BioXmark, Rectal Feasibility Trial

Before the start of the treatment planning during an extra sigmoidoscopy after enema preparation, 4 liquid marker spots will be placed 1 cm from the tumor; two in the in the cranial and two in the caudal direction of the tumor (4 markers in total per patient).

"As part of standard patient set-up directly before each radiotherapy treatment, kV cone-beam CTs will be acquired. Treatment positioning will be based on the regular clinical decision protocols for treatment of rectal cancer and not on the markers. During treatment potential fiducial movement will be assessed using an externally positioned ultra-sound probe, positioned against the abdominal or perineal skin of the patients depending on de position of the tumor/fiducials in the rectum. For patients in this study 2 orthogonal kV images will be made immediately after each radiation using the electronic portal imaging (EPI) device.~As part of standard clinical practice an MR of the rectum will be made for response evaluation 6-8 weeks after the end of neo-adjuvant chemo-radiotherapy."

"As part of standard clinical practice patients whose tumor has not responded completely will be operated on 8-12 weeks after the end of neoadjuvant chemo-radiotherapy. Patients with a complete response will be follow-upped according to the wait-and-see protocol."