Impact of Consolidation-to-Tumor Ratio on Prognosis After Radiotherapy for Lung Cancer with a Lesion Diameter of 3 cm or Less

Introduction Accurate risk stratification is essential for optimizing radiotherapy 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 radiotherapy. Methods This study included patients with NSCLC with a lesion diameter ≤ 3 cm, without lymph node or distant metastases, who underwent definitive radiotherapy alone between 2015 and 2022. Patients were categorized into three CTR groups: GGO-dominant (≤ 0.5), solid-dominant (> 0.5 to < 1.0), and pure-solid (1.0). Prognostic performance for progression-free survival (PFS) was compared between CTR-based and T-stage-based models using the Akaike Information Criterion (AIC) and Concordance Index (C-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 PFS (64.5% vs. 93.1%), with higher rates of distant metastasis. In multivariate analysis, the CTR-based model demonstrated a lower AIC (895.6 vs. 907.4) and a higher C-index (0.69 vs. 0.67) than the T-stage-based model, indicating better goodness-of-fit and predictive ability. Conclusion CTR is a robust prognostic indicator, superior to T-stage, in early-stage NSCLC treated with radiotherapy. Incorporating CTR into clinical decision-making may provide more accurate risk stratification than tumor size alone.