Cancer, by its very nature, is built to spread. While certain malignancies are slower-growing, other tumors advance more aggressively. When cancers spread from their original site to other organs or parts of the body, they become, by definition, metastatic cancer.
Kidney cancer, in particular, is a type of cancer that frequently metastasizes. That can happen when cancer cells spread to tissue surrounding the kidney, invade a blood vessel that leaves the kidney, spread to another nearby organ or get into the lymph system, which helps the body fight infection.
With advanced kidney cancer, that metastasis often involves the spongy organs into which we inhale life-giving breaths. "The most common site of kidney cancer spread is lung metastasis," says Dr. Cortney V. Jones, an oncologist at DMC Sinai-Grace Hospital in Detroit. And although it invades that organ, this metastasis is different from lung cancer -- or cancer that starts in the lungs.
The distinction isn't mere semantics either. It can impact how the cancer is addressed. In short, where cancer began in the body can affect treatment -- even though, by its makeup, cancer tends to expand its presence in the body if unabated.
"Appropriate drugs and treatment of any cancer depend to large extent on the site of origin of the cancer," says Dr. Edmund Folefac, a medical oncologist (specifically a genitourinary oncologist who treats mostly kidney cancer) with The Ohio State University Comprehensive Cancer Center - Arthur G. James Cancer Hospital and Richard J. Solove Research Institute.
As for what causes lung or kidney cancer, smoking is a risk factor for both. Both cancers affect men -- who are likelier to smoke -- more than women. But smoking, plus being around cigarettes or secondhand smoke, is far more of a driver for lung cancer -- the second most common cancer after skin cancer. Other prominent risk factors for kidney cancer include obesity and high blood pressure.
The U.S. Preventive Services Task Force, a panel of independent national experts, recommends annual screening for lung cancer using a low-dose CT scan for a select group: adults ages 55 to 80 years with a history of heavy smoking who currently smoke or have quit within the past 15 years.
Doctors may also recommend that patients with a high risk of kidney cancer have imaging tests to be checked for the disease. This may be done with regular imaging or ultrasound to look for tumors in the kidney. Those at high risk include people with a family history of kidney cancer and those with inherited conditions that predispose them to kidney cancer, such as von Hippel-Lindau disease. However, such screening tests aren't recommended for people of average risk.
It's also important to talk with a physician before proceeding with any screening recommendation, exploring the associated risks -- like false positives and unnecessary treatment, experts say -- as well as the potential benefits of early cancer detection. Unfortunately, kidney cancer can often grow undetected, not causing pain or other noticeable symptoms initially, and only be discovered after it advances.
"Metastatic lung and kidney cancer have similar features: poor appetite, pain and weight loss," Jones says. "Radiographic imaging is important." Metastatic kidney cancer may manifest in a large kidney mass and smaller masses in other organs, she notes. While metastatic lung cancer often features a large lung tumor and smaller cancerous growths, or lesions, elsewhere in the body.
Treating Kidney and Lung Cancer
Even as cancers advance, understanding where the uncontrolled growth of abnormal cells originated is helpful to control or prevent further spread. That's true whether the treatment is chemotherapy or radiation to zap the malignancy; immunotherapy that uses the body's own immune system to fight cancer -- which may be used when other approaches aren't successful or have limited effectiveness; or surgery, which varies in extensiveness, to remove cancerous tissue.
"If you knew something began in the kidney, sometimes you might even remove the kidney," says Dr. Roy Herbst, chief of medical oncology at Yale Cancer Center in New Haven, Connecticut.
Cancer's original location affects not only where treatment is focused, but the type of treatment. "If something began in the lung, it might affect whether you would do surgery or radiation therapy there," Herbst notes. "But also the treatments are different." Lung cancer is often treated with chemotherapy or a combination of chemo and immunotherapy.
At the same time, there is still some overlap in how kidney and lung cancer are treated. For both advanced kidney and lung cancer, immunotherapy is often an option. With metastatic cancer, the focus is generally on managing the cancer, to prevent or reduce further spread.
Targeted treatments may also be used. These drugs may block the growth of blood vessels that feed tumors or target proteins that help cancer spread called growth factors. Vascular endothelial growth factor, or VEGF, is common in kidney cancer, and, in a smaller proportion of cases, it may also contribute to the growth of some lung cancer tumors.
In some cases, including when treatment isn't well-tolerated or effective, it's worth inquiring about experimental therapies and ongoing trials.
Whatever your diagnosis, it's important to see an expert in the cancer you have. For example, genitourinary oncologists treat kidney, prostate and bladder cancer, while general oncologists may also treat lung and kidney cancer. Clinicians say it's key to see someone with strong experience treating the cancer you have.
"When the patient receives the diagnosis of either of these cancers, it is very important to consult with an expert, because how the cancer is treated may affect outcome," Folefac says. Patients should also make recommended lifestyle changes, such as quitting smoking, and be in regular conversation with their health providers about how they're doing in treatment.