Leuprolide therapy for prostate cancer. An association with scintigraphic "flare" on bone scan.

The scintigraphic "flare" phenomenon on bone imaging refers to an increase in intensity of tracer uptake in sites of bone metastases and/or the appearance of "new" lesions, which occur shortly after commencement of hormonal therapy or chemotherapy for breast, prostate, or lung cancer. In this study, we observed that scintigraphic flare can occur in patients with prostate cancer following treatment with the "hormone-like" luteinizing hormone releasing hormone analog, leuprolide acetate. Twenty-six patients with prostate cancer being treated with leuprolide acetate underwent serial bone scans at three-month intervals. Five (19.2%) of the 26 patients had findings consistent with a scintigraphic flare on bone scans obtained between three and six months after initiation of therapy. These scan findings should not be confused with progression of skeletal metastases.