The investigators will conducted a hospital-based cohort study in our 15-year experience with DA aimed at investigating the long-term outcomes of the patients with DA, along with analyzing the impact of the tumor characteristics, operations and adjuvant therapy on survival outcomes.

Numerous meta-analyses and systematic reviews have delved into the treatment of DA, yet the majority of the studies retrospective, single-center, and small sample size series, particularly in China. To bridge this knowledge gap, the investigators will conduct a hospital-based cohort study designed to investigate the long-term survival outcomes of the participants with the non-ampulla duodenal adenocarcinoma, and the effects of tumor characteristics, surgery, and adjuvant therapy on survival outcomes.

Inclusion criteria:

(1) histologically confirmed non-ampulla DA;

Exclusion criteria:

1. had other gastrointestinal cancer;
2. had incomplete medical records, or lost follow-up shortly after diagnosis;
3. refused clinical data collection.

The patients included in this study were drawn from a hospital-based cohort and included cases diagnosed and treated at the facility. Inclusion criteria were histologically confirmed non-ampulla DA, including all stages of disease at diagnosis. Patients were excluded if they had ampulla cancer or other forms of gastrointestinal cancer, had incomplete medical records, or lost follow-up shortly after diagnosis. This rigorous selection process ensured the homogeneity of the study population and the relevance of the findings to non-ampulla DA.