Has 3-D conformal radiotherapy (3D CRT) improved the local tumour control for stage I non-small cell lung cancer?

Abstract

Aims and background: The high local failure rates observed after radiotherapy in stage I non-small cell lung cancer (NSCLC) may be improved by the use of 3-dimensional conformal radiotherapy (3D CRT).

Materials and methods: The case-records of 113 patients who were treated with curative 3D CRT between 1991 and 1999 were analysed. No elective nodal irradiation was performed, and doses of 60 Gy or more, in once-daily fractions of between 2 and 3 Gy, were prescribed.

Results: The median actuarial survival of patients was 20 months, with 1-, 3- and 5-year survival of 71, 25 and 12%, respectively. Local disease progression was the cause of death in 30% of patients, and 22% patients died from distant metastases. Grade 2–3 acute radiation pneumonitis (SWOG) was observed in 6.2% of patients. The median actuarial local progression-free survival (LPFS) was 27 months, with 85 and 43% of patients free from local progression at 1 and 3 years, respectively. Endobronchial tumour extension significantly influenced LPFS, both on univariate (P=0.023) and multivariate analysis (P=0.023). The median actuarial cause-specific survival (CSS) was 19 months, and the respective 1- and 3-year rates were 72 and 30%. Multivariate analysis showed T2 classification (P=0.017) and the presence of endobronchial tumour extension (P=0.029) to be adverse prognostic factors for CSS. On multivariate analysis, T-stage significantly correlated with distant failure (P=0.005).

Conclusions: Local failure rates remain substantial despite the use of 3D CRT for stage I NSCLC. Additional improvements in local control can come about with the use of radiation dose escalation and approaches to address the problem of tumour mobility.

Introduction

Curative external beam radiotherapy offers an alternative for patients with stage I non-small cell lung carcinoma (NSCLC) who are medically inoperable or refuse surgery. The overall 5-year survival rates in these patients range from 6 to 32%, and cause-specific survival (CSS) rates at 3 years of between 22 and 42% have been reported [26]. As local recurrence is the most common pattern of failure, improved radiation techniques and/or radiation dose escalation are warranted for such patients. 3-Dimensional conformal radiotherapy (3D CRT) has gained wide acceptance as a more effective means of achieving improved tumour coverage without increasing doses to critical normal structures. The advantages of 3D technology include a more realistic appreciation of the gross tumour volume (GTV), a better assessment of the doses to critical structures, improved geometric coverage by external beams, as well as tools to compare and judge rival plans [6], [18].

Much of the published literature refers to series in which 3D CRT was not uniformly used. Our institution implemented beams eye view (BEV) treatment planning for all patients with stage I NSCLC in 1991. The aim of the present study was to establish the local and distant tumour control, and overall survival (OS) and CSS for our patients who were treated using 3D CRT.