Dose-Escalation Radiotherapy in Limited-Stage Small Cell Lung Cancer: A Phase III Randomized Trial

This is a phase III, prospective, randomized, multicenter trial designed to evaluate whether a dose escalation strategy using twice-daily hyperfractionated thoracic radiotherapy can improve outcomes in patients with limited-stage small cell lung cancer (LS-SCLC). Patients will be randomly assigned to one of three treatment arms: (A) standard-dose radiotherapy (45 Gy in 30 fractions BID), (B) escalated-dose radiotherapy (60 Gy in 40 fractions BID), or (C) standard-dose with a simultaneous integrated boost (45-54 Gy BID). All patients will receive concurrent chemotherapy with cisplatin and etoposide. The study aims to determine if intensified radiotherapy increases progression-free survival (PFS) and overall survival (OS). Secondary objectives include comparing toxicity profiles, quality of life (using EORTC QLQ-C30 and LC13/LC29), and exploratory analyses of circulating biomarkers. LS-SCLC has high recurrence rates despite aggressive treatment. Although BID thoracic radiotherapy (TRT) of 45 Gy is considered standard, new evidence suggests that higher doses may further improve survival without increasing toxicity. Modern radiotherapy techniques and improved imaging (e.g., PET-CT) allow more accurate targeting and potential dose escalation. The study plans to enroll 300 patients over 36 months across 10-15 Spanish centers, coordinated by the Instituto de Investigación Biomédica de Salamanca (IBSAL) and supported by SEOR-GOECP. An interim analysis will be conducted at year 1 and year 3, with a final analysis at 5 years. Data will be collected via REDCap and follow FAIR principles. The protocol has been approved by the Salamanca Research Ethics Committee. This trial seeks to define whether a higher radiotherapy dose improves long-term outcomes in LS-SCLC and to explore how biomarker data might inform future personalized treatments.