Dynamic quantitative bone scintigraphy in patients with prostatic carcinoma treated by orchiectomy.

Dynamic quantitative bone scintigraphy was performed on 31 men with prostatic carcinoma before orchiectomy as well as 2 weeks, 2 and 6 months postoperatively. After injection of technetium methylene diphosphonate Tc 99m (99mTc-MDP) the count rate was recorded as serial images over the lower thoracic and all the lumbar vertebrae from 1 to 240 min post-injection. Thirteen men had normal bone scintigrams with no changes in 99mTc-MDP content at the four different investigation times. Eighteen men had skeletal metastases. Throughout the study half of the abnormal vertebrae in these patients showed an abnormal count rate after only 6 min post-injection. After 1 h it was possible in almost all abnormal vertebrae to predict abnormal bone uptake. In response to therapy a "flare phenomenon" with an increase in count rate was seen 2 weeks after orchiectomy followed by a decrease 2 months postoperatively in most of the abnormal vertebrae. The count rate decreased even below the pre-operative level after 6 months. Also, the normal vertebrae in the patients with skeletal metastases showed a tendency towards the flare phenomenon, which was not seen in patients with normal bone scintigrams.