Assessment of Audit Methodologies for Bias Evaluation of Tumor Progression in Oncology Clinical Trials

Value of central review of RECIST v1.1 outcomes in the AGITG INTEGRATE randomised phase 2 international trial for advanced oesophago-gastric cancer

PURPOSE

Activity estimates should be accurately evaluated in phase 2 clinical trials to ensure appropriate decisions about proceeding to phase 3 trials. RECIST v1.1. progression-free survival (PFS) is a common endpoint in oncology; however, it can be influenced by assessment criteria and trial design. We assessed the value of central adjudication of investigator-assessed PFS times of participants in a double-blind, randomised phase 2 trial evaluating regorafenib versus placebo in advanced gastro-oesophageal cancer (AGITG INTEGRATE) to inform plans for central review in future trials.

METHODS

We calculated the proportion of participants with a disagreement between the site investigator assessment and blinded independent central review and in whom central review resulted in a change, then evaluated the effect of central review on study conclusions by comparing hazard ratios (HRs) for PFS based on site review versus central review. Post-progression unblinding was assessed with similar methods. Simulation studies explored the effect of differential and non-differential measurement error on treatment effect estimation and study power.

RESULTS

Disagreements between site assessments versus central review occurred in 8/147 (5.4%) participants, 5 resulting in amended date of progression (3.4%). PFS HRs (sites vs central review progression dates) were similar (0.39 vs 0.40). RECIST progression occurred in 82/86 (95%) of cases where post-progression unblinding was requested by the site investigator.

CONCLUSIONS

Blinded independent central review was feasible and supported the reliability of site assessments, trial results, and conclusions. Modelling showed that when treatment effects were large and outcome assessments blinded, central review was unlikely to affect conclusions.

Evaluation bias in objective response rate and disease control rate between blinded independent central review and local assessment: a study-level pooled analysis of phase III randomized control trials in the past seven years

Background

In previous studies, complete-case implementation of blind independent central review has been considered unnecessary based on no sign of systematic bias between central and local assessments. In order to further evaluate its value, this study investigated evaluation status between both assessments in phase III trials of anti-cancer drugs for non-hematologic solid tumors.

Methods

Eligible trials were searched in PubMed with the date of Jan 1, 2010 to Jun 30, 2017. We compared objective response rate (ORR) and disease control rate (DCR) between central and local assessments by study-level pooled analysis and correlation analysis. In pooled analysis, direct comparison was measured by the odds ratio (OR) of central-assessed response status to local-assessed response status; to investigate evaluation bias between central and local assessments, the above calculated OR between experimental (exp-) and control (con-) arms were compared, measured by the ratio of OR.

Results

A total of 28 included trials involving 17,466 patients were included (28 with ORR, 16 with DCR). Pooled analysis showed central assessment reported lower ORR and DCR than local assessment, especially in trials with open-label design, central-assessed primary endpoint, and positive primary endpoint outcome, respectively. However, this finding could be found in both experimental [exp-ORR: OR=0.81 (95% CI: 0.76-0.87), P<0.01, I²=11%; exp-DCR: OR=0.90 (0.81-1.01), P=0.07, I²=42%] and control arms [con-ORR: OR=0.79 (0.72-0.85), P<0.01, I²=17%; con-DCR: OR=0.94 (0.86-1.02), P=0.14, I²=12%]. No sign of evaluation bias between two assessments was indicated through further analysis [ORR: ratio of OR=1.02 (0.97-1.07), P=0.42, I²=0%; DCR: ratio of OR=0.98 (0.93-1.03), P=0.37, I²=0%], regardless of mask (open/blind), sample size, tumor type, primary endpoint (central-assessed/local-assessed), and primary endpoint outcome (positive/negative). Correlation analysis demonstrated a high-degree concordance between central and local assessments (exp-ORR, con-ORR, exp-DCR, con-DCR: r>0.90, P<0.01).

Conclusions

Blind independent central review remained irreplaceable to monitor local assessment, but its complete-case implementation may be unnecessary.

Comparison between site and central radiological assessments for patients with recurrent glioblastoma on a clinical trial

AIM

Assessment of magnetic resonance imaging (MRI) in glioblastoma can be challenging. For patients with recurrent glioblastoma managed on the CABARET trial, we compared disease status assessed at hospitals and subsequent blinded central expert radiological review.

METHODS

MRI results and clinical status at specified time points were used for site and central assessment of disease status. Clinical status was determined by the site. Response Assessment in Neuro-Oncology (RANO) criteria were used for both assessments. Site and central assessments of progression-free survival (PFS) and response rates were compared. Inter-rater variability for central review progression dates was assessed.

RESULTS

Central review resulted in shorter PFS in 45% of 89 evaluable patients (n = 40). Median PFS was 3.6 (central) versus 3.9 months (site) (hazard ratio 1.5, 95% confidence interval 1.3-1.8, P < 0.001). Responses were documented more frequently by sites (n = 16, 18%) than centrally (n = 11, 12%). Seven of 120 patients continued on trial without site-determined progression for more than 6 months beyond the central review determination of progression. Of scans reviewed by all three central reviewers, 33% were fully concordant for progression date.

