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.

Genitourinary (Prostate) Cancer
Session Type and Session Title: 
Poster Discussion Session, Genitourinary (Prostate) Cancer
Abstract Number: 
J Clin Oncol 31, 2013 (suppl; abstr 5026)
Howard I. Scher, Matthew R. Smith, Christopher Sweeney, Paul Gettys Corn, Christopher Logothetis, Nicholas J. Vogelzang, David C. Smith, Maha Hussain, Daniel J. George, Johann Sebastian De Bono, Celestia S. Higano, Eric Jay Small, Jonathan Goldin, Matthew S. Brown, Dana T. Aftab, Mojtaba Noursalehi, Aaron Weitzman, Ethan M. Basch; Memorial Sloan-Kettering Cancer Center, New York, NY; Massachusetts General Hospital Cancer Center, Boston, MA; Dana-Farber Cancer Institute, Boston, MA; The University of Texas MD Anderson Cancer Center, Houston, TX; Comprehensive Cancer Centers of Nevada, The US Oncology Network, Las Vegas, NV; University of Michigan Comprehensive Cancer Center, Ann Arbor, MI; Duke Cancer Institute, Durham, NC; The Institute of Cancer Research, The Royal Marsden NHS Foundation Trust, Sutton, United Kingdom; Fred Hutchinson Cancer Research Center, Seattle, WA; University of California, San Francisco, San Francisco, CA; University of California, Los Angeles, Los Angeles, CA; Center for Computer Vision and Imaging Biomarkers, University of California, Los Angeles, CA; Exelixis, Inc, South San Francisco, CA

Abstracts that were granted an exception in accordance with ASCO's Conflict of Interest Policy are designated with a caret symbol (^).

Abstract Disclosures


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.

Baseline characteristics, N=144.
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
Response categories
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