Kidney cancer may well be the least-known common cancer in the U.S. An estimated 81,800 new cases will be diagnosed this year, according to the American Cancer Society. In 2022, the disease was the eighth most common cancer, occurring more frequently than leukemia and thyroid cancer. Yet, when people are diagnosed, their reaction is often, “I didn’t even know you could get cancer of the kidneys,” says Dr. Alice C. Fan, an assistant professor of medicine in the division of oncology at Stanford University School of Medicine in Palo Alto, Calif.
Humans have two fist-sized kidneys (shaped like the eponymous beans)—one on each side of the body. They’re located below your rib cage, toward your back. And every day, the kidney’s million or so tiny filters process about 200 quarts of blood, removing toxins, excess minerals, and water, which become urine. The kidneys also secrete hormones, including ones that help maintain blood pressure, prompt bone marrow to make red blood cells, and convert Vitamin D from dietary sources or sun exposure into a form that can be used by the body.
The majority of kidney cancer originates in the tiny filters. Most of the time, it’s found when it’s still confined to the kidney. But when it spreads to other parts of the body, until recently, it made for a grim prognosis. That’s changed, thanks to advances in treatment over the last couple of decades. These are some of the myths about kidney cancer that experts like Fan encounter.
The myth: There’s only one kind of kidney cancer.
The facts: Cancers are usually referred to by the organ in which they originate. But those rough categories mask diversity in how those cancers look and behave. Kidney cancer is no exception. The most common type, which affects about 70% to 75% of kidney cancer patients, is clear cell renal cell carcinoma—so named because under the microscope, the cells look clear, says Dr. Chung-Han Lee, a genitourinary oncologist at Memorial Sloan Kettering Cancer Center in New York. A host of other types of cells give rise to the remaining cases, which are collectively called non-clear cell renal cell carcinoma and include papillary renal cell carcinoma, renal medullary carcinoma, and chromophobe renal cell carcinoma. To make things more complicated, subtypes can have “sarcomatoid” variants, which are very aggressive, explains Fan.
“The initial classification is really the pathologist looking under the microscope,” Lee says. “That will really drive the treatment choices down the line.” Because it’s so crucial, patients shouldn’t hesitate to ask that the pathology results be confirmed, or to seek a second opinion if there’s time.
The myth: Kidney cancer affects everyone equally.
The facts: Like most other cancers, the burden of the disease falls disproportionately on older folks: According to the American Cancer Society (ACS), most people are diagnosed between the ages of 65 and 74. Men are about twice as likely as women to get the disease, with the lifetime risk for men about 2%, and for women about 1%, the ACS says. It’s not known exactly why there’s a gender disparity. Race also matters. Black Americans are more likely to develop the rarer subtypes of kidney cancer than white Americans, which may be linked to risk factors including blood pressure, obesity, and genetics, says Lee.
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The myth: Most kidney cancers are preventable.
The facts: “One question I always get is: Why did I get kidney cancer?” says Dr. Sangeeta Goswami, an assistant professor of genitourinary medical oncology and immunology at MD Anderson Cancer Center in Houston. Only rarely is it inherited. In a small percentage of patients—5% to 8%, according to the National Cancer Institute—kidney cancer is linked to a hereditary syndrome that raises the risk of certain cancers. Von Hippel-Lindau syndrome, for example, causes tumors to grow in many organs, and raises the risk of kidney and pancreatic cancer.
Nor is there a very strong link with modifiable risk factors. Smoking, for example, is associated with about twice the risk of kidney cancer, says Lee. By comparison, smokers are 15 to 30 times more likely to get lung cancer than nonsmokers, according to the U.S. Centers for Disease Control and Prevention. There’s also a small association with obesity, and sometimes with high blood pressure, says Lee. Of course, it’s always good advice to avoid tobacco and excess alcohol, and prevent obesity, since those factors have been linked to a variety of diseases, including many types of cancer. But the associations with kidney cancer are relatively small. More often than not, kidney cancer is just bad luck. “That’s what is so devastating about it,” says Lee. “People can do everything right, go to the doctor regularly, and still get that call.”
The myth: You should be screened regularly for kidney cancer.
The facts: There is currently no equivalent of the mammogram or PSA test for screening the general population for kidney cancer. People at very high risk because of genetic conditions are regularly monitored via imaging tests, but that’s not practical for people at average risk.
