117P - Immunoprofile of adenosquamous carcinoma in gastric cancer

Background

Gastric adenosquamous carcinoma (GASC) is a rare subtype of gastric cancer. Research on GASC treatment is limited, and its outcome is usually poor. We investigated the clinical features, immunoprofile of GASC and determined the optimal treatment modality for these patients.

Methods

Patients with GASC from Taipei Veterans General Hospital were retrospectively reviewed. Clinical features and treatment outcomes were evaluated. Adequate samples were examined for surrogate biomarkers for immunotherapy by IHC staining.

Results

Total 14 (0.31%) GASC patients were found among 4514 gastric cancer patients. The median tumor size was 6.8 cm in 10 patients with stage III GASC, and all these patients underwent radical gastrectomy, followed by adjuvant therapy. The median progression-free survival (PFS) and overall survival (OS) were 6.0 and 11.5 months, respectively. Two patients with stage IV GASC received frontline immunotherapy. Their median PFS and OS were 9.0 and 12.5 months, respectively. In immunoprofiling, 42.9% (n = 3), 85.7% (n = 6), and 42.9% (n = 3) of the seven tumor samples had a combined positive score (CPS) of ≥10, a CPS of ≥1, and deficient mismatch repair (dMMR) protein, respectively. One patient with stage IV disease with CPS ≥10 and dMMR proteins received nivolumab monotherapy as frontline treatment that resulted 14-months PFS.

Conclusions

Patients with GASC are more likely to yield positive results for CPS and dMMR. Biomarkers should be examined, and immunotherapy can be considered as frontline systemic treatment.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.