Profound renal cell carcinoma stage migration seen in U.S. database

This was the conclusion of researchers led by Christopher J. Kane, MD, associate professor of urology, University of California, San Francisco, who discussed a study of new case diagnoses and stage migration over time at the recent AUA Western Section annual meeting. A key question they hoped to answer was whether tumors currently being diagnosed and treated are smaller than those treated 10 years ago.

The NCDB is a nationwide oncology data set comprising information drawn from 1,400 facility-based cancer registries of approximately 75% of all newly diagnosed cancer cases treated in the United States. Currently, this amounts to information on more than 17 million cases of reported cancer diagnoses from 1985 to 2003.

"What we saw was an increase in stage 1 disease from 42% to 56% (p<.0001) over 10 years, a decrease in stage 2 and stage 3 disease, and the largest decrease in stage 4 disease in over 180,000 patients with kidney cancer," said Dr. Kane.

Looking only at patients who actually went to surgery, stage migration was even more profound, from 51% to 60% with stage 1. Because less stage 4 disease is seen in pathologic staging, Dr. Kane suggested the actual percentage with stage 4 disease "is a snapshot of patients who were having cytoreductive nephrectomy. If we do further analyses, hopefully, we will see the expansion of cytoreductive nephrectomy because of the recently published literature documenting its benefit."

Smaller tumors found

In 1993, the mean size of stage 1 tumors of about 4.1 cm was down to 3.7 cm by 2003. Dr. Kane noted that this seemingly small difference in size in a population of 110,000 stage 1 patients was actually highly statistically significant.

He further observed that less change in size was apparent for stage 2 disease, with tumor size decreasing from a mean of about 10.8 cm to a mean of about 10 cm.

"We also analyzed clear cell and papillary and then 'not specified' survival," Dr. Kane said. "Survival was 90% at 5 years for the entire cohort with stage 1 disease, independent of histology code."

Stage 2 survival was 83%, independent of histology code. Stage 3 survival was down to 65%, while stage 4 survival was only 8.6% after 5 years, again, independent of histology code.

Histology was not specified in some reports to the tumor registry, but after 1998, Dr. Kane noted there was expansion of specific histology codes with a continuing trend for pathologists to report specific histology codes.