by Kidney cancer is one of the 10 most diagnosed cancers in the United States. Like many other cancers on this list – including colon and rectal cancer – kidney cancer is now more common than before. But unlike some others, it is often difficult to distinguish the underlying causes of kidney cancer.
For example, a significant proportion of breast cancers are due to inherited genetic mutations. But this is not the case for kidney cancer. Only 3% to 5% of these cancers are due to inherited factors. Northwestern University Feinberg School of Medicine chief of urologic oncology, Dr. “There are certain genetic conditions associated with increased risk, but the vast majority of kidney cancers are not familial,” says Shilajit Kundu. “Patients always ask me, ‘Why did I buy this?’ he asks. And it’s hard to give them an answer,” adds Kundu. “I often say it’s just bad luck.”
The medical term he and other cancer specialists use for this type of bad luck is “occasional,” meaning the disease tends to occur randomly for no apparent reason. However, not all kidney cancers arise out of the blue. There are a handful of established risk factors, including exposure to some known carcinogens. There are also demographic factors associated with increased risks, such as biological sex and race.
Here, Kundu and other kidney cancer experts detail medical science’s current understanding of these risk factors and how it may be possible to reduce your risk of disease.
a familiar criminal
When people hear the words “cigarette” and “cancer” in the same sentence, they often assume the subject is lung cancer. But smoking is an established risk factor for many other cancers, including kidney cancers.
While the odds of a smoker developing kidney cancer are relatively low, researchers estimate that smoking increases a person’s risk of the disease by 20-50%. A kidney cancer specialist at the University of Washington in St. Louis, Dr. “When you inhale the carcinogens in tobacco, they are absorbed through the lungs and into the bloodstream,” explains Zachary Smith. It is the kidneys’ job to clean and filter the blood. If this blood contains tobacco carcinogens, some of them will travel to the kidneys, where they may contribute to a cancer-causing mutation, he explains.
Smoking may also promote kidney cancer in some indirect ways. For example, smoking can cause high blood pressure, another risk factor for kidney cancer. (More in a minute.) “This is one of the few modifiable risk factors for disease that a person can control,” says Smith.
Men are at greater risk
About 80,000 Americans were expected to be diagnosed with kidney cancer in 2022. More than 50,000 of these new cases – more than 60% – will occur in men. D., a kidney cancer specialist and professor of medicine at Duke University Cancer Center. “Being a man almost doubles your risk of kidney cancer,” says Daniel George.
For a time, there was speculation that smoking might be responsible for these gender-based risk discrepancies. (Traditionally, men have smoked more than women.) However, this tobacco hypothesis was not confirmed by close research and was replaced by new theories. “Kidney cancer appears to have a hormonal basis,” says George. “The incidence in premenopausal women is much lower than in men of that age, but after menopause the incidence begins to stabilize.”
The female sex hormone estrogen may help explain risk disparities. Before menopause, women tend to have much higher estrogen levels than men. Some research has found that estrogen can help replace damaged kidney cells, and the cyclical estrogen changes caused by a woman’s menstrual cycle can also improve kidney health. “It’s a theory that has some evidence to back it up,” says George.
Read more: Coping with Side Effects of Kidney Cancer Treatment
Relationships with hypertension and obesity
Study after study has found that people with hypertension are at increased risk for kidney cancer. The higher a person’s blood pressure, the more likely they are to develop the disease. These correlations persist even after researchers control for obesity, drug use, and other confusing explanations.
While the link between hypertension and kidney cancer is well established, experts aren’t entirely sure how high blood pressure contributes to the development of the disease. “We know the relationship is there, but the exact causation isn’t clear,” Kundu says. One theory is that hypertension can cause a state of chronic inflammation that can impair kidney health in several ways that can increase the risk of kidney cancer. Hypertension can also lead to the formation of blood molecules called reactive oxygen species, which can promote tumor development and progression.
There is also evidence that hypertension is responsible for racial disparities in kidney cancer risk. For example, Black Americans are significantly more likely to develop kidney cancer than white Americans. Some researchers have determined that taking steps to reduce rates of hypertension, another condition more common among black Americans, will improve racial differences in kidney cancer risk.
Hypertension often goes hand in hand with obesity, another major risk factor for kidney cancer. By some estimates, excess body weight accounts for as much as 40% of kidney cancer cases. There is also evidence that the link here is dose-related, meaning that as a person’s weight increases, their risk of kidney cancer increases. (Kidney cancer rates have been climbing for decades in both the U.S. and other parts of the world, and experts think rising obesity rates may explain this trend.)
