KEY POINTS
- The guideline was developed through a modified Delphi process involving 25 international experts: 20 radiation oncologists, three clinical oncologists, one medical physicist and one image-registration specialist. Consensus required at least 80% agreement.
- The panel evaluated 52 initial statements and produced 42 recommendations and statements across eight clinical questions, covering selection, diagnostic work-up, target definition, fractionation, planning, cumulative dose, systemic therapy and follow-up.
- Curative-intent high-dose reirradiation should generally be reserved for patients with Eastern Cooperative Oncology Group performance status 0–1, anticipated survival of at least six months and no active widespread metastatic disease. A minimum interval of six months after prior thoracic radiotherapy was recommended.
- Restaging should include fluorodeoxyglucose positron emission tomography/computed tomography, contrast-enhanced chest computed tomography and brain magnetic resonance imaging. Pathological confirmation is recommended when technically feasible, particularly when recurrence cannot be reliably distinguished from post-treatment change.
- Elective nodal reirradiation is not recommended. Gross disease should receive involved-site treatment using no clinical target volume margin or an anatomically tailored expansion, while planning target volume margins should reflect institutional accuracy and not exceed 5 mm.
- For peripheral lesions measuring no more than 5 cm, stereotactic body radiotherapy delivering a biologically effective dose of at least 100 Gy using an alpha/beta ratio of 10 Gy is conditionally recommended. Central and ultracentral targets require individualized assessment of previous dose, interval and cumulative constraints.
- For patients unsuitable for stereotactic treatment, 60 Gy in 30 fractions or 55 Gy in 20 fractions were considered acceptable schedules when cumulative organ-at-risk limits can be respected. The guideline did not define a new universal set of thoracic cumulative dose constraints.
- Concurrent chemotherapy may be considered selectively, particularly for nodal recurrence, but increases severe toxicity risk. Because lethal events occurred in early reirradiation-immunotherapy series, checkpoint inhibition should preferably be sequential and used within trials or after individualized multidisciplinary review.
CLINICAL TAKEAWAY
The guideline provides a practical minimum standard for selecting, staging and treating patients considered for high-dose thoracic reirradiation. Many recommendations remain conditional or expert-opinion based, so multidisciplinary review, access to the prior dose distribution, rigorous registration and transparent cumulative-dose assessment remain essential.