Abstract

PurposeTo establish a dose volume–effect relationship for predicting late rectal complication (LRC) in locally advanced cervical cancer patients treated with external beam radiotherapy (EBRT) followed by combined intracavitary/interstitial brachytherapy (IC/IS-BT).Materials and MethodsA retrospective analysis was performed in 110 patients with locally advanced cervical cancer who underwent definitive radiotherapy combined with IC/IS-BT from July 2010 to September 2018. We report the 90% of the target volume receiving the minimum dose for high risk clinical target volume (HR-CTV D90) and intermediate risk clinical target volume (IR-CTV D90), and the minimum doses to the most exposed 0.1, 1, and 2 cm³ doses at the International Commission on Radiation Units and Measurements (DICRU) for organs at risk (OARs). The total dose of EBRT plus brachytherapy was transformed to the biologically equivalent dose in 2 Gy fractions (EQD2) with α/β value of 10 Gy for target, 3 Gy for organs at risk using the linear quadratic model. The morbidity was scored according to the Radiation Therapy Oncology Group (RTOG) criteria. The Probit model was used to establish a prediction model on rectum between the organs at risk for dose and LRC. The receiver operating characteristic (ROC) curve was used to evaluate the predictive value of dose volume parameters for LRC.ResultsThe median follow-up time was 72.3 months. The mean ( ± standard deviation) , and DICRU values of rectum were 64.72 ± 7.47 GyEQD2, 70.18 ± 5.92 GyEQD2, 79.32 ± 7.86 GyEQD2, and 67.22 ± 7.87 GyEQD2, respectively. The Probit model showed significant relationships between , and the probability of grade1–4, grade 2–4 rectal events at 1 year, and between and the probability of grade2–4 rectal events at 3 and 5 years. The dose values for 10% complication rates (ED10) of were 74.18 (70.42–76.71) GyEQD2, 67.80 (59.91, 71.08) GyEQD2, 66.37 (52.00, 70.27) GyEQD2 for grade 2–4 with rectal morbidity at 1, 3, and 5 years, respectively.ConclusionOur study proved that were considered as useful dosimetric parameters for predicting the risk of grade1–4 and grade2–4 LRC at 1-year, and might be an indicator for predicting grade2-4 LRC at 3/5years. The patients with rectal >66.37–74.18 GyEQD2 should be closely observed for grade2–4 LRC.

Highlights

  • Brachytherapy is a crucial component of radical radiotherapy of locally advanced cervical cancer [1], and it mainly includes intracavitary brachytherapy (ICBT), interstitial brachytherapy (ISBT), and hybrid intracavitary/interstitial brachytherapy (IC/ IS-BT)

  • 17 cases of the 110 patients with cervical cancer did not receive chemotherapy, 21 cases received neoadjuvant chemotherapy before radiotherapy, 34 cases received concurrent chemotherapy, 1 case received adjuvant chemotherapy after radiotherapy, 25 cases received neoadjuvant chemotherapy combined with concurrent chemotherapy, 9 cases received concurrent chemotherapy combined with adjuvant chemotherapy, and 3 cases received neoadjuvant chemotherapy combined with concurrent chemotherapy and adjuvant chemotherapy

  • The receiver operating characteristic (ROC) curve was used to evaluate and compare the predictive values of D1cm3 and D0:1cm3 of rectum for rectum morbidity at 1, 3, 5 years, see late rectal complication (LRC) is regarded as a major late side effect in patients with locally advanced cervical cancer who underwent treatment with external beam radiotherapy (EBRT) followed by brachytherapy boost [10]

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Summary

Introduction

Brachytherapy is a crucial component of radical radiotherapy of locally advanced cervical cancer [1], and it mainly includes intracavitary brachytherapy (ICBT), interstitial brachytherapy (ISBT), and hybrid intracavitary/interstitial brachytherapy (IC/ IS-BT). Several studies have reported a statistically significant correlation between D2cm and occurrence of LRC in cervical cancer patients who had brachytherapy [2, 3]. Several other studies found other dosimetric parameters, such as D1cm or DICRU, exhibited a statistically significant relationship [4, 5]. Few studies have compared the differences in rectal dosimetric parameters, while very few lacked a more reliable prediction model. In the present study, the role of three-dimensional dosimetric parameters D2cm , D1cm , D0:1cm , and two-dimensional dosimetric parameter DICRU in the prediction of LRC were analyzed and compared, and relevant models for locally advanced cervical cancer treatment with curative radiotherapy including IC/IS-BT were established

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