Thoracic reirradiation clinical and technical practices: a survey from the reirradiation Collaborative Group (ReCOG).

Introduction: Thoracic reirradiation is increasingly used globally, but prospective evidence is scarce, leading to practice based primarily on institutional experience. Recognizing the need for guidance, international multi-professional experts convened at the first Reirradiation Collaborative Group (ReCOG) Meeting. This report presents results from a survey on best practices, challenges, and knowledge gaps among experts on thoracic reirradiation. Methods: A comprehensive 50-question survey was developed by experts and discussed within the thoracic focus group at ReCOG. It included questions on participant demographics and clinical experience, patient-related clinical conditions and selection, imaging and targets, treatment planning, and dose accumulation. Participants were asked for perceived challenges as well as gaps in knowledge. Results: The survey was completed by 34/51 invited experts (67 % response rate). Most respondents (79 %) were experienced physicists and radiation oncologists (>10 years) primarily at university hospitals (65 %). The most common tumors treated were locally recurrent lung cancer, mediastinal nodes, or thoracic metastases. Reirradiation goals included prolonging local control and survival, and alleviating/preventing symptoms. Conditions precluding reirradiation were persistent grade 3+ toxicity and progressive disease. Major toxicity concerns were bleeding, airway injury/fistula, and esophageal ulceration/fistula. Technical practices varied with regards to image registration, dose accumulation and recovery factors. Advanced treatment planning techniques and IGRT were consistent amongst respondents. Major challenges included lack of clinical guidelines and lack of software support tools. Conclusion: Thoracic reirradiation is an increasingly prevalent area of interest despite scarcity of prospective data. The major focus currently still is primarily on treatment-related factors and the question of how to combine reirradiation with systemic therapy. However, there is little guidance on whether and how to modify a planned reirradiation dose based on patient comorbidities or recovery from the prior radiation course. This survey identified emerging areas of consensus as well as relevant variations and gaps in practice.