Small renal masses are a different breed of cancer

June 1, 2006

Brisbane, Australia-Small renal masses are a separate entity from renal cell carcinoma, according to Michael Jewett, MD, professor of surgery, University of Toronto, Canada.

Brisbane, Australia-Small renal masses are a separate entity from renal cell carcinoma, according to Michael Jewett, MD, professor of surgery, University of Toronto, Canada.

"All small renal masses are not the same. I am convinced that there is an entity in the renal cell carcinoma spectrum which has a very low potential to grow and progress to metastatic disease," Dr. Jewett said.

He proposed calling this clinical entity "renal neoplasia of low malignant potential" or "renal cell adenoma."

"What we are doing now has changed hugely in my practice lifetime, and some of my observations are quite provocative," he said.

"Non-selective treatment of small renal masses-taking a patient to the operating room as a presumed renal cell carcinoma case-is unlikely to reduce the overall mortality rate of kidney cancer. Even under long-term observation, progression doesn't seem to occur, as long as the patients are asymptomatic," Dr. Jewett said.

He cited the need for prognostic markers for small renal masses, especially as the median age of patients with small renal masses is 60 years, so standard treatments may not be appropriate. Traditional treatments are likely to be replaced by less-invasive treatments, including new targeted therapies.

Emerging therapies include cryotherapy, radiofrequency ablation, and high-intensity focused ultrasound. The safety profile of these treatments is well established, but efficacy has yet to be fully determined.

"This is a very dynamic area, and I am convinced that the combination of the natural history and biology of these small masses is going to make these therapies look good even if they are not ablating all of the lesions, but we can re-treat patients with these modalities."

New approach, new treatments

Dr. Jewett said there is an emerging role for biopsy of these small renal masses to establish the histology, which is often benign. In recent years, 48% to 66% of patients undergoing surgery have small tumors that have been incidentally detected on imaging. The natural history of the lesions is not well understood because these patients are usually treated at the time of diagnosis.

"When we look at treatment results [for specimen-confined partial nephrectomy], they are almost too good to be true. When you start having cancer-specific survivals in the 95% to 100% range, you have got to ask yourself whether what you are doing really needs to be done, or are we really benefiting from the natural history of these masses?" Dr. Jewett asked, noting that the recurrence rate of <2% is usually for new tumors.