Impact of Consolidation-to-Tumor Ratio on Prognosis After Radiation therapy for Lung Cancer With a Lesion Diameter of 3 cm or Less.

Purpose: Accurate risk stratification is essential for optimizing radiation therapy for early stage non-small cell lung cancer (NSCLC). This study evaluated whether the consolidation-to-tumor ratio (CTR) or conventional clinical T stage provides superior prognostic value for patients treated with definitive radiation therapy. Methods and Materials: This study included patients with NSCLC with a lesion diameter ≤3 cm, without lymph node or distant metastases, who underwent definitive radiation therapy alone between 2015 and 2022. Patients were categorized into 3 CTR groups: ground-glass opacity (GGO)-dominant (≤0.5), solid-dominant (>0.5 to <1.0), and pure-solid (1.0). Prognostic performance for progression-free survival was compared between CTR-based and T-stage-based models using the Akaike Information Criterion and Concordance Index. Results: In total, 265 patients (25 GGO-dominant, 39 solid-dominant, and 201 pure-solid) were analyzed. The median follow-up was 50.2 months. No recurrences or deaths were observed in the GGO-dominant group. The pure-solid group exhibited significantly poorer 3-year outcomes than the containing-GGO group (GGO-dominant + solid-dominant) for overall survival (79.0% vs 96.5%) and progression-free survival (64.5% vs 93.1%), with higher rates of distant metastasis. In multivariate analysis, the CTR-based model demonstrated a lower Akaike Information Criterion (895.6 vs 907.4) and a higher Concordance Index (0.69 vs 0.67) than the T-stage-based model, indicating better goodness-of-fit and predictive ability. Conclusions: CTR is a robust prognostic indicator, superior to T-stage, in early stage NSCLC treated with radiation therapy. Incorporating CTR into clinical decision-making may provide more accurate risk stratification than tumor size alone.