It is well known that type 2 diabetes (T2DM) is dramatically improved after bariatric surgery, although the mechanisms have not been clearly identified. The skill required for gastric surgery for gastric cancer is very similar to that needed in bariatric surgery. In this study, we evaluated the immediate improvement of T2DM after gastrectomy for gastric cancer.

A total of nine patients who were diagnosed with early gastric cancer (EGC) and already had T2DM underwent a 75 g oral glucose tolerance test (OGTT) before surgery and within two weeks after gastrectomy. Glucose, insulin, and c-peptide were measured before, and 30 and 60 minutes after ingesting 75 g of glucose. From these trials, we calculated the HOMA-IR, insulinogenic index, Matsuda index, and area under the curve (AUC).

The mean age of participants was 57.23 ± 11.08 years and eight of them were men. HOMA-IR (4.2 vs. 2.3, P = 0.012) levels were decreased after surgery. There were no significant differences of insulinogenic index, fasting blood sugar before and after surgery. The Matsuda index (3.3 vs. 8.3, P = 0.002) was significantly increased and AUC (512.9 vs. 388.7 mg-hr/dL, P > 0.001) upon 75 g OGTT was significantly decreased after surgery.

Insulin sensitivity was immediately improved after gastrectomy for early gastric cancer in patients with T2DM.