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- Alsadius, David, 1975, et al.
(författare)
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Mean Absorbed Dose to the Anal-Sphincter Region and Fecal Leakage among Irradiated Prostate Cancer Survivors.
- 2012
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Ingår i: International Journal of Radiation Oncology, Biology, Physics. - : Elsevier BV. - 1879-355X .- 0360-3016. ; 84:2
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To supplement previous findings that the absorbed dose of ionizing radiation to the anal sphincter or lower rectum affects the occurrence of fecal leakage among irradiated prostate-cancer survivors. We also wanted to determine whether anatomically defining the anal-sphincter region as the organ at risk could increase the degree of evidence underlying clinical guidelines for restriction doses to eliminate this excess risk. METHODS AND MATERIALS: We identified 985 men irradiated for prostate cancer between 1993 and 2006. In 2008, we assessed long-term gastrointestinal symptoms among these men using a study-specific questionnaire. We restrict the analysis to the 414 men who had been treated with external beam radiation therapy only (no brachytherapy) to a total dose of 70 Gy in 2-Gy daily fractions to the prostate or postoperative prostatic region. On reconstructed original radiation therapy dose plans, we delineated the anal-sphincter region as an organ at risk. RESULTS: We found that the prevalence of long-term fecal leakage at least once per month was strongly correlated with the mean dose to the anal-sphincter region. Examining different dose intervals, we found a large increase at 40 Gy; ≥40 Gy compared with <40 Gy gave a prevalence ratio of 3.8 (95% confidence interval 1.6-8.6). CONCLUSIONS: This long-term study shows that mean absorbed dose to the anal-sphincter region is associated with the occurrence of long-term fecal leakage among irradiated prostate-cancer survivors; delineating the anal-sphincter region separately from the rectum and applying a restriction of a mean dose <40 Gy will, according to our data, reduce the risk considerably.
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| 2. |
- Moiseenko, Vitali, et al.
(författare)
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A Primer on Dose-Response Data Modeling in Radiation Therapy.
- 2021
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Ingår i: International journal of radiation oncology, biology, physics. - : Elsevier BV. - 1879-355X .- 0360-3016. ; 110:1, s. 11-20
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Tidskriftsartikel (refereegranskat)abstract
- An overview of common approaches used to assess a dose response for radiation therapy-associated endpoints is presented, using lung toxicity data sets analyzed as a part of the High Dose per Fraction, Hypofractionated Treatment Effects in the Clinic effort as an example. Each component presented (eg, data-driven analysis, dose-response analysis, and calculating uncertainties on model prediction) is addressed using established approaches. Specifically, the maximum likelihood method was used to calculate best parameter values of the commonly used logistic model, the profile-likelihood to calculate confidence intervals on model parameters, and the likelihood ratio to determine whether the observed data fit is statistically significant. The bootstrap method was used to calculate confidence intervals for model predictions. Correlated behavior of model parameters and implication for interpreting dose response are discussed.
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| 3. |
- Olsson, C. E., et al.
(författare)
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Feasibility of Mastication-Structure-Sparing Radiotherapy for Head and Neck Cancer
- 2021
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Ingår i: International journal of radiation oncology, biology, physics. - : Elsevier BV. - 1879-355X .- 0360-3016. ; 111:3
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE/OBJECTIVE(S): Although radiation-induced side-effects affecting mastication functionality have been studied in head and neck cancer (HNC) radiotherapy (RT), dose constraints for the associated structures are rarely included during treatment plan optimization. Previous research has identified several radiation dose relationships with mean dose thresholds around 30-40 Gy for masseter muscles, 40-50 Gy for pterygoid muscles, and 15-60 Gy for temporomandibular joint (TMJ) relating to a 10% trismus risk post RT. The purpose of this work was to use a multi-criteria optimization (MCO) approach to investigate to what extent doses to these structures can be lowered without violating existing clinical treatment goals in inverse planning of HNC RT. MATERIALS/METHODS: This exploratory treatment planning study used data from 22 HNC patients treated to 68 Gy without mastication-structure-sparing intent in 2017-2019 at one institute in Sweden. Original volumetric-modulated arc therapy (VMAT) plans were re-activated in the treatment planning system and masseter muscles, pterygoid muscles (medial and lateral), and TMJ were consistently delineated according to a previously reported delineation manual4. Re-planning was done using the MCO function of the treatment planning system with the resulting dose distribution normalized to match the clinical target volume (CTV T) mean dose of the clinical treatment plan. Dose differences between MCO and clinical plans were not allowed to exceed 2 Gy for any original clinical treatment goal unless tolerance doses had been substantially exceeded in the clinical treatment plan. To what extent dose to mastication structures could be lowered without violating existing clinical treatment goals were quantified by group and by patient. RESULTS: Altogether, there were 334 clinical treatment goals in the clinical treatment plans (median=15, range: 7-24 per patient, depending on tumor location), which easily could be met in the corresponding MCO plans. Mean doses to the mastication structures were in most cases below proposed tolerance doses in the clinical plan but could on average be further reduced between 3-5 Gy in the MCO plans (Table). Of the 25/88 patient reductions below 5 Gy (28%), 18/25 (72%) were for the masseter (n=8) and medial pterygoid (n=10) muscles. CONCLUSION: With modern RT, it seems possible to reduce the dose to mastication structures below proposed trismus dose tolerance thresholds for most HNC patients without violating clinical treatment goals. Focusing on masseter and medial pterygoid muscle doses may prove to give the largest benefit in individual cases. Copyright © 2021. Published by Elsevier Inc.
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