Clinical Efficacy and Safety Comparison of 177Lu-EDTMP with 153Sm-EDTMP on an Equidose Basis in Patients with Painful Skeletal Metastases.

Unlabelled: This prospective study compared 177Lu-ethylene diamine tetramethylene phosphonate (EDTMP) with 153Sm-EDTMP for painful skeletal metastases.

Methods: Half of the 32 patients were treated with 177Lu-EDTMP and half with 153Sm-EDTMP, at 37 MBq/kg of body weight. Analgesic, pain, and quality-of-life scores (EORTC, Karnofsky, ECOG) and bone proliferation marker were used to examine efficacy. Hematologic toxicity was evaluated using NCI-CTCAE and compared between groups at baseline and each month till 3 mo after therapy. Pain relief was categorized as complete, partial, minimal, or none.

Results: Pain relief with 177Lu-EDTMP was 80%: 50% complete, 41.67% partial, and 8.33% minimal. Pain relief with 153Sm-EDTMP was 75%: 33.33% complete, 58.33% partial, and 8.33% minimal. The difference was not significant (P=1.000). Quality of life at 3 mo after therapy improved significantly in both groups as per ECOG score (P=0.014 and 0.005 for 177Lu-EDTMP and 153Sm-EDTMP, respectively), Karnofsky index (P=0.007 and 0.023 for 177Lu-EDTMP and 153Sm-EDTMP, respectively), and EORTC score (P=0.004 and <0.001 for 177Lu-EDTMP and 153Sm-EDTMP, respectively). Bone proliferation marker in responders of both groups dropped significantly (P=0.008 for 177Lu-EDTMP and P=0.019 for 153Sm-EDTMP), parallel to clinical response. For 177Lu-EDTMP, anemia, leukopenia, and thrombocytopenia were nonserious (grade I/II) in 46.67%, 46.67%, and 20%, respectively, and serious (grade III/IV) in 20%, 6.67%, and 0%, respectively. For 153Sm-EDTMP, anemia, leukopenia, and thrombocytopenia were nonserious (grade I/II) in 62.5%, 31.25%, and 18.75%, respectively, and serious (grade III/IV) in 18.75%, 0%, and 6.25%, respectively. One patient treated with 153Sm-EDTMP had grade IV thrombocytopenia but required no blood transfusion. Differences between groups were not significant for either nonserious or serious toxicity. For 177Lu-EDTMP, 3 of 12 responders experienced the flare phenomenon on the third day after therapy and one on the fifth day, showing no response to therapy. For 153Sm-EDTMP, 2 of 12 responders experienced the flare phenomenon, both on the third day after therapy.

Conclusion: 177Lu-EDTMP has pain response efficacy similar to that of 153Sm-EDTMP and is a feasible and safe alternative, especially in centers with no nearby access to 153Sm-EDTMP.