Abstract: AIM: To comparatively analyze the pain related factors levels and therapeutic response in patients treated with⁹⁹Tc-MDPand¹⁵³Sm-EDTMPfor painful skeletal metastases.METHODS: Plasma endothelin (ET), calcitonin gene-related peptide (CGRP), thromboxane B2 (TXB2) and 6-keto-prostaglandin F1α(6-k-PGF1α)levels were analyzed in 93 patients with painful skeletal metastases prior and 3 months after treatment.55 cases were just treated with¹⁵³Sm-EDTMP(grouPA);19 cases were treated only with⁹⁹Tc-MDP(grouPB);and 19 cases were treated with both¹⁵³Sm-EDTMPand⁹⁹Tc-MDP(grouPC).RESULTS: 69.1%, 73.7% and 89.5% of the patients were experienced pain relief 3 months after treatment in groups A , B and C , respectively.Comparative analysis shows that:ET and 6-k-PGF1αlevels increased significantly 3 months after treatment in all patients (P<0.01);CGRPlevels decreased significantly 3 months after treatment (P<0.05)in patients of groups B and C.No significant changes of CGRPand TXB2 levels were observed prior and after treatment in grouPA , nor do TXB2 levels in patients of groups B and C.CONCLUSION: Combined treatment with⁹⁹Tc-MDPand¹⁵³Sm-EDTMPwere found more efficient in patients with skeletal metastases than just treatment with¹⁵³Sm-EDTMP.The therapeutic response of⁹⁹Tc-MDPand¹⁵³Sm-EDTMPfor painful skeletal metastases may be closely related to the alteration of plasma ET , 6-k-PGF1αand CGRPlevels.

Key words: ⁹⁹Tc-MDP, ¹⁵³Sm-EDTMP, skeletal metastases, ET, CGRP, TXB₂, 6-k-PGF_1α