The following questions and responses have been lightly edited for grammatical purposes. 

1) Are there any myths about kidney cancer that you’d like to address?

Dr. Choueiri: The myth I want to address is this: that there’s nothing we can do for kidney cancer, and that patients with stage IV disease are inevitably going to die. That’s incorrect. It’s extremely important for patients, families, and providers to know this.

I think the first thing we all do, including myself, my friends, my wife, my parents, even kids, is Google it. Nowadays, we might even put it into ChatGPT.

When you search online, you need to understand that what you see is determined by algorithms. Sometimes they highlight the most morbid numbers. For example, you might see statistics about stage IV disease or survival data from 15–20 years ago. That information is technically correct for that time, but it ignores all the progress in research over the last two decades.

2) What are the main types of kidney cancer, and do treatment options differ between them?

Dr. Choueiri: Kidney cancer usually starts in the kidney. Very rarely, it can come from somewhere else—like lymphoma, lung cancer, or melanoma—but that’s extremely uncommon. I see maybe one case a year.

The kidney cell is not one type of cell. From the outside, there’s the epithelium, then a transition zone, then the collecting ducts where urine forms. Each area can develop a different type of kidney cancer.

The most common type is epithelial renal cell carcinoma, about 85–90% of cases. Then there’s urothelial cancer, which arises in the collecting ducts, treated similarly to bladder cancer. There are some in between where we sometimes use chemotherapy. Unlike lung cancer, with dozens of types, renal cell is the most common.

Even within renal cell carcinoma, there are “flavors.” Clear cell is the most common. It’s called clear cell because historically, under a microscope, the cells look clear—they have a lot of fat and glycogen. Non-clear cell types exist too, like chromophobe or papillary subtypes, which have different biology.

Interestingly, even though therapies were initially tailored for clear cell, usually driven by a VHL mutation, current treatments like immune checkpoint inhibitors or VEGF inhibitors often work across multiple types, though maybe less precisely. 

3) For someone who is newly diagnosed, how do you determine if their cancer may be slow-growing or aggressive?

Dr. Choueiri: Honestly, the only way to know for sure is retrospectively, what I call being a “Monday morning quarterback.” Tumors can behave unpredictably.

That said, there are clues. Tumor size and grade are very important. Grade describes how abnormal the cells look under a microscope. Low-grade tumors (grades 1–2) tend to be less aggressive, while high-grade tumors (grades 3–4) are more aggressive.

Some tumors have sarcomatoid features, meaning they look very different from typical kidney cancer cells. These tumors grow quickly, but interestingly, they can also be very responsive to immunotherapy. So, by combining pathology and emerging research, we can better predict tumor behavior, though never with 100% certainty.

4) How often does kidney cancer spread to the other kidney?

This is a great question, and it’s one I ask my residents and fellows because many people don’t really know why it comes up. 

Like with breast cancer, where disease can spread and sometimes return, bladder cancer can also come back. Kidney cancer, though, is a bit different. The chances of having bilateral kidney cancer are no more than 5%, likely even less.

Usually, we remove the kidney or part of the kidney. It’s not very common for it to spread to the other side, but if it does, we try to do a partial nephrectomy because we don’t want people ending up on dialysis. We really push to preserve kidney function whenever possible.

That said, it’s also important to consider situations where someone has multiple tumors in the same kidney, or tumors in both kidneys, especially if they’re young. In those cases, we need to think about whether there could be an underlying hereditary kidney cancer syndrome, something passed down from a parent. This accounts for less than 5%, but experience helps guide us.

Overall, it’s not common. When we remove a kidney and someone is at higher risk, the cancer usually comes back in places like the lymph nodes, the lung, or the liver. In about 5% of cases, it can appear in the other kidney, and that’s an important point.

Now, is that because cancer cells from the original tumor traveled to the other kidney? Or is it a completely new kidney cancer? Most of the time, we don’t know. Even if I run genetic testing on both tumors, I may still not know. For treatment, most of the time, it doesn’t matter.

Watch the full webinar here.