Application of Robotic Stereotactic Radiotherapy to Peripheral Stage I Non-small Cell Lung Cancer with Curative Intent

Abstract

Aims To determine the effectiveness of robotic stereotactic radiotherapy with image guidance and real-time respiratory tracking against early stage peripheral lung cancer. Materials and methods We treated patients with stage I non-small cell lung cancer (NSCLC) with CyberKnife ® and analysed their clinical characteristics and outcomes. All patients had co-morbid conditions that precluded lobectomy. The clinical target volume (CTV) included the gross tumour volume (GTV) and a 6 mm margin in all directions to account for microscopic extension. The planning target volume (PTV) equalled CTV + 2 mm in all directions for uncertainty. Tumour motion was tracked using a combination of Synchrony ® and Xsight ® Spine tracking methods with the aid of a single gold marker implanted in the centre of the tumour, or using the newer Xsight ® Lung method without markers for selected tumours. A 60–67.5 Gy dose was prescribed to the 60–80% isodose line (median 65%) and given in three to five fractions. Patients were followed every 3 months for a median of 27.5 months (range 24–53 months). Results Of the 67 patients with NSCLC stage IA or IB treated between January 2004 and December 2008, we report the results of a cohort of 31 with peripheral stage I tumours of 0.6–71 cm 3 volume treated between January 2004 and December 2007 with total doses between 60 and 67.5 Gy in three to five fractions. The median D max was 88.2 Gy and the median V 95 of the PTV was 99.6% or 27.9 cm 3. No grade 3 or above toxicity was encountered. Four cases of radiation pneumonitis and one case of oesophagitis were observed. In those patients whose pre- and post-treatment results were available, no change in pulmonary function tests was observed. Actuarial local control was 93.2% for 1 year and 85.8% for up to 4.5 years. One-year overall survival was 93.6% and 83.5% for up to 4.5 years, as projected by Kaplan–Meier analyses. Conclusions In this small cohort of patients with stage I peripheral NSCLC, robotic stereotactic radiotherapy seems to be a safe and obviously superior alternative to conventionally fractionated radiotherapy, with results that may be approaching those obtained with lobectomy without the associated morbidity.