コアマッスル減少と食道がん術後予後

コアマッスルの筋肉量減少は食道がん術後の生存期間悪化と関連するという論文を紹介します。

K. H. Sheetz, et al. Decreased core muscle size is associated with worse patient survival following esophagectomy for cancer. Diseases of the Esophagus, Article first published online: 25 JAN 2013, DOI: 10.1111/dote.12020

対象は非開胸食道切除術を施行した食道がん患者230人です。コアマッスルの筋肉量は、腹部CTでL4椎体レベルの腰筋（大腰筋）の筋肉量で評価しました。結果ですが、単変量解析では筋肉量は全体の生存期間と無病生存期間と有意な関連を認めました。

多変量解析では、術前補助療法を行わなかった64人で、筋肉量は全体の生存期間と無病生存期間と有意な関連を認めました。がんのステージ分類と同等以上に重要でした。一方、術前補助療法を行わなかった166人では、筋肉量と生存期間に有意な関連を認めませんでした。

以上より、コアマッスルの筋肉量は全体の生存期間と無病生存期間の独立した予測因子と思われるという結論です。術前の治療による筋肉量変化が交絡となっている可能性があります。術前のコアマッスルの筋肉量評価は、より客観的なリスク重症度分類に有用かもしれません。

消化器がんではCTを行いますので、コアマッスルのみにせよ全体の筋肉にせよ、その気になれば筋肉量評価が可能であり、行うべきだと考えます。これによって予後予測だけでなく、Prehabilitationを行ったほうがよい患者と行わなくてもよい患者を判別できる可能性があるのではと感じます。

Summary
Preoperative risk assessment, particularly for patient frailty, remains largely subjective. This study evaluated the relationship between core muscle size and patient outcomes following esophagectomy for malignancy. Using preoperative computed tomography scans in 230 subjects who had undergone transhiatal esophagectomy for cancer between 2001 and 2010, lean psoas area (LPA), measured at the fourth lumbar vertebra, was determined. Cox proportional hazards regression was employed to analyze overall survival (OS) and disease-free survival (DFS) adjusted for age, gender, and stage, and the Akaike information criterion was used to determine each covariate contribution to OS and DFS. Univariate analysis demonstrated that increasing LPA correlated with both OS (P = 0.017) and DFS (P = 0.038). In multivariate analysis controlling for patient and tumor characteristics, LPA correlated with OS and DFS in patients who had not received neoadjuvant treatment (n = 64), with higher LPA associated with improved OS and DFS. Moreover, LPA was of equivalent, or slightly higher importance than pathologic stage. These measures were not predictive among patients (n = 166) receiving neoadjuvant chemoradiation. Core muscle size appears to be an independent predictor of both OS and DFS, as significant as tumor stage, in patients following transhiatal esophagectomy. Changes in muscle mass related to preoperative treatment may confound this effect. Assessment of core muscle size may provide an additional objective measure for risk stratification prior to undergoing esophagectomy.