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Title: CT-guided intracavitary radiotherapy for cervical cancer: Comparison of conventional point A plan with clinical target volume-based three-dimensional plan using dose-volume parameters

Abstract

Purpose: To perform an intracavitary radiotherapy (ICR) plan comparison between the conventional point A plan (conventional plan) and computed tomography (CT)-guided clinical target volume-based plan (CTV plan) by analysis of the quantitative dose-volume parameters and irradiated volumes of organs at risk in patients with cervical cancer. Methods and Materials: Thirty plans for {sup 192}Ir high-dose-rate ICR after 30-40-Gy external beam radiotherapy were investigated. CT images were acquired at the first ICR session with artifact-free applicators in place. The gross tumor volume, clinical target volume (CTV), point A, and International Commission on Radiation Units and Measurements Report 38 rectal and bladder points were defined on reconstructed CT images. A fractional 100% dose was prescribed to point A in the conventional plan and to the outermost point to cover all CTVs in the CTV plan. The reference volume receiving 100% of the prescribed dose (V{sub ref}), and the dose-volume parameters of the coverage index, conformal index, and external volume index were calculated from the dose-volume histogram. The bladder, rectal point doses, and percentage of volumes receiving 50%, 80%, and 100% of the prescribed dose were also analyzed. Results: Conventional plans were performed, and patients were categorized on the basis of whether themore » 100% isodose line of point A prescription dose fully encompassed the CTV (Group 1, n = 20) or not (Group 2, n = 10). The mean gross tumor volume (11.6 cm{sup 3}) and CTV (24.9 cm{sup 3}) of Group 1 were smaller than the corresponding values (23.7 and 44.7 cm{sup 3}, respectively) for Group 2 (p = 0.003). The mean V{sub ref} for all patients was 129.6 cm{sup 3} for the conventional plan and 97.0 cm{sup 3} for the CTV plan (p = 0.003). The mean V{sub ref} in Group 1 decreased markedly with the CTV plan (p < 0.001). For the conventional and CTV plans in all patients, the mean coverage index, conformal index, and external volume index were 0.98 and 1.0, 0.23 and 0.34, and 3.86 and 2.15, respectively. Statistical analysis showed that the conformal index and external volume index improved significantly with the CTV plan, and this improvement was more marked in Group 1. The mean values of the bladder and rectal point doses and volume fractions receiving 50%, 80%, and 100% of the reference dose did not differ between plans for all patients. The reduction in the mean rectal and bladder point doses and irradiated volumes for the CTV plan was statistically significant in Group 1. Conclusion: Computed tomography-guided CTV planning of ICR is superior to conventional point A planning in terms of conformity of target coverage and avoidance of overdosed normal tissue volume. To ascertain the potential benefit of treatment outcome, ICR with image-guided three-dimensional plans will be pursued and correlated with the dose-volume parameters.« less

Authors:
 [1];  [2];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. Research Institute and Hospital, National Cancer Center, Goyang, Gyeonggi (Korea, Republic of)
  2. Research Institute and Hospital, National Cancer Center, Goyang, Gyeonggi (Korea, Republic of). E-mail: k2onco@ncc.re.kr
Publication Date:
OSTI Identifier:
20788285
Resource Type:
Journal Article
Resource Relation:
Journal Name: International Journal of Radiation Oncology, Biology and Physics; Journal Volume: 64; Journal Issue: 1; Other Information: DOI: 10.1016/j.ijrobp.2005.06.015; PII: S0360-3016(05)01122-3; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; BLADDER; CARCINOMAS; CAT SCANNING; DOSE RATES; IMAGES; ION CYCLOTRON-RESONANCE; IRIDIUM 192; IRRADIATION; PATIENTS; PLANNING; RADIATION DOSES; RADIOTHERAPY

Citation Formats

Shin, Kyung Hwan, Kim, Tae Hyun, Cho, Jung Keun, Kim, Joo-Young, Park, Sung Yong, Park, Sang-Yoon, Kim, Dae Yong, Chie, Eui Kyu, Pyo, Hong Ryull, and Cho, Kwan Ho. CT-guided intracavitary radiotherapy for cervical cancer: Comparison of conventional point A plan with clinical target volume-based three-dimensional plan using dose-volume parameters. United States: N. p., 2006. Web. doi:10.1016/J.IJROBP.2005.0.
