
|
++
|
+
|
+
|
+
|
9
|
Backes et al.
|
2018
|
+
|
+
|
+
|
+
|
++
|
+
|
+
|
+
|
9
|
Ruz-Caracuel et al.
|
2019
|
+
|
+
|
+
|
+
|
++
|
+
|
+
|
+
|
9
|
Kim et al.
|
2020
|
+
|
+
|
+
|
+
|
+
|
+
|
-
|
+
|
7
|
* If there is a positive symbol that means score one point
** A negative symbol means no point
|
Correlation Between MSI and Overall Survival in the EEC or Early-Stage EEC
The pooled HR for patients with EEC shown that MSI was significantly associated with shorter overall survival [HR = 1.37, 95% CI (1.00-1.86), p = 0.048]. Meanwhile, significant heterogeneity was observed (I2 = 60.6%), as shown in Fig. 2a.
In the subgroup analysis of patients with early-stage EEC, patients with MSI had a shorter overall survival [HR = 1.47, 95% CI (1.11–1.95), p = 0.07], and no heterogeneity was observed (I2 = 20.9%), as shown in Fig. 3a.
Correlation Between MSI and Disease-Free Survival in the EEC or Early-Stage EEC
The pooled HR for patients with EEC shown that MSI was associated with shorter disease-free survival [HR = 1.99, 95% CI (1.31–3.01), p = 0.000]. Meanwhile, heterogeneity was observed (I2 = 65.7%, p = 0.001), as shown in Fig. 2b.
In the subgroup analysis of early-stage EEC, patients with MSI had a shorter disease-free survival [HR = 4.17, 95% CI (2.37–7.41), p = 0.000], and no heterogeneity was identified (I2 = 0.0%), as shown in Fig. 3b.
Correlation Between MSI and EEC-Specific Survival in Patients with EEC
As shown in Fig. 2c, the pooled HR for patients with EEC shown a significant association between MSI with shorter EEC-specific survival [HR = 2.07, 95% CI (1.35–3.18), p = 0.001]. Meanwhile, no significant heterogeneity was observed (I2 = 31.6%).
Correlation Between MSI and Progression-Free Survival in Patients with Early-Stage EEC
As shown in Fig. 3c, the pooled HR for the early-stage EEC subgroup shown that MSI was significantly associated with shorter progression-free survival [HR = 2.41, 95% CI (1.05–5.54), p = 0.039]. Meanwhile, no heterogeneity was detected (I2 = 0.0%).
Correlation Between MSI and Recurrence-Free Survival in Patients with EEC
The pooled HR for patients with EEC shown that MSI was not significantly associated with shorter recurrence-free survival [HR = 1.35, 95% CI (0.27–6.60), p = 0.714]. Meanwhile, significant heterogeneity was observed (I2 = 92.7%) (Supplemental Fig. 1).
Correlation Between MSI and Recurrence Rate in Patients with EEC
The pooled OR for EEC shown that MSI was significantly associated with a higher recurrence rate [OR = 2.72, 95% CI (1.56–4.76), p = 0.000]. Heterogeneity in the recurrence rate was not observed (I2 = 0.0%) (Supplemental Fig. 2).
Publication Bias
No significant publication bias was detected in the funnel plot (Supplemental Fig. 3). Additionally, significant publication bias was not observed, and the p-values of Egger’s test for overall survival, disease-free survival and EEC-specific survival were significant (p = 0.131, p = 0.068 and p = 0.987, respectively).
Sensitivity Analysis
We omitted each study individually from the pooled analysis to explore the sensitivity of the pooled HR for overall survival, disease-free survival, and progression-free survival in EEC. The exclusion of any study did not have a significant effect on the results (Supplemental Fig. 4).