Factors Associated With Local Control and Toxicity of Hypofractionated Radiotherapy for Early and Late-Stage Ultracentral Lung Tumors.

Background: Treating ultracentral tumors near critical mediastinal structures is challenging due to severe toxicity risks. This retrospective study evaluates the safety and efficacy of hypofractionated body radiotherapy (HFRT) for ultracentral tumors at a single institution.

Methods: Ultracentral tumors were defined as those invading, abutting, or having an overlapping planning target volume with the proximal bronchial tree (PBT), heart, great vessels, or esophagus. Patients with primary lung cancer or metastases from nonlung primaries, and received HFRT (6-15 fractions) or stereotactic body radiotherapy (SBRT, ≤5 fractions) were included. Radiation-associated toxicities were recorded. Outcomes included overall survival (OS), progression-free survival (PFS), and local control (LC). Prognostic factors were analyzed using Cox regression analysis.

Results: Eighty-six patients with ultracentral tumors underwent 94 treatment courses (69 SBRT, 25 HFRT) between 2014 and 2023. Radiation pneumonitis (RP), pneumonia, and cardiotoxicities developed in 39.3%, 13.9%, and 9.6% of treatments, respectively. One patient experienced grade 3 pulmonary hemorrhage, with no cases of airway fistula or necrosis. Median follow-up was 17.9 months with 1-year and 2-year OS rates of 78.7% and 65.6%, and LC rates of 93.5% and 84.0%, respectively. BED ≥100 Gy was associated with improved OS on multivariable Cox regression analysis. RP of any grade was a risk factor for local failure (HR 4.63, 95% CI, 1.22-17.48).

Conclusions: HFRT can be safely administered to ultracentral tumors with excellent local control and low toxicity. Further research is needed to optimize treatment strategies and investigate associations between RP and increased local failure.