Conformity analysis to demonstrate reproducibility of target volumes for Margin-Intense Stereotactic Radiotherapy for borderline-resectable pancreatic cancer

Holyoake, D.; Robinson, M.; Grose, Derek; McIntosh, David E.; Sebag‐Montefiore, David; Radhakrishna, Ganesh; Patel, Neel; Partridge, Mike; Mukherjee, Somnath; Hawkins, M.

doi:10.1016/j.radonc.2016.08.001

Cited by 9 publications

(6 citation statements)

References 30 publications

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“…In addition, the inclusion of margin intensive boost yielded mostly equivalent results to Boost2, indicating that a boosting dose (40 Gy) to the margin of involved vasculature does not substantially increase GI‐OAR doses if the boosting area is away from GI‐OARs (1 cm in the current study). This result agrees with recent investigations on this strategy, opening the way for achieving a greater regression in this critical area of the tumor …”

Section: Discussionsupporting

confidence: 93%

Elective nodal irradiation with simultaneous integrated boost stereotactic body radiotherapy for pancreatic cancer: Analyses of planning feasibility and geometrically driven DVH prediction model

Nakamura

Prichard

et al. 2019

J Applied Clin Med Phys

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PurposeWe evaluate the feasibility of the elective nodal irradiation strategy in stereotactic body radiotherapy (SBRT) for pancreatic cancer.MethodsThree simultaneous integrated boost (SIB)‐SBRT plans (Boost1, Boost2, and Boost3) were retrospectively generated for each of 20 different patients. Boost1 delivered 33 and 25 Gy to PTV1 and PTV2, respectively. Boost2 delivered 40, 33, and 25 Gy to boostCTV, PTV1, and PTV2, respectively. Boost3 delivered 33 and 25 Gy to PTV1 and PTV3, respectively. PTV1 covered the initial standard SBRT plan (InitPlan) gross tumor volume (GTV). PTV2 covered CTVgeom which was created by a 10‐mm expansion (15 mm posterior) of GTV. PTV3 covered CTVprop which included elective nodal regions. The boostCTV included GTV as well as involved vasculature. The planning feasibility in each scenario and dose–volume histograms (DVHs) were analyzed and compared with the InitPlan (delivered 33 Gy only to PTV1) by paired t‐test. Next, a novel DVH prediction model was developed and its performance was evaluated according to the prediction accuracy (AC) of planning violations. Then, the model was used to simulate the impacts of GTV‐to‐organs at risk (OAR) distance and gastrointestinal (GI) OAR volume variations on planning feasibility.ResultsSignificant dose increases were observed in GI‐OARs in SIB‐SBRT plans when compared with InitPlan. All dose constraints were met in 63% of cases in InitPlan, Boost1, and Boost2, whereas Boost3 developed DVH violations in all cases. Utilizing previous patient anatomy, the novel DVH prediction model achieved a high AC in the prediction of violations for GI‐OARs; the positive predictive value, negative predictive value, and AC were 66%, 90%, and 84%, respectively. Experiments with the model demonstrated that the larger proximity volume of GI‐OAR at the shorter distance substantially impacted on planning violations.Conclusions SIB‐SBRT plan with geometrically defined prophylactic areas can be dosimetrically feasible, but including all nodal areas with 25 Gy in five fractions appears to be unrealistic.

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Section: Discussionsupporting

confidence: 93%

Elective nodal irradiation with simultaneous integrated boost stereotactic body radiotherapy for pancreatic cancer: Analyses of planning feasibility and geometrically driven DVH prediction model

Nakamura

Prichard

et al. 2019

J Applied Clin Med Phys

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“…For that matter, the tumor area close to vascular structures, or involving them, is considered as a region of complex anatomy for GTV delineation, requiring very accurate guidelines for volume definition, and a central benchmark contour review could be indicated for prospective clinical trials concerning SBRT in pancreatic cancer. A comprehensive radiotherapy quality assurance program to ensure consistency in target definition and radiotherapy delivery has been shown to reduce variation in target volume definition [36,37].…”

