Background:​ Bone loss is highly prevalent after gastrectomy in gastric cancer patients. Therefore, the efficacy of medical treatment should be evaluated in patients undergoing gastrectomy.

Methods:​ We conducted an unblinded, randomized controlled trial of patients who underwent gastrectomy to treat gastric cancer. The intention-to-treat participants (n = 107) were randomly assigned to receive either alendronate at a weekly dose of 70 mg and daily elemental calcium (500 mg) with cholecalciferol (1000 IU) or daily elemental calcium (500 mg) with cholecalciferol (1000 IU) only. The primary endpoint was defined by the changes in bone mineral density of four measurement sites:​ the lumbar spine, femur neck, total hip, and trochanter. Changes in bone turnover markers, osteocalcin and collagen I carboxyterminal telopeptide were also observed.

Results:​ At baseline, there were no differences between the two groups in bone mineral density. In the lumbar spine and trochanter, there were no significant percentage changes compared with the baseline in the alendronate group, but a significant decrease was noted in the control group (p < 0.001 for both lumbar spine and trochanter). In the femur neck and total hip, a larger decrease was observed compared with the baseline in the control group (p < 0.001 for both femur neck and total hip). Significant percentage increases in serum osteocalcin compared with baseline were noted in the control group (p for trend <0.001), but there was no change in the alendronate group (p for trend = 0.713). Collagen I carboxyterminal telopeptide significantly declined in the alendronate group over 12 months (p for trend <0.001).

Conclusions:​ Prevention and treatment with bisphosphonate effectively reduces bone loss by suppressing bone resorption in gastric cancer patients undergoing gastrectomy.