Sargent, Daniel J.

Purpose We previously validated disease-free survival (DFS) as a surrogate for overall survival (OS) in fluorouracil-based adjuvant colon cancer clinical trials. New therapies have extended survival after recurrence from 1 to approximately 2 years. We examined the possible impact of this improvement on the DFS/OS association. Methods The Adjuvant Colon Cancer Endpoints (ACCENT) data set of 20,898 patients was analyzed. In an exploratory fashion, time from recurrence to death in patients experiencing recurrence was extended using several algorithms, and the association of DFS after 3 years of median follow-up and OS after varying lengths of follow-up (median of 5, 6, and 7 years) was assessed. Results Seven thousand four hundred two patients (35%) experienced recurrence. Median time from recurrence to death was 24 months in the hypothetical data sets. When times from recurrence to death were doubled, the association between treatment effects on DFS and 5-year OS was modest (R2 = 0.51 for both 2- and 3-year DFS) but remained strong for DFS and 6-year OS (R2 = 0.67 for both 2- and 3-year DFS) and 7-year OS (R2 = 0.70 for both 2- and 3-year DFS). The reduced DFS/OS association with extended survival after recurrence was greater in stage II than stage III patients. Multiple simulations provided consistent findings. Conclusion Extended survival after recurrence reduces the association between treatment effects on 3-year DFS and 5-year OS, particularly in stage II patients; longer follow-up strengthens the association. In modern adjuvant trials, 6 or 7 years may be required to demonstrate OS improvements, further supporting DFS as the preferred primary end point for future adjuvant colon cancer clinical trials.

Purpose The sixth edition of the American Joint Committee on Cancer (AJCC) rectal cancer staging subdivided stage II into IIA (T3N0) and IIB (T4N0) and stage III into IIIA (T1-2N1M0), IIIB (T3-4N1M0), and IIIC (anyTN2M0). Subsequent analyses supported revised substaging of stage III as a result of improved survival with T1-2N2 versus T3-4N2 and survival of T4N1 more similar to T3-4N2 than T3N1. The AJCC Hindgut Taskforce sought population-based validation that depth of invasion interacts with nodal status to affect survival. Methods Surveillance, Epidemiology, and End Results (SEER) population-based data from January 1992 to December 2004 for 35,829 patients with rectal cancer were compared with rectal pooled analysis data (3,791 patients). T4N0 cancers were stratified by tumors that perforate visceral peritoneum (T4a) versus tumors that invade or are adherent to adjacent organs or structures (T4b). N1 and N2 were stratified by number of positive nodes as follows: N1a/N1b (one v two to three nodes) and N2a/N2b (four to six v ≥ seven nodes). Five-year observed and relative survival rates were obtained for each TN category. Results SEER rectal cancer analyses confirm that T1-2N2 cancers have better prognosis than T3-4N2, T4bN1 have similar prognosis to T4N2, T1-2N1 have similar prognosis to T2N0/T3N0, and T1-2N2a have similar prognosis to T2N0/T3N0 (T1N2a) or T4aN0 (T2N2a). Prognosis for T4a lesions is better than T4b by N category. The number of positive nodes affects prognosis. Conclusion This SEER population-based rectal cancer analysis validates the rectal pooled analyses and supports the shift of T1-2N2 lesions from IIIC to IIIA or IIIB and T4bN1 from IIIB to IIIC. SEER outcomes support subdividing T4, N1, and N2 and revised substaging of stages II and III. Survival by TN category suggests a complex biologic interaction between depth of invasion and nodal status.

Purpose The sixth edition of American Joint Committee on Cancer (AJCC) Cancer Staging Manual for colon cancer subdivided stage II into IIA (T3N0) and IIB (T4N0) and stage III into IIIA (T1-2N1M0), IIIB (T3-4N1M0), and IIIC (anyTN2M0). Subsequent analyses supported revised substaging of stage III because of improved survival for T1-2N2 versus T3-4N2 and T4N1 survival was more similar to T3-4N2 than to T3N1. The AJCC Hindgut Taskforce sought population-based validation that depth of invasion and nodal status interact to affect survival. Patients and Methods Surveillance, Epidemiology, and End Results (SEER) population-based data from January 1992 to December 2004 for 109,953 colon cancer patients were compared with National Cancer Data Base (NCDB) data on 134,206 patients. T4N0 cancers were stratified by tumors that perforate visceral peritoneum (T4a) versus tumors that invade or are adherent to adjacent organs or structures (T4b). N1 and N2 were stratified by number of involved positive lymph nodes (N+): N1a/N1b (1 v 2-3), N2a/N2b (4 to 6 v ≥ 7). Five-year observed and relative survival data were obtained for each TN category. Results SEER colon cancer analyses confirm that patients with T1-2N0 cancers have better survival than T3N0, T3N0 better than T4N0, T1-2N2 better than T3-4N2, and T4bN1 similar to T4N2. Patients with T4a lesions have better survival than T4b by N category. The number of positive nodes affects survival for each T category. Conclusion This SEER population-based colon cancer analysis is highly consistent with rectal cancer pooled analysis and SEER rectal cancer analyses, supporting the shift of T1-2N2 lesions from IIIC to IIIA/IIIB, shifting T4bN1 from IIIB to IIIC, subdividing T4/N1/N2, and revising substaging of stages II/III. Survival outcomes by TN category for colon and rectal cancer are strikingly similar.

