Phase I Study of Samarium-153 Lexidronam With Docetaxel in Castration-Resistant Metastatic Prostate Cancer

Purpose Early studies of patients with castration-resistant metastatic prostate cancer (CRMPC) suggest that chemotherapy administered with a dose of a bone-seeking radiopharmaceutical is superior to chemotherapy alone. To build on this strategy and fully integrate a repetitively dosed bone-seeking radiopharmaceutical into a contemporary chemotherapy regimen, we conducted a phase I study of docetaxel and samarium-153 (153Sm) lexidronam. Patients and Methods Men with progressive CRMPC were eligible. Cohorts of three to six patients were defined by dose escalations as follows: docetaxel 65, 70, 75, 75, 75 mg/m2 and 153Sm ethylenediaminetetramethylenephosphonate (EDTMP) 0.5, 0.5, 0.5, 0.75, 1 mCi/kg. Each cycle lasted a minimum of 6 (cohorts 1 through 5) or 9 (cohort 6) weeks. Docetaxel was administered on days 1 and 22 (and day 43 for cohort 6), and 153Sm-EDTMP was administered on day −1 to 1 of each cycle. Patients with acceptable hematologic toxicities were eligible to receive additional cycles until progr...