Background: Hyponatraemia (most commonly secondary to SIADH) is very common in cancer patients; it is associated with delays to oncology treatment and mortality.
Aim: To evaluate the number of patients with hyponatraemia at a tertiary referral cancer centre and assess adherence to national recommendations for investigations and treatment.
Methods: All biochemistry results (in-patient and outpatient) analysed at the Christie in September 2016 were screened for new-onset hyponatremia (serum Na <135 mmol/L). A structured checklist was used to extract data from laboratory results and patient records.
Results: 552 patients had a serum Na<135 mmol/L (n=108, Na<130 mmol/L). We studied 91 patients (47% female, mean age 66±11 yrs, 52% outpatients) with new onset hyponatraemia <130 mmol/L (n=19 Na<125 mmol/L) with lung (19%), GI (22%) and gynaecological (15%) malignancies being most frequent. Paired urine and serum osmolalities and urinary sodium were tested in only 19% of the study population (Na<125 mmol/l: 63%). Thyroid function and 9 am cortisol were checked in 20% (Na<125 mmol/l: 50%). Only 11% had all investigations performed within 24 hrs (Na<125 mmol/l: 50%). From a subcohort of 63 patients, fluid status, diagnosis, treatment plan and medication review was identified in 27%, 20%, 19% and 22.5% respectively and 15.9% (n=10) were referred to endocrinology (9 out of 10 had Na<125 mmol/l). 6-month mortality: 43% (Na<130 mmol/L) and 57% (Na<125 mmol/L).
Conclusion: >500 patients/month at a tertiary cancer centre have hyponatraemia. Only 11% of the evaluated patients with Na <130 mmol/l (Na <125 mmol/l: 50%) patients had complete investigations (paired serum and urine osmolalities, urinary sodium, TSH and cortisol). This does not compare favourably with recent global data (21.5% compliance in cancer subgroup of hyponatremia registry). Further work is required to establish efficient and safe pathways to investigate and manage these large numbers of hyponatremic patients and identify those who will benefit from treatment to prevent delays in chemotherapy.