ESTRO 2024 - Abstract Book

S1471

Clinical - Lower GI

ESTRO 2024

Keywords: rectal cancer, neoadjuvant radiotherapy, IMRT

References:

[1] Japanese Society for Cancer of the Colon and Rectum. Japanese Classification of Colorectal, Appendiceal and Anal Carcinoma: The 3d English Edition [Secondary Publication]. J. Anus Rectum Colon 2019, 3, 175–195.

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Digital Poster

SBRT in colorectal cancer patients with 1-10 metastases: a multicenter pilot study (NCT05375708)

Koen Zwart 1 , Manon N.G.J.A. Braat 2 , Frederieke H. van der Baan 1,3 , Anne M. May 3 , Jeanine Roodhart 1 , Hans-Martin M.M.B. Otten 4 , Maartje Los 5 , Tanja Oostergo 6 , Remond Fijneman 7 , Joyce M. van Dodewaard- de Jong 4 , Cornelis J.A. Punt 3 , Gert Meijer 8 , Jan J.W. Lagendijk 8 , Miriam Koopman 1 , Martijn Intven 8 , Guus M. Bol 1,8 1 University Medical Center Utrecht, Department of Medical Oncology, Utrecht, Netherlands. 2 University Medical Center Utrecht, Department of Radiology, Utrecht, Netherlands. 3 Julius Center for Health Sciences and Primary Care, Department of Epidemiology, Utrecht, Netherlands. 4 Meander Medical Centre, Department of Medical Oncology, Amersfoort, Netherlands. 5 St. Antonius, Department of Medical Oncology, Utrecht, Netherlands. 6 Diakonessenhuis, Department of Medical Oncology, Utrecht, Netherlands. 7 Netherlands Cancer Institute, Department of Pathology, Amsterdam, Netherlands. 8 University Medical Center Utrecht, Department of Radiotherapy, Utrecht, Netherlands In patients with oligometastatic disease emerging evidence shows that metastasis-directed stereotactic body radiation therapy (SBRT) can improve survival 1,2 . This treatment paradigm is based on tumor-agnostic trials and tumor-specific studies are needed to bring this into clinical practice 1 . We hypothesize that maintenance systemic therapy suppresses microscopic disease sufficiently whilst disease control can be prolonged by adding sub ablative metastasis-directed SBRT to suppress macroscopic disease in patients with 1-10 irresectable colorectal cancer metastases. This might postpone intensive systemic therapy, progression of disease, improve quality of life, and potentially extend overall survival. Recent developments in radiation oncology have made it possible to deliver high precision SBRT to 1-10 malignant lesions while limiting the chance of toxicity. Since feasibility and safety of SBRT in combination with systemic therapy in metastatic colorectal cancer (mCRC) patients with up to 10 malignant lesions is currently unknown, a pilot study was initiated before conducting a multicenter, randomized phase II trial. Our aim was to determine the feasibility and safety of SBRT in combination with systemic therapy in patients with polymetastatic CRC. Purpose/Objective:

Material/Methods:

A single-arm, open-label, multicenter, pilot study was conducted. Patients with mCRC and 1-10 metastases, with stable disease or partial response (according to RECIST 1.1) to initial systemic treatment (CAPOX-B, FOLFOX-B or FOLFOXIRI-B), and not amenable for curative-intent local treatment options were eligible. Patients received a