Sargent, Daniel J

It is widely accepted that traditional models of clinical investigation are becoming unsustainable in oncology and that trials must become more efficient in matching effective treatments to the patients most likely to benefit. In 2008, gastrointestinal oncologists from many countries began a collaboration to improve the design and conduct of clinical trials in their field, through the auspices of a French/U.S. charitable foundation, ARCAD. Whether this model of academic collaboration will be judged a success will depend on the quality of its scientific output during the next few years and whether this output, alongside that of other scientists, groups, and institutions, ultimately leads to more efficient trials and improved treatment options for patients.

PurposeAlthough the importance of obesity in colon cancer risk and outcome is recognized, the association of body mass index (BMI) with DNA mismatch repair (MMR) status is unknown.Patients and MethodsBMI (kg/m2) was determined in patients with TNM stage II or III colon carcinomas (n = 2,693) who participated in randomized trials of adjuvant chemotherapy. The association of BMI with MMR status and survival was analyzed by logistic regression and Cox models, respectively.ResultsOverall, 427 (16%) tumors showed deficient MMR (dMMR), and 630 patients (23%) were obese (BMI ≥ 30 kg/m2). Obesity was significantly associated with younger age (P = .021), distal tumor site (P = .012), and a lower rate of dMMR tumors (10% v 17%; P < .001) compared with normal weight. Obesity remained associated with lower rates of dMMR (odds ratio, 0.57; 95% CI, 0.41 to 0.79; P < .001) after adjusting for tumor site, stage, sex, and age. Among obese patients, rates of dMMR were lower in men compared with women (8% v 13%; P = .041). Obesity was associated with higher recurrence rates (P = .0034) and independently predicted worse disease-free survival (DFS; hazard ratio [HR], 1.37; 95% CI, 1.14 to 1.64; P = .0010) and overall survival (OS), whereas dMMR predicted better DFS (HR, 0.59; 95% CI, 0.47 to 0.74; P < .001) and OS. The favorable prognosis of dMMR was maintained in obese patients.ConclusionColon cancers from obese patients are less likely to show dMMR, suggesting obesity-related differences in the pathogenesis of colon cancer. Although obesity was independently associated with adverse outcome, the favorable prognostic impact of dMMR was maintained among obese patients.

Purpose Symptoms and complications of metastatic colorectal cancer (mCRC) differ by metastatic sites. There is a paucity of prospective survival data for patients with peritoneal carcinomatosis colorectal cancer (pcCRC). We characterized outcomes of patients with pcCRC enrolled onto two prospective randomized trials of chemotherapy and contrasted that with other manifestations of mCRC (non-pcCRC). Methods A total of 2,095 patients enrolled onto two prospective randomized trials were evaluated for overall survival (OS) and progression-free survival (PFS). A Cox proportional hazard model was used to assess the adjusted associations. Results The characteristics of the pcCRC group (n = 364) were similar to those of the non-pcCRC patients in median age (63 v 61 years, P = .23), sex (57% males v 61%, P = .23), and performance status (Eastern Cooperative Oncology Group performance status 0 or 1 94% v 96%, P = .06), but differed in frequency of liver (63% v 82%, P < .001) and lung metastases (27% v 34%, P = .01). Median OS (12.7 v 17.6 months, hazard ratio [HR] = 1.3; 95% CI, 1.2 to 1.5; P < .001) and PFS (5.8 v 7.2 months, HR = 1.2; 95% CI, 1.1 to 1.3; P = .001) were shorter for pcCRC versus non-pcCRC. The unfavorable prognostic influence of pcCRC remained after adjusting for age, PS, liver metastases, and other factors (OS: HR = 1.3, P < .001; PFS: HR = 1.1, P = .02). Infusional fluorouracil, leucovorin, and oxaliplatin was superior to irinotecan, leucovorin, and fluorouracil as a first-line treatment among pcCRC (HR for OS = 0.62, P = .005) and non-pcCRC patients (HR = 0.66, P < .001). Conclusion pcCRC is associated with a significantly shorter OS and PFS as compared with other manifestations of mCRC. Future trials for mCRC should consider stratifying on the basis of pcCRC status.

