Set-Up Errors, Organ Motion, Tumour Regression and its Implications on Internal Target Volume-Planning Target Volume During Cervical Cancer Radiotherapy: Results From a Prospective Study.

Abstract

AIMS:

Uterocervical motions and organ filling during cervical cancer conformal radiotherapy is complex. This prospective, observational study investigated set-up margins (clinical target vo, ume [CTV] to planning target volume [PTV]) for pelvic nodal CTV and internal margin (CTV to internal target volume [ITV]) expansions for uterocervical movements during cervical cancer radiotherapy.

MATERIALS AND METHODS:

During cervical cancer radiotherapy, a daily kilovoltage, cone-beam computed tomography (CBCT) scan was acquired. Bony anatomy-based rigid co-registration and matching to vessels/pelvic nodal region was carried out to document shifts, errors (systematic and random) and to calculate CTV to PTV margins. Subsequently, soft-tissue matching was carried out at the mid-cervical region and uterine fundus to record shifts, errors and to calculate CTV to ITV margins.

RESULTS:

In 67 patients, 1380 CBCT scans were analysed. The mean (±standard deviation) couch shifts for CTV pelvic nodal region in all directions were within 4.5-5.3 mm, systematic and random errors 3.0-3.6 mm and set-up margins of within 10 mm (except anterior margin 10.3 mm). For the mid-cervical region, mean shifts were 4.5-5.5 mm, systematic and random errors 2-4 mm amounting to <10 mm internal margins (CTV-ITV for cervix) and for uterine fundus mean (±standard deviation) shifts were larger in the superior direction (12.1 mm) but 4.0-7.5 mm in other directions, systematic and random errors 2-7 mm amounting to anisotropic margins in various directions (10 mm in anterior-posterior and lateral directions, 12-20 mm in superior-inferior directions) (CTV-ITV for uterine fundus).

CONCLUSION:

Our study suggests anisotropic CTV to ITV and CTV to PTV margins for cervical cancer radiotherapy.

• Authors: U Mahantshetty, P Naga, A Nachankar, Y Ghadi, A Dheera, L Scaria, D Epili, S Chopra, G Lavanya, S Shrivastava
• Journal: Clinical oncology (Royal College of Radiologists (Great Britain)) (Clin Oncol (R Coll Radiol)) Vol. 34 Issue 3 Pg. 189-197 (03 2022) ISSN: 1433-2981 [Electronic] England
• PMID: 34736842 (Publication Type: Journal Article, Observational Study, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2021 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

Topics

• Cervix Uteri (diagnostic imaging)
• Cone-Beam Computed Tomography
• Female
• Humans
• Organ Motion
• Prospective Studies
• Radiotherapy Dosage
• Radiotherapy Planning, Computer-Assisted (methods)
• Radiotherapy Setup Errors
• Radiotherapy, Image-Guided (methods)
• Uterine Cervical Neoplasms (diagnostic imaging, radiotherapy)