The dual-isotope ProstaScint imaging procedure - Clinical experience and staging results in 145 patients

Purpose: Whole-body, regional planar, and SPECT imaging using the In-111-la beled monoclonal antibody capromab pendetide (In-111 MAb; ProstaScint) has been shown to increase the detection of early disease spread in patients wi th prostate cancer. However, recognition of metastatic tumor sites can be d ifficult, especially if the involved nodes are near blood vessels. We have developed an alternate approach to the identification of metastatic sites t hat is based on a single simultaneous In-111 MAb and Tc-99m RBC SPECT acqui sition of the pelvis and abdomen on day 5 after injection. We have also dev eloped software that dynamically subtracts the Tc-99m RBC data set (vascula r component) from the In-111 MAb data set (prostate and lymph node componen t), which allows for easier identification of metastatic sites. Methods: We evaluated the effectiveness of Prosta Scint for staging 145 pat ients with prostate cancer, 19 newly diagnosed and 126 with recurrence, usi ng these two modifications. Results: With clinical follow-up in 13 of 19 (68%) patients with primary di sease, 10 of 13 (78%) had organ-confined disease. With follow-up in 64 of 1 26 (51%) patients with possible recurrent disease, 49 of 64 (77%) were foun d to have prostatic fossa activity only. Disease stage was deemed more adva nced in 3 of 13 (22%) patients with primary cancer and in 13 of 64 (20%) of those with recurrent disease based on ProstaScint findings when all other imaging tests were inconclusive. Six patients with recurrent disease had ne gative results of their scans. In the 16 patients with more advanced diseas e, 3 of 59 lesions (5%) were documented as false positive, and there were n o reported cases of false-negative findings. Conclusions: Using both the dual-isotope procedure and the subtraction anal ysis software with the Prosta Scint examination provides additional informa tion for staging primary and possibly recurrent prostate cancer compared wi th standard imaging techniques.