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Purpose Accurate assessments of recurrence risk and absolute treatment benefit are needed to inform colon cancer adjuvant therapy. The 12-gene Recurrence Score assay has been validated in patients with stage II colon cancer from the Cancer and Leukemia Group B 9581 and Quick and Simple and Reliable (QUASAR) trials. We conducted an independent, prospectively designed clinical validation study of Recurrence Score, with prespecified end points and analysis plan, in archival specimens from patients with stage II and III colon cancer randomly assigned to fluorouracil (FU) or FU plus oxaliplatin in National Surgical Adjuvant Breast and Bowel Project C-07. Methods Recurrence Score was assessed in 892 fixed, paraffin-embedded tumor specimens (randomly selected 50% of patients with tissue). Data were analyzed by Cox regression adjusting for stage and treatment. Results Continuous Recurrence Score predicted recurrence (hazard ratio for a 25-unit increase in score, 1.96; 95% CI, 1.50 to 2.55; P < .001), as well as disease-free and overall survival (both P < .001). Recurrence Score predicted recurrence risk (P = .001) after adjustment for stage, mismatch repair, nodes examined, grade, and treatment. Recurrence Score did not have significant interaction with stage (P = .90) or age (P = .76). Relative benefit of oxaliplatin was similar across the range of Recurrence Score (interaction P = .48); accordingly, absolute benefit of oxaliplatin increased with higher scores, most notably in patients with stage II and IIIA/B disease. Conclusion The 12-gene Recurrence Score predicts recurrence risk in stage II and stage III colon cancer and provides additional information beyond conventional clinical and pathologic factors. Incorporating Recurrence Score into the clinical context may better inform adjuvant therapy decisions in stage III as well as stage II colon cancer.

Purpose A greater understanding of the biology of tumor recurrence should improve adjuvant treatment decision making. We conducted a validation study of the 12-gene recurrence score (RS), a quantitative assay integrating stromal response and cell cycle gene expression, in tumor specimens from patients enrolled onto Cancer and Leukemia Group B (CALGB) 9581. Patients and Methods CALGB 9581 randomly assigned 1,713 patients with stage II colon cancer to treatment with edrecolomab or observation and found no survival difference. The analysis reported here included all patients with available tissue and recurrence (n = 162) and a random (approximately 1:3) selection of nonrecurring patients. RS was assessed in 690 formalin-fixed paraffin-embedded tumor samples with quantitative reverse transcriptase polymerase chain reaction by using prespecified genes and a previously validated algorithm. Association of RS and recurrence was analyzed by weighted Cox proportional hazards regression. Results Continuous RS was significantly associated with risk of recurrence (P = .013) as was mismatch repair (MMR) gene deficiency (P = .044). In multivariate analyses, RS was the strongest predictor of recurrence (P = .004), independent of T stage, MMR, number of nodes examined, grade, and lymphovascular invasion. In T3 MMR-intact (MMR-I) patients, prespecified low and high RS groups had average 5-year recurrence risks of 13% (95% CI, 10% to 16%) and 21% (95% CI, 16% to 26%), respectively. Conclusion The 12-gene RS predicts recurrence in stage II colon cancer in CALGB 9581. This is consistent with the importance of stromal response and cell cycle gene expression in colon tumor recurrence. RS appears to be most discerning for patients with T3 MMR-I tumors, although markers such as grade and lymphovascular invasion did not add value in this subset of patients.

Purpose We developed quantitative gene expression assays to assess recurrence risk and benefits from chemotherapy in patients with stage II colon cancer. Patients and Methods We sought validation by using RNA extracted from fixed paraffin-embedded primary colon tumor blocks from 1,436 patients with stage II colon cancer in the QUASAR (Quick and Simple and Reliable) study of adjuvant fluoropyrimidine chemotherapy versus surgery alone. A recurrence score (RS) and a treatment score (TS) were calculated from gene expression levels of 13 cancer-related genes (n = 7 recurrence genes and n = 6 treatment benefit genes) and from five reference genes with prespecified algorithms. Cox proportional hazards regression models and log-rank methods were used to analyze the relationship between the RS and risk of recurrence in patients treated with surgery alone and between TS and benefits of chemotherapy. Results Risk of recurrence was significantly associated with RS (hazard ratio [HR] per interquartile range, 1.38; 95% CI, 1.11 to 1.74; P = .004). Recurrence risks at 3 years were 12%, 18%, and 22% for predefined low, intermediate, and high recurrence risk groups, respectively. T stage (HR, 1.94; P < .001) and mismatch repair (MMR) status (HR, 0.31; P < .001) were the strongest histopathologic prognostic factors. The continuous RS was associated with risk of recurrence (P = .006) beyond these and other covariates. There was no trend for increased benefit from chemotherapy at higher TS (P = .95). Conclusion The continuous 12-gene RS has been validated in a prospective study for assessment of recurrence risk in patients with stage II colon cancer after surgery and provides prognostic value that complements T stage and MMR. The TS was not predictive of chemotherapy benefit.

