Spontaneous Regression of Renal Cell Carcinoma and the Role of Prognostic Factors

Spontaneous regression of metastatic renal cancer occurs in 4% to 6% of patients eligible for cytokine trials, in which response rates of 12% to 18% are reported. An increasingly recognized characteristic of trials in renal cell cancer was that response rates initially reported were often double those noted in later reports. Because of this, it was necessary to exclude the possibility that some of the responses reported for biologic treatment simply reflected episodes of spontaneous regression. This chapter reviews the long-term outcome of these cases, reviews the literature of reported cases, addresses the question of how much the reported response to modern therapies could be due to these spontaneous events, and considers how modern data from prognostic factor analysis may identify patients with a higher likelihood of spontaneous regression.