TREATMENT OF METASTATIC BONE PAIN WITH TIN-117M STANNIC DIETHYLENETRIAMINEPENTAACETIC ACID - A PHASE I II CLINICAL-STUDY/

The physical characteristics of Sn-117m combined with the biodistribut ion of the compound tin-117m (Stannic, 4+) diethylenetriaminepentaacet ic acid (Sn-117m DTPA) suggest that it should be an excellent agent fo r the palliation of pain from bony metastases. Prior work has establis hed the dosimetry and the safety for the material in human beings, The presence of low-energy conversion electrons should result in the rela tive sparing of the bone marrow while delivering a high radiation dose to sites of bony metastatic disease, Forty-seven patients with painfu l bone metastases from various malignancies were treated with Sn-117m DTPA. The patients were assigned to five different dose levels ranging from 2.64 to 10.58 MBq (71-286 mu Ci) per kg of body weight, Follow-u p included. review of pain diaries, performance scores, analgesic requ irements, blood chemistries, and hematological assessment, Three patie nts received a second treatment, There was an overall response rate fo r relief of pain of 75% (range, 60-83%) in the 40 treatments that coul d be evaluated, No correlation was apparent in this limited series bet ween response rate and the five dose levels used, The relief was compl ete in 12 patients (30%), The time to onset of pain relief was 19 +/- 15 days with doses less than or equal to 5.29 MBq/kg and 5 +/- 3 days with doses greater than or equal to 6.61 MBq/kg, Myelotoxicity was min imal, with only one patient having a marginal grade 3 WBC toxicity. On the basis of our data, Sn-117m DTPA should be an effective and safe r adiopharmaceutical for palliation of painful bony metastases, A large- scale trial is warranted to evaluate it in comparison to other similar agents.