Time to RCC recurrence prognostic threshold challenged

By Eleanor McDermid, Senior medwireNews Reporter

A large study confirms the prognostic value of time to recurrence after surgery for renal cell carcinoma (RCC), and also suggests the need to reduce the threshold for early recurrence.

Most studies have taken 5 years as the cutoff separating early and late recurrence, say Sabine Brookman-May (Ludwig-Maximilians-University Munich, Germany) and colleagues.

But 2 years was a more informative threshold in the researchers’ study of 13,107 patients who underwent surgery for RCC. They report that “up to this time prognosis of patients was reduced with every day that recurrence occurred earlier, but not beyond a threshold of 48 months.”

They add: “Vice versa, the prognosis of patients with recurrent disease is improved with every day a patient stays disease-free after surgery up to 4 years from surgery, but not beyond this time.”

There were 1712 recurrences, of which 1402 happened within 5 years after surgery, with just 310 occurring later. In a multivariate model including other prognostic factors, the risk for cancer-specific mortality was reduced by a significant 21% if recurrence happened after versus within a threshold of 12 months, by 16% after a threshold of 24 months, and by 17% after a threshold of 48 months.

Risk differences around later thresholds were nonsignificant, the researchers report in BJU International.

Time to recurrence was also prognostic as a continuous variable, with each month increase associated with a significant 1% reduction in cancer-specific mortality risk. However, incorporating this into a predictive model increased its accuracy by just 0.5% (from 61.7 to 62.2%). By contrast, incorporating time to recurrence with two thresholds at 12 and 60 months improved the baseline accuracy by 3.7%, and including it with a single 12-month threshold resulted in a “robust” improvement of 5.5%.

The other variables in the model were being female and having clear-cell carcinoma, which reduced the risk for cancer-specific mortality; older age and pT stage, which increased the risk; and Fuhrman grade and the presence of positive nodes and lymphovascular invasion, which did not influence mortality in isolation.

Finally, the researchers note that the 12% recurrence rate in their study is markedly lower than previously reported rates of 20–40%, suggesting that RCC prognosis has improved over time.

“This might be based on improvements in surgical treatment or on increasing detection of tumours at earlier stages with less risk of recurrence after surgery,” they suggest.

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