Metastatic Kidney Cancer or a Separate Lung Cancer? Expert Urges Patients, Doctors to Learn the Difference

Oftentimes, kidney cancer will metastasize to the lungs. However, in a small percentage of patients, lung tumors that happen simultaneously as those in the kidneys may actually be undiagnosed cancer that originated in the lungs — and the results could be fatal.

“In our case, we found that 3.5 percent of patients with kidney cancer had lung cancer. We estimate that the percentage could be as high as 10 percent,” James Brugarolas, M.D., Ph.D., director of the Kidney Cancer Program at UT Southwestern Medical Center said in an interview with CURE.

Brugarolas mentioned that so far, he has come across four patients in his practice who had lung cancer that was entirely separate than their kidney cancer. The first red flag is when a lung tumor, which was originally thought to be just a metastasis of the kidney cancer, is not responding to treatment. Then, doctors and patients will not truly know if it is lung cancer or metastatic kidney cancer until a biopsy is done to reveal the origin of the tumor.

Discovering the difference could have huge implications.

“If we have a patient that we think solely has metastatic kidney cancer but has cancer in the lungs, the cancer can grow and ultimately kill the patient,” Brugarolas said, mentioning that the treatment for lung cancer is different than the treatment for kidney cancer.

Kidney cancer and lung cancer do share some common risk factors, such as smoking, and both cancers tend to become more prevalent as people age. There may also be a genetic factor linking the two that researchers just aren’t aware of yet, Brugarolas said.

“I think patients need to be aware of this. If they’re being treated for kidney cancer and have a lesion in the lung and it’s not responding, they need to ask their oncologists ‘is it possible I have another cancer?’” he said.

But Brugarolas mentioned that not all lung lesions found in patients with kidney cancer will turn out to be a completely separate cancer, especially since about 60 percent of kidney metastases go to the lungs. Another common place for kidney cancer to metastasize is the brain — with about one in four patients getting brain metastases.

“We refer to the type of cancer based on the source. So, if the cancer arises in the kidney, then it’s kidney cancer regardless of where it goes. And the lungs, in fact, is the most common place where kidney cancer travels,” he said.

Brugarolas said that he hopes that better imaging techniques will soon develop so it will be easier — and quicker – to determine where a lesion is originating from. This could also help determine the molecular subtype of a patient’s kidney cancer.

“It could save lives,” he said.