Pelvic Organ Motion during Radiotherapy for Cervical Cancer: Understanding Patterns and Recommended Patient Preparation

Eminowicz, Gemma; Motlib, J.; Khan, Shahbaz; Perna, Carla; McCormack, Mary

doi:10.1016/j.clon.2016.04.044

Cited by 37 publications

(35 citation statements)

References 17 publications

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“… 18 We did not actually implement these preparations strategies, but they are already used to promote safety during some radiotherapy regimes to prostate and gynaecological tumours by reducing movement and inter fraction inconsistencies. 19 …”

Section: Discussionmentioning

confidence: 99%

MR guided high intensity focused ultrasound (MRgHIFU) for treating recurrent gynaecological tumours: a pilot feasibility study

Giles

Imseeh

Rivens

et al. 2019

BJR

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Objective: To assess the feasibility of targeting recurrent gynaecological tumours with MR guided high intensity focused ultrasound (MRgHIFU). Methods: 20 patients with recurrent gynaecological tumours were prospectively scanned on a Philips/Profound 3 T Achieva MR/ Sonalleve HIFU system. Gross tumour volume (GTV) and planning target volume (PTV) were delineated on T 2W and diffusion-weighted imaging (DWI). Achievable treatment volumes that (i) assumed bowel and/or urogenital tract preparation could be used to reduce risk of damage to organs-at-risk (TVoptimal), or (ii) assumed no preparations were possible (TVno-prep) were compared with PTV on virtual treatment plans. Patients were considered treatable if TVoptimal ≥ 50 % PTV. Results: 11/20 patients (55%) were treatable if preparation strategies were used: nine had central pelvic recurrences, two had tumours in metastatic locations. Treatable volume ranged from 3.4 to 90.3 ml, representing 70 ± 17 % of PTVs. Without preparation, 6/20 (30%) patients were treatable (four central recurrences, two metastatic lesions). Limiting factors were disease beyond reach of the HIFU transducer, and bone obstructing tumour access. DWI assisted tumour outlining, but differences from T 2W imaging in GTV size (16.9 ± 23.0%) and PTV location (3.8 ± 2.8 mm in phase-encode direction) limited its use for treatment planning. Conclusions: Despite variation in size and location within the pelvis, ≥ 50 % of tumour volumes were considered targetable in 55 % patients while avoiding adjacent critical structures. A prospective treatment study will assess safety and symptom relief in a second patient cohort. Advances in knowledge: Target size, location and access make MRgHIFU a viable treatment modality for treating symptomatic recurrent gynaecological tumours within the pelvis.

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Section: Discussionmentioning

confidence: 99%

MR guided high intensity focused ultrasound (MRgHIFU) for treating recurrent gynaecological tumours: a pilot feasibility study

Giles

Imseeh

Rivens

et al. 2019

BJR

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“…Bladder filling is the predominant factor driving cervixuterus motion, but to a lesser extent also rectal filling may affect especially cervix motion. 21 In our model, the rectum shape was explicitly deformed from the empty to the full bladder scan. In reality however, interfraction rectal motion is quite random, potentially leading to new cervix-uterus configurations.…”

