Purpose: We compare the detection of metastatic disease by helical computerized tomography (CT), positron emission tomography (PET) with F-18 fluorodeoxyglucose and monoclonal antibody scan with 111indium capromab pendetide in patients with an elevated prostate specific antigen (PSA) after treatment for localized prostate cancer.
Materials and methods: A total of 45 patients with an elevated PSA (median 3.8 ng./ml.) were studied following definitive local therapy with radical prostatectomy in 33, radiation therapy in 9 and cryosurgery in 3. CT of the abdomen and pelvis, and whole body PET were performed in all patients, of whom 21 also underwent monoclonal antibody scan. Lymph nodes 1 cm. in diameter or greater on CT were considered abnormal and were sampled by fine needle aspiration in 12 patients.
Results: PET and CT were positive for distant disease in 50% of 22 patients with PSA greater than 4, and in 4 and 17%, respectively, of 23 with PSA less than 4 ng./ml. The detection rate for metastatic disease was similar for CT and PET, and higher overall than that for monoclonal antibody scan. Monoclonal antibody scan was true positive in only 1 of 6 patients, while PET was true positive in 6 of 9 with CT guided fine needle aspiration proved metastases.
Conclusions: CT and PET each detected evidence of metastatic disease in 50% of all patients with a high PSA or PSA velocity (greater than 4 ng./ml. or greater than 0.2 ng./ml. per month, respectively). Both techniques are limited for detecting metastatic disease in patients with a low PSA or PSA velocity. Our data suggest that monoclonal antibody scan has a lower detection rate than CT or PET.