Sensitivity analysis is an important statistical technique that assesses whether the results of phase III trials are robust and likely to be generalizable. Until recently, sensitivity analyses were rarely included in phase III trials, and they remain poorly understood by many oncologists. Sensitivity analyses are critical to understanding the strength of conclusions made in the primary analysis of a late-stage clinical trial. They examine the influence of protocol design errors, unintended biases, deviations from assumptions underlying statistical models, and any unanticipated treatment delivery or practice patterns on trial results. In trials with complex or subjective end points, they also allow an understanding of the extent to which a positive outcome is driven by a single, possibly subjective, and therefore biased, element of an end point. The purposes of this article are to explain how sensitivity analyses are performed, to discuss areas of a clinical trial where sensitivity analyses should focus, and to illuminate the importance of this technique in the rigorous evaluation of late-stage clinical trial data, using specific examples. This article focuses on late-stage trials that use progression-free survival or time to progression as their primary end point, because sensitivity analyses are particularly important in these cases for which the end point is potentially subject to bias. Three sources of potential bias are explored: assessment time, symptomatic (ie, nonradiologic) disease progression, and missing data. For each source of potential bias, case studies are presented to highlight the role that sensitivity analyses play in determining whether the trial's conclusions are robust.

Abstract Multiple genome-wide association studies have identified several susceptibility variants for colon cancer at 8q24. However, the functional roles of these variants have yet to be elucidated. Here, we evaluated the potential role of these markers in tumor progression and examined association with commonly observed structural abnormalities in this region, c-MYC amplification and chromosome fragility at FRA8C and FRA8D. We first replicated the previously reported association by testing 1,178 cases and 1,009 clinic-based controls with eight markers localized to three specific regions at 8q24. We observed significant associations with colon cancer risk with markers rs13254738 (ordinal odds ratio, 0.82; 95% confidence interval, 0.072-0.94; Ptrend = 0.0037) and rs6983267 (ordinal odds ratio, 1.17; 95% confidence interval, 1.03-1.32, Ptrend = 0.013). Survival analysis was done using a separate set of 460 cases to evaluate the clinical significance of these markers. Overall, univariate analysis did not detect survival differences for any of the markers. We also tested a subset of the 460 cases (n = 380) for structural abnormalities at or near the c-MYC locus using fluorescence in situ hybridization analysis. Furthermore, we evaluated a small number of cases homozygous for the rs6983267 alleles to test for differences in fragile site induction. None of the 8q markers correlated with amplification at the c-MYC locus as detected by fluorescence in situ hybridization, and no clear pattern of breakage was observed at the FRA8C and FRA8D sites. In this study, we confirm the association for several single nucleotide polymorphisms at 8q24 in colon cancer but have not detected any structural role relating to c-MYC amplification or chromosomal fragility. Finally, these risk alleles do not seem to be associated with survival. (Cancer Epidemiol Biomarkers Prev 2009;18(9):2492–500)

Purpose Racial disparities in colorectal cancer (CRC) survival are documented, but there are few data on comparative response to chemotherapy. A subgroup analysis of a multisite National Cancer Institute–sponsored trial (N9741) was performed comparing outcomes of black and white patients with metastatic CRC receiving uniform treatment. Patients and Methods Adverse events (AEs), response rate (RR), time to progression (TTP), overall survival (OS), and dose-intensity were examined as a function of self-reported race in 1,412 patients treated with irinotecan/fluorouracil, fluorouracil/oxaliplatin, or irinotecan/oxaliplatin. Pharmacogenetic analysis was performed on 486 patients with blood available for germline DNA analysis. Results OS was 1.5 months shorter and TTP was 0.6 months shorter in black than white patients (OS: hazard ratio [HR] = 1.13; 95% CI, 0.90 to 1.42; TTP: HR = 0.91, 95% CI, 0.73 to 1.13); neither difference was statistically significant. RR was significantly higher in whites (41%) than blacks (28%; P = .008). Grade 3 or greater AEs were also higher in whites (48%) than blacks (34%; P = .004). These relationships were maintained in multivariate models adjusting for arm, age, sex, and performance status. There was no difference in dose-intensity of delivered therapy. Significant racial differences in prevalence of pharmacogenetic variants were observed, although small sample size precluded investigating the relationship between treatment, race, and genotype. Conclusion OS and TTP are similar in black and white patients treated per protocol with standardized therapy for metastatic CRC. However, RR and AEs vary considerably by race. The marked racial differences in relevant pharmacogenetics, a potential explanation for differing RR and AEs, are worthy of future study.