Longitudinal Quality-of-Life Trajectories Following Laparoscopic Distal Gastrectomy: A Comparison Between Billroth I and II Reconstruction Using the KOQUSS-40 Questionnaire.

Background/Objectives: Although Billroth I (BI) and Billroth II (BII) are standard reconstructions after distal gastrectomy, evidence on their longitudinal quality-of-life (QoL) trajectories remains inconclusive. This study compared postoperative QoL patterns between BI and BII groups using a validated gastric cancer-specific instrument. Methods: We analyzed 234 patients (BI n = 51, BII n = 183) who underwent laparoscopic distal gastrectomy. QoL was assessed using the KOQUSS-40 questionnaire at 1, 3, 6, 9, and 12 months postoperatively. To address selection bias, inverse probability of treatment weighting (IPTW) was applied alongside linear mixed-effects models to evaluate group effects and group × time interactions. Results: A significant main effect of group was observed (p = 0.032), with the BII group maintaining higher total scores. These findings remained consistent after IPTW adjustment. While the overall group × time interaction was not significant (p = 0.846), indicating parallel recovery trajectories, significant interactions were identified in specific domains, including dumping syndrome and constipation. In these domains, the BI group showed gradual improvement, whereas the BII group exhibited relatively stable scores. Conclusions: While both reconstruction methods demonstrated comparable overall QoL trajectories with no significant group × time interaction, the KOQUSS-40 revealed exploratory differences in specific symptom domains, notably dumping-related symptoms and constipation. These findings provide clinically meaningful insights for postoperative patient counseling, enabling tailored expectations during the first year after distal gastrectomy. However, these domain-specific results should be regarded as hypothesis generating and interpreted with caution.