An integrated strategy of biological and physical constraints in biological optimization for cervical carcinoma

Ziwei Feng,Cheng Tao,Jian Zhu,Jinhu Chen,Gang Yu,Yong Yin,Shaohua Qin,Dengwang Li

doi:10.1186/s13014-017-0784-1

Abstract

BackgroundFor cervical carcinoma cases, this study aimed to evaluate the quality of intensity-modulated radiation therapy (IMRT) plans optimized by biological constraints. Furthermore, a new integrated strategy in biological planning module was proposed and verified.MethodsTwenty patients of advanced stage cervical carcinoma were enrolled in this study. For each patient, dose volume optimization (DVO), biological model optimization (BMO) and integrated strategy optimization (ISO) plans were created using same treatment parameters. Different biological models were also used for organ at risk (OAR) in BMO plans, which include the LKB and Poisson models. Next, BMO plans were compared with their corresponding DVO plans, in order to evaluate BMO plan quality. ISO plans were also compared with DVO and BMO plans, in order to verify the performance of the integrated strategy.ResultsBMO plans produced slightly inhomogeneity and less coverage of planning target volume (PTV) (V95=96.79, HI = 0.10: p < 0.01). However, the tumor control probability (TCP) value, both from DVO and BMO plans, were comparable. For the OARs, BMO plans produced lower normal tissue complication probability (NTCP) of rectum (NTCP = 0.11) and bladder (NTCP = 0.14) than in the corresponding DVO plans (NTCP = 0.19 and 0.18 for rectum and bladder; p < 0.01 for rectum and p = 0.03 for bladder). V95, D98, CI and HI values that were produced by ISO plans (V95 = 98.31, D98 = 54.18Gy, CI = 0.76, HI = 0.09) were greatly better than BMO plans (V95 = 96.79, D98 = 53.42Gy, CI = 0.71, HI = 0.10) with significant differences. Furthermore, ISO plans produced lower NTCP values of rectum (NTCP = 0.14) and bladder (NTCP = 0.16) than DVO plans (NTCP = 0.19 and 0.18 for rectum and bladder, respectively) with significant differences.ConclusionsBMO plans produced lower NTCP values of OARs compared to DVO plans for cervical carcinoma cases, and resulted in slightly less target coverage and homogeneity. The integrated strategy, proposed in this study, could improve the coverage, conformity and homogeneity of PTV greater than the BMO plans, as well as reduce the NTCP values of OARs greater than the DVO plans.

Highlights

For cervical carcinoma cases, this study aimed to evaluate the quality of intensity-modulated radiation therapy (IMRT) plans optimized by biological constraints
Kan et al indicated that the amount of hot spots and the maximum doses within targets could be substantially reduced by adding the physical constraints in biological optimization [18]
Patient selection Twenty patients with cervical carcinoma were selected for this study, which pathology diagnosis ranged from stage IIIB to IV

Summary

Introduction

This study aimed to evaluate the quality of intensity-modulated radiation therapy (IMRT) plans optimized by biological constraints. In conventional IMRT plan designing, physical constraints (dose volume parameters) are usually implemented for optimization and plan evaluation. Biological constraints, such as generalized equivalent uniform dose (gEUD), tumor control probability (TCP) and normal tissue complication probability (NTCP), have been used in IMRT planning process [4]. Additional physical constraints involved in the biological optimization have been proposed in several studies in order to improve the target dose homogeneity and conformity [4, 12, 15,16,17,18]. Kan et al indicated that the amount of hot spots and the maximum doses within targets could be substantially reduced by adding the physical constraints in biological optimization [18]

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