Cone-beam computed tomography for organ motion evaluation in locally advanced rectal cancer patients

• Published in: Radiologia medica Vol. 126; no. 1; pp. 147 - 154
• Main Authors: Rosa, Consuelo, Caravatta, Luciana, Di Tommaso, Monica, Fasciolo, David, Gasparini, Lucrezia, Di Guglielmo, Fiorella Cristina, Augurio, Antonietta, Vinciguerra, Annamaria, Vecchi, Claudio, Genovesi, Domenico
• Format: Journal Article
• Language: English
• Published: Milan Springer Milan 2021; Springer Nature B.V
• Subjects: Adult; Aged; Aged, 80 and over; Amplification; Cancer; Computed tomography; Cone-Beam Computed Tomography - methods; Diagnostic Radiology; Evaluation; Female; Humans; Imaging; Interventional Radiology; Male; Medicine; Medicine & Public Health; Middle Aged; Neoadjuvant Therapy; Neuroradiology; Organ Motion; Patient Positioning; Prone position; Radiation therapy; Radiology; Radiotherapy; Rectal Neoplasms - diagnostic imaging; Rectal Neoplasms - radiotherapy; Retrospective Studies; Supine position; Ultrasound; Organ motion; Rectal cancer; Cone-beam computed tomography; Radiotherapy; Dose intensification
• ISSN: 0033-8362; 1826-6983
• DOI: 10.1007/s11547-020-01193-z

Purpose
Due to a reported dose–response relationship in rectal cancer radiotherapy, a greater interest in dose intensification on small boost volume arises. Considering the need of an appropriate target movements evaluation, this retrospective study aimed to use cone-beam computed tomography (CBCT) for GTV and mesorectum organ motion (OM) evaluation, in locally advanced rectal cancer (LARC) patients treated with neoadjuvant chemo-radiotherapy, in prone and supine position.
Methods
Thirty-two LARC patients were analyzed. GTV and mesorectum were delineated on MRI co-registrated with CT simulation. GTV and mesorectum OM was estimated on all CBCTs, performed during treatment, co-registrated with CT simulation. OM evaluation was obtained, as mean shift in left and right (L–R), postero–anterior (P–A) and cranio–caudal (Cr–C) directions. Volumes variability was calculated by DICE index.
Results
A total of 296 CBCTs were analyzed. Mean shifts of the GTV and mesorectum in prone position were − 0.16 cm and 0.15 cm in L–R direction, 0.28 cm and − 0.40 cm in P–A direction, and 0.14 cm and − 0.21 cm, in Cr–C direction; for supine position the mean shifts of the GTV were − 0.10 cm and 0.17 cm in R–L direction, 0.26 cm and − 0.23 cm in A–P direction, 0.09 cm and − 0.11 cm in Cr–C direction. Mean DICE index for GTV and mesorectum was 0.74 and 0.86, in prone position, and 0.78 and 0.89 in supine position, respectively.
Conclusion
GTV and mesorectum OM was less than 4 mm in all directions in both positions, with a 1 mm less deviation in supine position. CBCTs resulted effective for OM assessment, and it could be an appropriate method for the implementation on an intensification treatment.