Serum immunosuppressive acidic protein doubling time as a prognostic factor for recurrent renal cell carcinoma after nephrectomy

Objectives. To identify the prognostic factors in patients with recurrent renal cell carcinoma after nephrectomy, various factors were assessed, with special attention to serum immunosuppressive acidic protein (IAP) and its doubling time. Methods. Age, sex, stage, grade, histopathologic type, primary tumor size, site and number of metastatic organs, time to recurrence, IAP levels before nephrectomy and at the diagnosis of recurrence, and IAP doubling time just before recurrence were analyzed in 125 patients with recurrent renal cell carcinoma after nephrectomy. Results. Univariate analysis identified stage, grade, histopathologic type, primary tumor size, time to recurrence, IAP level at the diagnosis of recurrence, and IAP doubling time as significant prognostic factors. After exclusion of confounding factors, multivariate analysis showed that IAP doubling time was the most potent independent prognostic factor. Patient survival rates dichotomized according to IAP doubling time were compared at 100-day intervals from 100 to 700 days and 1000 and 2000 days. The maximal difference in survival rate was found when the cutoff level in the IAP doubling time was set at 200 days. Conclusions. The results of our study have shown that the IAP doubling time is a potent prognostic factor in patients with recurrent renal cell carcinoma. Periodic checkups with serum IAP level monitoring are recommended to predict prognosis after recurrence.