Prognostic Impact of Tumor Solid Components in Stereotactic Body Radiotherapy for Clinical Stage Tis-1N0M0 Lung Cancer.

Purpose: This study aimed to assess the potential of prognostic factors including consolidation tumor ratio (CTR) on treatment outcomes in patients with clinical stage 0-IA non-small cell lung cancer (NSCLC) undergoing stereotactic body radiotherapy (SBRT).

Methods: The analysis included data of 63 patients with 67 lesions of clinical stage 0-IA NSCLC treated with SBRT. According to the Union for International Cancer Control 8th edition, the following tumor stages were observed: Tis, 3; T1mi, 2; T1a, 11; T1b, 29; and T1c, 22. The prescribed dose was 48 (range, 42-52) Gy in four fractions.

Results: The median follow-up was 29.3 (range: 2.4-120.5) months. The five-year local control (LC), overall survival, and progression-free survival (PFS) rates were 89.4%, 60.3%, and 40.5%, respectively. Squamous cell carcinoma (Sq) and D < 125 Gy for planning target volume (PTV) were associated with a worse LC (p = 0.001 and 0.017, respectively). Patients with Sq, T1b-c, CTR > 0.25, PTV ≥ 30 cm tumors were associated with worse PFS than those with non-Sq, ≤ cT1a, CTR ≤ 0.25, PTV < 30 cm tumors (p = 0.049, 0.004, 0.038, and 0.004, respectively). No recurrences, metastases, or deaths were found in patients with CTR ≤ 0.25 (n = 5).

Conclusion: In patients with stage 0-IA lung cancer treated with SBRT, tumors classified as ≤ T1a showed a better PFS than T1b-c. NSCLC with a low CTR of ≤ 0.25 seemed to have a low risk of recurrence after SBRT.