Image guided adaptive external beam radiation therapy for cervix cancer: Evaluation of a clinically implemented plan-of-the-day technique

Martin Buschmann*, Katarina Majercakova, Alina Sturdza, Stephanie Smet, Dina Najjari, Michaela Daniel, Richard Pötter, Dietmar Georg, Yvette Seppenwoolde

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

21 Citations (Scopus)

Abstract

Background: Radiotherapy for cervix cancer is challenging in patients exhibiting large daily changes in the pelvic anatomy, therefore adaptive treatments (ART) have been proposed. The aim of this study was the clinical implementation and subsequent evaluation of plan-of-the-day (POTD)-ART for cervix cancer in supine positioning. The described workflow was based on standard commercial equipment and current quality assurance (QA) methods. Materials and methods: A POTD strategy, which employs a VMAT plan library consisting of an empty bladder plan, a full bladder plan and a motion robust backup plan, was developed. Daily adaption was guided by cone beam computed tomography (CBCT) imaging after which the best plan from the library was selected. Sixteen patients were recruited in a clinical study on ART, for nine POTD was applied due to their large organ motion derived from two computed tomography (CT) scans with variable bladder filling. All patients were treated to 45 Gy in 25 fractions. Plan selection frequencies over the treatment course were analyzed. Daily doses in the rectum, bladder and cervix-uterus target (CTV-T) were derived and compared to a simulated non-adapted treatment (non-ART), which employed the robust plan for each fraction. Additionally, the adaption consistency was determined by repeating the plan selection procedure one month after treatment by a group of experts. ART-specific QA methods are presented. Results: 225 ART fractions with CBCTs were analyzed. The empty bladder plan was delivered in 49% of the fractions in the first treatment week and this number increased to 78% in the fifth week. The daily coverage of the CTV-T was equivalent between ART and the non-ART simulation, while the daily total irradiated volume V42.75 Gy (95% of prescription dose) was reduced by a median of 87 cm3. The median delivered V42.75 Gy was 1782 cm3. Daily delivered doses (V42.75 Gy, V40 Gy, V30G) to the organs at risk were statistically significantly reduced by ART, with a median difference in daily V42.75 Gy in rectum and bladder of 3.2% and 1.1%, respectively. The daily bladder V42.75 Gy and V40 Gy were decreased by more than 10 percent points in 30% and 24% of all fractions, respectively, through ART. The agreement between delivered plans and retrospective expert-group plan selections was 84%. Conclusion: A POTD-ART technique for cervix cancer was successfully and safely implemented in the clinic and evaluated. Improved normal tissue sparing compared to a simulated non-ART treatment could be demonstrated. Future developments should focus on commercial automated software solutions to allow for a more widespread adoption and to keep the increased workload manageable.

Original languageEnglish
Pages (from-to)184-195
Number of pages12
JournalZeitschrift fur Medizinische Physik
Volume28
Issue number3
DOIs
Publication statusPublished - Aug 2018

Bibliographical note

Acknowledgements:
We thank Elke Dörr for patient management. The financial support by the Austrian Federal Ministry of Science, Research and Economy and the National Foundation for Research, Technology and Development is gratefully acknowledged.

Publisher Copyright: © 2017

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