Asynchronous Recovery of Body Composition After Curative Surgery for Gastric and Colorectal Cancer: A Prospective Longitudinal Study

Background and Aims: Postoperative recovery of body composition in patients with gastric cancer (GC) and colorectal cancer (CRC) is a complex and dynamic process. However, longitudinal recovery patterns across multiple physiological domains remain incompletely characterized. This study aimed to describe longitudinal changes in body composition over 12 months after curative surgery in patients with GC and CRC. Methods: This prospective longitudinal study evaluated serial changes in body composition parameters, including body weight, skeletal muscle index (SMI), phase angle (PhA), and the extracellular water to total body water ratio (ECW/TBW), from the preoperative period to 12 months after curative surgery in 138 patients, comprising 61 patients with GC and 77 patients with CRC. Results: Distinct and time-dependent recovery patterns were observed across body composition domains. Body weight and SMI gradually declined after surgery, reaching their lowest levels at approximately 3 months postoperatively, followed by partial recovery at 6 and 12 months; however, complete restoration to preoperative values was not achieved in several subgroups. In contrast, PhA declined abruptly on postoperative day 1, while ECW/TBW peaked at the same time point, representing the most prominent early postoperative changes in these parameters. Descriptive subgroup patterns suggested less complete recovery of SMI, PhA, and ECW/TBW among elderly, low skeletal muscle mass, advanced-stage, and chemotherapy-treated patients. Patients with low skeletal muscle mass showed persistently lower SMI values, whereas advanced-stage and chemotherapy-treated patients appeared to show slower normalization of PhA and ECW/TBW. Conclusions: Postoperative changes in body composition appeared to occur asynchronously across multiple physiological domains in patients with gastric and colorectal cancer. Several clinically vulnerable subgroups, including older patients, patients with low skeletal muscle mass or advanced-stage disease, and patients who received chemotherapy, showed descriptive patterns suggestive of less complete recovery. Serial body composition assessment over an extended follow-up period may help characterize postoperative changes and provide a basis for future hypothesis-driven studies.