Abstract 448P
Background
The efficacy of pre-treated advanced gastric or gastroesophageal junction cancer (G/GEJC) with HER2 expressed (IHC 2+/3+) remains unsatisfactory. This study aims to analyze the safety and efficacy of RC48 combined with programmed death-1 (PD-1) inhibitor in pre-treated patients with advanced G/GEJC in the real-world.
Methods
This retrospective study enrolled consecutive patients with advanced G/GEJC treated with RC48 plus PD-1 inhibitor or RC48 monotherapy from four hospitals in China from July 1, 2021 to September 1, 2023. These patients were detected as HER2 2+/3+ and ECOG score was 0-3. The ORR, DCR, PFS, OS, and TrAE were assessed.
Results
In this study, 57 patients were enrolled and divided into two groups: 36 received RC48 plus PD-1 inhibitor (combination group) and 21 received only RC48 (monotherapy group). The combination group showed better ECOG score (P=0.030) and lower proportion of liver metastasis (P=0.026). The ORR of the combination group was significantly better than that of the monotherapy group (41.7% vs. 9.5%, P=0.011). The DCR were 75.0% in the combination group and 57.1% in the monotherapy group (P=0.162). The median follow-up time was 11.5 months. The mPFS was longer in the combination group but without statistical difference (5.8 months vs. 2.9 months, P=0.142). The mOS was significantly prolonged in the combination group (13.2 months vs. 7.1 months, P=0.040). Although not statistically significant, patients treated with RC48 as second-line therapy and those with HER2 3+ was associated with higher ORR. The HER2 3+ patients also had a longer mPFS compared to HER2 2+. The incidence of grade 3-4 TrAEs were comparable between the combination group and the monotherapy group (41.7% vs. 38.1%) (Table), with no TrAE-related deaths. Table: 448P
The efficacy and safety of the combination group and the monotherapy group
| Characteristics | No. | ORR (%) | DCR (%) | mPFS (months) | mOS (months) | Grade 3-4 TrAEs (%) | |||||
| Monotherapy group | 21 | 9.5 | OR=0.15 P=0.011 | 57.1 | OR=0.44 P=0.162 | 2.9 | HR=0.64 P=0.142 | 7.1 | HR=0.47 P=0.040 | 38.1 | P=0.791 |
| Combination group | 36 | 41.7 | 75.0 | 5.8 | 13.2 | 41.7 | |||||
| Second-line therapy | 15 | 60.0 | P=0.059 | / | 5.8 | P=0.912 | 12.6 | P=0.965 | / | ||
| ≥ Third-line therapy | 21 | 28.6 | 5.7 | 13.5 | |||||||
| HER2 2+ | 23 | 30.4 | P=0.069 | / | 5.0 | P=0.037 | 12.6 | P=0.205 | / | ||
| HER2 3+ | 13 | 61.5 | 6.1 | 13.2 |
Conclusions
RC48 plus PD-1 inhibitor for pre-treated advanced G/GEJC patients with HER2 2+/3+ showed superior efficacy than RC48 monotherapy and favorable safety.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.