Comparison of graphical optimization or IPSA for improving brachytheraphy plans associated with inadequate target coverage for cervical cancer

Zhijie Liu,Min Lu,Xiaodong Zhu,Ye Deng,Tingjun Luo,Chaofeng Yang,Qingguo Fu,Huanqing Liang,Xiao Wang,Haiming Yang

doi:10.1038/s41598-017-16756-w

Abstract

Many studies have reported that inverse planning by simulated annealing (IPSA) can improve the quality of brachytherapy plans, and we wanted to examine whether IPSA could improve cervical cancer brachytherapy plans giving D90 < 6 Gy (with 7 Gy per fraction) at our institution. Various IPSA plans involving the tandem and ovoid applicators were developed for 30 consecutive cervical cancer patients on the basis of computed tomography: IPSA1, with a constraint on the maximum dose in the target volume; IPSA1-0, identical to IPSA1 but without a dwell-time deviation constraint; IPSA2, without a constraint on the maximum dose; and IPSA2-0, identical to IPSA2 but without a dwell-time deviation constraint. IPSA2 achieved similar results as graphical optimization, and none of the other IPSA plans was significantly better than graphical optimization. Therefore, other approaches, such as combining interstitial and intracavitary brachytherapy, may be more appropriate for improving the quality of brachytherapy plans associated with inadequate target coverage.

Highlights

Cervical cancer is very common in China, and brachytherapy plays an important role in its treatment[1]
A direct linear relationship was observed between high-risk clinical target volume (HR-CTV) D90 and high dose in the target (Fig. 2)
The IPSA2 line lies beneath the two straight lines of IPSA1 and graphical optimization (GrO) indicating that

Summary

Introduction

Cervical cancer is very common in China, and brachytherapy plays an important role in its treatment[1]. Inverse planning by simulated annealing (IPSA) can allow the use of lower radiation doses while maintaining or improving target coverage when planning brachytherapy involving tandem and ovoid applicators in cervical cancer[6]. Other studies have reported similar results when comparing IPSA with dose point optimization, manual optimization of dwell weights/times and geometric optimization for planning brachytherapy involving a tandem and ovoid[7,8,9,10,11]. Some brachytherapy plans based on the graphical optimization (GrO) algorithm do not give adequate target coverage (providing D90 < 6 Gy and 7 Gy per fraction) when the dose to organs at risk is kept within recommended limits routinely used at our institution. Our primary criterion for improvement was D90, and secondary criteria were V150, V200 and dwell time

Methods

Results

Conclusion