IL-6はがん悪液質の臨床アウトカムの最適な前炎症性マーカーではない

IL-6はがん悪液質の臨床アウトカムの最適な前炎症性マーカーではないという論文を紹介します。

Celena Scheede-Bergdahl, et al: Is IL-6 the best pro-inflammatory biomarker of clinical outcomes of cancer cachexia? Clinical Nutrition doi:10.1016/j.clnu.2011.07.010

がん悪液質の臨床症状（筋力低下、食欲低下、サルコペニア）と最も関連する前炎症性マーカーが何かを調査した論文です。マーカーとして4つのサイトカイン（IL-6, IL-1β, IL-8 and TNF-α）と臨床症状の関連を調査しました。

その結果、IL-6よりもIL-1βのほうががん悪液質の臨床症状と関連していました。悪液質のマーカーとしてCRPは別として、IL-6が測定されることが少なくありませんでしたが、今回の結果からIL-6が最適な指標ではない可能性があります。その他のサイトカインも調査すべきという結論です。

臨床現場ではCRPが0.3～0.5mg/dlを超えているかどうかが目安だと考えています。なかなかIL-6やIL-1β、TNF-αをルーチンで計測するのは難しいと思います。安価で最適な悪液質の検査指標が早く決まるとよいのですが。

Abstract
Background & aims
Despite the descriptive presence of cancer cachexia (CC) in clinical practice, the underlying mechanisms and diagnostic definition have not been clearly identified. Recent work, attempting to establish diagnostic and staging criteria for CC, has identified IL-6 as a biomarker. This study aimed to investigate the clinical relevance of plasma levels of four pro-inflammatory cytokines (IL-6, IL-1β, IL-8 and TNF-α) in advanced cancer patients (ACP) to further establish their potential in the diagnostic definition of CC.

Methods
Blood was obtained from 83 ACP (47 male and 36 female, aged 34 to 85 years) and analyzed for white blood cells, lymphocytes, C-reactive protein, albumin and cytokines. Subjects completed questionnaires to establish weakness, loss of appetite, fatigue, quality of life and weight loss; completed tests to determine strength, body composition and sarcopenia; and consented to chart review to calculate survival and total days admitted to hospital.

Results
This study shows that, in ACP, IL-1β is better associated with clinical features of the cachectic condition, such as weakness, loss of appetite, weight loss and sarcopenia, than IL-6.

Conclusion
IL-6 may not best represent the clinical correlates of CC in ACP. Additional cytokines should be considered in the definition of this condition.