The use of CA-50 radioimmunoassay test in diagnosis of urologic malignancy. Tie for second place Jobst award.

Circulating levels of the oncofetal antigen, CA-50, have been used to differentiate benign and malignant disease of the prostate, bladder, and kidney, taking 17 units/ml as the upper limit of normal. All 60 normal subjects and 59 of 61 (97%) patients with benign prostatic hypertrophy had levels below 17 units/ml. The test was positive in 29 of 68 (43%) patients with prostatic carcinoma, including 24 of 34 (75%) with metastases, but only five of 34 (15%) patients without metastases (P less than 0.01). Positivity also correlated with histologic grade: 0 per cent with well-differentiated tumors (n = 8), 33 per cent with moderately differentiated (n = 11), and 66 per cent with poorly differentiated tumors (n = 27). All 14 patients with benign bladder disease had negative values, whereas 13 of 21 (62%) patients with bladder carcinoma had positive. Noninvasive tumors were less likely to give a positive value than invasive tumors (42 vs 89%; P less than 0.05). One of 11 (9%) patients with benign renal conditions was positive as opposed to seven of 15 (47%) patients with renal carcinoma. The overall sensitivity of the CA-50 test for urologic malignancy was 47 per cent and specificity was 97 per cent; moreover, serum levels correlated with stage and grade of disease.