Samarium-153-EDTMP bone uptake rate and its relation to therapeutic effect.

Objective: To evaluate the measurement of Samarium-153 ethylenediaminetetramethylene phosphonic acid ((153)Sm-EDTMP) bone uptake rate using whole-body scintigraphy and analyze the relationship between bone uptake rate and therapeutic effect.

Methods: Sixty-six patients with painful bony metastases from prostate (n = 15), lung (n = 20), breast (n= 18), nasopharyngeal carcinoma (NPC) (n=5), colon (n=2), kidney (n=2) and unknown cause (n=4) carcinoma were examined with whole-body scintigraphy 10 min and 5 h post administration of (153)Sm-EDTMP. Bone uptake rate was then calculated. (1 ) Complete response (CR): disappearance of > 2 metastases, Karnofsky Performance Score (KPS) increase > 20, moderate or complete remission of bone pain 7 d post injection of (153)Sm-EDTMP. (2) Partial response (PR): disappearance of 1-2 metastases, KPS increase 10-20, moderate remission of bone pain in 3 wk. (3) Non-response (NR): no disappearance or shrinkage of metastases, KPS increase < 10, no or slight remission of bone pain.

Results: The range of bone uptake rate in 66 patients was 31 .9% - 86.6% (mean = 56. 0%). The bone uptake rate in the CR group (17 cases, 25.7%), PR group (24 cases, 36.4%), and NR group (25 cases, 37.9%) was 52.4% - 86.6% (mean = 68.7%), 43.7% - 70.4% (mean = 58.3%), and 31.9%- 51 .5% (mean = 41 . 0%) respectively. Statistical analysis showed that there was a significant difference between the CR and PR groups ( t = 4.258, P = 0.001 ) as well as between PR and NR groups ( t = 8.48,P = 0.001 ).

Conclusions: Using a simple and reliable whole-body scintigraphic technique to calculate prospectively the bone uptake rate, we have, for the first time in China, reported the relationship between bone uptake rate and therapeutic effect. This allows nuclear medicine physicians to calculate a safe and effective dose of (153)Sm-EDTMPin individual patients to palliate bone cancer pain without myelotoxicity.