P6320 - Immunohistochemical Profiling of PD-L1 and HER-2 in Latin American Gastric Cancer Patients

Erick Cantor, MD¹, Henry Vargas, MD¹, Javier Mauricio Segovia, MD¹, Luis Eduardo Pino, MD¹, John Alejandro Murillo, MD¹, Rocio Lopez, MD¹, Ivan Camilo Triana, MD¹, Gabriel Herrera Almario, MD¹, Andres Bejarano, MD², Laura Chacón Zambrano, MD¹, Fernando Sierra-Arango, MD, MSc(Epi)¹
1Fundacion Santa Fe de Bogota, Bogotá, Distrito Capital de Bogota, Colombia; 2Independent researcher, Bogotá, Distrito Capital de Bogota, Colombia

Introduction: The expression of Programmed Death-Ligand 1 (PD-L1) and Human Epidermal Growth Factor Receptor 2 (HER-2), in gastric cancer has been associated with high mortality rates and short overall survival periods, emphasizing the importance of their early identification for timely selection of appropriate treatments.

Methods: Descriptive observational study of a retrospective cohort of patients with up to 5 years of follow-up, diagnosed with advanced-stage gastric cancer and treated at an oncology center in Bogotá, Colombia. Additionally, these patients underwent immunohistochemical (IHC) testing for the detection of PD-L1 and HER-2. The objective of this study is to determine the frequency of expression of the PD-L1 and HER-2 biomarkers in a sample of Colombian patients. A univariate analysis was conducted to determine and compare the frequency of HER-2 and PD-L1 expression in Latin American patients with advanced gastric cancer.

Results: 155 patients diagnosed with gastric cancer were included, of which 58% were men. Histologically, 90% corresponded to adenocarcinoma, predominating in males. 47% were poorly differentiated, 21% exhibited signet ring cells, 11% showed tubular pattern. PD-L1 positivity was observed in 27%, with 61% being men; 58% combined positive score (CPS) >10, 22% CPS 5-9, and 17% CPS 1-4. HER-2 positivity was detected in 7%, with 5% being men of the total patient pool. The 2% of patients had a positive result for HER-2 and PD-L1. Follow-up was conducted on 22% of patients over a 60-month period, with an overall survival (OS) of 22.2 months and a progression free survival (PFS) of 6.6 months. 18% presented involvement of adjacent tissues, 9% cervical lymph node involvement, and 6% peritoneal involvement. Immunotherapy was administered to 35% of patients; 17% deceased, with an OS mean of 21.7 months and a PFS of 6.5 months. For the group of patients receiving chemotherapy alone, 41% deceased, with an OS mean of 22.5 months and a PFS mean of 6.7 months.

Discussion: PD-L1 expression affects approximately a quarter of the Colombian population, while HER-2 expression is infrequent in our population. Immunotherapy and chemotherapy exhibited similar overall survival means; however, the use of chemotherapy alone was associated with a higher number of deaths.

Disclosures:
Erick Cantor indicated no relevant financial relationships.
Henry Vargas indicated no relevant financial relationships.
Javier Mauricio Segovia indicated no relevant financial relationships.
Luis Eduardo Pino indicated no relevant financial relationships.
John Alejandro Murillo indicated no relevant financial relationships.
Rocio Lopez indicated no relevant financial relationships.
Ivan Camilo Triana indicated no relevant financial relationships.
Gabriel Herrera Almario indicated no relevant financial relationships.
Andres Bejarano indicated no relevant financial relationships.
Laura Chacón Zambrano indicated no relevant financial relationships.
Fernando Sierra-Arango indicated no relevant financial relationships.

Erick Cantor, MD¹, Henry Vargas, MD¹, Javier Mauricio Segovia, MD¹, Luis Eduardo Pino, MD¹, John Alejandro Murillo, MD¹, Rocio Lopez, MD¹, Ivan Camilo Triana, MD¹, Gabriel Herrera Almario, MD¹, Andres Bejarano, MD², Laura Chacón Zambrano, MD¹, Fernando Sierra-Arango, MD, MSc(Epi)¹. P6320 - Immunohistochemical Profiling of PD-L1 and HER-2 in Latin American Gastric Cancer Patients, ACG 2025 Annual Scientific Meeting Abstracts. Phoenix, AZ: American College of Gastroenterology.