Shin, Kyung Hwan, Kim, Tae Hyun, Cho, Jung Keun, Kim, Joo-Young, Park, Sung Yong, Park, Sang-Yoon, Kim, Dae Yong, Chie, Eui Kyu, Pyo, Hong Ryull, & Cho, Kwan Ho. CT-guided intracavitary radiotherapy for cervical cancer: Comparison of conventional point A plan with clinical target volume-based three-dimensional plan using dose-volume parameters. United States. doi:10.1016/J.IJROBP.2005.0.
Shin, Kyung Hwan, Kim, Tae Hyun, Cho, Jung Keun, Kim, Joo-Young, Park, Sung Yong, Park, Sang-Yoon, Kim, Dae Yong, Chie, Eui Kyu, Pyo, Hong Ryull, and Cho, Kwan Ho. Sun . "CT-guided intracavitary radiotherapy for cervical cancer: Comparison of conventional point A plan with clinical target volume-based three-dimensional plan using dose-volume parameters". United States. doi:10.1016/J.IJROBP.2005.0.
@article{osti_20788285,
title = {CT-guided intracavitary radiotherapy for cervical cancer: Comparison of conventional point A plan with clinical target volume-based three-dimensional plan using dose-volume parameters},
author = {Shin, Kyung Hwan and Kim, Tae Hyun and Cho, Jung Keun and Kim, Joo-Young and Park, Sung Yong and Park, Sang-Yoon and Kim, Dae Yong and Chie, Eui Kyu and Pyo, Hong Ryull and Cho, Kwan Ho},
abstractNote = {Purpose: To perform an intracavitary radiotherapy (ICR) plan comparison between the conventional point A plan (conventional plan) and computed tomography (CT)-guided clinical target volume-based plan (CTV plan) by analysis of the quantitative dose-volume parameters and irradiated volumes of organs at risk in patients with cervical cancer. Methods and Materials: Thirty plans for {sup 192}Ir high-dose-rate ICR after 30-40-Gy external beam radiotherapy were investigated. CT images were acquired at the first ICR session with artifact-free applicators in place. The gross tumor volume, clinical target volume (CTV), point A, and International Commission on Radiation Units and Measurements Report 38 rectal and bladder points were defined on reconstructed CT images. A fractional 100% dose was prescribed to point A in the conventional plan and to the outermost point to cover all CTVs in the CTV plan. The reference volume receiving 100% of the prescribed dose (V{sub ref}), and the dose-volume parameters of the coverage index, conformal index, and external volume index were calculated from the dose-volume histogram. The bladder, rectal point doses, and percentage of volumes receiving 50%, 80%, and 100% of the prescribed dose were also analyzed. Results: Conventional plans were performed, and patients were categorized on the basis of whether the 100% isodose line of point A prescription dose fully encompassed the CTV (Group 1, n = 20) or not (Group 2, n = 10). The mean gross tumor volume (11.6 cm{sup 3}) and CTV (24.9 cm{sup 3}) of Group 1 were smaller than the corresponding values (23.7 and 44.7 cm{sup 3}, respectively) for Group 2 (p = 0.003). The mean V{sub ref} for all patients was 129.6 cm{sup 3} for the conventional plan and 97.0 cm{sup 3} for the CTV plan (p = 0.003). The mean V{sub ref} in Group 1 decreased markedly with the CTV plan (p < 0.001). For the conventional and CTV plans in all patients, the mean coverage index, conformal index, and external volume index were 0.98 and 1.0, 0.23 and 0.34, and 3.86 and 2.15, respectively. Statistical analysis showed that the conformal index and external volume index improved significantly with the CTV plan, and this improvement was more marked in Group 1. The mean values of the bladder and rectal point doses and volume fractions receiving 50%, 80%, and 100% of the reference dose did not differ between plans for all patients. The reduction in the mean rectal and bladder point doses and irradiated volumes for the CTV plan was statistically significant in Group 1. Conclusion: Computed tomography-guided CTV planning of ICR is superior to conventional point A planning in terms of conformity of target coverage and avoidance of overdosed normal tissue volume. To ascertain the potential benefit of treatment outcome, ICR with image-guided three-dimensional plans will be pursued and correlated with the dose-volume parameters.},
doi = {10.1016/J.IJROBP.2005.0},
journal = {International Journal of Radiation Oncology, Biology and Physics},
number = 1,
