Loss of skeletal muscle mass during palliative chemotherapy is a poor prognostic factor in patients with advanced gastric cancer

Cancer causes muscle mass loss, which is associated with a poor prognosis. Chemotherapy may also reduce muscle mass. We investigated skeletal muscle mass change during palliative chemotherapy for advanced gastric cancer (AGC) and its association with treatment outcomes. We retrospectively reviewed 111 consecutive AGC patients who underwent first-line palliative chemotherapy. Skeletal muscle area was measured before and after chemotherapy at the third lumbar vertebra level using computed tomography scans. We compared skeletal muscle index (SMI), body mass index (BMI), and body weight changes to chemotherapy response and survival. The 80 male and 31 female patients’ median age was 65 (range 31–87) years, and 46.8% had sarcopenia at baseline. Median pre-chemotherapy to post-chemotherapy SMI, BMI, and body weight decreases were − 4.5 cm 2 /m 2 (− 11.3%) (P < 0.001); − 0.7 kg/m 2 (− 3.2%) (P < 0.001); and − 2.0 kg (− 3.5%) (P < 0.001), respectively. Median SMI decreases for patients with objective response, stable disease, and disease progression were − 4.0 cm 2 /m 2 (range − 20.1 ~ 9.5); − 4.5 cm 2 /m 2 (range − 19.8 ~ 0.8); and − 3.8 cm 2 /m 2 (range: − 17.6 ~ 0.1), respectively. Response to chemotherapy was not associated with SMI decrease (P = 0.463). In multivariable analysis, sarcopenia at baseline (HR 1.681; 95% CI 1.083–2.609, P = 0.021), decreased SMI (HR 1.620; 95% CI 1.041–2.520; P = 0.032) were significant poor prognostic factors for survival. Skeletal muscle mass decreased significantly during chemotherapy in AGC patients, but was not associated with chemotherapy response. Decreased SMI was a poor prognostic factor in AGC patients during first-line palliative chemotherapy.