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Stereotactic body radiotherapy to the prostate and pelvic lymph nodes: A detailed dosimetric analysis of a phase II prospective trial.

ABSTRACT: OBJECTIVE:To evaluate the dosimetric ramifications of simultaneously irradiating the prostate and pelvic lymph nodes (PLNs) with a stereotactic body radiotherapy approach based on rigid registration to intraprostatic markers (IPMs). METHODS AND MATERIALS:Nineteen patients received concurrent SBRT to the prostate and PLNs on a phase II clinical trial. The translational and rotation shifts required for rigid registration to bony anatomy and changes in bladder and rectal anatomy were compared between patients with > 90%?and < 90% coverage of the nodal clinical target volume (CTVN ) as drawn on fractional kilovoltage cone-beam CTs. Stepwise multivariable regression models evaluated relationships between these anatomical parameters and the change in V100%CTVN. RESULTS:The average V100%CTVN per patient was 92.4 % (IQR, 90.2 - 96.4 %). For five patients (26.3%), the average was 85.0 % (IQR, 82.4-88.3 %). The left-right and superior-inferior translational shifts, sagittal rotational shift, and change in bladder volume were significantly different ( p < 0.05 for all via Student's t-test). Changes in bladder height, left/right shift, superior/inferior shift, 3-D shift, and axial rotation as significant predictors of change in dosing of V100%CTVN. CONCLUSION:While simultaneous SBRT to the prostate and PLNs based on rigid registration to IPMs provides adequate PLN coverage in most instances, overall coverage may be lower than anticipated if anatomy is unstable. Careful evaluation of bladder filling on kV-CBCT before treatment may be the most practical method for estimating accuracy prior to treatment. ADVANCES IN KNOWLEDGE:Simultaneous SBRT to the prostate and PLNs based on rigid registration to IPMs provides adequate PLN coverage in most instances.

SUBMITTER: Kishan AU

PROVIDER: S-EPMC6636273 | biostudies-literature | 2019 Jul

REPOSITORIES: biostudies-literature

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Stereotactic body radiotherapy to the prostate and pelvic lymph nodes: A detailed dosimetric analysis of a phase II prospective trial.

Kishan Amar U AU Tyran Marguerite M Weng Julius J Upadhyaya Shrinivasa S Lamb James J Steinberg Michael M King Christopher C Cao Minsong M

The British journal of radiology 20190403 1099

<h4>Objective</h4>To evaluate the dosimetric ramifications of simultaneously irradiating the prostate and pelvic lymph nodes (PLNs) with a stereotactic body radiotherapy approach based on rigid registration to intraprostatic markers (IPMs).<h4>Methods and materials</h4>Nineteen patients received concurrent SBRT to the prostate and PLNs on a phase II clinical trial. The translational and rotation shifts required for rigid registration to bony anatomy and changes in bladder and rectal anatomy were ...[more]

PMID: 30912957

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Project description:BackgroundProstate cancer rates have been steadily increasing in recent years. As high-precision radiation therapy methods, stereotactic body radiation therapy (SBRT) and carbon-ion radiation therapy (CIRT) have unique advantages. Analyzing the dosimetric differences between SBRT and CIRT in the treatment of localized prostate cancer can help provide patients with more accurate, individualized treatment plans.MethodsWe selected computed tomography positioning images and the contours of target volumes of 16 patients with localized prostate cancer who received radiotherapy. We delineated the organs at risk (OARs) on the CyberKnife (CK) treatment planning system (TPS) MultiPlan4.0, which were imported into the CIRT uniform scanning TPS HIMM-1 ci-Plan. Two treatment plans, SBRT and CIRT, were designed for the same patient, and we used SPSS 22.0 for the statistical analysis of data.ResultsBoth SBRT and CIRT plans met the prescribed dose requirements. In terms of target volume exposure dose, D2 (P<0.001), D5 (P<0.001), D50 (P<0.001), D90 (P=0.029), D95 (P<0.001), D98 (P<0.001), and Dmean (P<0.001) under SBRT were significantly higher than those under CIRT; the conformity index (CI) under SBRT was significantly better than that under CIRT (P<0.001); the target volume coverage rate (V95%) and dose homogeneity index (HI) under CIRT were significantly better than those under SBRT (P<0.001). In terms of OAR exposure dosage, the Dmax of the bladder and rectum under SBRT was significantly lower than that under CIRT (P<0.001), but Dmean was in the other direction; the exposure dose of the intestinal tract under CIRT was significantly lower than that under SBRT (P<0.05); Dmax of the femoral head under CIRT was significantly lower than that under SBRT (P<0.05), and there was no statistical difference between them at other doses.ConclusionsIn this study, we found that when CIRT was used for treating localized prostate cancer, the dose distribution in target volume was more homogeneous and the coverage rate was higher; the average dose of OARs was lower. SBRT had a better CI and higher dose in target volume; the dose hotspot was lower in OARs. It is important to comprehensively consider the dose relationship between local tumor and surrounding tissues when selecting treatment plans.

Project description:Prostate cancer is the most common non-cutaneous cancer in males. There are a number of options for patients with localized early stage disease, including active surveillance for low-risk disease, surgery, brachytherapy, and external beam radiotherapy. Increasingly, external beam radiotherapy, in the form of dose-escalated and moderately hypofractionated regimens, is being utilized in prostate cancer, with randomized evidence to support their use. Stereotactic body radiotherapy, which is a form of extreme hypofractionation, delivered with high precision and conformality typically over 1 to 5 fractions, offers a more contemporary approach with several advantages including being non-invasive, cost-effective, convenient for patients, and potentially improving patient access. In fact, one study has estimated that if half of the patients currently eligible for conventional fractionated radiotherapy in the United States were treated instead with stereotactic body radiotherapy, this would result in a total cost savings of US$250 million per year. There is also a strong radiobiological rationale to support its use, with prostate cancer believed to have a low ?/? ratio and therefore being preferentially sensitive to larger fraction sizes. To date, there are no published randomized trials reporting on the comparative efficacy of stereotactic body radiotherapy compared to alternative treatment modalities, although multiple randomized trials are currently accruing. Yet, early results from the randomized phase III study of HYPOfractionated RadioTherapy of intermediate risk localized Prostate Cancer (HYPO-RT-PC) trial, as well as multiple single-arm phase I/II trials, indicate low rates of late adverse effects with this approach. In patients with low- to intermediate-risk disease, excellent biochemical relapse-free survival outcomes have been reported, albeit with relatively short median follow-up times. These promising early results, coupled with the enormous potential cost savings and implications for resource availability, suggest that stereotactic body radiotherapy will take center stage in the treatment of prostate cancer in the years to come.

Dataset Information

Stereotactic body radiotherapy to the prostate and pelvic lymph nodes: A detailed dosimetric analysis of a phase II prospective trial.

Publications

Stereotactic body radiotherapy to the prostate and pelvic lymph nodes: A detailed dosimetric analysis of a phase II prospective trial.

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