Volumetric modulated arc therapy with flattening filter free (FFF) beams for stereotactic body radiation therapy (SBRT) in patients with medically inoperable early stage non small cell lung cancer (NSCLC)

Abstract

Purpose: To assess the impact of volumetric modulated arc therapy (VMAT) with flattening filter free (FFF) beams for stereotactic body radiotherapy (SBRT) in inoperable stage I NSCLC. Current data were compared against a cohort of patients previously treated with advanced conformal techniques (3DCRT) based on conformal arcs.

Methods and materials: From July 2006 to December 2011 132 patients underwent SBRT, 86 by 3DCRT with flattened beams (FF), while the last 46 with VMAT RapidArc and unflattened beams (FFF). All patients were treated with 48 Gy in four fractions of 12 Gy each. Patients underwent follow-up. Clinical outcome was evaluated with thoracic and abdominal CT scan and 18FDG-CTPET before and after treatment.

Results: Both techniques achieved adequate dose conformity to the target but with a statistically significant reduction of ipsilateral lung doses in RapidArc plans and also of Beam-on-Time (BOT) with FFF mode. The median follow up was 16 months (range 2-24 months). At 1 year, local control rate was 100% with FFF beams compared with 92.5% with FF beams (p=0.03).

Conclusions: SBRT with FFF beams permitted us a safe delivery of high dose per fraction in a short treatment time and resulted in an earlier radiological response compared with FF beams.

Keywords: NSCLC; SBRT; Volumetric modulated Arc Therapy.