A two‐stage model for evaluating both trial‐level and patient‐level surrogacy of correlated time‐to‐event endpoints has been introduced, using patient‐level data when multiple clinical trials are available. However, the associated maximum likelihood approach often suffers from numerical problems when different baseline hazards among trials and imperfect estimation of treatment effects are assumed. To address this issue, we propose performing the second‐stage, trial‐level evaluation of potential surrogates within a Bayesian framework, where we may naturally borrow information across trials while maintaining these realistic assumptions. Posterior distributions on surrogacy measures of interest may then be used to compare measures or make decisions regarding the candidacy of a specific endpoint. We perform a simulation study to investigate differences in estimation performance between traditional maximum likelihood and new Bayesian representations of common meta‐analytic surrogacy measures, while assessing sensitivity to data characteristics such as number of trials, trial size, and amount of censoring. Furthermore, we present both frequentist and Bayesian trial‐level surrogacy evaluations of time to recurrence for overall survival in two meta‐analyses of adjuvant therapy trials in colon cancer. With these results, we recommend Bayesian evaluation as an attractive and numerically stable alternative in the multitrial assessment of potential surrogate endpoints. Copyright © 2011 John Wiley & Sons, Ltd.

Abstract Purpose: Assessing impact of poor accrual on premature trial closure requires a relevant metric. We propose defining accrual sufficiency on apparent ability to address primary endpoints (PE) rather than attaining accrual targets. Experimental Design: All phase III trials open January 1, 1993, to December 31, 2002, by five U.S. oncology Clinical Trials Cooperative Groups (CTCG) were evaluated for accrual sufficiency and scientific results. Sufficient accrual included meeting accrual target, CTCGs documentation attesting adequate accrual, or conclusive results at interim analysis; insufficient accrual included poor accrual as cited closure reason or other reasons rendering a trial unable to address its primary endpoints. Closure rates based on our accrual sufficiency definition are compared with rates of meeting accrual targets and addressing the primary endpoints. A percentage of target accrual above which trials commonly answer the intended scientific question was identified to serve as an alternative to meeting full target accrual in designating accrual success. Results: Of 238 eligible trials, 158 (66%) closed with sufficient accrual. Among 80 trials with insufficient accrual, 70 (29%) closed specifically because of poor accrual. Inadequate accrual rates are overemphasized when defining accrual success solely by meeting accrual targets. Nearly 75% of trials conclusively addressed the primary endpoints with positive results in 39% of trials. Exceeding 80% of target accrual serves as a reliable proxy for answering the intended scientific question. Conclusions: Approximately one third of phase III trials closed with insufficient accrual to address the primary endpoints, primarily due to poor accrual. Defining accrual sufficiency broader than meeting accrual targets represents a fairer account of trial closures. Clin Cancer Res; 18(1); 256–62. ©2011 AACR.

PurposeProgression-free survival (PFS) is not an optimal end point to evaluate therapeutic strategies in advanced colorectal cancer (ACRC). Therefore, composite end points have been proposed to evaluate a chemotherapy strategy when sequential treatments are available: duration of disease control (DDC) and time to failure of strategy (TFS). The goal of this study was to evaluate these alternative end points and their potential surrogacy for overall survival (OS).MethodsWe pooled individual patient data from three randomized trials evaluating chemotherapy strategy, which accrued 1,042 patients with previously untreated ACRC. In these trials, first-line treatment was either oxaliplatin- or irinotecan-based chemotherapy. Compared with TFS, DDC included neither time interval between progression and next sequence of treatment nor time to progression if the best result of the next sequence of treatment was progression.ResultsThere was good correlation between DDC and OS (correlation of median: r, 0.62; correlation of hazard ratio [HR]: adjusted copula R2, 0.72) and between TFS and OS (correlation of median: r, 0.59; correlation of HR: adjusted copula R2, 0.67). There was no correlation between PFS and OS (correlation of median: r, 0.45; correlation of HR: adjusted copula R2, 0.47).ConclusionDDC and TFS roughly achieved the same results. Both are acceptable new end points to evaluate a therapeutic strategy in ACRC. Although TFS achieved a pragmatic evaluation of a multiline strategy, DDC captured the effect of a specific sequence in a therapeutic strategy.

