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Page 8 of 15 Brolese et al. Hepatoma Res 2020;6:34 I http://dx.doi.org/10.20517/2394-5079.2020.15

Table 2. Clinical characteristics and primary outcomes of studies included in the meta-analysis
Mean total Comorbidity Cirrhosis Minor Major
Study Year CP score A bilirubin (mg/dL) (pathological history) (presence) resection resection
MILR OLR MILR OLR MILR OLR MILR OLR MILR OLR MILR OLR
Badawy et al. [18] 2017 39/40 38/40 0.8 7/40 40/40 40/40 40/40 40/40 6/40 6/40 22 23.5
Chan et al. [19] 2014 17/17 33/34 0.5 9/17 17/17 34/34 17/17 34/34 3/17 12/34 30 30
Amato et al. [20] 2016 11/11 18/18 na 11/11 11/11 16/18 11/11 16/18 0 0 35.45 39.83
Nomi et al. [21] 2020 na na 0.7 na 156/221 154/409 156/221 154/409 na na 25 38
Wang et al. [22] 2015 30/30 59/60 0.8 14/30 30/30 60/60 30/30 60/60 3/30 7/60 40 50
Tee et al. [23] 2019 na na 0.76 na 427/487 801/1282 427/487 801/1282 na na na na
Wang et al. [24] 2018 59/63 168/177 na 15/63 60/63 169/177 60/63 169/177 8/63 35/177 36.3 30.5
Chen et al. [25] 2017 81/81 81/81 na 37/81 47/81 49/81 47/81 49/81 na na na na
MILR: mini-invasive liver resection; OLR: open liver resection; CP: Child-Pugh

Table 3. Further primary outcomes of studies included in the meta-analysis
Challenge segment Operative Blood loss LOS
Study Year resection time (min) Liver failure (mL) Morbidity Mortality (Day)
MILR OLR MILR OLR MILR OLR MILR OLR MILR OLR MILR OLR MILR OLR
Badawy et al. [18] 2017 na na 259 308.5 5/40 11/40 30 517 6/40 15/40 0/40 0/40 10 23
Chan et al. [19] 2014 0/17 0/34 195 210 0/17 0/34 150 330 4/17 6/34 0/17 0/34 6 8
Amato et al. [20] 2016 0/11 1/18 190.9 196.9 0/11 0/18 198 310 0/11 6/18 0/11 0/18 3.18 5.7
Nomi et al. [21] 2020 na na na na 7/221 36/409 100 562 40/221 149/409 2/221 3/409 11 14
Wang et al. [22] 2015 1/30 7/60 133 170 na na 100 300 3 /30 10/60 0/30 0/60 5 10
Tee et al. [23] 2019 na na 196.2 229.0 62/487 2/1282 na na 81/487 346/1282 9/487 51/1282 na na
Wang et al. [24] 2018 na na 296 182 0/63 1/177 206 267 7/63 27/177 0/63 0/177 6.21 8.18
Chen et al. [25] 2017 10/81 29/81 343 220 0/81 0/81 282 263 4/81 4/81 0/81 0/81 7.5 10.1
MILR: mini-invasive liver resection; LOS: length of hospital stay; OLR: open liver resection

more common in the MILR than in the OLR group (RR = 0.34, 95%CI: 0.19-0.63). The risk for the mini-
invasive group with respect to the open group was reduced by 66%, but the result showed considerable
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[25]
heterogeneity (I = 95%) and these results were however related to only one study .
Among the thirteen outcomes, estimated blood loss, morbidity according to Clavien-Dindo
classification, and LOS showed statistical significance in favor of the mini-invasive approach. In
particular, on average, mini-invasive intervention decreased blood loss by 161.43 (95%CI: 250.24-
2
72.61) mL, although this result showed a substantial percentage of statistical heterogeneity (I = 85%)
between studies. The mini-invasive approach decreased the risk of morbidity by 42% with respect to
open resection (P < 0.01), and these pooled data were strengthened by no important heterogeneity
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between studies (I = 0%). LOS indicated an average decrease of 4 (95%CI: 7-2) days for mini-invasive
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with respect to open surgery, even if this effect showed considerable heterogeneity (I = 92%) between
studies. Finally, postoperative mortality showed a risk reduction of 47% for mini-invasive compared
to open surgery, although not significant (P = 0.06). Due to zero events both in the mini-invasive and
open groups, 6 out of 8 studies were not informative for this outcome. Consequently, this outcome
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was estimated by 2 out of 8 studies, that demonstrated no important statistical heterogeneity (I = 0%).
Funnel plots of each outcome showed no graphical asymmetry, indicating no publication bias, although the
number of studies was too low to support strong deductions.

Secondary outcomes
Meta-analyses of the outcomes considered are shown in Figure 3. Number of lesions (single/multiple),
readmission rate, recurrence rate, survival at 1, 3, and 5 years showed no statistical differences between the
mini-invasive and open groups. Tumor size plotting analysis reported a mean pooled size reduction of 4.22 mm
in the MILR group, although this result was not statistically significant (95%CI: 9.57-1.13, P = 0.12), and
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heterogeneity was substantial (I = 84%). In particular, the recurrence outcome, estimated by two studies,