However, the exact mechanisms linking body weight to kidney cancer have not been fully elucidated here. “Obesity is a risk factor for many malignancies, including kidney tumors, but we don’t know the exact mechanisms involved,” Smith says. Excess body weight can lead to endocrine (hormonal) changes that can contribute to the development of kidney cancers. Insulin resistance and blood-oxygen imbalances caused by being overweight can also be factors. It’s possible that these and other weight-related biological changes may ultimately explain the obesity-kidney cancer link, but more work is needed.
Hereditary risk factors
Again, only a small percentage (roughly 3% to 5%) of kidney cancers are caused by inherited genetic mutations. So far, researchers have identified at least 12 inherited genes or mutations that can be passed on in families that increase the risk of kidney cancer.
People who carry these genes are more likely to develop the disease early in life. “We control for genetic risk factors, especially in younger patients,” says George.
The best-studied of these inherited mutations are associated with a syndrome called von Hippel Lindau (vHL) disease. People who carry the vHL gene – approximately 1 in 35,000 worldwide – have a 70% chance of developing kidney cancer by age 50 and are almost certain to develop kidney cancer at some point in their life. However, most of these vHL cancers are diagnosed early before they have spread to other parts of the body, and only 1 in 3 people with the vHL gene go on to develop metastatic cancer.
Chemical exposures
Analysis of 2020 in the journal Environmental Science and Technology found that there are more than 150,000 individual chemicals registered for commercial use. Mapping the short- and long-term health effects of exposure to these chemicals, alone or in combination, is a huge challenge. But researchers have already determined that certain chemical exposures are risk factors for kidney cancer.
An example is trichloroethylene (TCE), a solvent primarily used to degrease machine parts. (Lessly, TCE also occurs in chemicals used in the dry cleaning, leatherworking, agricultural, and electronics industries.) The U.S. Environmental Protection Agency has classified TCE as a “human carcinogen,” and some studies suggest that people are exposed to heavy amounts of TCE in the workplace. (mostly those who worked in industrial manufacturing before the 1980s) were up to 50% more likely to develop kidney cancer than those who were not exposed.
Thanks to research linking TCE to cancer, the chemical’s use has been largely phased out. But experts say other chemical exposures are more likely to emerge as kidney cancer risk factors. “The kidneys are our filters, and so any chemical we take in, absorb, or breathe can become concentrated in the kidneys,” says George.
Some preliminary research has found that environmental toxins such as nitrates and radon, which can occur in drinking water, may also increase a person’s risk of kidney cancer. “The longer I stayed as an oncologist, the more hippie I became when it came to chemical exposure,” says Smith. “Everyone is paying attention to what is used in heavy industrial processes or pesticides, but I think there are other things in our environment right now – in our food or in our homes or workplaces – that will emerge as risk factors over time.”
Read more: Changing Cancer Care So Patients No Longer Feel Like a Number
How can you reduce your risks?
Some of the risk factors mentioned above are “modifiable,” meaning people have some control over them. “Avoiding smoking is a big thing,” Smith says. Other experts echo his advice, adding that living generally healthy, such as avoiding processed foods and getting plenty of exercise, can also make a difference.
There is some evidence, albeit limited, that the more a person exercises, the less likely they are to develop kidney cancer. There is also research showing that people who eat diets rich in whole fruits and vegetables have a reduced risk of disease. Avoiding processed meats (such as salami and delicatessen like smoked sausage) may also reduce your risks.
Surprisingly, there are quite a few studies linking alcohol consumption with a reduced risk of kidney cancer. According to a 2018 research review Journal of Clinical Oncology, A handful of studies have found that moderate drinkers – usually defined as those who drink one to two drinks a day – have a 20% reduced risk of kidney cancer compared to light drinkers or non-drinkers. However, alcohol consumption as a whole is associated with an increased risk of cancers, including cancers of the breast, esophagus, liver, and colon. If you’re worried about cancer, drinking less (or no drinking) seems like the best approach.
While there are things a person can do to reduce their cancer risk, experts reiterate that kidney cancer is often a complex disease caused by a number of factors. “If people can use this as motivation to develop healthier habits, that’s great, but I wouldn’t go so far as to tell them they can prevent kidney cancer,” says George. “We have identified some important risk factors and trends, but more research is needed to understand why the incidence is increasing.”
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