Abstract 450P
Background
Therapy with immune checkpoint inhibitors are highly effective in the treatment of metastatic gastric carcinoma (GC) with mismatch repair deficient/microsatellite instability (dMMR/MSI). However, the role of the immunotherapy in patients (pts) with resectable GC is still not well established.
Methods
The analysis included a retrospective experience from 3 centers. The inclusion criteria were pts with resectable GC and gastro-esophageal carcinoma who underwent surgery, stage I - IVA (AJCC 8th edition), dMMR/MSI status, preoperative use of anti-PD-1 monoclonal antibodies (alone or with chemotherapy). Clinical and pathological TNM and tumor regression grade by Mandard were evaluated.
Results
A total of 32 pts were included in the analysis. The median age was 67 years (45-80 years), 56% of pts were males, 66% of pts had a distal location of tumor, 29 pts with cT3-4b and 26 pts with cN+ respectively. Sixteen pts received anti-PD-1 antibody alone (9 with nivolumab, 7 with pembrolizumab) and 16 pts received chemotherapy (13 with FOLFOX, 3 with FLOT) plus anti-PD-1 antibody (12 with nivolumab, 4 with prolgolimab). The median number of preoperative cycles was 6 (range 4-8). Two pts experienced immune-related adverse events of grade 1-2. All 32 pts underwent surgery (19 total gastrectomy, 11 distal gastrectomy, 2 proximal gastrectomy). After surgical resection, 18 out of 32 patients (56.3%) achieved TRG-1(pCR) (Table). With a median follow-up of 14 months (3-51 months), the only one patient with R1 resection and TRG-3 relapsed at 12 months. Table: 450P
| TRG-1(pCR) | TRG-2 | TRG-3 | TRG-4 | |
| Mono-immunotherapy, n=16 (%) | 8 (50%) | 3 (18.75%) | 2 (12.5%) | 3 (18.75%) |
| Chemo-immunotherapy, n=16 (%) | 10 (62.5%) | 3 (18.75%) | 3 (18.75%) | 0 |
Conclusions
Neoadjuvant immunotherapy alone or combination with chemotherapy induces tumor regression with a major clinical and pathological response in dMMR/MSI-H GC. While these data are still considered preliminary, it is yet to be determined whether these promising results will lead to long-term benefits.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.