Hyponatremia timing, incidence, and associated risk factors in patients treated with cisplatin for lung cancer: a retrospective study.

The incidence of cisplatin-derived hyponatremia remains unknown, although nausea, vomiting, and renal dysfunction are common adverse events of cisplatin, a platinum-based preparation. The factor contributing to hyponatremia is described but not well known. This study aimed to retrospectively investigate the incidence of hyponatremia, timing, and associated risk factors. This study surveyed patients with lung cancer who received cisplatin chemotherapy from August 2013 to July 2019 at Shizuoka Cancer Center. The severity of hyponatremia was evaluated based on Common Terminology Criteria for Adverse Events. A total of 814 patients were included in this study. 682 (83.7%) patients had hyponatremia of any grade: grade 1 (<135-130 mmol/L), grade 3 (<130-120 mmol/L), and grade 4 (<120 mmol/L) hyponatremia were observed in 619 (76.0%), 51 (6.3%), and 12 (1.5%) patients, respectively. Of 63 patients with grade 3-4 hyponatremia, 43 (68.3%) developed it in the first treatment cycle. In multivariate analysis, the short hydration regimen (<3000 mL/day) has a lower incidence of grade 3-4 hyponatremia than a normal (>3000 mL) hydration regimen (OR: 0.35 [0.16-0.80], p = 0.013). In addition, if the Na⁺ value before the start of administration is < 135mmol/L, the incidence of grade3 and 4 hyponatremia is higher (OR:0.14 [0.07-0.28], p < 0.001). Hyponatremia due to cisplatin is likely to occur in patients with low Na levels before administration, such as the elderly. Since short hydration might avoid diuretics, hydration methods might need to be reconsidered to prevent hyponatremia.