Section: Discussionmentioning

confidence: 99%

Magnetic resonance imaging (MRI) compared with computed tomography (CT) for interobserver agreement of gross tumor volume delineation in pancreatic cancer: a multi-institutional contouring study on behalf of the AIRO group for gastrointestinal cancers

et al. 2019

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Genovesi (2019) Magnetic resonance imaging (MRI) compared with computed tomography (CT) for interobserver agreement of gross tumor volume delineation in pancreatic cancer: a multiinstitutional contouring study on behalf of the AIRO group for gastrointestinal cancers, Acta Oncologica, 58:4, 439-447, ABSTRACT Background: Due to the high soft tissue resolution, magnetic resonance imaging (MRI) could improve the accuracy of pancreatic tumor delineation in radiation treatment planning. A multi-institutional study was proposed to evaluate the impact of MRI on inter-observer agreement in gross tumor volume (GTV) and duodenum delineation for pancreatic cancer compared with computer tomography (CT). Material and Methods: Two clinical cases of borderline resectable (Case 1) and unresectable (Case 2) pancreatic cancer were selected. In two sequential steps, diagnostic contrast-enhanced CT scan and MRI sequences were sent to the participating centers. CT-GTVs were contoured while blinded to MRI data sets. DICE index was used to evaluate the spatial overlap accuracy. Results: Thirty-one radiation oncologists from different Institutions submitted the delineated volumes. CT-and MRI-GTV mean volumes were 21.6 ± 9.0 cm 3 and 17.2 ± 6.0 cm 3 , respectively for Case 1, and 31.3 ± 15.6 cm 3 and 33.2 ± 20.2 cm 3 , respectively for Case 2. Resulting MRI-GTV mean volume was significantly smaller than CT-GTV in the borderline resectable case (p < .05). A substantial agreement was shown by the median DICE index for CT-and MRI-GTV resulting as 0.74 (IQR: 0.67-0.75) and 0.61 (IQR: 0.57-0.67) for Case 1; a moderate agreement was instead reported for Case 2: 0.59 (IQR:0.52-0.66) and 0.53 (IQR:0.42-0.62) for CT-and MRI-GTV, respectively. Conclusion: Diagnostic MRI resulted in smaller GTV in borderline resectable case with a substantial agreement between observers, and was comparable to CT scan in interobserver variability, in both cases. The greater variability in the unresectable case underlines the critical issues related to the outlining when vascular structures are more involved. The integration of MRI with contrast-enhancement CT, thanks to its high definition of tumor relationship with neighboring vessels, could offer a greater accuracy of target delineation.

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“…However, it became evident that soft tissue discrimination on these non-contrasted scans was poor, subsequently resulting in inconsistent ITV contours, even when performed by the same physician. Published studies of inter-physician contouring variability also illustrate this point (12), and MRI-based planning has been shown to result in smaller contours than CT-based planning (13).…”

Section: Discussionmentioning

confidence: 94%

Daily breathing inconsistency in pancreas SBRT: a 4DCT study

Sarkar

Lloyd

Paxton

et al. 2018

J. Gastrointest. Oncol

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Background: Stereotactic body radiation therapy (SBRT) treatments of pancreatic cancer typically employ relatively small margins. This study characterizes the motion of high visibility structures in close proximity to the pancreas to determine how much the motion envelope of such a structure changes due to respiratory variation between fractions. Methods: Fanbeam, four-dimensional computed tomography (4DCT) studies acquired initially for planning and again prior to each treatment for 6 patients were used to fully characterize the change in motion of high-contrast structures in close proximity to the pancreas. Results: Three of the six patients investigated had structures that showed a change in motion over the course of treatment that would not have been covered when using the typical 3 mm planning target volume (PTV) margins. For most of these large changes in motion envelope, a 4 mm uniform PTV margin would have allowed for coverage of the tumor. Conclusions: Half of the patients showed a change in motion envelope greater than would be covered by the commonly used PTV margins in pancreas SBRT. This shows that the impact of small margins must be very carefully considered during the planning process.

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Conformity analysis to demonstrate reproducibility of target volumes for Margin-Intense Stereotactic Radiotherapy for borderline-resectable pancreatic cancer

Cited by 9 publications

References 30 publications

Elective nodal irradiation with simultaneous integrated boost stereotactic body radiotherapy for pancreatic cancer: Analyses of planning feasibility and geometrically driven DVH prediction model

Elective nodal irradiation with simultaneous integrated boost stereotactic body radiotherapy for pancreatic cancer: Analyses of planning feasibility and geometrically driven DVH prediction model

Magnetic resonance imaging (MRI) compared with computed tomography (CT) for interobserver agreement of gross tumor volume delineation in pancreatic cancer: a multi-institutional contouring study on behalf of the AIRO group for gastrointestinal cancers

Daily breathing inconsistency in pancreas SBRT: a 4DCT study

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