Prior cancer diagnosis ups future renal cancer risk

Study author Joel W. Slaton, MD, assistant professor of urology at the University of Minnesota, Minneapolis, reviewed the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) Program database for renal cancer incidence among patients who had other primary cancers. The cancer database represented some 1.3 million patients in the 20-year time period of his review, from 1973 to 1993.

"That was before the recent dramatic expansion in imaging studies which find incidental kidney cancers," said Dr. Slaton, who presented his findings at the AUA annual meeting here.

"With some neoplasms which are followed by abdominal CT scans, you will, in effect, already be automatically screening for renal masses," Dr. Slaton said. "It is a little harder to correct for which tumors were found by such screening and which were found by onset of new symptoms since these phenomena are not always recorded in the SEER database. Thus, someone who has a primary colorectal cancer will get a CT scan, and that will probably identify higher numbers of patients with kidney cancer."

Dr. Slaton found that the higher-risk patients were those who had prostate cancer or lung cancer, who had a 3.5- to 4.5-fold risk, respectively, of being identified with kidney cancer. That is compared with a 2.5-fold increased risk of patients with head and neck cancer.

When patients were subdivided by gender, Dr. Slaton found that men with lung and colon cancer had the higher risks (3.9- and 4.5-fold, respectively) of developing renal cancer after primary cancer, compared with women who had a relative increased risk of 2.6-fold for developing renal cancer if they had lung cancer and 1.9-fold if they had colon cancer.

"Men, in general, tend to have a somewhat higher risk of kidney cancer than women," Dr. Slaton said. "In particular, that risk is exaggerated by those who have had lung and colon cancer before.

"This risk remains high regardless of the stage of the first cancer."

According to Dr. Slaton, patients who have a prior cancer are two to five times at higher risk of being identified with a renal tumor. That number is relatively small when considering that if a patient has any kind of tumor, that patient's risk of developing another tumor of some other origin is about 9%. The chance that it will be a renal cancer is .06%.

While colon cancer patients are probably already undergoing CT scans, those with prostate, head and neck, and other cancers might not.

"And it may be that the lower stage primary tumors may not be undergoing this screening," Dr. Slaton said. "So, the question becomes, do all our patients with prostate cancer now get CTs looking for kidney cancer?

"No, because the increased incidence probably is not high enough to justify it. It's just that when patients are symptomatic that you should keep a low threshold for looking for renal cancer."