Majority of kidney cancers diagnosed at earliest stage

May 19 2008

Patients in the United States today are now much more likely to be diagnosed with smaller tumors, in the earliest, most treatable stage of kidney cancer than a decade ago, leading to a slightly higher survival rate, according to the results of a national study led by a UC San Diego Medical Center researcher.

Christopher J. Kane, M.D., chief of urology at UC San Diego Medical Center and the Moores UCSD Cancer Center, and a team of researchers, analyzed records of more than 200,000 kidney cancer patients described in the National Cancer Data Base to look at how kidney cancer presentation has changed over a twelve-year period. The National Cancer Database is sponsored by the American College of Surgeons and the Joint Commission on Cancer and includes information from hospital tumor registries in the U.S. The study will be published online for the May 2008 edition of Cancer.

"The changes in kidney cancer presentation are visible nationally and quite dramatic. If you are diagnosed with kidney cancer today, it is more likely to be at the earliest 'stage I' level as opposed to more advanced 'stage II, III or IV' just a decade ago," said Kane, a surgeon who specializes in treating kidney and prostate cancers. "The study also reveals a small but significantly higher survival rate for recently diagnosed kidney cancers. This is good news for the more than 50,000 kidney cancer patients who will be identified this year."

The analysis looked at kidney cancer data between 1993 and 2004. Findings reveal that stage I kidney cancers increased from approximately 43% in 1993 to 57% in 2004, but decreased in stages II-IV of the disease. The average size of the stage I tumors decreased from 4.1 cm in 1993 to 3.6 cm in 2003. Overall survival for all patients with kidney cancer increased 3.3% between 1993 and 2003. The 5-year survival rate for people with stage I kidney cancer is now 88% or better.

While the reason for the downward trend is not known with certainty, the low stage presentation of tumors appears to be due to the more widespread use of medical imaging such as ultrasound, CT scans, and MRIs being conducted to evaluate other medical conditions. The cancerous growths, which often have not yet caused symptoms, are found unexpectedly as a result of these imaging tests. These "incidentally detected" masses are more likely to be benign, smaller, and when confirmed to be kidney cancer to have better rates of survival.

"What we are seeing is that gynecologic or abdominal imaging to evaluate pain or other complaints is picking up other forms of disease such as kidney cancer," said Kane. "The increased and widespread use of medical imaging in the United States is helping to diagnose cancer in its non-symptomatic stages when it is easier to treat successfully."

Kidney cancer is considered a "silent killer" rarely causing signs or symptoms in its early stages. In the later stages, kidney cancer symptoms may include blood in the urine, back pain, weight loss, fatigue and intermittent fever. Deaths due to kidney cancer account for about 3% of all cancer deaths in the U.S with approximately 12,890 deaths in 2007.

"The message to patients is not to go out and request an ultrasound or CT scan," said Kane. "Keep in mind that this is a rare form of cancer. However, if abdominal imaging is done and a mass or masses in the kidney are recognized, evaluation by an urologist is recommended."

The progression of a cancer is divided into four stages to describe how much a cancer has spread. The stage takes into account the size of a tumor, how deep it has penetrated, and whether it has invaded adjacent or distant organs or lymph nodes. Staging of cancer is important because the stage at diagnosis is the most powerful predictor of survival, and treatments are often changed based on the stage.