Ferritin, carcinoembryonic antigen (CEA), beta 2-microglobulin (beta 2-MG) and prostatic acid phosphatase (PAP) levels in serum from 77 patients with cancer (6 with renal adenocarcinoma, 9 with renal pelvic and ureteral cancer, 29 with bladder cancer and 33 with prostatic cancer) at various stages