Supplementary Material for: Clinical impact of skeletal muscle mass and nutritional status in patients with recurrent or advanced gastric cancer treated with nivolumab

Background
This study aimed to evaluate the clinical impact of skeletal muscle mass and nutritional status in gastric cancer patients treated with nivolumab monotherapy as late-line treatment.
Methods
We conducted a multi-institutional retrospective study of 90 gastric cancer patients who previously received anti-PD-1 therapy (nivolumab). On computed tomography images captured before nivolumab induction, the skeletal muscle index (SMI, cm2/m2) was defined as the erector muscle area (cm2) divided by the height (m) squared. Patients were divided into two groups: those with SMI-high (n = 45) and those with SMI-low (n = 45). Prognostic nutritional index (PNI) was also calculated before nivolumab induction. The associations of SMI and PNI with response rate (RR), progression-free survival (PFS), overall survival (OS), disease control rate (DCR), and safety were analyzed.
Results
The cutoff values for SMI were determined as 13.45 for males and 10.41 for females. SMI-high was significantly associated with a higher RR (odds ratio = 12.36, p = 0.02) and DCR (odds ratio = 2.97, p = 0.02). Although not significant, PNI-high also tended to be associated with a higher RR. Multivariate analysis showed that SMI-high was independently associated with a higher RR and higher DCR in gastric cancer. Moreover, prognostic analyses revealed that SMI-high (log-rank test p = 0.008) and PNI-high (log-rank test p = 0.0008) were significantly associated with longer OS since nivolumab induction. SMI-high was also associated with longer PFS (log-rank test p = 0.03). There were no significant differences in irAE between SMI-low and SMI-high.

Conclusions
SMI and PNI were associated with nivolumab efficacy in gastric cancer patients. Management of skeletal muscle loss and nutritional status in gastric cancer patients who will receive nivolumab would be beneficial to enhance survival outcomes.