Intensity-modulated radiotherapy increases dose to the brachial plexus compared with conventional radiotherapy for head and neck cancer

Objective: The preferential use of intensity-modulated radiotherapy (IMRT) over conventional radiotherapy (CRT) in the treatment of head and neck cancer has raised concerns regarding dose to non-target tissue. The purpose of this study was to compare dose-volume characteristics with the brachial plexus between treatment plans generated by IMRT and CRT using several common treatment scenarios. Method: The brachial plexus was delineated on radiation treatment planning CT scans from 10 patients undergoing IMRT for locally advanced head and neck cancer using a Radiation Therapy Oncology Group-endorsed atlas. No brachial plexus constraint was used. For each patient, a conventional three-field shrinking-field plan was generated and the dose-volume histogram (DVH) for the brachial plexus was compared with that of the IMRT plan. Results: The mean irradiated volumes of the brachial plexus using the IMRT vs the CRT plan, respectively, were as follows: V50 (18 +/- 5 ml) vs (11 +/- 6 ml), p=0.01; V60 (6 +/- 4 ml) vs (3 +/- 3 ml), p=0.02; V66 (3 +/- 1 ml) vs (1 +/- 1 ml), p=0.04, V70 (0 +/- 1 ml) vs (0 +/- 1 ml), p=0.68. The maximum point dose to the brachial plexus was 68.9 Gy (range 62.3-78.7 Gy) and 66.1 Gy (range 60.2-75.6 Gy) for the IMRT and CRT plans, respectively (p=0.01). Conclusion: Dose to the brachial plexus is significantly increased among patients undergoing IMRT compared with CRT for head and neck cancer. Preliminary studies on brachial plexus-sparing IMRT are in progress.