volume = 64,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • Purpose: To compare CT-based volumetric calculations and International Commission on Radiation Units and Measurements (ICRU) reference-point estimates of radiation doses to the bladder and rectum in patients with carcinoma of the uterine cervix treated with definitive low-dose-rate intracavitary radiotherapy (ICRT). Methods and Materials: Between November 2001 and March 2003, 60 patients were prospectively enrolled in a pilot study of ICRT with CT-based dosimetry. Most patients underwent two ICRT insertions. After insertion of an afterloading ICRT applicator, intraoperative orthogonal films were obtained to ensure proper positioning of the system and to facilitate subsequent planning. Treatments were prescribed using standard two-dimensional dosimetrymore » and planning. Patients also underwent helical CT of the pelvis for three-dimensional reconstruction of the radiation dose distributions. The systems were loaded with {sup 137}Cs sources using the Selectron remote afterloading system according to institutional practice for low-dose-rate brachytherapy. Three-dimensional dose distributions were generated using the Varian BrachyVision treatment planning system. The rectum was contoured from the bottom of the ischial tuberosities to the sigmoid flexure. The entire bladder was contoured. The minimal doses delivered to the 2 cm{sup 3} of bladder and rectum receiving the highest dose (D{sub BV2} and D{sub RV2}, respectively) were determined from dose-volume histograms, and these estimates were compared with two-dimensionally derived estimates of the doses to the corresponding ICRU reference points. Results: A total of 118 unique intracavitary insertions were performed, and 93 were evaluated and the subject of this analysis. For the rectum, the estimated doses to the ICRU reference point did not differ significantly from the D{sub RV2} (p = 0.561); the mean ({+-} standard deviation) difference was 21 cGy ({+-} 344 cGy). The median volume of the rectum that received at least the ICRU reference-point dose was 2.1 cm{sup 3}. In 66 (71%) of 93 cases, <5 cm{sup 3} was treated to this dose. However, for the bladder, the estimated doses to the ICRU reference point were significantly lower than the D{sub BV2} (p <0.001); the mean difference was 680 cGy ({+-} 543 cGy). The median volume of the bladder that received at least the ICRU reference-point dose was 13.0 cm{sup 3}. Conclusions: Our data suggest that the estimated dose to the ICRU rectal point may be a reasonable surrogate for the D{sub RV2}. However, this result may not be applicable to other treatment guidelines and ICRT applicator systems. In contrast, the dose to the ICRU bladder point does not appear to be a reasonable surrogate for the D{sub BV2}. Correlation with late complications are needed to define the role of three-dimensional dosimetry in treatment planning.« less
  • Objective: To create and compare consensus clinical target volume (CTV) contours for computed tomography (CT) and 3-Tesla (3-T) magnetic resonance (MR) image-based cervical-cancer brachytherapy. Methods and Materials: Twenty-three experts in gynecologic radiation oncology contoured the same 3 cervical cancer brachytherapy cases: 1 stage IIB near-complete response (CR) case with a tandem and ovoid, 1 stage IIB partial response (PR) case with tandem and ovoid with needles, and 1 stage IB2 CR case with a tandem and ring applicator. The CT contours were completed before the MRI contours. These were analyzed for consistency and clarity of target delineation using an expectationmore » maximization algorithm for simultaneous truth and performance level estimation (STAPLE), with κ statistics as a measure of agreement between participants. The conformity index was calculated for each of the 6 data sets. Dice coefficients were generated to compare the CT and MR contours of the same case. Results: For all 3 cases, the mean tumor volume was smaller on MR than on CT (P<.001). The κ and conformity index estimates were slightly higher for CT, indicating a higher level of agreement on CT. The Dice coefficients were 89% for the stage IB2 case with a CR, 74% for the stage IIB case with a PR, and 57% for the stage IIB case with a CR. Conclusion: In a comparison of MR-contoured with CT-contoured CTV volumes, the higher level of agreement on CT may be due to the more distinct contrast medium visible on the images at the time of brachytherapy. MR at the time of brachytherapy may be of greatest benefit in patients with large tumors with parametrial extension that have a partial or complete response to external beam. On the basis of these results, a 95% consensus volume was generated for CT and for MR. Online contouring atlases are available for instruction at (http://www.nrgoncology.org/Resources/ContouringAtlases/GYNCervicalBrachytherapy.aspx)« less
