SERUM FERRITIN AS A CLINICAL MARKER FOR RENAL-CELL CARCINOMA - INFLUENCE OF TUMOR VOLUME

Objectives. At present, 35% to 50% of patients with clinically localiz ed renal cell carcinoma (RCC) unpredictably have a recurrence after su rgical therapy. Presently, no clinical serum marker exists to detect o ccult metastases and to allow measurement of response to therapy in RC C. Serum ferritin was previously reported to correlate with pathologic stage. We postulated that this increase in serum ferritin with increa sing stage might reflect tumor volume, since higher stage tumors are o ften larger. Methods. Serum ferritin levels were measured preoperative ly in 30 patients with radiologic evidence of RCC. Tumor Volume and th e largest tumor dimension were calculated from either the pathologic s pecimen (n = 24) or from the computed tomography or magnetic resonance imaging (n = 30). Pathologic stage was determined for all patients un dergoing surgery (T1 = 3, T2 = 12, and T3 = 9). Results. Preoperative serum ferritin levels did not correlate with age, blood urea nitrogen levels, creatinine levels, hematocrit, race, or gender. Although mean serum ferritin levels increased with increasing stage (T1 = 113 +/- 75 , T2 = 254 +/- 270, and T3 = 425 +/- 257 ng/mL), these differences did not reach statistical significance (P > 0.05). Serum ferritin did, ho wever, correlate with tumor volume (R = 0.75; P < 0.0001) and the larg est tumor dimension measured from radiographic studies (R = 0.8; P < 0 .0001). Serum ferritin measured intraoperatively from the renal vein ( 666 ng/mL) and the inferior vena cava (564 ng/ml) from a patient with a 500 cc tumor (preoperative serum ferritin, 552 ng/ml) suggested that the tumor was the source of the elevated ferritin levels, Histologic sections from tumors taken from patients with high serum ferritin leve ls were more necrotic and stained intensely positively for iron and im munohistochemically for ferritin, whereas adjacent histologically norm al tissue did not. Conclusions, These data suggest that ferritin may b e a useful serum marker for monitoring patients with RCC, but the actu al source of the ferritin remains unclear and dictates further investi gation.