Urea for Treatment of SIAD Induced Hyponatremia: Experience of an Oncology Center.

[INTRODUCTION] Inappropriate antidiuresis syndrome (SIAD) induced hyponatremia is the most common electrolyte disturbance found in cancer patients. Available treatment options are limited by their poor efficacy, tolerability, or cost. Urea is a promising alternative, but its use in the oncology setting remains insufficiently characterized. We aimed to evaluate the efficacy and safety of urea in the management of chronic SIAD-induced hyponatremia in patients with cancer.

[METHODS] We conducted a retrospective observational study of patients diagnosed with SIAD and treated with oral urea at our Oncology Center between August 2021 and June 2023. Sodium levels were recorded before urea initiation, at the first reevaluation and at the last available follow-up.

[RESULTS] The cohort included 28 patients, mostly men (71%), with a mean age of 63.9 ± 10.0 years; 86% had metastatic disease. Lung cancer was the most frequent diagnosis, mostly small cell lung carcinoma. Urea treatment resulted in a statistically significant increase in serum sodium both in inpatients (mean increase of 2.4 ± 3.5 mmol/L after 12 (23) hours, p = 0.016) and outpatients (mean increase of 8.6 ± 6.6 mmol/L after 8 (11) days, p = 0.003). No cases of sodium overcorrection or clinically significant adverse events were reported. One patient complained of urea taste, with no impact on treatment adherence. Sodium normalization following cancer treatment allowed for urea discontinuation in 21% of cases. Median follow-up was 84 days (range 3 days-20.9 months).

[CONCLUSION] Our study suggests that urea may be a safe, effective, and well-tolerated option for the long-term management of SIAD-related hyponatremia in oncology patients, but further studies are necessary to confirm these observations.