Evaluation of hyponatraemia in lung cancer patients: A U.K. teaching hospital experience.

197 Background: Hyponatraemia, defined as a serum Na < 135mEq/L, is the commonest electrolyte abnormality in oncology practice. We describe the demographics, oncological management and response of hyponatraemia to oncological treatment modalities in our patient group. Methods: We retrospectively analysed serum sodium levels in lung cancer patients admitted to a teaching hospital in the UK between 2007 and 2013. Data was collected on baseline demographics, histology, tumour stage and grade of hyponatraemia. Mild hyponatraemia was defined as a serum sodium between 130-135mEq/L, moderate 125-129mEq/L and severe as < 124mEq/L. Results: 182 (108 male; 74 female) patients with lung cancer and documented hyponatraemia were hospitalised between 2007 and 2013. The median age of patients on admission was 69.2 years (range 33-92 years). 119(65%) had mild, 58(32%) moderate and 5(3%) severe hyponatraemia. 74(40%) were adenocarcinomas, 58(32%) squamous carcinomas, 43(24%)SCLC and 7(4%) had unspecified NSCLC. 89(49%) had metastatic disease on diagnosis. 18/43(42%)small-cell, 14/58(33%) squamous, 23/74 (31%)adenocarcinoma patients had moderate to severe hyponatraemia. 132(74%) of this cohort had active oncological treatment: 93(51%) chemotherapy, 25(14%) radiotherapy, 17(9%) surgery whilst 47(26%) had best supportive care. 28(15%) had a biochemical response to their treatment, 11(39%) of these patients were adenocarcinomas, 10(36%) squamous carcinomas and 7(25%) SCLC. Conclusions: Hyponatraemia in lung cancer patients is widely distributed in various age groups and histological subtypes. Among those admitted with hyponatraemia, severe cases were rare. Higher rates of SIADH are seen in SCLC than in any other malignancy and proportionately more SCLC patients had moderate - severe hyponatremia than NSCLC. Hyponatraemia responds to active oncological treatment including chemotherapy, radiotherapy and surgery. Although historically, hyponatraemia is considered a poor prognostic marker and has been associated with shorter survival duration, this should not preclude active oncological management. Further studies are needed to evaluate the prognostic value of hyponatraemia and its treatment in cancer patients.