Purpose: Three-dimensional conformal radiation therapy (3D-CRT) represents an advance in the better delineation of the target contours and more accurate dose distributions. The purpose of this study was to identify local control prognostic factors in patients with locally advanced non-small cell lung cancer (LA-NSCLC) treated with 3D-CRT.
Material and methods: Between April 1995 and March 2002, 65 patients (NSCLC stage IIIA: 20%, IIIB: 77%) were treated with cisplatin-based induction and concurrent chemotherapy chemotherapy and hyperfractioned 3D-CRT (1.2Gy b.i.d.; median dose: 72.8 (range: 67-85.9). Clinical parameters (sex, age, performance status, stage, histology, tumor location), therapeutic factors (chemotherapy schedule, 3D-CRT dose, treatment response) and dosimetric factors (volume and dose of GTV, PTV-2, CTV and PTV-1) were evaluated. Local recurrences were divided into three dosimetric categories: those with more than 80% of their volume within high dose region (95% of prescription dose) were considered "central"; those between 20% and 80% were considered "marginal", and those with less than 20% of their volume within high dose region were considered "out-of-field". Local-failure free survival (LFFS) was obtained using the Kaplan-Meier method. Univariate and multivariate analyses were performed.
Results: There were 18 local failures (nine central, eight marginal and one out-of-field). The 2 and 5 year LFFS were 73% and 53%, respectively. In multivariate analysis, PTV-1>1146cc (HR=2.9, CI 95%: 1.1-7.5, p=0.026) was the only factor associated with worse LFFS.
Conclusions: This study shows that local control was independently related to PTV-1 size. The great majority of local recurrences were located in the high-dose region. Dosimetric parameters may contribute to improving radiotherapy results in multidisciplinary treatment for LA-NSCLC.