523 Background: The 12-gene colon cancer assay is the first commercially available molecular assay to predict the risk of recurrence in stage II/III colon and rectal cancer. Rigorous evidence for clinical validity and utility of an assay is imperative since the result is used for treatment decision-making. This summary outlines the studies that meet an established definition of clinical validation and additional studies that support the utility of the assay. Methods: Prospectively designed studies using archival tissue with pre-specified methods, clinical outcomes, and analysis plan were considered clinical validation studies (Simon et al. JNCI 2009). Additional studies that demonstrated the utility of the assay in a clinical setting were considered supportive. Results: The assay has been clinically validated in four independent studies with 3315 patients (2390 stage II/628 stage III colon and 130 stage II/167 stage III rectal). All four studies demonstrated a significant association (p

3512 Background: Standardized clinical tools which accurately quantify recurrence risk are needed for optimal adjuvant treatment of colon cancer. The 12-gene RS has been validated in stage II colon cancer pts from QUASAR and CALGB 9581. We conducted a large prospectively-designed clinical validation study of RS, w/ pre-specified endpoints, methods, and analysis plan, in stage II and III colon cancer pts randomized to FU or FU+Ox in NSABP C-07. Methods: 50% of C-07 pts w/ tissue were randomly selected, stratified on stage (AJCC 6th) and recurrence. Gene expression was quantitated by RT-PCR on 25 µm manually microdissected fixed colon tumor tissue. Data were analyzed by Cox regression controlling for stage and treatment (TRT). Results: RT-PCR was successful in 892/921 pts (97%): 449 FU, 443 FU + Ox; 264 st II, 409 st IIIA/B, 219 st IIIC. The primary endpoint was met: RS predicted recurrence (HR/25 units=1.96, 95% CI 1.50-2.55 p

3518 Background: The 12-gene RS (Genomic Health, Inc.) has been shown to predict risk of recurrence in stage II colon cancer (CC) pts in QUASAR. We conducted a validation study in tumor specimens f...

526 Background: High tumor grade is included in practice guidelines as a marker of higher recurrence risk in stage II colon cancer. Multiple systems for tumor grading exist, without a standardized approach. We characterize agreement of 2 methods for tumor grading and association with recurrence in the context of clinical, pathologic, and genomic tumor features including mismatch repair (MMR) and the 12-gene recurrence score (RS). Methods: Colon tumors were graded independently by 2 academic GI pathologists (P1, P2). Grade was defined by % tumor with gland-like structures: well (> 95%), moderately (50-95%) and poorly (< 50%) differentiated. P1 used this 3-tier system while P2 used 2-tier scheme with well and moderately differentiated tumors defined as low grade and poorly differentiated as high grade. All mucinous tumors were high-grade by P2 but not P1. Relationship to recurrence-free interval (RFI) was assessed by Cox regression. Results: Primary tumors from 504 stage II colon cancer treated with surgery alone were included. 18% (P1) and 31% (P2) were high grade. High grade tumors were more likely right-sided (≥ 60%) and MMR deficient (≥ 35%) for P1 and P2 (all p < 0.001). Proportion of mucinous tumors was similar for high and low grade by P1 (25% vs. 21%, p = 0.39). P2 high grade trended to lower recurrence (HR = 0.63, p = 0.10) while P1 grade was not associated w/ RFI (p = 0.46). In multivariate analyses including grade and RS, P2 high grade was associated with lower recurrence (p = 0.007) but P1 grade was not associated w/ RFI (p = 0.30). Neither grade was associated w/ RFI (p > 0.30) after controlling for RS, MMR, tumor location and mucinous histology. Using the two-tier scheme, agreement b/w the 2 pathologists was low (kappa = 0.30, 95% CI 0.21-0.39) in all pts and moderate if mucinous tumors were excluded (kappa = 0.52, 95% CI 0.40-0.64). Conclusions: High tumor grade was not found to be a marker of higher recurrence risk in stage II colon cancer. Other markers validated in stage II colon cancer, such as MMR and RS, should be considered. Interpathologist agreement on colon tumor grade is modest, even with central expert review. [Table: see text]

3503 Background: An understanding of biologic similarities and differences between st II and III colon cancer is needed to inform clinical practice and trial design. We compare pathologic markers a...