Among patients with early stage (pT1) renal cell carcinoma (RCC), a larger kidney size is associated with an increased the risk of dying from the malignancy, new data show.

In a study of 191 patients with pT1 RCC who underwent radical nephrectomy, investigators at Mayo Clinic reported that each 1-cm increment in kidney size (i.e., largest measured dimension) was associated with an 18% increased risk of RCC-related death, even after adjusting for well-known prognostic variables such as tumor size, nuclear grade, and the presence of necrosis, according to a report in Urology (2012;80:147-150).

In addition, after multivariable adjustment, pT1 RCC patients with a kidney size of 12 cm or greater had a significant 95% increased risk of death from RCC compared with those patients with a kidney size less than 12 cm, the researchers, led by Alexander S. Parker, PhD, of Mayo Clinic Florida in Jacksonville, found.

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Given that deaths among patients with pT1 RCC are uncommon, the authors used a case-cohort design to compare 144 pT1 RCC patients who were alive or died from other causes (mean follow-up 12.2 years) to 47 similar patients who died from RCC (mean follow-up of 6.3 years).

Based on data from prostate cancer research showing that a larger prostate volume is associated with a lower risk of biochemical recurrence, the researchers had hypothesized that a larger kidney size might offer better survival for patients with pT1 RCC. Their results showed the opposite, however. “One explanation could be that those patients with larger kidneys also have larger tumors, and it is well accepted that a larger tumor size is a strong predictor of a poor outcome,” they wrote.  The authors underscored, however, that the fact that the association remains after adjustment for tumor size casts some doubt on this potential explanation.

With respect to study limitations, Dr. Parker’s group pointed out they their study population consisted only of patients with pT1 organ-confined clear-cell RCC. Consequently, they did not have information on whether kidney size has a similar association with an increased risk of RCC death among patients with larger tumors or other RCC subtypes. In addition, all study patients underwent radical nephrectomy, so they could not draw conclusions about the effects of kidney size on survival among those undergoing partial nephrectomy.