Evaluating the association between hyponatremia and prognosis in hospitalized patients with cancer.

308 Background: Hyponatremia is frequently seen during hospital admissions for patients (pts) with cancer. Pts with active malignancy are at higher risk for developing hyponatremia with common drivers including syndrome of inappropriate antidiuretic hormone secretion (SIADH) and hypervolemic hyponatremia. We sought to look at hyponatremia among hospitalized pts with cancer and assess whether treatment affects outcomes. Methods: Adult pts with active cancer admitted to an academic tertiary care hospital between 1/1/2023 and 12/31/2023 with a serum sodium less than 130 mEq/L were included. Pts with leukemia were excluded. Clinicopathologic factors, etiology and management of hyponatremia, and outcomes were extracted by retrospective chart review. Extracted outcomes included recurrent hyponatremia within 30 days of discharge, 30-day readmission rate, and transition to hospice or death from any cause within the next 6 months. Distributions of continuous and categorical variables were compared using t-test and chi-square test, respectively. Pts were defined as treated for hyponatremia if they received tolvaptan, hypertonic saline, salt tablets, urea, fluid restriction, or a renal consult. Results: In total, 210 pts accounting for 356 admissions were included; 88% had stage IV cancer (88%), and 41%, 16%, and 12% had gastrointestinal (GI), genitourinary, and thoracic cancers, respectively. Most common etiologies of hyponatremia included hypovolemia from GI loss (15%), SIADH (36%), low solute intake (45%), and hypervolemia (20%). The median minimum sodium value during the hospital stay was 126 mEq/L. Inpatient interventions included normal saline or lactated ringer’s intravenous fluids (38% each), fluid restriction (24%), salt tablets (18%), diuretics (15%), renal consult (12%), and no intervention (18%). 165 (46%) of encounters were followed by readmission within 30 days. Based off their first 2023 encounter, 47% of pts transitioned to hospice and 57% of pts had death from any cause within the next 6 months. When separated into treated and untreated groups, the treated group (N=125) had a significantly lower minimum sodium (124 vs 127 mEq/L, p 129 mEq/L upon discharge (62% vs 74%, p=0.02) and less likely to have readmission within 30 days (37% vs 52%, p=0.01) but more likely to transition to hospice within the next 6 months (56% vs 42%, p=0.04), whereas the two groups had similar six month mortality (59% vs 56%, p=0.30). Conclusions: Hospital admission with moderate to severe hyponatremia was a poor prognostic sign for pts with cancer with high rates of death within 6 months, regardless of treatment. While there may be some utility to treatment with relatively lower 30-day readmission rates, pts would overall benefit from earlier goals of care/advanced care planning.