“…The CTV-N should cover the GTV-N with a 1.0-1.5 cm margin but excluding uninvolved bone, muscle or air CTV-high risk (CTV-HR) Should cover the entire mesorectum, the right and left internal iliac lymph nodes inferior to the inferior-most level of the sacroiliac joint, and the inguinal or external iliac lymphatics if the inguinal nodes are uninvolved To cover the iliac lymphatics, a 0.7-cm margin around the iliac vessels should be drawn (excluding muscle and bone) (Myerson et al 2009 ;Taylor et al 2005 ) To cover the external iliac nodes, an additional 1 cm margin anterolaterally around the vessels is needed. Any adjacent small nodes should be included (Myerson et al 2009 ;Taylor et al 2005 ) Anteriorly, a margin of 1-1.5 cm should be added into the bladder to account for changes in the bladder and rectal fi lling (Myerson et al 2009 ;Daly et al 2011 ) A 1.8-cm wide volume between the external and internal iliac vessels is needed to cover the obturator nodes (Taylor et al 2005 ) CTV-low risk (CTV-LR) Should include the uninvolved inguinal, external iliac, and internal iliac nodes superior to the inferior-most level of the sacroiliac joint To cover the iliac lymphatics, a 0.7-cm margin around the iliac vessels should be drawn (excluding muscle and bone) (Myerson et al 2009 ;Taylor et al 2005 ) To cover the external iliac nodes, an additional 1 cm margin anterolaterally around the vessels is needed. Any adjacent small nodes should be included (Myerson et al 2009 ;Taylor et al 2005 ) Anteriorly, a margin of 1-1.5 cm should be added into bladder to account for changes in the bladder and rectal fi lling (Myerson et al 2009 ;Daly et al 2011 ) A 1.8-cm wide volume between the external and internal iliac vessels is needed to cover the obturator nodes (Taylor et al 2005 ) Planning target volume (PTV) Each CTV should be expanded by 0.5-1 cm, depending on the physician's comfort level with setup accuracy, frequency of imaging, and the use of IGRT Fig.…”