Complication Probability as Assessed from Dose-Volume Histograms

The present study compared the dosimetry of intensity‐modulated radiation therapy (IMRT) and three‐dimensional conformal radiation therapy (3D‐CRT) techniques in patients treated for high‐grade glioma. A total of 20 patients underwent computed tomography treatment planning in conjunction with magnetic resonance imaging fusion. Prescription dose and normal‐tissue constraints were identical for the 3D‐CRT and IMRT plans. The prescribed dose was 59.4 Gy delivered at 1.8 Gy per fraction using 4 – 10 MV photons. Normal‐tissue dose constraints were 50 – 54 Gy for the optic chiasm and nerves, and 55 – 60 Gy for the brainstem.The IMRT plan yielded superior target coverage as compared with the 3D‐CRT plan. Specifically, minimum and mean planning target volume cone down doses were 54.52 Gy and 61.74 Gy for IMRT and 50.56 Gy and 60.06 Gy for 3D‐CRT (p≤0.01). The IMRT plan reduced the percent volume of brainstem receiving a dose greater than 45 Gy by 31% (p=0.004) and the percent volume of brain receiving a dose greater than 18 Gy, 24 Gy, and 45 Gy by 10% (p=0.059), 14% (p=0.015), and 40% (p≤0.0001) respectively. With IMRT, the percent volume of optic chiasm receiving more than 45 Gy was also reduced by 30.40% (p=0.047). As compared with 3D‐CRT, IMRT significantly increased the tumor control probability (p≤0.005) and lowered the normal‐tissue complication probability for brain and brainstem (p<0.033).Intensity‐modulated radiation therapy improved target coverage and reduced radiation dose to the brain, brainstem, and optic chiasm. With the availability of new cancer imaging tools and more effective systemic agents, IMRT may be used to intensify tumor doses while minimizing toxicity, therefore potentially improving outcomes in patients with high‐grade glioma.PACs number: 87.53 Tf

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“…We calculated the NTCP of an organ for a uniform dose D to a volume V using the Lyman—Kutcher—Burman method, ( 28 – 30 ) which is given by

N T C P = \frac{1}{\sqrt{2 π}} \int_{- \infty}^{t} e^{- t^{2 / 2}} \cdot d t,

…”

Section: Methodsmentioning

confidence: 99%

Intensity modulated radiation therapy versus three‐dimensional conformal radiation therapy for the treatment of high grade glioma: a dosimetric comparison

MacDonald

Ahmad

Kachris

et al. 2007

J Applied Clin Med Phys

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“…We chose to translate the rectal DVHs into a normal tissue complication probability (NTCP) as a metric representative of a clinical end point using Lyman's model 19, 20, 21. Table 4 also summarizes the rectal NTCP statistics from the 17 datasets.…”

Section: Resultsmentioning

confidence: 99%

A quantitative assessment of the consequences of allowing dose heterogeneity in prostate radiation therapy planning

Sun

Smith

Ghose

et al. 2018

J Applied Clin Med Phys

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Target dose uniformity has been historically an aim of volumetric modulated arc therapy (VMAT) planning. However, for some sites, this may not be strictly necessary and removing this constraint could theoretically improve organ‐at‐risk (OAR) sparing and tumor control probability (TCP). This study systematically investigates the consequences of PTV dose uniformity that results from the application or removal of an upper dose constraint (UDC) in the inverse planning process for prostate VMAT treatments. OAR sparing, target coverage, hotspots, and plan complexity were compared between prostate VMAT plans with and without the PTV UDC optimized using the progressive resolution optimizer (PRO, Varian Medical Systems, Palo Alto, CA). Removing the PTV UDC, the median D1cc reached 144.6% for the CTV and the PTV, and an average increase of 3.2% TCP was demonstrated, while CTV and PTV coverage evaluated by D99% was decreased by less than 0.6% with statistical significance. Moreover, systematic improvement in the rectum dose volume histograms was shown (a 5–10% decrease in the volume receiving 50% to 75% prescribed dose), resulting in an average decrease of 1.3% (P < 0.01) in the rectum normal tissue complication probability. Additional consequences included potentially increased dose to the urethra as evaluated by PTV D0.035cc (median: 153.4%), delivering 283 extra monitor units (MUs), and slightly higher degrees of modulation. In general, the results were consistent when a different optimizer (Photon Optimizer, Varian Medical Systems) was used. In conclusion, removing the PTV UDC is acceptable for localized prostate cases given the systematic improvement of rectal dose and TCP. It can be particularly useful for cases that do not meet the rectum dose constraints with the PTV UDC on. This comes with the foreseeable consequences of increased dose heterogeneity in the PTV and an increase in MUs and plan complexity. It also has a higher requirement for reproducing the position and size of the target and OARs during treatment. Finally, with the PTV UDC completely removed, in some cases the maximum doses within the PTV did approach levels that may be of concern for urethral toxicity and therefore in clinical implementation it may still be necessary to include a PTV UDC, but one based on limiting toxicity rather than enforcing dose homogeneity.

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“…The prostate was outlined following a definition consistent with the planning prostate contours on the kVCT. The rectal wall Dose Volume Histogram (DVH) is regarded as a useful metric for prediction of rectal bleeding (14). The definition of rectal wall was a simple ring expansion of the inner rectal wall of 3 mm at the level of the balloon, and as a solid structure below the level of the balloon.…”

Section: Methodsmentioning

confidence: 99%

On Voxel-by-voxel Accumulated Dose for Prostate Radiation Therapy using Deformable Image Registration

Hardcastle

Jeong

et al. 2015

Technol Cancer Res Treat

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Since delivered dose is rarely the same with planned, we calculated the delivered total dose to ten prostate radiotherapy patients treated with rectal balloons using deformable dose accumulation (DDA) and compared it with the planned dose. The patients were treated with TomoTherapy using two rectal balloon designs: five patients had the Radiadyne balloon (balloon A), and five patients had the EZ-EM balloon (balloon B). Prostate and rectal wall contours were outlined on each pre-treatment MVCT for all patients. Delivered fractional doses were calculated using the MVCT taken immediately prior to delivery. Dose grids were accumulated to the last MVCT using DDA tools in Pinnacle3 ™ (v9.100, Philips Radiation Oncology Systems, Fitchburg, USA). Delivered total doses were compared with planned doses using prostate and rectal wall DVHs. The rectal NTCP was calculated based on total delivered and planned doses for all patients using the Lyman model. For 8/10 patients, the rectal wall NTCP calculated using the delivered total dose was less than planned, with seven patients showing a decrease of more than 5% in NTCP. For 2/10 patients studied, the rectal wall NTCP calculated using total delivered dose was 2% higher than planned. This study indicates that for patients receiving hypofractionated radiotherapy for prostate cancer with a rectal balloon, total delivered doses to prostate is similar with planned while delivered dose to rectal walls may be significantly different from planned doses. 8/10 patients show significant correlation between rectal balloon anterior-posterior positions and some VD values.

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Complication Probability as Assessed from Dose-Volume Histograms

Cited by 491 publications

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Intensity modulated radiation therapy versus three‐dimensional conformal radiation therapy for the treatment of high grade glioma: a dosimetric comparison

Intensity modulated radiation therapy versus three‐dimensional conformal radiation therapy for the treatment of high grade glioma: a dosimetric comparison

A quantitative assessment of the consequences of allowing dose heterogeneity in prostate radiation therapy planning

On Voxel-by-voxel Accumulated Dose for Prostate Radiation Therapy using Deformable Image Registration

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