For the regression analysis of factors associated with denosumab-induced hypocalcaemia, variables were extracted manually from medical charts. Evaluated variables included factors that could potentially impact the development of hypocalcaemia: demographic data (sex, age, height, weight, body mass index, and body surface area), number of cycles, concomitant medications (PPIs, steroids), cancer type, presence of comorbidity (diabetes mellitus), and laboratory test values (serum calcium, albumin, ALP, haemoglobin, creatinine, and estimated creatinine clearance). Creatinine clearance was estimated using the Cockcroft and Gault equation based on serum creatinine, sex, age, and weight. Clinical information was extracted before the first dose of denosumab. Concomitant medication was defined as administration of another drug for ≥ 2 weeks at the time of evaluation. The level of denosumab-induced hypocalcaemia based on an albumin-adjusted serum calcium concentration was evaluated by NCI‑CTCAE version 5. The evaluation time was the time of onset of hypocalcaemia (Grade 1 or higher) for patients who developed hypocalcaemia, and as the lowest calcium level within 1 month after final denosumab administration for patients who did not develop hypocalcaemia.