サルコペニアと膵がん術後の予後

サルコペニアが膵がん術後の予後に与える影響に関する論文を紹介します。

Peng P, Hyder O, Firoozmand A, Kneuertz P, Schulick RD, Huang D, Makary M, Hirose K, Edil B, Choti MA, Herman J, Cameron JL, Wolfgang CL, Pawlik TM. Impact of Sarcopenia on Outcomes Following Resection of Pancreatic Adenocarcinoma. J Gastrointest Surg. 2012 Jun 13. [Epub ahead of print]

リサーチクエスチョンは以下の通りです。

P：膵がん術後で
E：サルコペニアを認めると
C：サルコペニアを認めない場合と比較して
O：生命予後が悪い
D：後ろ向きコホート研究

対象は557人の膵がん術後です。筋肉量は横断画像（おそらくCT）で大腰筋の筋面積を評価して、性別でみて下位1/4の筋肉量の場合にサルコペニアと判断しています。3カ月後、1年後、3年後の死亡率を調査しました。

結果ですが、3カ月後、1年後、3年後の死亡率はそれぞれ3.1％、32.1％、64.3％でした。サルコペニアを認めると、3年後の死亡率が有意に高い（単変量解析、多変量解析とも）という結果でした。これよりサルコペニアは長期予後と関連するという結論です。

サルコペニアの診断基準はやや微妙ですが、筋肉量が少ないと膵がん術後の長期予後が不良な可能性はありそうです。できれば悪液質の有無でどうなのかも知りたいところです。おそらくサルコペニアより悪液質のほうがより予後に関連する気がします。

Abstract
INTRODUCTION: Assessing patient-specific risk factors for long-term mortality following resection of pancreatic adenocarcinoma can be difficult. Sarcopenia-the measurement of muscle wasting-may be a more objective and comprehensive patient-specific factor associated with long-term survival.

METHODS: Total psoas area (TPA) was measured on preoperative cross-sectional imaging in 557 patients undergoing resection of pancreatic adenocarcinoma between 1996 and 2010. Sarcopenia was defined as the presence of a TPA in the lowest sex-specific quartile. The impact of sarcopenia on 90-day, 1-year, and 3-year mortality was assessed relative to other clinicopathological factors.

RESULTS: Mean patient age was 65.7 years and 53.1 % was male. Mean TPA among men (611 mm(2)/m(2)) was greater than among women (454 mm(2)/m(2)). Surgery involved pancreaticoduodenectomy (86.0 %) or distal pancreatectomy (14.0 %). Mean tumor size was 3.4 cm; 49.9 % and 88.5 % of patients had vascular and perineural invasion, respectively. Margin status was R0 (59.0 %) and 77.7 % patients had lymph node metastasis. Overall 90-day mortality was 3.1 % and overall 1- and 3-year survival was 67.9 % and 35.7 %, respectively. Sarcopenia was associated with increased risk of 3-year mortality (HR = 1.68; P < 0.001). Tumor-specific factors such as poor differentiation on histology (HR = 1.75), margin status (HR = 1.66), and lymph node metastasis (HR = 2.06) were associated with risk of death at 3-years (all P < 0.001). After controlling for these factors, sarcopenia remained independently associated with an increased risk of death at 3 years (HR = 1.63; P < 0.001).

CONCLUSIONS: Sarcopenia was a predictor of survival following pancreatic surgery, with sarcopenic patients having a 63 % increased risk of death at 3 years. Sarcopenia was an objective measure of patient frailty that was strongly associated with long-term outcome independent of tumor-specific factors.