Dosimetric Advantages of Midventilation Compared With Internal Target Volume for Radiation Therapy of Pancreatic Cancer

Lens, E.; Horst, Astrid van der; Versteijne, Eva; Tienhoven, Geertjan van; Bel, Arjan

doi:10.1016/j.ijrobp.2015.02.015

Cited by 18 publications

(13 citation statements)

References 28 publications

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“…Other delineation approaches with improved contrast between tumor and surrounding tissue to define the tumor borders and including the respiration motion should be investigated such as midventilation and particularly the midposition approach. Previous research showed that a midventilation approach results in significant PTV reduction and significant dose reductions to OARs compared to the iGTV approach, although the delineation process had not been investigated yet [6]. …”

Section: Discussionmentioning

confidence: 99%

“…For the remaining uncertainties, such as organ motion and set-up uncertainties, an additional margin is added to form the planning target volume (PTV). Nowadays, a four-dimensional CT (4DCT) scan is increasingly used to account for tumor motion during respiration [1, 2], for example combined with the internal target volume (ITV) [5] or mid-ventilation approach [6]. For pancreatic cancer patients treated at our department, we combine 4DCT with a modified ITV approach.…”

Section: Introductionmentioning

confidence: 99%

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Considerable interobserver variation in delineation of pancreatic cancer on 3DCT and 4DCT: a multi-institutional study

et al. 2017

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BackgroundThe delineation of pancreatic tumors on CT is challenging. In this study, we quantified the interobserver variation for pancreatic tumor delineation on 3DCT as well as on 4DCT.MethodsEight observers (radiation oncologists) from six institutions delineated pancreatic tumors of four patients with (borderline) resectable pancreatic cancer. The study consisted of two stages. In the 3DCT-stage, the gross tumor volume (GTV) was delineated on a contrast-enhanced scan. In the 4DCT-stage, the internal GTV (iGTV) was delineated, accounting for the respiratory motion. We calculated the volumes of the (i)GTV, the overlap of the delineated volumes (expressed as generalized conformity index: CIgen), the local observer variation (local standard deviation: SD) and the overall observer variation (overall SD). We compared these results between GTVs and iGTVs. Additionally, observers were asked to fill out a questionnaire concerning the difficulty of the delineation and their experience in delineating pancreatic tumors.ResultsThe ratios of the largest to the smallest delineated GTV and iGTV within the same patient were 6.8 and 16.5, respectively. As the iGTV incorporates the GTV during all respiratory phases, the mean volumes of the iGTV (40.07 cm3) were larger than those of the GTV (29.91 cm3). For all patients, CIgen was larger for the iGTV than for the GTV. The mean overall observer variation (root-mean-square of all local SDs over four patients) was 0.63 cm and 0.80 cm for GTV and iGTV, respectively. The largest local observer variations were seen close to biliary stents and suspicious pathological enlarged lymph nodes, as some observers included them and some did not. This variation was more pronounced for the iGTV than for the GTV. The observers rated the 3DCT-stage and 4DCT-stage equally difficult and treated on average three to four pancreatic cancer patients per year.ConclusionsA considerable interobserver variation in delineation of pancreatic tumors was observed. This variation was larger for 4D than for 3D delineation. The largest local observer variation was found around biliary stents and suspicious pathological enlarged lymph nodes.Electronic supplementary materialThe online version of this article (doi:10.1186/s13014-017-0777-0) contains supplementary material, which is available to authorized users.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Considerable interobserver variation in delineation of pancreatic cancer on 3DCT and 4DCT: a multi-institutional study

et al. 2017

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“…Also, the tumor motion magnitude during BH varied considerably from one BH to the next and this could result in substantial inter-fractional uncertainties in the tumor position that would also need to be accounted for. It might be better to use a mid-ventilation approach combined with free breathing as this results in target volumes that are significantly smaller compared with the use of an internal target volume [4].…”

Section: Discussionmentioning

confidence: 99%

“…Alternatively, other planning techniques can be used such as mid-ventilation. In mid-ventilation, the tumor is delineated in its mean respiratory position and a safety margin is calculated by regarding the respiratory tumor motion as random motion [4]. Abdominal compression or technically more challenging techniques such as gating or tracking can also be employed to limit or account for tumor motion [5,6].…”

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confidence: 99%

Considerable pancreatic tumor motion during breath-holding

et al. 2016

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Background: Breath-holding (BH) is often used to reduce abdominal organ motion during radiotherapy. However, for inhale BH, abdominal tumor motion during BH has not yet been investigated. The aim of this study was to quantify tumor motion during inhale BH and tumor position variations between consecutive inhale BHs in pancreatic cancer patients. Material and methods: Twelve patients with intratumoral fiducials were included and asked to perform three consecutive 30-second inhale BHs on each of three measurement days. During BH, lateral fluoroscopic movies were obtained and a two-dimensional (2D) image correlation algorithm was used to track the fiducials and the diaphragm, yielding the tumor and diaphragm motion during each BH. The tumor position variation between consecutive BHs was obtained from the difference in initial tumor position between consecutive BHs on a single measurement day. Results: We observed tumor motion during BH with a mean absolute maximum displacement over all BHs of 4.2 mm (range 1.0-11.0 mm) in inferior-superior (IS) direction and 2.7 mm (range 0.5-8.0 mm) in anterior-posterior (AP) direction. We found only a moderate correlation between tumor and diaphragm motion in the IS direction (Pearson's correlation coefficient jrj>0.6 in 45 of 76 BHs). The mean tumor position variation between consecutive BHs was 0.2 [standard deviation (SD) 1.7] mm in the inferior direction and 0.5 (SD 0.8) mm in the anterior direction. Conclusion: We observed substantial pancreatic tumor motion during BH as well as considerable position variation between consecutive BHs on a single day. We recommend further quantifying these uncertainties before introducing breath-hold during radiation treatment of pancreatic cancer patients. Also, the diaphragm cannot be used as a surrogate for pancreatic tumor motion.

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“…However, several groups have shown that the respiratory motion of pancreatic tumors measured on a single pretreatment 4DCT is not representative for daily tumor motion [2][3][4]. This discrepancy could limit the benefit of all 4DCT-based respiratory motion management techniques, such as using mid-ventilation [5].…”

Section: Introductionmentioning

confidence: 99%

Abdominal organ motion during inhalation and exhalation breath-holds: pancreatic motion at different lung volumes compared

Lens

Gurney‐Champion

Tekelenburg

et al. 2016

Radiotherapy and Oncology

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Dosimetric Advantages of Midventilation Compared With Internal Target Volume for Radiation Therapy of Pancreatic Cancer

Cited by 18 publications

References 28 publications

Considerable interobserver variation in delineation of pancreatic cancer on 3DCT and 4DCT: a multi-institutional study

Considerable interobserver variation in delineation of pancreatic cancer on 3DCT and 4DCT: a multi-institutional study

Considerable pancreatic tumor motion during breath-holding

Abdominal organ motion during inhalation and exhalation breath-holds: pancreatic motion at different lung volumes compared

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