Muscle volume loss after the induction of first-line chemotherapy as a novel prognostic factor in metastatic colorectal cancer patients.

Abstract

558 Background: Muscle volume loss (MVL) is observed in end-stage cancer patients as cachexia. However, the impact of MVL on tumor response and survival still remains unclear during chemotherapy in metastatic colorectal cancer (mCRC) patients. The aim of this study is to evaluate correlation between MVL and oncologic outcomes in mCRC patients. Methods: A total of 91 mCRC patients who received first-line chemotherapy were identified in our prospective registry between February 2007 and April 2013. Skeletal muscle index at the level of L3 vertebra (SMI) was calculated by muscle volume normalized by stature at the time of the induction of first-line chemotherapy (bSMI) and first evaluation of tumor response (fSMI). Patients whose SMI decreased more than 10% were classified as MVL group. The impact of these variables on oncologic outcomes (overall survival [OS], progression free survival [PFS], and tumor response rate [RR]) were analyzed. Results: Mean bSMI and fSMI were 35.0 (SD: 7.11) cm2/m2, and 34.2 (SD: 6.85) cm2/ m2, respectively. Eighteen patients were classified into the MVL group. The patients in MVL group significantly responded to the chemotherapy (RR of MVL: 11.1% vs. RR of non-MVL: 49.3%, p < 0.01). There was no significant difference in terms of high grade adverse effect between MVL and non-MVL group. Patients in MVL group had a significant shorter median PFS (MVL: 5.5 [2.5 - 10.1] months vs. non-MVL: 12.8 (3.8-80.5) months, p < 0.01) and median OS (MVL: 13.9 [6.2-61.2] months vs. non-MVL: 29.3 (8.2-94.0) months, p < 0.01). Multivariate analysis demonstrated that patients with MVL had significantly worse prognostic factor (OS: HR 3.51 [1.99-6.21], p < 0.01 and PFS: HR 8.27 [2.91-23.5], p < 0.01. Conclusions: The findings of this study suggested that MVL after the induction of the first line chemotherapy could be a novel predictive factor for chemotherapy response and prognosis. Further investigation should be required to clarify the mechanistic background.