We have located links that may give you full text access.
Role of IMRT in reducing penile doses in dose escalation for prostate cancer.
PURPOSE: In three-dimensional conformal radiotherapy (3D-CRT), penile tissues adjacent to the prostate are exposed to significant doses of radiation. This is likely to be a factor in development of posttreatment erectile dysfunction. In this study, we investigate whether intensity-modulated radiation therapy (IMRT) leads to lower radiation exposure to proximal penile tissues (PPT) when compared with 3D-CRT.
MATERIALS AND METHODS: Ten randomly selected patients with clinically localized prostate cancer constituted the study group. Using identical structure sets, 3D-CRT and IMRT plans were designed for each patient. For IMRT, both tomographic (TOMO) and step-and-shoot (SS) techniques were used. Treatment plans were developed using 18 MV photons for 3D-CRT, 6 MV photons for TOMO, and 6 MV and 18 MV photons for SS plans. The PPT up to the beginning of the penile shaft (usually measuring 2-3 cm) was outlined by a team composed of a board-certified urologist and a radiation oncologist. The outlined PPT was subdivided into three segments (P1, P2, P3), and the radiation dose to each segment and to the entire structure was calculated. In addition, PPT was subdivided into corporal cavernosa (CC) and corpus spongiosum (bulb). The prostate dose was escalated from 73.8 Gy to 81 Gy to 90 Gy. Target D(95) (dose to 95% volume), critical structure D(5) (dose to 5% volume), and D(mean) (mean dose) were used in the comparison among treatment plans. Because 3D-CRT uses larger field margins than does IMRT, target and critical structure doses were recalculated in 3D-CRT plans employing field margins obtained from IMRT plans. Planning target volumes in original and modified 3D-CRT plans were the same.
RESULTS: Compared with 3D-CRT plans, the mean PPT doses were reduced by 40.2%, 43.6%, and 46.2%, respectively, at the three prescription dose levels in TOMO plans. The average D(mean) for CC was lower by 46.4%, 48.4%, and 51.4%, whereas the average bulb D(mean) was reduced by 44.2%, 44.9%, and 47.9%, respectively. There was also considerable sparing of P1, with a reduction in average D(mean) of 41.9%, 45.5%, and 48.5% compared with 3D-CRT. All differences between 3D-CRT and IMRT doses were statistically significant (p < 0.001). Similar improvements were noticed in maximum doses (D(5)) for penile structures. The percent dose reduction with IMRT plans improved as prostate dose was escalated. When compared with 3D-CRT plans with reduced fields, IMRT plans showed slightly smaller but still significant improvements in critical structure doses (p < 0.001). Compared with SS plans, TOMO plans produced improved sparing of dose to critical structures.
CONCLUSIONS: IMRT allows for dose escalation in prostate cancer while keeping penile tissue doses significantly lower compared to conformal radiotherapy. This may result in improved potency rates over current results observed with 3D-CRT.
MATERIALS AND METHODS: Ten randomly selected patients with clinically localized prostate cancer constituted the study group. Using identical structure sets, 3D-CRT and IMRT plans were designed for each patient. For IMRT, both tomographic (TOMO) and step-and-shoot (SS) techniques were used. Treatment plans were developed using 18 MV photons for 3D-CRT, 6 MV photons for TOMO, and 6 MV and 18 MV photons for SS plans. The PPT up to the beginning of the penile shaft (usually measuring 2-3 cm) was outlined by a team composed of a board-certified urologist and a radiation oncologist. The outlined PPT was subdivided into three segments (P1, P2, P3), and the radiation dose to each segment and to the entire structure was calculated. In addition, PPT was subdivided into corporal cavernosa (CC) and corpus spongiosum (bulb). The prostate dose was escalated from 73.8 Gy to 81 Gy to 90 Gy. Target D(95) (dose to 95% volume), critical structure D(5) (dose to 5% volume), and D(mean) (mean dose) were used in the comparison among treatment plans. Because 3D-CRT uses larger field margins than does IMRT, target and critical structure doses were recalculated in 3D-CRT plans employing field margins obtained from IMRT plans. Planning target volumes in original and modified 3D-CRT plans were the same.
RESULTS: Compared with 3D-CRT plans, the mean PPT doses were reduced by 40.2%, 43.6%, and 46.2%, respectively, at the three prescription dose levels in TOMO plans. The average D(mean) for CC was lower by 46.4%, 48.4%, and 51.4%, whereas the average bulb D(mean) was reduced by 44.2%, 44.9%, and 47.9%, respectively. There was also considerable sparing of P1, with a reduction in average D(mean) of 41.9%, 45.5%, and 48.5% compared with 3D-CRT. All differences between 3D-CRT and IMRT doses were statistically significant (p < 0.001). Similar improvements were noticed in maximum doses (D(5)) for penile structures. The percent dose reduction with IMRT plans improved as prostate dose was escalated. When compared with 3D-CRT plans with reduced fields, IMRT plans showed slightly smaller but still significant improvements in critical structure doses (p < 0.001). Compared with SS plans, TOMO plans produced improved sparing of dose to critical structures.
CONCLUSIONS: IMRT allows for dose escalation in prostate cancer while keeping penile tissue doses significantly lower compared to conformal radiotherapy. This may result in improved potency rates over current results observed with 3D-CRT.
Full text links
Related Resources
Trending Papers
Heart failure with preserved ejection fraction: diagnosis, risk assessment, and treatment.Clinical Research in Cardiology : Official Journal of the German Cardiac Society 2024 April 12
Proximal versus distal diuretics in congestive heart failure.Nephrology, Dialysis, Transplantation 2024 Februrary 30
Efficacy and safety of pharmacotherapy in chronic insomnia: A review of clinical guidelines and case reports.Mental Health Clinician 2023 October
World Health Organization and International Consensus Classification of eosinophilic disorders: 2024 update on diagnosis, risk stratification, and management.American Journal of Hematology 2024 March 30
Get seemless 1-tap access through your institution/university
For the best experience, use the Read mobile app
All material on this website is protected by copyright, Copyright © 1994-2024 by WebMD LLC.
This website also contains material copyrighted by 3rd parties.
By using this service, you agree to our terms of use and privacy policy.
Your Privacy Choices
You can now claim free CME credits for this literature searchClaim now
Get seemless 1-tap access through your institution/university
For the best experience, use the Read mobile app