CONVERT: An international randomised trial of concurrent chemo-radiotherapy (cCTRT) comparing twice-daily (BD) and once-daily (OD) radiotherapy schedules in patients with limited stage small cell lung cancer (LS-SCLC) and good performance status (PS).

8504Background: cCTRT is the standard of care for good PS LS-SCLC but there is no international consensus on a standard regimen. BD RT has not been adopted widely due to concerns regarding logistics and toxicity. Our aim was to compare overall survival and toxicity of BD with OD RT using modern conformal RT techniques given concurrently with chemotherapy. Methods: Patients were randomised 1:1 to receive 45Gy in 30 BD fractions over 3 weeks or 66Gy in 33 OD fractions over 6.5 weeks starting on day 22 of cycle 1 chemotherapy (4 to 6 cycles of Cisplatin 25mg/m2 days 1-3 or 75mg/m2 day 1 with Etoposide 100mg/m2 days 1-3), followed by PCI if indicated. RT was planned using 3D conformal or IMRT. Patients were stratified by centre, 4/6 cycles CT and PS 0,1/2. The primary endpoint was 2-year survival and all analyses were by intention to treat. Results: 547 patients (274 BD and 273 OD) were recruited between April 2008 and November 2013 from 88 centres. Patients’ characteristics were well balanced in both arms. 8...