Abstract: The invention relates to the radiation treatment of colorectal cancerous tissue in the rectum of a human or animal subject. In particular the invention relates to an endorectal probe device for effecting radiation treatment of colorectal cancerous tissue in the rectum of a human or animal subject. Furthermore the invention relates to an afterloading apparatus for effecting radiation treatment of colorectal cancerous tissue in the rectum of a human or animal subject using an endorectal probe device according to the invention. Moreover the invention relates to a method for effecting radiation treatment of colorectal cancerous tissue in the rectum of a human or animal subject, wherein the method implements the endorectal probe device according to the invention.