Precision Stereotactic Body Radiotherapy for Ultra-Central NSCLC: Tailored Margins Reduce Toxicity Without...

Area of Science:

• Radiation Oncology
• Medical Physics
• Thoracic Oncology

Background:

• Stereotactic body radiation therapy (SBRT) is a standard treatment for early-stage non-small cell lung cancer (NSCLC).
• Treating ultra-central NSCLC (UCNLC) adjacent to critical organs poses significant challenges due to dose constraints.
• Optimizing SBRT for UCNLC requires precise planning to balance efficacy and toxicity.

Purpose of the Study:

• To evaluate the efficacy and safety of SBRT using tailored non-uniform planning target volume (PTV) margins for stage I-II unresectable UCNLC.
• To identify factors influencing treatment outcomes, including local control (LC), progression-free survival (PFS), and overall survival (OS).

Main Methods:

• Retrospective analysis of 66 patients with UCNLC treated with SBRT between 2020-2023.
• UCNLC defined by planning target volumes (PTVs) abutting/overlapping vital structures or internal target volumes (ITVs) within 1 cm.
• Application of tailored SBRT plans with non-uniform PTV margins in 45.5% of cases.

Main Results:

• Median follow-up was 32.2 months. Median PFS was 42.9 months; 3-year PFS rate was 68.8%.
• Median LC and OS were not reached. 3-year LC and OS rates were 84.6% and 88.7%, respectively.
• Toxicities were predominantly grade 1-2, with one case of grade 3 pneumonitis. Larger ITV predicted poorer LC and PFS; T stage predicted PFS and OS.

Conclusions:

• Tailored SBRT with non-uniform PTV margins is a safe and effective strategy for managing UCNLC.
• This approach achieves high rates of local control and survival without significant toxicity.
• Non-uniform PTV margins allow dose escalation while sparing critical structures, supporting their use in UCNLC treatment.