Gamma Knife Boost for Head and Neck Cancers with Skull Base Extension: A Case Series

Abstract

Background: Reirradiation (reRT) for locoregional recurrences can provide durable control and improved symptoms and progression-free survival for select NSCLC patients. Thoracic reRT, however, is particularly challenging due to its considerable risk and the current lack of standardized approaches, guidelines and dose constraints. To date, no systematic review on the safety and efficacy of reRT for NSCLC exists, and no dedicated guidelines are available. Objectives: This ARS-ACR Appropriate Use Criteria Systematic Review and Guidelines on Reirradiation for NSCLC provides direct guidance on the safety and efficacy of reRT and recommends consensus dose constraints for thoracic reRT to minimize risks of high grade toxicities. Methods: A PRISMA systematic review assessed all studies published through 3/2019 evaluating toxicities, local control and/or overall survival for NSCLC thoracic reRT. Of 236 articles, 49 remained after exclusions (3 prospective) and formed the basis for these recommendations on: 1) the role of concurrent chemotherapy with reRT, 2) factors associated with toxicity from reRT and 3) what reRT modalities, dose-fractionation schemas and dose rates should be used. Composite dose constraints were also recommended. Results: The available data suggest potential benefit in clinical outcomes with concurrent chemoradiation for reRT, but the decision should be based on patient performance status, tolerance to prior systemic therapy and other individual patient/tumor characteristics. There are no data to guide the use of concurrent targeted therapy or immunotherapy with reRT, and this is not recommended outside of a clinical trial. Acute esophagitis and pneumonitis and late pulmonary, cardiac/great vessel, esophageal, brachial plexus and spinal toxicities are dose limiting for reRT. Limited data exist regarding the use of hyperfractionation and low-or high-dose rate reRT for NSCLC. For conventionally fractionated reRT, intensity-modulated radiation therapy (IMRT) is recommended over 3D conformal radiation therapy (3DCRT) to increase dose conformality. Particle therapy may further reduce toxicities and/or enable safer reRT dose escalation compared with 3DCRT and IMRT. Stereotactic body radiation therapy (SBRT) can provide increased conformality and dose escalation and is optimal for primary-alone failures, but caution is needed for central reRT with SBRT. Recommended reRT composite dose constraints in 2 Gy equivalent dose are: esophagus V60 <40% and DMax <100-110 Gy, lung V20 <40%, heart V40 <50%, aorta/great vessels DMax <120 Gy, trachea and proximal bronchial tree DMax <110 Gy, spinal cord DMax <57 Gy, and brachial plexus DMax <85 Gy. Conclusions: For the first time, consensus dose constraints for thoracic reRT are recommended to minimize the risks of high-grade and potentially fatal toxicities from repeat radiotherapy. Additional prospective data are needed, and toxicities should be correlated with reRT course and composite dose constraints.