Abstract

<jats:p> 4062 </jats:p><jats:p> Background: CD133 has been routinely used to identify colon cancer stem cells. A recent study indicated that elevated levels of CD133 plasma mRNA correlated with colon cancer recurrence. Furthermore plasma levels of CD133+ progenitor cells have been found to be decreased after treatment with BV. We tested whether potentially functional frequently occurring germline variations in the 3’UTR-region of the CD133 gene (rs2240688, rs3130 and rs2286455), might be associated with clinical outcome in first- and second-line treated mCRC pts. Methods: Genomic DNA was extracted either from peripheral blood (79 pts, who were enrolled in a phase-II clinical trial with FOLFOX/BV or XELOX/BV) or formalin-fixed paraffin-embedded tumor samples (186 pts, who were enrolled in the EPIC phase III clinical trial, US-sites only) of mCRC pts. Pts received either first-line treatment with FOLFOX/ BV (33 pts) or XELOX/BV (46 pts) or second-line treatment with CB/IR (84 pts, arm A) or IR (102 pts, arm B) alone. Genotyping was performed using PCR-RFLP assays. Results: 79 pts (47 men, 32 women) received FOLFOX/BV or XELOX/BV. Radiologic response: 43 pts (54%) CR/PR, 35 pts (45%) SD/PD. Median PFS was 10.8 months (95%CI: 8.1–14.9). The second cohort consisted of 186 pts (103 men, 83 women). Radiologic response: Arm A 11 pts (13%) CR/PR, 73 pts (87%) SD/PD. Arm B 6 pts (6%) CR/PR, 96 pts (94%) SD/PD. Median PFS (arm A) was 3.0 months (95%CI: 2.4–4.1) vs. 2.7 months (arm B,95%CI: 2.2–2.9). Combined analysis of rs2286455 and rs3130 showed a significant association with PFS (p= 0.010, log-rank test) in pts receiving FOLFOX/BV or XELOX/BV. In pts receiving IR alone rs2240688 was significantly associated with OS (p=0.0128, log-rank test). Multivariate analysis showed a significant association with PFS in first-line setting for rs2286455 and rs3130 (adjusted p=0.012) and a trend in second-line setting for rs2240688 (adjusted p=0.086). Conclusions: These are the first data to show that polymorphisms in CD133 predict outcome in mCRC pts in first- and second- line setting, suggesting that CD133 may be a potential predictive marker. These results need to be confirmed in larger prospective studies. </jats:p><jats:p> [Table: see text] </jats:p>