The rising incidence of kidney cancer may be due to an increase in the number of small, treatable kidney tumors, according to a study in the September 20 issue of the Journal of the National Cancer Institute.

The incidence of a type of kidney cancer called renal cell carcinoma has been increasing over the past two decades. Despite the increased rates of surgery that have accompanied this trend, death rates have not decreased.

Brent K. Hollenbeck, M.D., of the University of Michigan in Ann Arbor, and colleagues identified 34,503 cases of kidney cancer using data from nine Surveillance, Epidemiology, and End Results registries collected between 1983 and 2002.

They observed that cancer incidence rose from 7.1 cases per 100,000 to 10.8 cases per 100,000. Tumors 4 cm or smaller, called small renal masses, accounted for the majority of this increase. Surgeries rose at the same rate, but mortality rates also increased. The authors suggest that surgery may not be an appropriate treatment for those tumors, which are often slow-growing and discovered in patients without symptoms related to kidney problems.

"These data do not encourage an abrupt departure from the current treatment paradigm for kidney cancer; rather, they prompt reflection on our clinical practice and suggest the need for investigation to address the observed 'treatment disconnect' that we are treating more and more small renal masses but are not impacting mortality," they write.