Preoperative low skeletal muscle volume can result in insufficient administration of S-1 adjuvant chemotherapy in older patients with stage II/III gastric cancer.

Background And Purpose: Older patients are more likely to encounter difficulties receiving chemotherapy, but the factors involved in the continuation of chemotherapy in these patients remain unclear. We investigated the importance of muscle mass as a factor involved in delivering a sufficient dose of postoperative S-1 adjuvant chemotherapy (ACT) to older patients with gastric cancer.

Methods: The subjects of this study were 79 patients aged ≥ 65 years with stage II/III gastric adenocarcinoma, who underwent curative gastrectomy and received S-1 ACT.

Results: The overall median relative dose intensity (RDI) was 75.0% (18.8-93.5%). Patients were divided into two groups for receiver operating characteristic analysis according to the cutoff value. Significantly more patients in the high skeletal muscle index (SMI) group achieved > 62% RDI of S-1 ACT (p = 0.03). Conversely, more patients in the low SMI group suffered from S-1-induced nausea (p = 0.03) and discontinued chemotherapy because of adverse events (p = 0.02). Multivariate analysis identified low SMI as an independent factor for insufficient S-1 dose delivery (p = 0.03, hazard ratio = 2.87).

Conclusion: Preoperative SMI is an indicator of the low-dose intensity of S-1 ACT in older patients following curative gastrectomy.