Longitudinal Quality of Life and Bowel Function After Low Anterior Resection Versus Intersphincteric Resection for Low Rectal Cancer: A Retrospective Cohort Study

<title>Abstract</title> <p>Purpose For patients with low rectal cancer, laparoscopic low anterior resection (LAR) and intersphincteric resection (ISR) both achieve sphincter preservation, yet their comparative impact on longitudinal quality of life (QoL) and bowel function remains inadequately characterized. This study compared 12-month QoL trajectories and bowel function outcomes between these two surgical strategies. Methods This retrospective cohort study included 200 patients undergoing laparoscopic LAR (n = 100) or ISR (n = 100) between 2015 and 2020. QoL was assessed prospectively using the Functional Assessment of Cancer Therapy-Colorectal (FACT-C) questionnaire at baseline, 3, 6, and 12 months. Bowel function was evaluated using the Low Anterior Resection Syndrome (LARS) score. Linear mixed-effects models, inverse probability of treatment weighting (IPTW), and exploratory trajectory clustering were employed. Results Groups were comparable except for tumor distance from the dentate line (LAR: 3.7 cm vs. ISR: 2.0 cm, P &lt; 0.001), reflecting distinct surgical indications. The 12-month FACT-C total difference was 2.3 points (Cohen's d = 0.47, P = 0.002), below the minimal clinically important difference (MCID, 5–6 points). The surgical strategy involving ISR (as a proxy for very low tumor location) was associated with delayed early QoL recovery (3-month delta: -0.5 vs. +10.9, P &lt; 0.001) and higher transient major LARS at 6 months (20.0% vs. 7.0%, P = 0.028), which largely resolved by 12 months (major LARS: 2.9% vs. 0%, P = 0.24). Group-level ecological analysis revealed strong CCS-LARS correlation (r_s = -0.80) despite absent individual-level correlation. The neoadjuvant therapy rate was only 10–11%; thus, these findings are primarily applicable to patients who did not receive neoadjuvant chemoradiotherapy. Conclusion LAR and ISR achieved comparable global QoL at 12 months. The surgical strategy involving ISR (reflecting very low tumor location) was associated with delayed early recovery and higher transient major LARS burden. These findings inform shared surgical decision-making and highlight the importance of early functional rehabilitation. Due to the inherent anatomical confounding and low neoadjuvant therapy rate, results should be interpreted as associations rather than causal effects, and are primarily applicable to non-neoadjuvant-treated patients.</p>