O'Connell, M J

4010 Background: Prior studies suggested that older and younger pts with colon cancer receive similar benefit from IV fluoropyrimidine (FU) adjuvant (adj) therapy (rx). Combination and/or oral FU rx are increasingly given as adj rx. We sought to determine the impact of pts age <70 v ≥70 yrs on colon cancer recurrence and mortality from adj rx with these newer options. Methods: We used data from 10,499 pts <70 yrs and 2,170 pts ≥70 yrs in 6 phase III adj rx trials comparing IV FU to combinations with irinotecan, oxaliplatin or oral FU (capecitabine and UFT/LV) in stage II/III colon cancer from the ACCENT database. Endpoints were overall survival (OS; time to death), disease-free survival (DFS; time to recurrence or death), and time to recurrence (TTR; censoring at last follow-up). Cox models were stratified by age and adjusted for gender and stage; interaction testing was used to explore the differential benefit by age. Results: Approximately 75% of pts had stage III disease (74% age<70, 77% age≥70). OS, DFS, and TTR were statistically significantly improved for those in the experimental v control arms among pts <70 but not those >70 ( table ); the interaction between age and rx was statistically significant for all endpoints (p=0.01 for OS, DFS, and TTR). These results were consistent whether experimental rx was oxaliplatin-based, irinotecan-based or oral FU. Deaths in first 6 month of adj rx were not statistically significantly different between experimental and control arm. Conclusions: Our results show conclusively that pts >70 do not receive the same benefit from combination and/or oral FU as those <70. Any benefit, if present, compared to IV FU/LV would not be clinically meaningful. Outcomes of experimental (combination or oral FU) vs control (IV 5-FU) by treatment and age [Table: see text] [Table: see text]

20023 Background: EGFR is a transmembrane receptor tyrosine kinase belonging to the ErbB family of proteins. Anti-EGFR antibodies have shown efficacy as monotherapy and can enhance cytotoxic chemotherapy in patients with advanced colorectal cancers. We studied EGFR expression in primary colon cancers and its association with, microsatellite instability (MSI), clinicopathological variables and patient survival rates. Methods: Archival colon carcinomas were studied from patients with high risk Dukes’ stage B2 (n = 78) and C (n = 230) patients enrolled in a prior adjuvant trial of 5-fluorouracil, leucovorin plus standard dose or high-dose levamisole (NCCTG 91–46–53). EGFR expression (anti-EGFR H11 antibody, DAKO) was analyzed by immunohistochemistry (IHC) and intensity (0–3+), extent and their product (weighted score) were determined. MSI was analyzed using BAT26 and expression of hMLH1, hMSH2 and hMSH6 proteins by IHC. Patients were censored at 5 years after randomization for DFS and censored at 8 years post study randomization for overall survival (OS) data. Results: EGFR protein expression was detected in 216 of 308 (70%) of Dukes’ B2 and C primary colon carcinomas from patients and localized to the plasma membrane. EGFR expression variables (intensity, extent, weighted score) were increased in poor/undifferentiated compared to moderate/well differentiated tumors (p ≤ 0.036). Similar EGFR expression levels were found in MSI-H (n = 27) versus MSS (n = 203) colon cancers and for other clinicopathological variables. EGFR intensity was more likely moderate (2+) or strong (3+) in Dukes’ C versus B2 tumors (p = 0.088). In addition, higher EGFR intensity (2+, 3+) showed a trend toward worse disease-free survival (5 yr DFS %: 62.2 vs. 71.7; p = 0.095), but not overall survival (p = 0.14). Conclusions: EGFR overexpression is associated with increased tumor aggressiveness as indicated by poor tumor cell differentiation and reduced DFS in colon cancer patients receiving adjuvant 5-FU and levamisole. These findings indicate that EGFR may be an important therapeutic target in the adjuvant setting. [Table: see text]

10529 Background: BAX mutations are associated with defective DNA mismatch repair (MMR) in human colon cancers. However, the impact of BAX inactivation upon tumor cell apoptosis and proliferation in vivo remain unknown. We analyzed and compared caspase-3 and Ki-67 expression in tumors with and without BAX mutations. Methods: TNM stage II and III (n= 377) colon carcinomas were studied from participants in a 5-FU-based adjuvant therapy trial. Archival tumors were analyzed for instability at the BAT26 mononucleotide locus using polymerase chain reaction and hMLH1, hMSH2 and hMSH6 by immunohistochemistry (IHC). Frameshift mutations in a tract of eight deoxyguanosines within BAX were analyzed. Expression of caspase-3 and Ki-67 proteins were analyzed by IHC. Results: Thirty-nine of 377 (10%) tumors showed defective MMR defined as instability at BAT26 and loss of either hMLH1, hMSH2 and/or hMSH6 proteins. BAX mutations were found in 20 of 37 (54%) MMR deficient tumors and in 1 of 50 (2%) tumors with intact MMR. Mean and median number of caspase-3-positive cells were increased in tumors with defective MMR (p= 0.04), but did not differ based upon BAX status [ Table ]. However, tumors with BAX mutations showed higher Ki-67 labeling indices compared to those with wild type BAX (p= 0.01)[ Table ]. Neither BAX mutations nor caspase-3- positive cells were prognostic in a univariate analysis. Tumors with lower Ki-67 extent had improved overall survival (p=0.06), but not DFS (p=0.24). Defective MMR (vs intact) was associated with better DFS in a multivariate analysis (p= 0.03). Conclusion: MMR deficient colon cancers show frequent BAX inactivation, yet have increased apoptotic rates as indicated by increased caspase-3 expressing tumor cells. BAX mutation was associated with hyperproliferation suggesting a growth advantage compared to wild type tumors. [Table: see text] No significant financial relationships to disclose.

4017 Background: Published reports suggest that CC pts of A descent have inferior survival compared to W pts. Whether these differences are explained by clinical factors at diagnosis, socioeconomic factors impacting access to care, or intrinsic differences in the biology of the tumors or the response to therapy is unclear. Pts in clinical trials have data collected for important baseline clinical factors and should receive comparable oncologic care regardless of socioeconomic factors. Methods: We analyzed data from 13,435 individual pts on 11 phase III adjuvant CC trials accrued from 1977 to 2002. Analysis was restricted to stage II and III pts, with race reported as black or white. Endpoints were overall survival (OS - time to death), recurrence-free survival (RFS - time to recurrence or death), and recurrence-free interval (RFI - time to recurrence censoring for death). Cox models stratified by study controlled for gender, stage, age, and treatment type (rx) to determine the effect of race. Kaplan-Meier estimates (KM) were adjusted (adj) by the Xie-Liu method for study, gender, stage, age, and rx. Results: A pts (n=1134, 8.4%) were younger than W (median 58 vs 61, p<0.001) and more likely female (55 vs 45%, p<0.001). A pts had poorer OS than W pts ( table ). OS results were consistent in subsets defined by gender, stage, and age. RFS results were attenuated compared to OS, but still favored improved RFS in W pts ( table ). RFI results were further attenuated and not significantly different by race ( table ). Conclusions: Even with identical rx for CC in controlled clinical trials, A pts have poorer OS and RFS than W pts. The OS deficit was consistent across subgroups, and neither deficit was explained by differences in gender, stage, age, or rx. RFI was similar for both races, suggesting that the OS and RFS differences may be largely due to deaths unrelated to CC. [Table: see text] [Table: see text]