Optimizing the parameters of the Lyman–Kutcher–Burman, Källman, and Logit+EUD models for the rectum – a comparison between normal tissue complication probability and clinical data

•The LKB, Källman, and Logit+EUD models have been used to calculate NTCP for the rectum.•The parameters of the models for the rectum have been optimized.•χ2 Statistics were calculated as a check of goodness of optimization.

Minimizing the late rectal toxicity of prostate cancer patients is a very important and widely-discussed topic. Normal tissue complication probability (NTCP) models can be used to evaluate competing treatment plans. In our work, the parameters of the Lyman–Kutcher–Burman (LKB), Källman, and Logit+EUD models are optimized by minimizing the Brier score for a group of 302 prostate cancer patients. The NTCP values are calculated and are compared with the values obtained using previously published values for the parameters. χ2 Statistics were calculated as a check of goodness of optimization.