Purpose: The development of tumor-specific markers to select targeted therapies and to assess clinical outcome remains a significant area of unmet need. We evaluated the association of baseline circulating tumor cell (CTC) number with clinical characteristics and survival in patients with castrate metastatic disease considered for different hormonal and cytotoxic therapies. Experimental Design: CTC were isolated by immunomagnetic capture from 7.5-mL samples of blood from 120 patients with progressive clinical castrate metastatic disease. We estimated the probability of survival over time by the Kaplan-Meier method. The concordance probability estimate was used to gauge the discriminatory strength of the informative prognostic factors. Results: Sixty-nine (57%) patients had five or more CTC whereas 30 (25%) had two cells or less. Higher CTC numbers were observed in patients with bone metastases relative to those with soft tissue disease and in patients who had received prior cytotoxic chemotherapy relative to those who had not. CTC counts were modestly correlated to measurements of tumor burden such as prostate-specific antigen and bone scan index, reflecting the percentage of boney skeleton involved with tumor. Baseline CTC number was strongly associated with survival, without a threshold effect, which increased further when baseline prostate-specific antigen and albumin were included. Conclusions: Baseline CTC was predictive of survival, with no threshold effect. The shedding of cells into the circulation represents an intrinsic property of the tumor, distinct from extent of disease, and provides unique information relative to prognosis.

Our finding that ALC at baseline and at 6 weeks on treatment is positively correlated with the OS provides an easily obtained predictive marker. Our result that the previous radiation is associated with higher ANC and lower ALC during treatment supports that the combination of radiation therapy with immunotherapy should be carefully applied and potentially peripheral blood counts can be utilized to stratify patients for this approach.

A B S T R A C T PurposeEarly 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 ( 153 Sm) lexidronam. Patients and MethodsMen 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/m 2 and 153 Sm 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 153 Sm-EDTMP was administered on day Ϫ1 to 1 of each cycle. Patients with acceptable hematologic toxicities were eligible to receive additional cycles until progression. ResultsTwenty-eight men were treated in six cohorts. Maximum-tolerated dose was not reached, because full doses of both agents were well tolerated, even using an every-6-week dosing schedule of 153 Sm-EDTMP. Patients received an average of 5.6 docetaxel doses (range, one to 13 doses) and 2.9153 Sm-EDTMP doses (range, one to six doses). Fifteen patients demonstrated a more than 50% decline in prostate-specific antigen. Treatment significantly reduced indices of bone deposition and resorption. Conclusion Docetaxel and153 Sm-EDTMP can be combined safely at full doses over repeated cycles. Responses were seen in the small group of patients with taxane-resistant disease tested. The optimal phase II doses for patients with taxane-naïve disease may differ from those optimal for patients with taxane-resistant disease.