Introduction: In the field of oncology, sarcopenia is associated with worse survival. There are two methods of calculating skeletal muscle area on CT, skeletal muscle index (SMI) and psoas muscle index (PMI), both of which can express sarcopenia. Programmed death (PD)-1 inhibitors, such as nivolumab, are useful for treating many types of advanced cancer, including metastatic renal cell carcinoma (eRCC). There remains insuficient information regarding a clear and easy-to-use biomarker for predicting the response to nivolumab. Recent studies have indicated that nutritional parameters may be able to predict the response to PD-1 inhibitors. However, there have been no reports on the relationship between sarcopenia and the therapeutic effect of nivolumab.
Methods: This study evaluated 96 patients with RCC who received nivolumab. CT image taken at the induction of nivolumab were analyzed. L3 was set as a landmark, the cross-sectional areas of the skeletal muscle complement were identified. The image was calculated for each patient and normalized for stature using the formula, SMI (cm²/m²)=([skeletal muscle cross-sectional area at the level of L3]/[height]²). To calculate PMI, the outer margin of the cross-section of the major psoas muscle at the level of the L3 was manually traced on CT images, and the sum of the left and right cross-sectional areas was divided by the square of the height. Kaplan-Meier curves were constructed, and the log rank test was used to compare PFS and OS between groups. The relationship between clinical variables and PFS and OS was examined using the Cox proportional hazard model.
Results: Based on the definition of sarcopenia by SMI, it was determined that there were 74.0% patients with sarcopenia. However, based on the definition of sarcopenia by PMI, 34.3% patients were diagnosed as sarcopenia. Univariate analyses revealed several variables were significantly associated with OS, including metastatic status (HR 2.62), IMDC poor risk (HR 2.62), and sarcopenia based on PMI (HR 4.53, table 2). A multivariate analysis identified sarcopenia based on PMI as a significant and independent predictor of OS (HR 3.85), along with IMDC poor risk (HR 1.90). Sarcopenia based on SMI was not associated with OS in this study. Multiple analysis showed that although neither of the sarcopenia was a significant predictor for PFS, IMDC poor risk and histological status were significant prognostic factors.
Conclusions: Sarcopenia based on PMI was a prognostic factor for RCC patients treated by nivolumab.
On the other hand, SMI based sarcopenia was not a prognostic factor.
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