Tumors used to be found mostly on the basis of symptoms such as blood in the urine or pain in the side of your back. In advanced cases, patients might report feeling very fatigued. If you do have those symptoms, you should definitely report them to your physician. (And don’t panic; blood in the urine can mean many different things, including a urinary tract infection.) Nowadays, kidney cancer is usually found when physicians are looking for something else. “People are being scanned for something else—maybe they were in a car accident—and cancer is found in the kidney,” says Goswami.
Some of those tumors will turn out to be small or slow growing, but about a third will have already spread beyond the kidneys when they’re diagnosed. The search is on for ways to detect kidney cancer before it progresses and is harder to treat. “It’s an especially hard nut to crack,” says Fan. Many screening tests rely on finding “a positive signal—a mutation or something in the blood,” she says. But in kidney cancer, there’s often a loss of a piece of chromosome, and with it, a tumor suppressor gene. It’s very difficult to detect the loss of a piece of chromosome amidst all the intact chromosomes in the blood from the body’s normal cells, Fan says. “You’re not looking for a needle in a haystack, but for the loss of a needle in the haystack. That’s much more of a challenge.”
Fan and her colleagues are exploring novel approaches to finding kidney cancer, including looking for autoantibodies. “If the immune system is important for kidney cancer, it might remember if it’s seen a kidney cancer cell and gotten rid of it,” she says. Another line of research in its early stages: looking at platelets as reporters, since their RNA signature changes based on what they encounter in the body.
The myth: The usual treatment for stage 1-3 kidney cancer is surgery followed by chemotherapy.
The facts: This is half right. Surgery is indeed often the first step for most patients diagnosed when their cancer is in stages 1, 2, or 3. (Some early-stage cancers are very small and growing slowly, so they might be observed over time or treated non-surgically.) If the entire kidney needs to be removed, most people can function just fine with the other one.
But unlike many other types of cancer, clear cell renal cell carcinoma isn’t sensitive to chemotherapy. The usual approach after surgery has been active surveillance—that is, regular scans to look for any recurrence, says Goswami. In some cases, physicians may use newer drugs (more on those later) after surgery in patients with early-stage disease who are at high risk of recurrence, but studies haven’t provided clear evidence that they prolong life, she says. If medication after surgery is an option, “you should have a very transparent conversation about the pros and cons,” she says.
The myth: People only get kidney cancer in the kidneys.
The facts: When kidney cancer spreads, it’s still kidney cancer, even if it ends up in another organ. “Cancer is like a weed,” explains Lee. “When it shows up in a place it shouldn’t be, that doesn’t change what it is.” So, if the cancer metastasizes to the lung, brain, or adrenal system, it will still be treated like kidney cancer, not like the tumors that originate in those organs.
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The myth: There are no good treatment options for metastatic kidney cancer.
The facts: This was true up until the last 20 years or so. About one-third of patients are diagnosed with stage 4—or advanced—disease, meaning it’s spread beyond the kidneys and is much more difficult to treat. And some early-stage cases will spread even after surgery. “It used to be that if you were stage 4, you usually only had months to live,” says Fan.
Two kinds of drugs changed that. The first were targeted therapies that capitalized on the discovery that kidney cancer cells lose their ability to sense oxygen, and in response, start forming many more blood vessels in order to grow and thrive, says Fan. Drugs called angiogenesis inhibitors, the first of which was approved for kidney cancer in 2005, curb that blood vessel formation. With those drugs, the median survival at stage 4 increased from less than a year to about two and a half years.
More recently, and more significantly, drugs that harness the power of the body’s own immune system to identify and attack tumor cells have been approved for use in kidney cancer. They’re called checkpoint inhibitors because they target a protein on the body’s own T cells that normally keeps the immune system in check and prevents it from overreacting (which can cause its own health problems). These therapies have been approved for use right off the bat in stage 4 patients, without trying other treatments first. And importantly, these drugs don’t have the difficult side effects of earlier types of immunotherapy, Lee says.
They’re also used in combination with each other, and with targeted therapies, which seem to be even better than single drugs or classes alone. With combinations of immunotherapies, about half of patients live at least another five years, says Lee. But only about one-third of renal cell carcinoma patients have a prolonged response to immunotherapy.
In some other cancers, the expression of a certain protein (PD-L1) in tumor cells can predict a better response to immunotherapy, but that’s not universally true in kidney cancer, says Fan. (Some renal cell carcinomas respond even without any measurable PD-L1 protein.) A patient who is immunosuppressed will also have a lesser response. Some research is focusing on the role of the microbiome—gut bacteria—in a person’s response to immunotherapy, she says.
“It’s still baby steps in the bigger scheme of things, but we have made tremendous progress in the past 10 years where we could significantly prolong the lives of patients with advanced kidney cancer,” Goswami says.