Outcome prediction based on single nucleotide polymorphisms (SNPs) in DNA repair paths in patients (pts) with esophageal adenocarcinoma (EAC) treated with preoperative (preop) cisplatin (C)-based chemoradiation (CRT): Results from the Eastern Cooperative Oncology Group (ECOG)

Abstract

4530 Background: EAC has eluded cure even with platin-based CRT. Stratifying pts by likelihood of success is one approach to improving outcomes. We assessed whether SNPs in DNA repair paths are associated with complete pathologic response (pCR) in EAC pts who received C-based CRT followed by surgery. Methods: Patients and specimens: Pretreatment biopsy or post-CRT resection samples were obtained from pts (EAC, stage II-IVa) treated on a randomized phase II trial, E1201 (n=86), of preop CRT (RT to 45 Gy). Arm A: Preop C 30 mg/m2 + irinotecan (I) 50 mg/m2 days (d) 1, 8, 22, 29 with RT. Post-op C 30 mg/m2 + I 65 mg/m2 d 1, 8 q21 days x 3. Arm B: Preop C 30 mg/m2 + paclitaxel (P) 50 mg/m2 d 1, 8, 15, 22, 29 with RT. Post-op C 75 mg/m2 + P 175 mg/m2 d 1 q21 days x 3. Clinical outcome - pCR: (A) 14% [95% CI 5.5%, 28.5%]; (B) 16% [95% CI 6.7%, 30.1%]. Median overall survival (OS): (A) 34.9 m (months) [90% CI 23.5, not reached]; (B) 20.9 m [90% CI 17.4, 46.7]. Experimental procedure: Normal tissue was microdissected from unstained sections of paraffin-embedded tissue. DNA was extracted (Qiagen). Genotyping was performed by matrix-assisted laser desorption/ionization time-of-flight (Sequenom) for all SNPs. Each SNP was dichotomized a priori into: (1) major homozygote vs (2) minor (heterozygote plus minor homozygote) allele groups. Data analysis was performed centrally, with lab investigators blinded to clinical data. Exact logistic regression was used to derive ORs for non-pCR, using the major homozygote as the reference (2-sided p values). Results: Germline DNA was available in 68 pts; 60 were eligible and began therapy ( Table ). Conclusions: In this homogenous, well-defined cohort, the XRCC1 Arg399Gln minor allele group was associated with lower pCR (p=0.06). Lab data on a panel of additional SNPs have been collected and are under analysis for presentation at the meeting. [Table: see text] [Table: see text]