Of course, I do not know all the details of your case. However, here are some of the problems. A cancer mass of that size does not just sit there; it is often attached to surrounding tissues. A mass at that location is sitting right on top of the aorta, a huge artery carrying so much blood that if it was nicked during surgery you could bleed to death in less than half an hour. Also, the vena cava sits there, and this vein carries all of the blood from the bottom half the body back to the heart. Damage to that vein would also pose a major bleeding risk.

What about radiation? The major problem there is that your intestines sit right over the top of the mass. The bowel is very sensitive to radiation and radiation damage to the bowel can be very unpleasant. This may change as the ability to focus radiation is improving rapidly.

For all of these reasons, it is standard practice to place a stent in the ureter to keep it open and hope that medications can shrink the cancer.