Impact of a fiducial marker based ART strategy on margins in postoperative IMRT of gynecological tumors

• Published in: Radiotherapy and oncology 2021-05, Vol.158, p.1-6
• Main Authors: Buijs, Monica, Bloemers, Monique C.W.M., Remeijer, Peter
• Format: Article
• Language: English
• Subjects: Gynecological tumors; Interfractional vaginal motion; IVM; Postoperative IMRT; PTV margins; VMAT
• ISSN: 0167-8140; 1879-0887
• DOI: 10.1016/j.radonc.2021.01.039

•An ART strategy is proposed to reduce the geometrical errors due to vaginal motion.•This strategy reduces the interfractional systematic vaginal motion with 54%.•This strategy provides an opportunity to reduce the PTV margins by 13–20 percent. To investigate the potential of an offline Adaptive Radiotherapy (ART) strategy, based on the interfractional vagina motion (IVM) measured using fiducial markers (FM) during an initial number of fractions, on the CTV to PTV margins in post-operative gynecological patients. In 18 patients, treated post-operatively for gynecological tumors, the systematic residual IVM was quantified after simulating an offline ART procedure, utilizing the average IVM measured with FM for a varying initial numbers of fractions to find the optimal moment to adapt the treatment plan and a threshold for selecting patients for replanning. Clinical margins for a zero, 2 and 5 mm threshold based strategy were calculated to assess the possible margin reduction. Applying an ART strategy based on the average IVM of the initial 5 fractions reduces the systematic IVM significantly (P