Abstract Background Adjuvant chemotherapy for stage II colorectal cancer (CRC) is considered appropriate for patients with risk factors for recurrence, rather than for all patients uniformly. However, the risk factors for recurrence remain controversial, and there is limited information, especially for elderly patients. The Geriatric Nutritional Risk Index (GNRI) is widely used as a simple nutritional screening tool in the elderly and is associated with cancer prognosis and recurrence. This study aimed to investigate the risk factors for recurrence in the elderly with stage II CRC, focusing on the GNRI. Methods We enrolled 348 elderly patients (≥ 75 years) with stage II CRC who underwent curative resection at the Department of Surgery, Tottori University and our 10 affiliated institutions. The patients were divided into GNRIhigh (≥ 93.465) and GNRIlow (< 93.465) groups. Results The GNRIlow group showed a significantly worse overall survival (OS), cancer-specific survival (CSS), and relapse-free survival (RFS) (P < 0.001, P < 0.001, and P < 0.001, respectively). In a multivariate analysis, GNRIlow (hazard ratio [HR]: 2.244, P < 0.001), pathologic T4 stage (HR: 1.658, P = 0.014), and moderate to severe lymphatic or venous invasion (HR: 1.460, P = 0.033) were independent factors affecting RFS. By using these three factors to score the risk of recurrence from 0 to 3 points, the prognosis was significantly stratified in terms of OS, CSS, and RFS (P < 0.001, P < 0.001, and P < 0.001, respectively). The recurrence rate for each score was as follows: 0 points, 9.8%; 1 point, 22.0%; 2 points, 37.3%; and 3 points, 61.9%. Conclusions GNRIlow, pathologic T4 stage, and moderate to severe lymphatic or venous invasion are high-risk factors for recurrence in the elderly with stage II CRC. The scoring system using these three factors appropriately predicted their recurrence and outcome.
