A comprehensive evaluation of adaptive daily planning for cervical cancer HDR brachytherapy.

Rebecca Meerschaert,Jay Burmeister,Arun Paul,Steven Miller,Adrian Nalichowski,Ling Zhuang,Zhenghui Hu

doi:10.1120/jacmp.v17i6.6408

Abstract

The purpose of this study was to evaluate adaptive daily planning for cervical cancer patients who underwent high‐dose‐rate intracavitary brachytherapy (HDR‐BT) using comprehensive interfractional organ motion measurements. This study included 22 cervical cancer patients who underwent 5 fractions of HDR‐BT. Regions of interest (ROIs) including high‐risk clinical tumor volume (HR‐CTV) and organs at risk (OARs) were manually contoured on daily CT images. All patients were clinically treated with adaptive daily plans (ADP), which involved ROI delineation and dose optimization at each treatment fraction. Single treatment plans (SP) were retrospectively generated by applying the first treatment fraction's dwell times adjusted for decay and dwell positions of the applicator to subsequent treatment fractions. Various existing similarity metrics were calculated for the ROIs to quantify interfractional organ variations. A novel similarity (JRARM) score was established, which combined both volumetric overlap metrics (DSC, JSC, and RVD) and distance metrics (ASD, MSD, and RMSD). Linear regression was performed to determine a relationship between interfractional organ variations of various similarity metrics and D2cc variations from both plans. Wilcoxon signed‐rank tests were used to assess ADP and SP by comparing EQD2D2cc(α/β=3) for OARs. For interfractional organ variations, the sigmoid demonstrated the greatest variations based on the JRARM, DSC, and RMSD metrics. Comparisons between paired ROIs showed differences in metrics at each treatment fraction. RVD, MSD, and RMSD were found to be significantly correlated to D2cc variations for bladder and sigmoid. The comparison between plans found ADP provided lower EQD2 D2cc of OARs than SP. Specifically, the sigmoid demonstrated statistically significant dose variations (p=0.015). Substantial interfractional organ motion occurs during HDR‐BT based on comprehensive measurements and may significantly affect D2cc of OARs. Adaptive daily planning provides improved dose sparing for OARs compared to single planning with the extent of sparing being different among OARs.PACS number(s): 87.55.D, 87.55.de, 87.55.kh, 87.57.nj

Highlights

Cervical cancer is the third most prevalent cancer in females worldwide.[1]. The current standard of care for locally advanced cervical cancer is a combination of external beam radiotherapy (EBRT) and intracavitary brachytherapy (BT) with concurrent chemotherapy, providing high rates of local disease control.[2,3] High-dose-rate (HDR) BT is an important component in the curative management of cervix carcinoma and BT is typically delivered in 4 to 6 fractions using ring and tandem (R+T) or tandem and ovoid (T+O) applicators.[4]. A single plan (SP) approach for HDR treatments involves contouring and treatment planning at the first fraction and applying the treatment plan to remaining treatment fractions
This relation between interfractional organ motion and dose variation has been studied for variations in organ volume and organ distance-to-applicator with respect to variations in mean organ dose, reference point dose, and volume dose.[6,16,18,19,20] a comprehensive method to analyze the relationship between interfractional organ and dose variations that takes into account both volumetric and organ displacement variations is lacking
While the Dice similarity coefficient (DSC) results show the bladder has a lower degree of variation compared to other Regions of interest (ROIs), the JRARM score results demonstrate that the bladder and high-risk clinical tumor volume (HR-CTV) both have less motion compared to the rectum and sigmoid

Summary

Introduction

Cervical cancer is the third most prevalent cancer in females worldwide.[1] The current standard of care for locally advanced cervical cancer is a combination of external beam radiotherapy (EBRT) and intracavitary brachytherapy (BT) with concurrent chemotherapy, providing high rates of local disease control.[2,3] High-dose-rate (HDR) BT is an important component in the curative management of cervix carcinoma and BT is typically delivered in 4 to 6 fractions using ring and tandem (R+T) or tandem and ovoid (T+O) applicators.[4] A single plan (SP) approach for HDR treatments involves contouring and treatment planning at the first fraction and applying the treatment plan to remaining treatment fractions This approach does not take into account interfractional applicator positioning variations and organ motion that may lead to substantial differences between planned and delivered doses.[5,6,7,8,9]. Research involving adaptive planning has been implemented using daily MR images.[9,22,23,24] Due to the lack of MRI scanner availability in most Radiation Oncology departments, along with the MRI distortion issue, MR scanner availability and staff resources, this method lacks wide use.[25,26] Limited research has been done on CT imaging based adaptive daily planning,(8,27) in this study, ADP was further evaluated by performing a plan comparison with SP

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