Comparative effectiveness of Neoadjuvant and adjuvant therapies in surgically treated non-metastatic gastric cancer.

Objectives

This study evaluates survival differences among patients with non-metastatic gastric cancer based on treatment strategy. It compares three groups: surgery alone, neoadjuvant therapy plus surgery, and surgery followed by adjuvant therapy.

Methods

A retrospective cohort study using data from the Hérault Tumor Registry in France included patients diagnosed with non-metastatic gastric cancer (ICD C16) from 1997 to 2021. Patients who underwent surgery were classified into three treatment groups. Therapies include chemotherapy, radiotherapy, or immunotherapy. Net survival was estimated using the Pohar-Perme method, adjusting for expected general population mortality. Group comparisons used the Log-Rank test, and Cox proportional hazards models provided adjusted hazard ratios. Follow-up ended on December 31, 2023.

Results

Among 1268 patients, those receiving neoadjuvant therapy plus surgery had significantly lower mortality than surgery alone: adjusted hazard ratios were 0.36 (95% CI: 0.24-0.55) at 1 year, 0.65 (95% CI: 0.51-0.83) at 3 years, and 0.69 (95% CI: 0.55-0.86) at 5 years. At 1-year, net survival was highest for neoadjuvant therapy (90.7%) versus surgery alone (82.3%) and adjuvant therapy (79.8%). By 5 years, surgery alone showed the highest survival (67.5%), exceeding neoadjuvant (52.8%) and adjuvant groups (43.4%). Survival differences were significant (p < 0.0001). No benefit was seen for adjuvant therapy.

Conclusion

Neoadjuvant therapy followed by surgery was associated with a lower adjusted hazard of death in surgically treated patients with non-metastatic gastric cancer. However, substantial baseline differences between treatment groups and the potential for residual confounding should be considered when interpreting these findings. Careful patient selection based on clinical stage, age, and tumor biology remains essential.