Table 3.

NTCP parameters

Organ	End point	TD50 (Gy)	m	n	Source
Principal rectal NTCP evaluation
Rectum	Grade 2+ late toxicity or rectal bleeding	76.9	0.13	0.09	Michalski et al (21)
Supplementary anorectal NTCP evaluation
Rectum	Severe rectal bleeding†- all patients	81	0.14	0.13	Peeters et al (22)
Rectum	Severe rectal bleeding†- patients without history of abdominal surgery	85	0.14	0.11	Peeters et al (22)
Rectum	Severe rectal bleeding†- patients with history of abdominal surgery	78	0.14	0.11	Peeters et al (22)
Rectum	Severe frequency‡- all patients	84	0.24	0.39	Peeters et al (22)
Anus∗	Severe anal incontinence§, all patients	105	0.43	1	Peeters et al (22)
Anus∗	Severe anal incontinence§, patients without history of abdominal surgery	157	0.45	1	Peeters et al (22)
Anus∗	Severe anal incontinence§, patients with history of abdominal surgery	74	0.45	1	Peeters et al (22)
Bladder	Contracture/volume loss	80	0.11	0.5	Burman et al (37)
Femoral heads	Necrosis	65	0.12	0.25	Burman et al (37)

Abbreviations: m = dose-response parameter; n=volume effect parameter; NTCP = normal tissue complication probability; TD₅₀ = Dose resulting in 50% probability of complication in a uniformly irradiated tissue.

^∗Anus was defined as the most caudal 3 cm of the rectal structure.

^†Defined as bleeding that requires transfusion or laser treatment.

^‡Defined as stool frequency of 6 or greater times per day.

^§Defined as loss of mucous, stools or blood necessitating the use of pads at least twice per week.