Diagnosis and Management of Hyponatremia in Cancer Patients

Abstract

Hyponatremia, a common electrolyte abnormality in oncology practice, may be a negative prognostic factor in cancer patients based on a systematic analysis of published studies. The largest body of evidence comes from small-cell lung cancer (SCLC), for which hyponatremia was identified as an independent risk factor for poor outcome in six of 13 studies. Hyponatremia in the cancer patient is usually caused by the syndrome of inappropriate antidiuretic hormone (SIADH), which develops more frequently with SCLC than with other malignancies. SIADH may be driven by ectopic production of arginine vasopressin (AVP) by tumors or by effects of anticancer and palliative medications on AVP production or action. Other factors may cause hypovolemic hyponatremia, including diarrhea and vomiting caused by cancer therapy. Hyponatremia may be detected on routine laboratory testing before or during cancer treatment or may be suggested by the presence of mostly neurological symptoms. Treatment depends on several factors, including symptom severity, onset timing, and extracellular volume status. Appropriate diagnosis is important because treatment differs by etiology, and choosing the wrong approach can worsen the electrolyte abnormality. When hyponatremia is caused by SIADH, hypertonic saline is indicated for acute, symptomatic cases, whereas fluid restriction is recommended to achieve a slower rate of correction for chronic asymptomatic hyponatremia. Pharmacological therapy may be necessary when fluid restriction is insufficient. The orally active, selective AVP receptor 2 (V 2 )-receptor antagonist tolvaptan provides a mechanism-based option for correcting hyponatremia caused by SIADH or other conditions with inappropriate AVP elevations. By blocking AVP effects in the renal collecting duct, tolvaptan promotes aquaresis, leading to a controlled increase in serum sodium levels. The Oncologist 2012;17:756 -765

Hyponatraemia—Evaluation of Prevalence in Patients Hospitalized in the Pulmonary Department and Prognostic Significance in Lung Cancer Patients

“…Almost 20% of cancer patients with hyponatraemia were also diagnosed with COPD, 6.6% with inflammation of the upper airways and 5.1% with tuberculosis, which are potential causes of SIADH. It is also known that SIADH may be caused by numerous drugs used in oncological practice, among others cisplatin, narcotic analgesics, carbamazepine and antidepressants [4]. We noticed that almost 60% of cancer patients with hyponatraemia were treated with cisplatin, 36.8% were administered analgesics, and 4.4% -carbamazepine.…”

“…In 2 out of 3 projects, hyponatraemia turned out to be a bad prognostic indicator both in univariate and in multivariate analysis [4].…”

“…Hyponatraemia in cancer patients is usually diagnosed in the case of SCLC [4]. In 9 studies including in total 1,684 patients with SCLC, summarised by Lassen et al [5], hyponatraemia < 136 mmoL/L was found in 24.6%.…”

“…It was noticed that hyponatraemia, regardless of cause, might be the factor that increases in-hospital and post-hospital mortality and prolongs hospitalization [2,4,12]. Even mild hyponatraemia influences the higher risk of in-hospital deaths [11].…”

“…Hyponatraemia was combined with a significantly shorter survival time in univariate analysis (7/13 research projects) and in multivariate analysis (6/13 research projects). However, it was impossible to formulate meta-analysis based on the data from these research projects due to a lack of HR value for survival in the majority of them [4]. In the study carried out by Hermes et al on a group of 395 patients with newly diagnosed SCLC (the study was not included in the above-mentioned analysis) it was also shown that hyponatraemia is a negative predictor in both uni-and multivariate survival analysis [15].…”