Stereotactic Ablative Radiotherapy for Oligometastatic Pericolonic Soft Tissue Metastases Using Daily Cone-Beam Computed Tomography-Guided Online Adaptive Radiotherapy

• Published in: Curēus (Palo Alto, CA) CA), 2024-09, Vol.16 (9), p.e69937
• Main Authors: Mou, Benjamin, Hyde, Derek, Becker, Nathan
• Format: Article
• Language: English
• Subjects: Medical Physics; Oncology; Radiation Oncology
• ISSN: 2168-8184; 2168-8184
• DOI: 10.7759/cureus.69937

A 74-year-old woman with pathologic T4a N1 M0 adenocarcinoma of the cecum, initially treated with right hemicolectomy, developed rising serum carcinoembryonic antigen levels while receiving adjuvant chemotherapy. Re-staging investigations demonstrated two soft tissue metastases in the right abdomen comprised of a retrocolic lesion immediately posterior to the colon and a retroperitoneal lesion with no other sites of metastases. The patient was treated with stereotactic ablative radiotherapy (SABR) to a dose of 40 Gy in five daily fractions to both pericolonic soft tissue metastases simultaneously. A standard volumetric modulated arc therapy (VMAT) plan had suboptimal dose coverage of the retrocolic metastasis adjacent to the colon, so cone-beam computed tomography (CBCT)-guided online adaptive radiotherapy (ART) was employed to maximize radiation dose to the tumors due to the radioresistant histology. An intensity-modulated radiotherapy (IMRT) plan was created using artificial intelligence tools integrated with the treatment unit. Median contouring and plan creation for each fraction was 21.5 minutes (range 14.9-28.1). For the retrocolic metastasis, compared to the standard VMAT plan, the CBCT-guided online ART plan improved coverage of the gross target volume by the prescription dose from 80.0% to 99.7%. SABR to pericolonic soft tissue metastases was feasible using CBCT-guided online ART and can significantly improve target volume coverage when targets are adjacent to mobile normal organs, which may be particularly important for radioresistant histologies for local control.