Predictive value of serum immunosuppressive acidic protein for staging renal cell carcinoma: comparison with other tumour markers.

Abstract

To examine the usefulness of serum immuno-suppressive acidic protein (IAP) as a predictor for staging renal cell carcinoma (RCC), using receiver-operator characteristic (ROC) analysis, and to compare IAP with other tumour markers. From September 1983 to December 1995, serum IAP was measured in 133 untreated patients with RCC (mean age 60.1 years, SD 11.4. range 31-84). The erythrocyte sedimentation rate (ESR), the levels of fibrinogen, C-reactive protein (CRP), and alpha 2-globulin were also measured. To compare these markers as predictors of local involvement of the renal capsule, lymph node and distant metastasis, the area under the corresponding ROC curve was calculated. Tumour size at the time of resection was added in this analysis for comparison with the levels of these tumour markers. The final pathological stage was T1 or T2 in 101 patients and T3 or T4 in 32, while it was N0 in 122 patients, N1-3 in seven, M0 in 114 patients and M1 in 19. The area of the ROC curve for tumour size was greatest (0.843) for staging of the local extent (T1/T2 versus T3/T4) and that for IAP was 0.714, similar to the values for fibrinogen, ESR and CRP. For predicting lymph node metastasis, IAP and fibrinogen were the most important (0.864). However, IAP alone (0.894) was the most important predictor of distant metastasis. Using an IAP threshold of 600 micrograms/mL gave a high sensitivity and specificity for detecting lymph node and distant metastasis. IAP is a valuable predictor of lymph node and distant metastasis in patients with RCC, although it is inferior to tumour size in predicting local involvement of the renal capsule. The appropriate threshold value of IAP for detecting lymph node and distant metastasis is 600 micrograms/mL.