Characteristics of studies
Sixteen studies including 1503 patients were finally identified for inclusion into the study via full-text review and data extraction. The details of the selection process were in line with the PRISMA flowchart (Fig. 1). The characteristics of the 16 included studies are summarized in Table 1. Pie charts were drawn based on the primary tumor site and metastatic sites (Fig. 2A and 2B). The quality of studies was evaluated using the QUADAS-2 tool. There was a low-risk bias in “patient selection”, and most of the unclear risk of bias was found in the “reference standard”. The detailed information of each study is shown in Fig. 3.
Table 1
Main characteristics of included studies.
Author(year)
|
Case
|
Age
|
Genotype (N)
|
Microsatellite instability status
|
PD-L1 expression
|
Intervention methods
|
WT
|
BRAF MU
|
KRAS MU
|
Unknown
|
≥ 1%
|
༜1%
|
Unknown
|
Overman (2018)
|
119
|
58(21–88)
|
31
|
29
|
44
|
15
|
MSI-H 119
|
26
|
65
|
28
|
Nivolumab(PD-1)
+Ipilimumab(CTLA-4)
|
Overman (2017)
|
74
|
53(44–66)
|
29
|
12
|
26
|
7
|
MSI-H 74
|
21
|
47
|
6
|
Nivolumab(PD-1)
|
Le D T (2019)
|
124
|
56(21–84)
|
17
|
14
|
46
|
-
|
MSI-H 124
|
-
|
-
|
-
|
Pembrolizumab(PD-1)
|
O’Neil (2017)
|
23
|
57(40–78)
|
-
|
-
|
-
|
-
|
MSI-H 1
MSS 22
|
23
|
-
|
-
|
Pembrolizumab (PD-1)
|
Le D T (2015)
|
32
|
54(24–79)
|
-
|
19
|
19
|
-
|
MSI-H 11
MSS 21
|
-
|
-
|
-
|
Pembrolizumab (PD-1)
|
André T (2020)
|
307
|
63(24–93)
|
69
|
77
|
74
|
90
|
MSI-H 307
|
-
|
-
|
-
|
Pembrolizumab(PD-1)
|
Fukuoka (2020)
|
25
|
55(31–77)
|
-
|
-
|
6
|
-
|
MSI-H 3
MSS 22
|
9
|
16
|
-
|
Nivolumab(PD-1)
+Regorafenib
|
Herting (2020)
|
30
|
49(28–74)
|
21
|
0
|
14
|
26
|
MSI-H 2
MSS 9
Unknown 19
|
-
|
-
|
-
|
Pembrolizumab(PD-1)
+Modified FOLFOX6
|
Kawazoe (2020)
|
50
|
58(25–79)
|
4
|
28
|
19
|
13
|
MSI-H 10
MSS 40
|
4
|
-
|
-
|
Pembrolizumab(PD-1)
+Napabucasin"
|
Eng C (2019) A
|
183
|
58 (51–67)
|
258
|
9
|
99
|
-
|
MSI-H 3
MSS 170
Unknown 10
|
79
|
84
|
20
|
Atezolizumab(PD-L1)
+ Cobimetinib
|
Eng C (2019) B
|
90
|
56 (51–64)
|
128
|
3
|
49
|
-
|
MSI-H 3
MSS 83
Unknown 4
|
35
|
42
|
13
|
Atezolizumab(PD-L1)
|
Hellmann (2019)
|
84
|
56(23–79)
|
63
|
40
|
24
|
41
|
MSI-H 2
MSS 61
Unknown 21
|
-
|
-
|
-
|
Atezolizumab(PD-L1)
+ Cobimetinib
|
Patel (2021)
|
18
|
56(40–70)
|
-
|
1
|
12
|
-
|
MSS 18
|
-
|
-
|
-
|
Nivolumab(PD-1)
+Rifluridine/Tipitaka (FTD/TPI)
|
Cousin (2021)
|
48
|
62 (26–83)
|
-
|
3
|
30
|
-
|
MSS 48
|
6
|
-
|
-
|
Aveluma (PD-L1)
+ Regorafenib
|
Chen (2020)
|
180
|
65 (36–87)
|
-
|
-
|
-
|
-
|
MSI-H 2
MSS 166
Unknown
12
|
-
|
-
|
-
|
Durvalumab(PD-L1)+
Tremelimumab(CTLA-4)
|
Martinelli (2021)
|
77
|
-
|
48
|
19
|
19
|
3
|
MSI-H 3
MSS 71
Unknown 4
|
-
|
-
|
-
|
Avelumab(PD-L1)
+cetuximab
|
Wang (2021)
|
39
|
52(37–69)
|
13
|
2
|
20
|
4
|
MSS 38
MSI-L 1
|
-
|
-
|
-
|
Toripalimab(PD-1)
+ regorafenib
|
Abbreviations: vs, versus; WT, Wild type; MU, Mutant; MSI-H: Microsatellite instability-high; MSS: Microsatellite-stable; MSI-L: Microsatellite instability-low |
Meta-analysis
Efficacy[15–30]: The ORR of anti PD-1/PD-L1 therapy for advanced CRC was 23% [95%CI (0.14, 0.31) P < 0.001] (Fig. 4A). The DCR was 49% [95% CI (0.36, 0.62) P < 0.001] (Fig. 4B). The 1-year PFSR was 46% [95% CI (0.23, 0.68) P < 0.001] (Fig. 4C). The 1-year OSR) was 57% [95% CI (0.42, 0.73) P < 0.001] (Fig. 4D). The median progression-free survival (mPFS) was 2.44 months [95% CI (2.16, 2.71), P < 0.001] (Fig. 4E).
