Estimation of late rectal normal tissue complication probability parameters in carbon ion therapy for prostate cancer

Mai Fukahori; Naruhiro Matsufuji; Takeshi Himukai; Nobuyuki Kanematsu; Hideyuki Mizuno; Akifumi Fukumura; Hiroshi Tsuji; Tadashi Kamada

doi:10.1016/j.radonc.2015.11.023

Estimation of late rectal normal tissue complication probability parameters in carbon ion therapy for prostate cancer

Radiother Oncol. 2016 Jan;118(1):136-40. doi: 10.1016/j.radonc.2015.11.023. Epub 2015 Dec 14.

Authors

Mai Fukahori¹, Naruhiro Matsufuji², Takeshi Himukai³, Nobuyuki Kanematsu², Hideyuki Mizuno², Akifumi Fukumura², Hiroshi Tsuji², Tadashi Kamada²

Affiliations

¹ Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Japan. Electronic address: fukahori@nirs.go.jp.
² Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Japan.
³ Ion-Beam Therapy Center, SAGA HIMAT Foundation, Japan.

PMID: 26700600
DOI: 10.1016/j.radonc.2015.11.023

Abstract

Purpose: The aim of this study was to estimate normal tissue complication probability (NTCP) parameters for late rectal complications after carbon ion radiotherapy (C-ion RT) for prostate cancer.

Methods and materials: A total of 163 patients were used to derive NTCP parameters. These patients were treated with relative biological effectiveness (RBE)-weighted dose ranging from 57.6 Gy (RBE) up to 72 Gy (RBE) and included in dose escalation trials. The Lyman-Kutcher-Burman (LKB) model was used and the model parameters were fit to the relation between dose and complication observed after C-ion RT.

Results: The resulting NTCP parameters were the volume effect parameter; n=0.035 (95% CI: 0.024-0.047), the steepness of the NTCP curve; m=0.10 (0.084-0.13), the tolerance dose associated with 50% probability of complication; TD50=63.6 Gy (RBE) (61.8-65.4 Gy (RBE)) for Grade⩾1, n=0.012 (0.0050-0.023), m=0.046 (0.033-0.062), TD50=69.1 Gy (RBE) (67.6-70.9 Gy (RBE)) for Grade⩾2.

Conclusion: A new set of rectal NTCP parameters in C-ion RT was determined. The rather small n values suggest that the rectum was consistent with being strictly serial organ. The new derived parameter values facilitate estimation of rectal NTCP in C-ion RT.

Keywords: Carbon ion radiotherapy; NTCP; Prostate cancer.

MeSH terms

Heavy Ion Radiotherapy / adverse effects*
Humans
Male
Probability
Prostatic Neoplasms / radiotherapy*
Radiotherapy Dosage
Rectum / radiation effects*
Relative Biological Effectiveness