The impact of interfractional anatomical changes on the accumulated dose in carbon ion therapy of pancreatic cancer patients

Houweling, Antonetta C.; Fukata, Kyohei; Kubota, Yoshiki; Shimada, Hirofumi; Rasch, Coen R. N.; Ohno, Tatsuya; Bel, Arjan; Horst, Astrid van der

doi:10.1016/j.radonc.2016.03.004

Cited by 35 publications

(47 citation statements)

References 21 publications

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“…2). In particle therapy, changes in gastrointestinal gas can severely affect target dose coverage, as established for carbon ion and proton therapy in earlier studies of our group 17, 27. The observed limited effects of changes in gastrointestinal gas in our current study illustrate the inherent robustness of photon radiation therapy.…”

Section: Discussionsupporting

confidence: 64%

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Dosimetric effects of anatomical changes during fractionated photon radiation therapy in pancreatic cancer patients

Horst

Houweling

Tienhoven

et al. 2017

J Applied Clin Med Phys

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Pancreatic tumors show large interfractional position variation. In addition, changes in gastrointestinal gas volumes and body contour take place over the course of radiation therapy. We aimed to quantify the effect of these anatomical changes on target dose coverage, for the clinically used fiducial marker‐based patient position verification and, for comparison, also for simulated bony anatomy‐based position verification. Nine consecutive patients were included in this retrospective study. To enable fraction dose calculations on cone‐beam CT (CBCT), the planning CT was deformably registered to each CBCT (13–15 per patient); gas volumes visible on CBCT were copied to the deformed CT. Fraction doses were calculated for the clinically used 10 MV VMAT treatment plan (with for the planning target volume (PTV): D98% = 95%), according to fiducial marker‐based and bony anatomy‐based image registrations. Dose distributions were rigidly summed to yield the accumulated dose. To evaluate target dose coverage, we defined an iCTV +5 mm volume, i.e., the internal clinical target volume (iCTV) expanded with a 5 mm margin to account for remaining uncertainties including delineation uncertainties. We analyzed D98%, Dmean, and D2% for iCTV +5 mm and PTV (i.e., iCTV plus 10 mm margin). We found that for fiducial marker‐based registration, differences between fraction doses and planned dose were minimal. For bony anatomy‐based registration, fraction doses differed considerably, resulting in large differences between planned and accumulated dose for some patients, up to a decrease in D98% of the iCTV +5 mm from 95.9% to 85.8%. Our study shows that fractionated photon irradiation of pancreatic tumors is robust against variations in body contour and gastrointestinal gas, with dose coverage only mildly affected. However, as a result of interfractional tumor position variations, target dose coverage can severely decline when using bony anatomy for patient position verification. Therefore, the use of intratumoral fiducial marker‐based daily position verification is essential in pancreatic cancer patients.

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Section: Discussionsupporting

confidence: 64%

“…Therefore, using a method previously applied by our group,17, 18 we deformably registered the pCT [Fig. 1(a)] to each CBCT (Velocity, version 3.1, Varian Medical Systems, Palo Alto, CA, USA).…”

Section: Methodsmentioning

confidence: 99%

Dosimetric effects of anatomical changes during fractionated photon radiation therapy in pancreatic cancer patients

Horst

Houweling

Tienhoven

et al. 2017

J Applied Clin Med Phys

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“…Kumagai et al [10] pointed out variations on the D95 CTV of 10% due to intra-fractional bowel changes using a passive delivery system, which matches with our results using a single beam in the anterior or lateral direction in the presence of inter-fractional changes. An interesting study of Houweling et al [19] used alternatively the routinely acquired cone-beam CT (CBCT) to assess the inter-fractional changes in the patient anatomy, through dose calculations in a CT, obtained by deformable registration of the planning CT to these CBCTs. This method results in an increase of the available data but the deformable registration adds new uncertainties to the evaluation.…”

