Dosimetric comparison of 3-dimensional conformal radiation therapy and intensity modulated radiation therapy and impact of setup errors in lower limb sarcoma radiation therapy

Abstract

Purpose: This study compared dosimetric data between 3-dimensional conformal radiation therapy (3DCRT) and intensity modulated radiation therapy (IMRT) plans in a population of patients with lower limb sarcoma immobilized with an in-house device and quantified the impact of systematic and random errors on these techniques. The dosimetric effects of displacements on target coverage and organs at risk (OARs) were considered.

Methods and materials: Plans were created for 11 postoperative patients using both 3DCRT and IMRT. The techniques were compared dosimetrically. Population-based systematic and random errors were applied and the results compared with the initial plans.

Results: Higher target D95, D2, D98, and D50 and the best homogeneity index resulted with IMRT compared with 3DCRT. Systematic errors increased target D2 in IMRT. Random errors decreased target homogeneity in IMRT. Maximum bone dose was higher in IMRT than in 3DCRT. Neither error type increased OAR dose for either technique.

Conclusions: IMRT could become the favored lower limb sarcoma radiation therapy technique because of superior target coverage and homogeneity. Offline imaging can adequately correct for systematic errors in these patients when an in-house immobilization device is used.