Upper tract chemoablation (mitomycin gel)

The kidney collects urine in small cups called calyces and a funnel called the renal pelvis, which drains down the ureter to the bladder. These are lined by the urothelium, the same lining as the bladder. Cancer that grows from this lining inside the kidney is called upper tract urothelial cancer. When it is low grade, meaning slow growing and unlikely to spread, the kidney can often be kept.

Upper tract chemoablation uses mitomycin, a chemotherapy medicine used for decades in the bladder, mixed into a special gel. The gel is liquid when cold and turns into a soft gel at body temperature. Once placed in the kidney, it stays in contact with the tumor for hours instead of washing out in minutes, then slowly melts and passes out in the urine. The medicine is sold as Jelmyto and was approved by the U.S. Food and Drug Administration in 2020 for low-grade upper tract urothelial cancer.

The treatment is given once a week for 6 weeks. Each time, a thin catheter is passed up the ureter from the bladder with a scope, usually with anesthesia, or the gel is given through a nephrostomy tube, a small tube placed through the back into the kidney. About 3 months after starting, your urologist looks inside the kidney with a scope to see whether the tumor is gone.

In the main study that led to approval, about 6 in 10 people had no visible tumor at that check. The most important side effect is narrowing of the ureter, called ureteral stenosis, which can block the kidney and may need a stent. Teams have adjusted how they give the treatment to lower that risk.

The parts of your body involved

Inside each kidney, urine collects in several small cups, the calyces, which join into the renal pelvis, a funnel that narrows into the ureter. The whole system is lined by urothelium. Low-grade tumors here often look like small fronds of seaweed growing from the lining. Because the system has many branches and corners, a scope and laser cannot always reach every tumor, which is where a gel that fills the whole space helps. The ureter is narrow, about the width of a drinking straw, so swelling or scarring in it can block urine flow.

• Calyces

  The small cups where urine first collects. The gel fills these to reach tumors in corners.

• Renal pelvis

  The funnel that gathers urine from the calyces. A common place for these tumors.

• Urothelium

  The lining where the tumor grows and which the gel coats.

• Ureter

  The tube to the bladder that the catheter passes through. It can narrow as a side effect.

• Cortex

  The outer filtering part of the kidney, which is preserved.