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A simple technique for determining the whole body retention of 99mTc labeled methylene diphosphonate (MDP) at 4-h and 24-h was applied to 28 adult patients (22 prostate cancer, 6 osteoporosis). Following administration of 20 mCi (740 MBq) 99mTc-MDP, a qualitative scintigram was performed and whole body retention was recorded at 4 and 24 h. The prostate cancer patients all had positive bone scintigrams, and of this group, 7 were in relapse and 15 in remission on chemotherapy. The osteoporotic groups whole body retention values were determined prior to the initiation of drug therapy. Mean percent whole body retention values were significantly greater at 4 and 24 h for the cancer patients in relapse relative to both the prostate cancer patients in remission and the osteoporotics: 4-h%/24-h%; equals 74.3/60.2, 57.5/33.5, and 48.0/30.3, respectively. The whole body retention values of the latter two groups, however, were only significantly different at 4-h. An additional index of skeletal pathology was developed by combining the 4-h/24-h values to calculate the biological half time (t1/2b) for this time period using a single exponential model. Again the cancer patients in relapse exhibited a significantly longer half time relative to those in remission and the osteoporotics (70.4 vs 25.7 h and 29.2 h, respectively). The combination of 4 and 24-h whole body retention values with the associated t1/2b has potential for following and classifying patients during the course of their skeletal disease. These values have been shown to be especially valuable with cancer patients with metastatic disease.

The status of patients with skeletal metastases from prostatic carcinoma was determined from a quantitative uptake and retention measurement of the bone scanning radiopharmaceutical 99mtechnetium-methylene diphosphonate. Whole body counts were performed 5 minutes and 24 hours after intravenous administration of 99mtechnetium-methylene diphosphonate, and were expressed as the percentage uptake by the skeleton at 24 hours. Skeletal uptake determinations were done in 29 patients with prostatic cancer (17 with osseous metastases) who were evaluated at 3 to 6-month intervals. Group 1 consisted of patients who responded to therapy and achieved remission, group 2 included patients with relapse or progressive disease, group 3 consisted of those with metastases who were in remission for longer than 6 months and group 4 included those without evidence of any bony metastases. The baseline mean +/- standard deviation 24-hour skeletal uptake values were 46.1 +/- 12.0 per cent in group 1, 34.3 +/- 13.9 per cent in group 2, 27.0 +/- 5.9 per cent in group 3 and 28.9 +/- 5.5 per cent in group 4. At 3 to 6 months the values in group 1 (responders) decreased by 18 per cent, while those in group 2 (relapse or progression) increased by 19 per cent and those in group 3 (remission) increased by 1.5 per cent. The quantitative 24-hour skeletal uptake test was performed easily, reproducible and at least as useful as concurrent chemical blood tests and subjective bone scan interpretations.