A comparison of ICRU point doses and volumetric doses of organs at risk (OARs) in brachytherapy for cervical cancer

作者：Vinod Shalini K^*; Caldwell Kate; Lau Annie; Fowler Allan R

来源：Journal of Medical Imaging and Radiation Oncology, 2011, 55(3): 304-310.

DOI：10.1111/j.1754-9485.2011.02272.x

• bladder
• brachytherapy
• cervix cancer
• dose volume histogram
• radiotherapy planning
• rectum

Introduction: In brachytherapy for cervix cancer, doses to organs at risk (OARs) are traditionally calculated using the ICRU-38 point doses to rectum and bladder. Three-dimensional image-guided brachytherapy allows assessment of OAR dose with dose volume histograms (DVHs). The purpose of this study was to analyse the correlation between DVHs and ICRU point doses.
Methods: Using the PLATO (TM) planning system, the bladder, rectum and sigmoid were retrospectively contoured on 62 CT datasets for 20 patients treated with definitive radiotherapy. The median external beam radiotherapy dose was 45 Gy. Brachytherapy was delivered using a CT-MRI compatible tandem and ovoids to a median dose of 24 Gy in three fractions. DVHs were calculated, and the minimum dose to 2 cc of tissue receiving the highest dose (D(2cc)) was recorded and compared with the ICRU point doses (D(ICRU)).
Results: The mean rectal D(ICRU) was 4.01 Gy compared with D(2cc) of 4.28 Gy. The mean bladder D(ICRU) was 6.74 Gy compared with D(2cc) of 8.65 Gy. The mean sigmoid D(2cc) was 4.58 Gy. The mean dose ratios (D(2cc)/D(ICRU)) were 1.08 for rectum and 1.39 for bladder. D(ICRU) correlated with D(2cc) for rectum (r = 0.76, P = 0.001) and for bladder (r = 0.78, P = 0.01).
Conclusion: OAR doses assessed by DVH criteria were higher than ICRU point doses. The significant correlation between D(2cc) and D(ICRU) has allowed us to set DVH dose constraints for CT-based brachytherapy and thus begin the transition from two-dimensional to three-dimensional image-guided brachytherapy planning.

• 出版日期2011-6