Impact of loss of skeletal muscle mass within 6-12 months after gastrectomy and S1 adjuvant chemotherapy on the survival prognosis of elderly patients with gastric cancer

Background and purpose: We investigated the impact of postoperative changes in the psoas muscle mass index (PMI) after gastrectomy and S1 adjuvant chemotherapy (AC) on the long-term outcomes of elderly patients with gastric cancer.

Methods: We reviewed the medical records of 228 patients aged over 75 years, who underwent distal, proximal, or total gastrectomy between January, 2013 and March 2017. Among these patients, 78 with pStage IIA-IIIC who survived for at least 1 year without recurrence after gastrectomy were the subjects of this analysis.

Results: The log-rank test using the cut-off value from the rate of change in PMI from 6 to 12 months after gastrectomy (late rate of decrease) showed significantly poorer prognosis for the group above the cut-off value for both overall survival (OS) and recurrence-free survival (RFS) (RFS: PMI decrease ≥ 1.55%, p < 0.001; OS: PMI decrease ≥ 1.55%, p < 0.001). Patients with a relative dose intensity of S1 below 68.7% and a late rate of decrease in PMI above 1.55% were found to have a poor prognosis.

Conclusion: It is necessary to prevent decline in the PMI of elderly patients from 6 months after gastrectomy and to administer adjuvant chemotherapy with about two-thirds or more RDI of S1 to improve their survival prognosis.