围手术期骨骼肌指数（SMI）变化与结直肠癌（CRC）结果之间的关联仍不清楚。我们的目的是探索 SMI 的围手术期变化模式，并评估其对 CRC 患者长期结局的影响。这项回顾性队列研究包括 2012 年至 2019 年间接受根治性切除的 I-III 期 CRC 患者。第三腰椎水平的 SMI 为使用计算机断层扫描计算。分别为男性和女性定义 SMI 的最佳截止值，并在术前和术后 3、6、9 和 12 个月分为高或低。 SMI 状态进一步分为不同的围手术期 SMI 变化模式：高前-高后、高前-低后、低前-高后和低前-低后。使用 Cox 比例风险模型检查与无复发生存期 (RFS) 和总生存期 (OS) 的关联。总共 2222 名患者（中位[四分位距]年龄，60.00 [51.00-68.00] 岁；1302 名患者（58.60%）男性；222 名（9.99%）术前 SMI 较低的患者接受了评估。在中位随访 60 个月期间，375 名患者（16.88%）死亡，617 名患者（27.77%）复发。多变量Cox模型分析显示，与高前-高后的患者相比，高前-低后的患者（HR = 3.32, 95% CI: 1.60-6.51; HR = 2.54, 95% CI: 1.03-6.26; HR = 2.93, 95 % CI：1.19-7.19，所有 p< 0.05）RFS 和 OS 显着较差（HR = 4.07，95% CI：1.55-10.69；HR = 4.78，95% CI：1.40-16.29；HR = 9.69，95% CI：1.40-16.29；HR = 9.69，95% CI ：2.53-37.05，所有p<0.05），分别在术后6、9和12个月。低术后低位患者是术后 12 个月 OS 较差的独立预后因素（HR = 3.20，95% CI：1.06-9.71，p = 0.040）。术后3、6和12个月时，低pre-highpost患者与高pre-highpost患者相比，RFS风险相似（HR = 1.49，95% CI：0.75-2.98；HR = 1.05，95% CI：0.45-2.43；HR = 1.05，95% CI：0.45-2.43； HR = 1.36，95% CI：0.31-6.06，均 p > 0.05），术后 3、6、9 和 12 个月的 OS 风险相似（均 p > 0.05）。术前 SMI 较高但术后下降的患者预后较差RFS 和操作系统。持续较低的 SMI 也与较差的操作系统相关。 SMI 较低但切除后 SMI 升高的患者并不表示预后较好。术后（而不是术前）常规测量 SMI 是必要的。 SMI 低的患者复发和死亡的风险增加，尤其是在术后第一年内。© 2024 作者。 《恶病质、肌肉减少症和肌肉杂志》由 Wiley periodicals LLC 出版。

The association between perioperative changes in the skeletal muscle index (SMI) and colorectal cancer (CRC) outcomes remains unclear. We aim to explore perioperative change patterns of SMI and evaluate their effects on long-term outcomes in CRC patients.This retrospective cohort study included Stage I-III CRC patients who underwent curative resection between 2012 and 2019. SMI at the third lumbar vertebra level was calculated using computed tomography scans. Optimal cut-off values for SMI were defined separately for males and females and classified as high or low preoperatively and at 3, 6, 9 and 12 months postoperatively. SMI status was further categorized into different perioperative SMI change patterns: highpre-highpost, highpre-lowpost, lowpre-highpost and lowpre-lowpost. The association with recurrence-free survival (RFS) and overall survival (OS) was examined using Cox proportional hazards models.A total of 2222 patients (median [interquartile range] age, 60.00 [51.00-68.00] years; 1302 (58.60%) men; 222 (9.99%) with preoperative low SMI) were evaluated. During a median follow-up of 60 months, 375 patients (16.88%) died, and 617 patients (27.77%) experienced a recurrence. Multivariate Cox model analysis showed that, compared to patients with highpre-highpost, those with highpre-lowpost (HR = 3.32, 95% CI: 1.60-6.51; HR = 2.54, 95% CI: 1.03-6.26; HR = 2.93, 95% CI: 1.19-7.19, all p < 0.05) had significantly worse RFS and OS (HR = 4.07, 95% CI: 1.55-10.69; HR = 4.78, 95% CI: 1.40-16.29; HR = 9.69, 95% CI: 2.53-37.05, all p < 0.05), at postoperative 6, 9 and 12 months, respectively. Patients with lowpre-lowpost were an independent prognostic factor for worse OS at postoperative 12 months (HR = 3.20, 95% CI: 1.06-9.71, p = 0.040). Patients with lowpre-highpost had similar risk of RFS compared to those with highpre-highpost at postoperative 3, 6 and 12 months (HR = 1.49, 95% CI: 0.75-2.98; HR = 1.05, 95% CI: 0.45-2.43; HR = 1.36, 95% CI: 0.31-6.06, all p > 0.05) and similar risk of OS at postoperative 3, 6, 9 and 12 months (all p > 0.05).Patients with a high preoperative SMI that decline postoperatively have poor RFS and OS. Consistently low SMI also correlates with worse OS. Patients with low SMI but increased after resection are not an indicator of better prognosis. Routine measurement of postoperative, rather than preoperative, SMI is warranted. Patients with low SMI are at an increased risk for recurrence and death, especially within the first year after surgery.© 2024 The Author(s). Journal of Cachexia, Sarcopenia and Muscle published by Wiley Periodicals LLC.