Effects of target coverage on local recurrence in stereotactic body radiotherapy for early-stage lung squamous cell carcinoma.

Background And Purpose: This study investigated effects of target coverage on local recurrence (LR) in stereotactic body radiotherapy (SBRT) for early-stage lung squamous cell carcinoma (SCC).

Materials And Methods: Patients with clinical stage IA1-IIA lung SCC treated with SBRT were included in the analysis. Doses of 48-52 Gy were prescribed to the isocenter of the planning target volume according to the tumor diameter. The primary endpoint was LR. To examine the independent effects of dosimetric factors on LR after adjustment for clinical factors, Fine-Gray model with death as a competing risk was used for evaluation.

Results: Among all 59 patients analyzed, the median follow-up was 42 months. The 3-year LR rate was 24.0%. Univariate analysis of clinical factors showed that biologically effective dose calculated with an α/β value of 10 (BED) was associated with LR (p = 0.033). After adjustment for clinical factors, internal target volume (ITV) Dmean was associated with LR (p = 0.049). Subgroup analysis was performed for each prescribed dose group. The results of Fine-Gray model and receiver operating characteristic curve analysis showed that ITV Dmean > 100% of the prescribed dose was the best indicator of preventing LR.

Conclusions: ITV coverage may be particularly important in SBRT for early-stage lung SCC.