Alexandra N. De Leo: Department of Radiation Oncology, University of Florida College of Medicine, 2000 SW Archer Road, PO Box 100385, Gainesville, FL 32610, USA. lopeal@shands.ufl.edu
The authors regret that the above article contained an incorrect reference list. The authors would like to apologise for any inconvenience caused. The correct Refs. [10,12,13,16,18,22,32–34,42,48,65] are as follows: