RESUMO
INTRODUCTION: Carcinoma cervix is a common gynecologic malignancy in India and is treated with radical chemoradiation where intracavitary brachytherapy (ICR) is an integral part. In ICR of cervix, the two-dimensional (2D) point-based dosimetry cervix is the most common method used in high-volume centers with rectal dose calculation at modified ICRU rectal point with rectal wire placement. The rectal dose measurement using this method underestimates the dose to the rectum, and rectal dose also varies with the type of applicator used. The aim of our study is to compare the rectal dose calculated by ICRU 38 method versus rectal dose calculated by the rectal wire method using Henschke applicator. MATERIALS AND METHODS: This is a single-institute, dosimetric comparison study done prospectively. Fifty patients were planned for ICR after 2D orthogonal radiograph-based, computer planning by iridium 192 high-dose rate remote afterloading technique after placing the appropriate Henschke applicator. The vaginal packing was done using sterile gauze with contrast material for defining the ICRU 38 rectal point, and a rectal wire was placed for the modified ICRU rectal point. Rectal doses were calculated by both the methods and compared. RESULTS: The modified ICRU rectal point recorded a lower rectal dose (mean of 25%) compared to ICRU 38 rectal point in the study patients. There were ten patients (20%) with either too much or too little contrast material which made the visualization of the rectal point and radiation planning difficult. P value by paired t-test method was 0.0001, which was statistically significant. CONCLUSION: The modified ICRU rectal point is easier to visualize than ICRU 38 method (100% vs. 80%) for dosimetry, but it underestimates the rectal doses when compared to ICRU 38 rectal point. There needs to be a correction factor applied (25% in our study for Henschke applicator) when evaluating the rectal doses calculated by rectal wire method, to reduce the rectal toxicity.
RESUMO
INTRODUCTION: Cervical cancer is the second most common cancer among Indian women. Radical radiotherapy with external beam radiation therapy (EBRT) and brachytherapy is the standard treatment for FIGO stage IB2 to IVA. An appropriate selection of brachytherapy applicator is needed according to the patient's anatomy. The two most commonly used applicators for intracavitary radiotherapy (ICR), Fletcher's and Henschke, have dosimetric differences which are not well studied with two-dimensional (2D)-based planning which is the most common method used for women with carcinoma cervix in India. The purpose of our study was to compare and evaluate the dosimetric differences between these two applicators, which would help in better selection of the applicator in cervical cancer patients. MATERIALS AND METHODS: This is a single-institute prospective study. Fifty patients randomly included in the study received EBRT and ICR by Ir192 HDR remote afterloading technique with computer-based 2D planning. Fletcher's and Henschke applicators were used alternately for first two fractions. RESULTS: The results of the study showed lower bladder and rectal doses with Fletcher's applicator and similar doses to point A for both applicators. However, point B doses are lower with Fletcher's applicator. CONCLUSION: Our results showed a favorable dosimetry with Fletcher's applicator in ICR of carcinoma cervix. The feasibility of placement is much better for Henschke but dosimetric advantages of Fletcher's encourage use of Fletcher's applicator for patients with favorable anatomy to reduce organs at risk doses but with the disadvantage of lower dose to point B.