Section: Discussionmentioning

confidence: 99%

Planning strategies for inter-fractional robustness in pancreatic patients treated with scanned carbon therapy

et al. 2017

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BackgroundManaging inter-fractional anatomy changes is a challenging task in radiotherapy of pancreatic tumors, especially in scanned carbon-ion delivery. This treatment planning study aims to focus on clinically feasible solutions, such as the beam angle selection and margin design to increase the robustness against inter-fractional uncertainties.MethodsThis study included 10 patients with weekly 3D-CT imaging and physician-approved Clinical Target Volume (CTV). The study was directed to keep the CTV-coverage using six beam angle configurations in combination with different Internal Target Volume (ITV) concepts. These were: geometric-margin (symmetric 3 and 5 mm margin); range-equivalent margins with an isotropic HU replacement; and to evaluate the need of asymmetric margins the water-equivalent range path (WEPL) was determined per patient from the set of CTs.Plan optimization and forward dose calculation in each week-CT were performed with the research treatment planning system TRiP98 and the plan quality evaluated in terms of CTV coverage (V95CTV) and homogeneity dose (HCTV = D5-D95).ResultsThe beam geometry had a substantial impact on the target irradiation over the treatment course, with the single posterior or two beams showing the best average coverage of the CTV. The use of geometric margins for the more robust beam geometries showed acceptable results, with a V95CTV of (99.2 ± 1.2)% for the 5 mm-margin. For the non-robust configurations, due to substantial changes in the radiological depth, the use of this margin results in a V95CTV that might be below 80%, only showing improvement when the range changes are included.ConclusionsSelection of adequate beam configurations and treatment margins in ion-beam therapy of pancreatic tumors is of great importance. For a single posterior beam or two beam configurations, application of geometrical margins compensate for dose degradation induced by inter-fractional anatomy changes for the majority of the analyzed treatment fractions.Electronic supplementary materialThe online version of this article (doi:10.1186/s13014-017-0832-x) contains supplementary material, which is available to authorized users.

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“…Detailed guidance on the delineation of the duodenum has now been published in the recent RTOG upper GI atlas, but the authors of this guideline noted that the fourth part of the duodenum was frequently missed by the contributing clinicians, meaning that existing data relating to this organ may be affected by this inconsistency in anatomical delineation [18]. While the duodenum is less mobile than other parts of the small bowel, large inter-fractional variations in volume still occur and which can lead to significant differences in delivered dosimetry compared to that which is planned [34], [35], [36]. Very few publications have investigated the delivered or accumulated dose to upper GI organs [37], and the data used here rely on planned dose as a surrogate.…”

Section: Discussionmentioning

confidence: 99%

Modelling duodenum radiotherapy toxicity using cohort dose-volume-histogram data

Holyoake

Aznar

Mukherjee

et al. 2017

Radiotherapy and Oncology

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Background and purposeGastro-intestinal toxicity is dose-limiting in abdominal radiotherapy and correlated with duodenum dose-volume parameters. We aimed to derive updated NTCP model parameters using published data and prospective radiotherapy quality-assured cohort data.Material and methodsA systematic search identified publications providing duodenum dose-volume histogram (DVH) statistics for clinical studies of conventionally-fractionated radiotherapy. Values for the Lyman-Kutcher-Burman (LKB) NTCP model were derived through sum-squared-error minimisation and using leave-one-out cross-validation. Data were corrected for fraction size and weighted according to patient numbers, and the model refined using individual patient DVH data for two further cohorts from prospective clinical trials.ResultsSix studies with published DVH data were utilised, and with individual patient data included outcomes for 531 patients in total (median follow-up 16 months). Observed gastro-intestinal toxicity rates ranged from 0% to 14% (median 8%). LKB parameter values for unconstrained fit to published data were: n = 0.070, m = 0.46, TD50(1) [Gy] = 183.8, while the values for the model incorporating the individual patient data were n = 0.193, m = 0.51, TD50(1) [Gy] = 299.1.ConclusionsLKB parameters derived using published data are shown to be consistent to those previously obtained using individual patient data, supporting a small volume-effect and dependence on exposure to high threshold dose.

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The impact of interfractional anatomical changes on the accumulated dose in carbon ion therapy of pancreatic cancer patients

Cited by 35 publications

References 21 publications

Dosimetric effects of anatomical changes during fractionated photon radiation therapy in pancreatic cancer patients

Dosimetric effects of anatomical changes during fractionated photon radiation therapy in pancreatic cancer patients

Planning strategies for inter-fractional robustness in pancreatic patients treated with scanned carbon therapy

Modelling duodenum radiotherapy toxicity using cohort dose-volume-histogram data

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