Safety [15–30]: The incidence of any grade TRAEs associated with the treatment of advanced CRC with anti- PD-1/PD-L1 was 85% [95% CI (0.80, 0.91), P < 0.001] (Fig. 5A). The occurrence rate of grade 3 to 5 AEs was 33% [95% CI (0.25, 0.50), P < 0.001] (Fig. 5B). The most common AEs were diarrhea (36.0%), fatigue (32.82%), poor appetite (28.50%), nausea (25.10%), increased AST (22.46%), rash (22.37%), abdominal pain (20.60%), fever (19.88%), increased ALT (17.90%), hypothyroidism (12.62%), and pancreatitis (10.23%). Detailed descriptions of the adverse reactions are shown in Table 2.
Table 2
The incidence of grade1-2 TRAEs and grade ≥ 3 TRAEs
|
|
Grade1-2
|
Grade ≥ 3
|
TRAE Name
|
Studies
|
Heterogeneity Rate (95% CI) %
|
Heterogeneity Rate (95% CI) %
|
Diarrhoea
|
15–21,23,24,26–28,30
|
Random 28 (18, 38)
|
Random 4 (2, 6)
|
Rash
|
15–20,21,23,24,27,
28,30
|
Random 15 (9, 21)
|
Random 2 (1, 3)
|
Fatigue
|
15–20,21,23,24,26–28,30
|
Random 26 (17, 35)
|
Random 4 (2, 6)
|
Nausea
|
15–20,23,24,26–28
|
Random 21 (14, 28)
|
Random 1 (0, 2)
|
Poor appetite
|
18–20,23,24,26–28,30
|
Random 23 (14, 33)
|
Random 2 (0, 4)
|
Abdominal pain
|
15,17,20,24,26,28,30
|
Random 15 (8, 23)
|
Random 3 (1, 5)
|
Pyrexia
|
15–17,20,23,24,26,
27,30
|
Random 16 (11, 21)
|
Random 2 (0, 3)
|
Increased AST
|
16,17,20,23,27,28
|
Random 16 (5, 27)
|
Random 4 (2, 6)
|
Increased ALT
|
15–17,20,27,28
|
Random 12 (5, 19)
|
Random 3 (2, 5)
|
Hypothyroidism
|
15–17,20,23,27,30
|
Random 11 (7, 16)
|
Random 1 (-1, 2)
|
Pancreatitis
|
13,14,16,17,24,25
|
Random 7 (2, 12)
|
Random 5 (1, 9)
|
Subgroup analysis
Microsatellite status[16–18, 23–25]: There were six studies analyzing microsatellite status. The ORR, DCR, and mPFS in MSI-H/dMMR patients were 37%, 69%, and 10.06 months, respectively, whereas those in microsatellite stable/mismatch repair proficient (MSS/pMMR) patients were 10%, 57%, and 2.86 months, respectively (Fig. 6A–C). The results indicated that anti-PD-1/PD-L1 therapy was associated with clinical benefit in more than one-third of MSI-H/dMMR mCRC patients. The ORR of MSS patients who did not respond to previous single-drug treatment reached 10% after immunotherapy combined with other therapies.
Different genotypes[16–18, 24, 25, 29, 30] :Seven studies evaluated the OS of patients with different genotypes. The ORR of the BRAF mutant subgroup, RAS mutant subgroup, and wild-type subgroup was 42%, 19%, and 25%, respectively (Fig. 7). The results indicated that immunotherapy was effective for BRAF mutant and KRAS/NRAS(RAS) mutant CRC, which may become a biomarker for the assessment of immunotherapy efficacy.
PD-L1 status[16, 18, 19, 21, 23, 24] :Six articles analyzed the effect of PD-L1 expression. In patients receiving anti-PD-1/PD-L1 therapy, the ORR of PD-L1(≥ 1%) patients was 14%, whereas that of the PD-L1(< 1%) subgroup was 32% (Fig. 8). PD-L1 expression was positively associated with decreased ORR.
Publication bias: Publication bias Funnel plots were used to investigate the potential publication bias of the studies included in the meta-analysis. As shown in Figs. 9 and 10, the funnel plots were asymmetric, suggesting a medium risk of publication bias because of insufficient RCT articles.