Immunoscintigraphic evaluation of lymph node involvement in prostatic carcinoma.

Five patients who were candidates for radical prostatectomy were investigated. One milligram of diethylene triamine pentaacetic acid derivatives of purified F(ab')2 fragments of monoclonal antibodies against prostatic acid phosphatase, labeled with 99mTc, were bilaterally injected into the periprostatic space. The amount of radioactivity injected varied between 3 and 7 mCi. Imaging took place dynamically for the first hour following injection, then at 6 and 24 hr. In one patient, lymph node metastases were detected in the left paraaortic, iliac, and obturator lymph nodes by this technique. The lesions incorporating radioactivity were confirmed to be metastases of prostatic cancer following staging pelvic lymphadenectomy. Immunolabeling electron microscopy studies revealed internalized antibody in prostatic cancer cells. In the four other patients, radioimaging did not show any lymph node metastases, and this negative finding was confirmed at surgery. These early data indicate the possibility of preoperative staging of prostatic cancer using radiolabeled derivatives of monoclonal antibodies raised against prostatic acid phosphatase and injected into the periprostatic area.