“…However, a safe rectal radiation dose cutoff is difficult to establish as most studies find marked rectal radiation dose overlap between symptomatic and asymptomatic patients, and some patients with exceedingly high rectal doses develop no complications [6][7][8] , suggesting individual susceptibility factors. Some patient characteristics that have been associated with increased risk of late radiation toxicity include vascular disease, diabetes, connective tissue disease, inflammatory bowel disease, HIV infection, smoking, and genetic variations [5] .…”