Syndrome of Inappropriate Antidiuretic Hormone (SIADH) in Lung Cancer 12 months experience from a Cancer Unit Bulusu V R, Jessop S, Jeffs Y P, Thomas E, Adu Poku K, Sa’d A, Prasad B, Azher M, Barclay C Bedford Hospital, Kempston road, Bedford MK42 9DJ UK. Introduction: SIADH is an uncommon complication associated with lung cancer. The exact incidence of SIADH in lung cancer patients in United Kingdom is not well known. We report on the incidence, presenting symptoms, treatment and outcomes in patients with SIADH over 12 months in our unit. Methods Results All patients with SIADH and lung cancer from July 2013 to June 2014 were reviewed. Patient demographics, tumour histology and stage, serum sodium levels at presentation, presenting features, treatment and outcomes were recorded. The local algorithm developed for management of SIADH was followed1. SIADH was confirmed using standard diagnostic parameters. 101 lung cancer patients were diagnosed between July 2013 and June 2014. 19 pts were diagnosed with small cell lung cancer (SCLC). 5 of SCLC patients had a confirmed SIADH (26% of SCLC & 5% of all lung cancers). M:F ratio 3:2, median age = 63 years (range 56-79), WHO PS 0-3. Table 1 summarizes the presentation, sodium levels and treatment. 2 patients had prior fluid restriction; all were treated with oral Tolvaptan 15 mg once a day until the serum sodium had normalised and patient started on chemotherapy. Median duration of Tolvaptan=8 days (range 5 to 16). All patients were treated as day/outpatients. Fig 1 shows the serum sodium response to Tolvaptan in pt 1. Table 1 Patient Number Age (years)/ Gender Tumour Stage WHO PS Symptoms at presentation Baseline Na+ (mEq/litre) at diagnosis Treatment Tolvaptan duration (days) 1 56/Female T4N1M0 2 Lethargy, nausea, insomnia blurred vision 112 Fluid restriction & Tolvaptan 12 63/Male T4N3M1a Lethargy Unwell feeling 118 8 3 T2aN1M0 Leg weakness, falls, shaking 113 Tolvaptan 16 4 76/Female T3N3M1b Falls with head injury 126 7 5 79/Male T2N2M1b Left arm weakness Conclusions: In our experience, 26% of SCLC patients in the cohort had SIADH. Serum sodium response to Tolvaptan was prompt and was associated with significant symptomatic benefit. Tolvaptan was well tolerated and reduced inpatient stay. We believe Tolvaptan should be the new standard of care for the treatment of cancer related SIADH.   Reference: Hyponatraemia in Oncology: Magnitude of the problem: Proposed Management Algorithm for Syndrome of Anti Diuretic Hormone associated with Cancer: A Joint Acute Oncology & Acute Medicine Project: Bulusu V R, Jeffs Y P, Barclay C, Melvin A. Lung Cancer Vol 75, Suppl1, S35, Jan 2012. Ramesh.bulusu@nhs.net