BACKGROUND: The relationship of the ABO blood group system with the immune response is known, but its relationship with immune checkpoint inhibitors (ICIs) has not been clearly investigated until now. OBJECTIVE: In this study, the relationship between different blood groups and nivolumab treatment response in patients with advanced malignant melanoma was investigated. METHODS: The data of patients who used nivolumab for advanced malignant melanoma between April 2018 and April 2021 were retrospectively reviewed. RESULTS: A total of 73 patients were included in the study. In the progression-free survival (PFS) analysis according to blood groups, it was 3.9 months, 16.1 months, 20.0 months and 3.0 months for A, B, AB and O, respectively (p= 0.1). Overall survival (OS) analysis according to blood groups was 5.1 months, 25.0 months, 20.0 months and 9.3 months for A, B, AB and O, respectively (p= 0.1). The B antigen group (B or AB) had significantly longer PFS and OS than the non-B antigen group (A or O) (16.1 vs. 3.5 months for PFS, respectively, p= 0.03; 20.0 vs. 7.4 months for OS, respectively, p= 0.02). CONCLUSIONS: The presence of B antigen provides a significant advantage in terms of survival in patients using ICIs for advanced melanoma.

Objective: Neuroendocrine neoplasms (NENs) originate from the diffuse neuroendocrine cell system and constitute a heterogeneous group of tumors exhibiting diverse clinical and biological characteristics. NENs include well-differentiated neuroendocrine tumors (NETs) and poorly differentiated neuroendocrine carcinomas (NECs). In the present study, we performed a retrospective analysis of patients diagnosed with NET to evaluate clinicopathological characteristics, treatment and outcomes. Material and Methods: Data from 153 patients diagnosed with NET who were treated and followed up at three tertiary care centers from November 2002 to June 2021 were retrospectively evaluated. Clinicopathological and prognostic factors, treatment modalities and survival data were analyzed. Kaplan–Meier analysis was used to assess survival data and comparisons were performed using the logrank test. Results: Median age (IQR) was 53 (18–80) years. 85.6% of the patients had gastro-entero-pancreatic (GEP)-NET. The primary tumor was resected in 95 patients (62.1%) and metastasectomy were performed in 22 patients (14.4%). Seventy-eight patients received systemic therapy for metastatic disease. Patients were followed up for a median of 22 (IQR = 33.8) months. The estimated one-year and three-year survival rate was 89.8% and 74.4%, respectively. Median progression-free survival (PFS) were 10.1, 8.5, and 4.2 months after first-, second- and third-line therapy, respectively. Conclusion: The number of systemic treatment options and diagnostic tools for NETs has significantly improved in the last few years. NET classification, which treatment will be more appropriate for which group of patients, the molecular basis of this disease and the development of treatment strategies are open-ended questions that still need to be investigated.