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An exploratory analysis of bone scan lesion area (BSLA), circulating tumor cell (CTC) change, pain reduction, and overall survival (OS) in patients (pts) with castration-resistant prostate cancer (CRPC) treated with cabozantinib (cabo): Updated results of a phase II nonrandomized expansion (NRE) cohort.
J Clin Oncol 31, 2013 (suppl; abstr 5026)
Abstracts that were granted an exception in accordance with ASCO's Conflict of Interest Policy are designated with a caret symbol (^).
Background: The results of 144 pts with metastatic CRPC treated in a phase II NRE cohort with daily cabo 100 mg and 40 mg starting doses have been previously reported. Substantial rates of bone scan improvement, reductions in CTC counts and pain relief were observed. To better understand the implication of these effects, the association with OS was explored. Methods: Relevant baseline variables (LDH, BSLA, visceral disease, pain, hemoglobin, CTCs) and post-treatment changes at week 6: ≥30% reduction in BSLA using computer-aided assessment, CTC conversion (>5 vs. 4 or less/7.5 ml of blood), and pain intensity (7 day averaged worst pain score; BPI scale; using an IVR system) were associated with OS in 144 CRPC pts with bone metastasis who progressed within 6 months of docetaxel (D) treatment (≥225 mg/m2) in either bone or soft tissue. Median OS was compared between responders and non-responders for each of the above outcomes categories using a Cox proportional hazard model. The findings were examined further after adjusting for significant baseline covariates selected from a stepwise Cox regression model. Results: See Table. Conclusions: Recognizing the limitations of associating response with survival, this retrospective analysis of decreases in BSLA, CTC conversions and reductions in pain intensity support further study in ongoing phase III trials. Clinical trial information: NCT00940225.
|Median age||66||Sites of disease, %|
|Prior therapies, %||Bone||100|
|≥2 prior lines therapy including docetaxel||73||Visceral||31|
|Cabazitaxel||24||Moderate to severe pain (BPI≥4), %||47|
|Abiraterone||43||Median CTC count||37|
|Progression <1 mo from last taxane dose, %||36||CTC count ≥5, %||80|
|Median overall survival, mos||10.8 (CI, 9.1-13.0)|
|Univariate analysis||Analysis adjusted for covariates|
||HR (95% CI)||P||HR (95% CI)||P|
|Bone scan response||0.62 (0.38-1.00)||0.054||0.47 (0.28-0.79)||0.005|
|CTC conversion||0.40 (0.21-0.78)||0.007||0.42 (0.19-0.92)||0.031|
|Pain||0.65 (0.34-1.24)||0.186||0.51 (0.24-1.11)||0.090|
Abstracts by H. I. Scher:
A first-in-human, open-label, phase I/II safety, pharmacokinetic, and proof-of-concept study of ARN-509 in patients with progressive advanced castration-resistant prostate cancer (CRPC).Category: Genitourinary Cancer - Prostate Cancer
A phase I dose-escalation trial of vaccine replicon particles (VRP) expressing prostate-specific membrane antigen (PSMA) in patients (pts) with castration-resistant prostate cancer (CRPC): Final results.Category: Genitourinary Cancer - Prostate Cancer