Subgroup analysis
Considering the high heterogeneity shown in the pooled results, subgroup
analysis was performed to identify the sources of the heterogeneity. We
chose several common factors that related to effectiveness including
age, ECOG performance status (PS), primary site of tumor, region, and
HER2 expression status as classification variables. However, only ORR
data were used for subgroup analysis due to the limited data.
The results showed (Figure 4 A-D) that none of the differences in age,
ECOG PS, primary tumor type or region was a source of heterogeneity, and
there was no significant difference between the subgroups (p=0.941;
p=0.748; p=0.625, p=0.734, respectively). The HER2 status subgroup
analysis showed (Figure 4E) that the ORR of HER2-positive and HER2-low
patients were significant different (39% vs 19%, p=0.037). The
heterogeneity of ORRs in both the HER2-postive group
(I2=35.5%, p =0.171) and HER2-low group
(I2=0.0%, p =0.843) was reduced significantly
compared to the pooled results (I2=53.0%,p =0.037), indicating that HER2 expression status was one of the
factors leading to heterogeneity.
Given T-DXd was the only drug which has been used as intervention
regimen in more than one study in this meta-analysis, we further
calculated the efficacy of T-DXd in patients with HER-2 overexpression.
As the results showed (Figure 4 F-I), the pooled ORR and DCR were
respectively 43% (95% CI: 36%-49%) and 83% (95% CI: 79%-88%).
The pooled mOS and mPFS were respectively 12.36 months (95% CI:
10.53-14.19 months) and 5.60 months (95% CI: 4.59-6.61 months). And no
heterogeneity was observed among these results.