  • Purpose: To determine the effects of Fletcher Suit Delclos ovoid shielding on dose to the bladder and rectum during intracavitary radiotherapy for cervical cancer. Methods and Materials: The Monte Carlo method was used to calculate the dose in 12 patients receiving low-dose-rate intracavitary radiotherapy with both shielded and unshielded ovoids. Cumulative dose-difference surface histograms were computed for the bladder and rectum. Doses to the 2-cm{sup 3} and 5-cm{sup 3} volumes of highest dose were computed for the bladder and rectum with and without shielding. Results: Shielding affected dose to the 2-cm{sup 3} and 5-cm{sup 3} volumes of highest dose formore » the rectum (10.1% and 11.1% differences, respectively). Shielding did not have a major impact on the dose to the 2-cm{sup 3} and 5-cm{sup 3} volumes of highest dose for the bladder. The average dose reduction to 5% of the surface area of the bladder was 53 cGy. Reductions as large as 150 cGy were observed to 5% of the surface area of the bladder. The average dose reduction to 5% of the surface area of the rectum was 195 cGy. Reductions as large as 405 cGy were observed to 5% of the surface area of the rectum. Conclusions: Our data suggest that the ovoid shields can greatly reduce the radiation dose delivered to the rectum. We did not find the same degree of effect on the dose to the bladder. To calculate the dose accurately, however, the ovoid shields must be included in the dose model.« less
  • Purpose: To compare the dose-volume histogram (DVH) parameters obtained by three-dimensional gynecologic brachytherapy planning with the rectosigmoid mucosal changes observed by flexible sigmoidoscopy. Methods and Materials: Between January 2004 and July 2005, 71 patients with International Federation of Gynecology and Obstetrics Stage IB-IIIB uterine cervical cancer underwent computed tomography-based high-dose-rate intracavitary brachytherapy. The total dose (external beam radiotherapy [RT] plus intracavitary brachytherapy) to the International Commission of Radiation Units and Measurements rectal point (ICRU{sub RP}) and DVH parameters for rectosigmoid colon were calculated using the equivalent dose in 2-Gy fractions ({alpha}/{beta} = 3 Gy). Sigmoidoscopy was performed every 6 monthsmore » after RT, with the 6-scale scoring system used to determine mucosal changes. Results: The mean values of the DVH parameters and ICRU{sub RP} were significantly greater in patients with a score of {>=}2 than in those with a score <2 at 12 months after RT (ICRU{sub RP}, 71 Gy{sub {alpha}}{sub /{beta}}{sub 3} vs. 66 Gy{sub {alpha}}{sub /{beta}}{sub 3}, p = 0.02; D{sub 0.1cc}, 93 Gy{sub {alpha}}{sub /{beta}}{sub 3} vs. 85 Gy{sub {alpha}}{sub /{beta}}{sub 3}, p = 0.04; D{sub 1cc}, 80 Gy{sub {alpha}}{sub /{beta}}{sub 3} vs. 73 Gy{sub {alpha}}{sub /{beta}}{sub 3}, p = 0.02; D{sub 2cc}, 75 Gy{sub {alpha}}{sub /{beta}}{sub 3} vs. 69 Gy{sub {alpha}}{sub /{beta}}{sub 3}, p = 0.02). The probability of a score of {>=}2 showed a significant relationship with the DVH parameters and ICRU{sub RP} (ICRU{sub RP}, p = 0.03; D{sub 0.1cc}, p = 0.05; D{sub 1cc}, p = 0.02; D{sub 2cc}, p = 0.02). Conclusion: Our preliminary data have shown that DVH values of the rectosigmoid colon obtained by computed tomography-based three-dimensional brachytherapy planning are reliable and predictive of score {>=}2 rectosigmoid mucosal changes.« less
  • Purpose: To quantify the effect of bladder volume on the dose distribution during intracavitary brachytherapy for cervical cancer. Methods and Patients: The study was performed on 10 women with cervical cancer who underwent brachytherapy treatment. After insertion of the brachytherapy applicator, the patients were transferred to the computed tomography unit. Two sets of computed tomography slices were taken, including the pelvis, one with an empty bladder and one after the bladder was filled with saline. The target and critical organs were delineated by the radiation oncologist and checked by the expert radiologist. The radiotherapy plan was run on the Platomore » planning system, version 14.1, to determine the dose distributions, dose-volume histograms, and maximal dose points. The doses and organ volumes were compared with the Wilcoxon signed ranks test on a personal computer using the Statistical Package for Social Sciences, version 11.0, statistical program. Results: No significant difference regarding the dose distribution and target volumes between an empty or full bladder was observed. Bladder fullness significantly affected the dose to the small intestine, rectum, and bladder. The median of maximal doses to the small intestine was significantly greater with an empty bladder (493 vs. 284 cGy). Although dosimetry revealed lower doses for larger volumes of bladder, the median maximal dose to the bladder was significantly greater with a full bladder (993 vs. 925 cGy). The rectal doses were also affected by bladder distension. The median maximal dose was significantly lower in the distended bladder (481vs. 628 cGy). Conclusions: Bladder fullness changed the dose distributions to the bladder, rectum, and small intestine. The clinical importance of these changes is not known and an increase in the use of three-dimensional brachytherapy planning will highlight the answer to this question.« less