Nutritional safety of oncometabolic surgery for early gastric cancer patients: a prospective single-arm pilot study using a historical control group for comparison

Oncometabolic surgery (OS) is a modification of the Roux-en Y reconstruction method, in which the lengths of the biliopancreatic and Roux limbs are longer than that with conventional surgery (CS). Although OS is performed to improve postoperative glycemic control in gastric cancer patients with type 2 diabetes mellitus (T2DM), its postoperative nutritional safety has not been clarified. This prospective pilot study evaluated the safety and feasibility of OS in early gastric cancer patients. This study evaluated 20 patients with clinical T1N0 stage and preoperative body mass index (BMI) ≥ 32.5 kg/m2, or ≥ 27.5 kg/m2 with comorbidities, who underwent OS. Primary outcomes were cumulative incidences of anemia and deficiencies in iron and vitamin B12 after 1 year. The outcomes were compared to those of a matched historical control group. The cumulative incidences of anemia (15.0% vs. 10.0%, P = 0.99), iron deficiency (15.0% vs. 10.0%, P = 0.99), and vitamin B12 deficiency (10.0% vs. 0%, P = 0.47) did not differ significantly in the OS and CS groups. However, median vitamin B12 concentration tended to be lower (395.8 vs. 493.7 pg/mL, P = 0.06) and reductions in vitamin B12 concentration tended to be greater (174.7 vs. 123.0 pg/mL, P = 0.07) in the OS group. BMI loss was similar in the two groups (2.9 vs. 2.8 kg/m2, P = 0.80). Remission rates of hypertension (68.8% vs. 41.2%, P = 0.22) and T2DM (77.8% vs. 50.0%, P = 0.58) were higher in the OS group. Nutritional parameters did not differ significantly in the OS and CS groups. Vitamin B12 levels should be carefully monitored after OS.