Abstract 570P
Background
The current study aimed to evaluate the expression status of immune checkpoints (PDL-1, LAG3, TIM3, OX40L) and determine MSI status in patients with GEP-NETs.
Methods
Immunohistochemistry stainings of 61 GEP-NET patients were carried out to detect PDL-1 (IC or TC), LAG3, TIM3, OX40L and MSI (MLH1, MSH2, MSH6, PMS2) retrospectively.
Results
A total of 61 patients were analyzed, and 32.8% (n=20) of patients had metastatic disease. The median age at diagnosis was 55.4 (IQR:43.6-63.8). Thirty three (52.4%) patients were male, and 29 (47.6%) patients were female. Pancreas (n=22) is the most common primary tumor localisation, and there were 4 patients with unknown primary tumor. It was observed that 17 patients had G1, 27 patients had G2, and 17 patients had G3 GEP-NET. It was found that 12 patients were PDL-1 positive, 5 patients were MSI-H, 3 patients were TIM3 positive, 10 patients were OX40L positive, and none of the patients were LAG3 positive. At all, PDL-1 positivity was the most common in G3 tumors, and MSI-H was in G1 tumors (table). Of Note, 67.3% of PDL-1 positivity and 80% of MSI-H status were observed in locoreginoal diseases. Table: 570P
Immune checkpoints expressions and MSI status
| Localisation | PDL-1 (+), n (%) | LAG3 (+), n (%) | TIM3 (+), n (%) | OX40L (+), n (%) | MSI-H, n (%) |
| Unkown Primary (n=4) Grade 1 Grade 2 Grade 3 | 2 1 (50) 0 1 (50) | 0 0 0 0 | 0 0 0 0 | 0 0 0 0 | 0 0 0 0 |
| Pancreas (n=22) Grade 1 Grade 2 Grade 3 | 3 1 (33.3) 2 (67.7) 0 | 0 0 0 0 | 1 1 (100) 0 0 | 4 1 (25) 3 (75) 0 | 2 1 (50) 1 (50) 0 |
| Stomach (n=17) Grade 1 Grade 2 Grade 3 | 6 0 1 (16.6) 5 (83.4) | 0 0 0 0 | 1 0 1 (100) 0 | 2 0 0 2 (100) | 1 1 (100) 0 0 |
| Small intestine (n=11) Grade 1 Grade 2 Grade 3 | 1 1 (100) 0 0 | 0 0 0 0 | 1 1 (100) 0 0 | 2 0 1 (50) 1 (50) | 1 1 (100) 0 0 |
| Colorectal + appendix (n=7) Grade 1 Grade 2 Grade 3 | 0 0 0 0 | 0 0 0 0 | 0 0 0 0 | 2 1 (50) 0 1 (50) | 1 1 (100) 0 0 |
| Total (n=61) Grade 1 Grade 2 Grade 3 | 12 3 (25) 3 (25) 6 (50) | 0 0 0 0 | 3 2 (67.2) 1 (33.3) 0 | 10 2 (20) 4 (40) 4 (40) | 5 4 (80) 1 (20) 0 |
Conclusions
While PDL-1 positivity is higher in higher grade tumor, MSI-H status is higher in lower grade tumors. Both PDL-1 positivity and MSI-H status were prominent in locoregional diseases.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Gazi University.
Disclosure
All authors have declared no conflicts of interest.