Section: Discussionmentioning

confidence: 99%

A biomechanical finite element model to generate a library of cervix CTVs

et al. 2020

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To generate a series of physiologically plausible cervix CTVs by biomechanically modeling organ deformation as a consequence of bladder filling. This series can serve as planning CTVs for radiotherapy treatment of cervical cancer patients using a library of plans (LoP) strategy. Methods: The model was constructed based on the full and empty bladder scans of 20 cervical cancer patients, for which the bladder, rectum and the clinical target volume (CTV) of the cervix were delineated. Finite element modeling (FEM) was used to deform empty to full bladder anatomy. This deformation comprised two steps. In the first step, the surfaces of the bladder and rectum of the empty bladder anatomy were explicitly deformed to the full bladder anatomy and imported as enforced displacements into the biomechanical model. These surface displacements cause volumetric deformations of the bladder, rectum and cervix CTV meshes, dictated by their respective elastic properties and the type of contact among them. In the second step, the residual offset between the simulated and target CTV was corrected by an additional thin plate spline warp. Intermediate structural outputs of a linear superposition of the biomechanical and residual warp then constituted the library of CTVs for each patient. The residual warp was minimized by optimizing the FEM parameters over the 20 patients. Finally, the model was tested for nine healthy volunteers for which repeat MR scans were available as the bladder filled from empty to full. Small and large movers were identified depending on the extent of CTV motion, and analyzed separately. The proposed method was compared against the method currently used in our institute, in which intermediate structures are linearly interpolated between full and empty bladder anatomy, using a thin plate spline warp. The comparison metrics used were the ability to preserve CTV volume throughout the deformation, and residual offsets between repeat and library CTV. Results: Optimal model parameters were found to be compatible with published values. While for the current method, the median CTV volume shrunk by 4% for large movers halfway the deformation (and by up to 10% for individual cases), the proposed FEM-based method preserved CTV volumes throughout the deformation. Regional residual errors between repeat and library CTV reduced by up to 3 mm when averaged over the group of large movers. For individual cases this regional error reduction could be as large as 8 mm. Conclusions: We developed a robust and automatic method to create a patient-specific FEM-based LoP. The FEM-based method resulted in more accurate library of planning CTVs as compared to the current method, with the greatest improvements observed for patients with large CTV motion. The biomechanical model simulates volumetric deformations from empty to full bladder anatomy, paving the way for dose accumulation in an LoP setting.

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“…In a retrospective cohort study of 1080 patients treated with 3D-CRT to the prostate, use of both an empty rectum and comfortably full bladder was associated with reduced biochemical and clinical relapse and risk of dying from prostate cancer [40]. However, some full bladder protocols used for prostate radiotherapy have been shown to result in greater inter-fraction variation in prostate position compared to empty bladder protocols, especially in the superior and anterior directions, and therefore may be less reproducible [41]. Jadon et al reviewed studies in cervical cancer and observed that daily variation in bladder volume was common and maintaining a consistently large bladder volume may become more difficult later in a course of radiotherapy because of early radiation cystitis and intravenous fluid administered with chemotherapy [2].…”

Section: Bladder Filling Protocolsmentioning

confidence: 99%

Overview of patient preparation strategies to manage internal organ motion during radiotherapy in the pelvis

Slevin

Beasley²,

Speight³

et al. 2019

J Radiother Pract

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Introduction:Pelvic internal organs change in volume and position during radiotherapy. This may compromise the efficacy of treatment or worsen its toxicity. There may be limitations to fully correcting these changes using online image guidance; therefore, effective and consistent patient preparation and positioning remain important. This review aims to provide an overview of the extent of pelvic organ motion and strategies to manage this motion.Methods and Materials:Given the breadth of this topic, a systematic review was not undertaken. Instead, existing systematic reviews and individual high-quality studies addressing strategies to manage pelvic organ motion have been discussed. Suggested levels of evidence and grades of recommendation for each strategy have been applied.Results:Various strategies to manage rectal changes have been investigated including diet and laxatives, enemas and rectal emptying tubes and rectal displacement with endorectal balloons (ERBs) and rectal spacers. Bladder-filling protocols and bladder ultrasound have been used to try to standardise bladder volume. Positioning the patient supine, using a full bladder and positioning prone with or without a belly board, has been examined in an attempt to reduce the volume of irradiated small bowel. Some randomised trials have been performed, with evidence to support the use of ERBs, rectal spacers, bladder-filling protocols and the supine over prone position in prostate radiotherapy. However, there was a lack of consistent high-quality evidence that would be applicable to different disease sites within the pelvis. Many studies included small numbers of patients were non-randomised, used less conformal radiotherapy techniques or did not report clinical outcomes such as toxicity.Conclusions:There is uncertainty as to the clinical benefit of many of the commonly adopted interventions to minimise pelvic organ motion. Given this and the limitations in online image guidance compensation, further investigation of adaptive radiotherapy strategies is required.

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Pelvic Organ Motion during Radiotherapy for Cervical Cancer: Understanding Patterns and Recommended Patient Preparation

Cited by 37 publications

References 17 publications

MR guided high intensity focused ultrasound (MRgHIFU) for treating recurrent gynaecological tumours: a pilot feasibility study

MR guided high intensity focused ultrasound (MRgHIFU) for treating recurrent gynaecological tumours: a pilot feasibility study

A biomechanical finite element model to generate a library of cervix CTVs

Overview of patient preparation strategies to manage internal organ motion during radiotherapy in the pelvis

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