Background Intermediate outcome variables can often be used as auxiliary variables for the true outcome of interest in randomized clinical trials. For many cancers, time to recurrence is an informative marker in predicting a patient's overall survival outcome and could provide auxiliary information for the analysis of survival times. Purpose To investigate whether models linking recurrence and death combined with a multiple imputation procedure for censored observations can result in efficiency gains in the estimation of treatment effects and be used to shorten trial lengths. Methods Recurrence and death times are modeled using data from 12 trials in colorectal cancer. Multiple imputation is used as a strategy for handling missing values arising from censoring. The imputation procedure uses a cure model for time to recurrence and a time-dependent Weibull proportional hazards model for time to death. Recurrence times are imputed, and then death times are imputed conditionally on recurrence times. To illustrate these methods, trials are artificially censored 2 years after the last accrual, the imputation procedure implemented, and a log-rank test and Cox model used to analyze and compare these new data with the original data. Results The results show modest, but consistent gains in efficiency in the analysis using the auxiliary information in recurrence times. Comparison of analyses show the treatment effect estimates and log-rank test results from the 2-year censored imputed data to be in between the estimates from the original data and the artificially censored data, indicating that the procedure was able to recover some of the lost information due to censoring. Limitations The models used are all fully parametric, requiring distributional assumptions of the data. Conclusions The proposed models may be useful in improving the efficiency in estimation of treatment effects in cancer trials and shortening trial length.

Abstract Purpose: The categorical definition of response assessed via the Response Evaluation Criteria in Solid Tumors has documented limitations. We sought to identify alternative metrics for tumor response that improve prediction of overall survival. Experimental Design: Individual patient data from three North Central Cancer Treatment Group trials (N0026, n = 117; N9741, n = 1,109; and N9841, n = 332) were used. Continuous metrics of tumor size based on longitudinal tumor measurements were considered in addition to a trichotomized response [TriTR: response (complete or partial) vs. stable disease vs. progression). Cox proportional hazards models, adjusted for treatment arm and baseline tumor burden, were used to assess the impact of the metrics on subsequent overall survival, using a landmark analysis approach at 12, 16, and 24 weeks postbaseline. Model discrimination was evaluated by the concordance (c) index. Results: The overall best response rates for the three trials were 26%, 45%, and 25%, respectively. Although nearly all metrics were statistically significantly associated with overall survival at the different landmark time points, the concordance indices (c-index) for the traditional response metrics ranged from 0.59 to 0.65; for the continuous metrics from 0.60 to 0.66; and for the TriTR metrics from 0.64 to 0.69. The c-indices for TriTR at 12 weeks were comparable with those at 16 and 24 weeks. Conclusions: Continuous tumor measurement–based metrics provided no predictive improvement over traditional response–based metrics or TriTR; TriTR had better predictive ability than best TriTR or confirmed response. If confirmed, TriTR represents a promising endpoint for future phase II trials. Clin Cancer Res; 17(20); 6592–9. ©2011 AACR.

Background Research on barriers to accrual has typically emphasized factors influencing participation after trial activation. Purpose We sought to identify factors influencing trial design and accrual predictions prior to trial activation associated with sufficient accrual. Methods A 30-question web-based survey was sent to the study chair and lead statistician for all 248 phase III trials open in 1993–2002 by five Clinical Trials Cooperative Groups. Questions addressed prior trial experience, trial design elements, accrual predictions, and perceived accrual influences. Accrual sufficiency categorization was derived from Clinical Trials Cooperative Group records: sufficient accrual included trials closed with complete accrual or at interim analysis, insufficient accrual included trials closed with inadequate accrual. Responses were analyzed by respondent role (study chair/lead statistician) and accrual sufficiency. Results Three hundred and nine eligible responses were included (response rate, 63%; lead statisticians, 81%; and study chairs, 45%), representing trials with sufficient (63%) and insufficient accruals (37%). Study chair seniority or lead statistician experience was not linked to accrual sufficiency. Literature review, study chair's personal experience, and expert opinion within Clinical Trials Cooperative Group most commonly influenced control arm selection. Clinical Trials Cooperative Group experience most influenced accrual predictions. These influences were not associated with accrual sufficiency. Among respondents citing accrual difficulties (41%), factors negatively influencing accrual were not consistently identified. Respondents credited three factors with positively influencing accrual: clinical relevance of study, lack of competing trials, and protocol paralleling normal practice. Limitations Perceptions of lead statisticians and study chairs may not accurately reflect accrual barriers encountered by participating physicians or patients. Survey responses may be subject to recall bias. Conclusion Consistent factors explaining poor accrual were not identified, suggesting reasons for poor accrual are not well understood and warrant further study. Alternate strategies for accrual prediction are needed since Clinical Trials Cooperative Group experience is linked to successful and unsuccessful accrual.