Stage I-III limited-stage small cell lung cancer (SCLC) is a highly aggressive yet potentially curable disease with concurrent chemoradiotherapy. Thoracic radiation therapy (RT) plays a central role in the management of stage I-III SCLC; however significant variation exists in staging, target volume delineation, dose prescription, and integration with systemic therapy. This document provides an updated European recommendations on the use of RT in stage I-III SCLC, reflecting recent evidence and advancements in clinical practice. A panel of European experts was convened under the auspices of the ESTRO Guidelines Committee, in collaboration with EORTC Lung Cancer Group, and to review the available evidence and develop recommendations. Key topics addressed included disease staging, radiotherapy planning and delivery, and the integration with chemotherapy and immunotherapy. Accurate staging should include PET-CT and brain MRI. Thoracic RT should be initiated early during chemotherapy. Standard dose schedules include 45 Gy in 30 fractions (BID) or 66 Gy in 33 fractions once daily, using conformal techniques such as IMRT/VMAT, involved field nodal irradiation, respiratory motion management (e.g., 4D-CT, breath-hold) and image guidance (e.g., cone-beam CT [CBCT]). Concurrent chemotherapy with 4-6 cycles platinum-etoposide followed by consolidation durvalumab for up to two years is the standard of care in fit patients. Prophylactic cerebral irradiation (PCI) continues to represent the standard approach following treatment response; while hippocampal-sparing PCI and MRI surveillance strategies are being actively evaluated in ongoing studies. In selected cases, stereotactic body radiotherapy (SBRT) may be appropriate for medically inoperable early-stage disease without nodal involvement, and adjuvant RT can be considered for R1 resections or pN2 involvement. Emerging strategies, including adaptive RT, dose escalation and the integration of precision medicine have the potential to improve the therapeutic ratio. Integration with immunotherapy and/or novel agents, such as delta-like ligand 3 (DLL3)-targeted therapies, is under active investigation. Biomarker-guided treatment personalisation remains investigational. These updated European guidelines provide a comprehensive framework for standardized, high-quality care in stage I-III SCLC and establish a reference standard to harmonize radiotherapy approaches and inform the design of upcoming clinical trials.

Unresectable locally advanced non-small cell lung cancer (LA-NSCLC) remains a therapeutic challenge, despite the paradigm shift established by the PACIFIC trial (concurrent chemoradiation followed by Durvalumab consolidation). A substantial number of patients still experience disease progression and significant toxicity. This narrative review explores innovative radiation therapy (RT) strategies and their integration with systemic therapy. Key innovations analyzed include: 1. Systemic Therapy Intensification: Induction chemo-immunotherapy or novel multi-agent consolidation regimens show promise, but managing increased toxicity remains critical. The integration of DNA damage response inhibitors with RT is also being actively explored to maximize radiosensitization. 2. RT Dose and Volume Modulation: Recent data suggests that dose escalation via highly conformal hypofractionation or stereotactic ablative body radiotherapy (SABR) may enhance efficacy, particularly when combined with immunotherapy. Conversely, risk-adapted de-escalation of dose or volumes is studied to reduce immunosuppression and treatment-related toxicity, allowing more patients, including the elderly and frail, to complete consolidation. 3. Organ-at-Risk (OAR) Sparing: Advanced techniques like intensity-modulated radiation therapy (IMRT), adaptive RT (ART), and proton beam therapy (PBT) are crucial for minimizing dose to OARs and new substructures, such as specific cardiac subregions and lymphoid tissues. This OAR sparing is strongly correlated with improved OS and reduced immunosuppression. In conclusion, this narrative review focuses on the future of LA-NSCLC treatment, which is moving toward personalized, precision RT, embracing both intensification and thoughtful de-escalation, supported by synergistic systemic agents, to maximize curative potential and minimize toxicity.