CONCLUSION

While the difference between site and central PFS dates was statistically significant, the 0.3-month median difference is small. The variability within central review is consistent with previous studies, highlighting the challenges in MRI interpretation in this context. A small proportion of patients benefited from treatment well beyond the centrally determined progression date, reinforcing that clinical status together with radiology results are important determinants of whether a therapy is effective for an individual.

Investigator and independent review committee exploratory assessment and verification of tumor response in a non-Hodgkin lymphoma study

Interpretation of endpoints (e.g. overall response rate) in clinical trials depends on the accurate and reliable measurement and identification of tumors. Regulatory agencies recommend blinded reviews of imaging data by independent review committees (IRCs). Differences in response outcomes that arise between IRCs and site investigators raise regulatory/sponsor concerns. Here, we evaluate discrepant tumor response assessments by the IRC and unblinded investigators (complete versus partial response, respectively) occurring in 52 (13% of 393 IRC-assessed responders) of 447 enrolled patients with treatment-naïve non-Hodgkin lymphoma from a randomized study. The IRC and investigators were 'likely correct' in 73% and 25% of cases, respectively (p < .001). Investigators were more likely to make errors by misinterpreting lymph node data and not utilizing PET results. This post hoc finding suggests a possible role for post-training site evaluation/audit, with retraining as needed, and a specialized consensus committee for concurrent blinded review of site/central data.

Model free audit methodology for bias evaluation of tumour progression in oncology

Many oncology studies incorporate a blinded independent central review (BICR) to make an assessment of the integrity of the primary endpoint, progression free survival. Recently, it has been suggested that, in order to assess the potential for bias amongst investigators, a BICR amongst only a sample of patients could be performed; if evidence of bias is detected, according to a predefined threshold, the BICR is then assessed in all patients, otherwise, it is concluded that the sample was sufficient to rule out meaningful levels of bias. In this paper, we present an approach that adapts a method originally created for defining futility bounds in group sequential designs. The hazard ratio ratio, the ratio of the hazard ratio (HR) for the treatment effect estimated from the BICR to the corresponding HR for the investigator assessments, is used as the metric to define bias. The approach is simple to implement and ensures a high probability that a substantial true bias will be detected. In the absence of bias, there is a high probability of accepting the accuracy of local evaluations based on the sample, in which case an expensive BICR of all patients is avoided. The properties of the approach are demonstrated by retrospective application to a completed Phase III trial in colorectal cancer. The same approach could easily be adapted for other disease settings, and for test statistics other than the hazard ratio.

Palbociclib in Hormone-Receptor-Positive Advanced Breast Cancer

BACKGROUND

Growth of hormone-receptor-positive breast cancer is dependent on cyclin-dependent kinases 4 and 6 (CDK4 and CDK6), which promote progression from the G1 phase to the S phase of the cell cycle. We assessed the efficacy of palbociclib (an inhibitor of CDK4 and CDK6) and fulvestrant in advanced breast cancer.

METHODS

This phase 3 study involved 521 patients with advanced hormone-receptor-positive, human epidermal growth factor receptor 2-negative breast cancer that had relapsed or progressed during prior endocrine therapy. We randomly assigned patients in a 2:1 ratio to receive palbociclib and fulvestrant or placebo and fulvestrant. Premenopausal or perimenopausal women also received goserelin. The primary end point was investigator-assessed progression-free survival. Secondary end points included overall survival, objective response, rate of clinical benefit, patient-reported outcomes, and safety. A preplanned interim analysis was performed by an independent data and safety monitoring committee after 195 events of disease progression or death had occurred.

RESULTS

The median progression-free survival was 9.2 months (95% confidence interval [CI], 7.5 to not estimable) with palbociclib-fulvestrant and 3.8 months (95% CI, 3.5 to 5.5) with placebo-fulvestrant (hazard ratio for disease progression or death, 0.42; 95% CI, 0.32 to 0.56; P<0.001). The most common grade 3 or 4 adverse events in the palbociclib-fulvestrant group were neutropenia (62.0%, vs. 0.6% in the placebo-fulvestrant group), leukopenia (25.2% vs. 0.6%), anemia (2.6% vs. 1.7%), thrombocytopenia (2.3% vs. 0%), and fatigue (2.0% vs. 1.2%). Febrile neutropenia was reported in 0.6% of palbociclib-treated patients and 0.6% of placebo-treated patients. The rate of discontinuation due to adverse events was 2.6% with palbociclib and 1.7% with placebo.

CONCLUSIONS

Among patients with hormone-receptor-positive metastatic breast cancer who had progression of disease during prior endocrine therapy, palbociclib combined with fulvestrant resulted in longer progression-free survival than fulvestrant alone. (Funded by Pfizer; PALOMA3 ClinicalTrials.gov number, NCT01942135.).

Progression-free survival by local investigator versus independent central review: comparative analysis of the AGO-OVAR16 Trial

BACKGROUND

Analysis of progression-free survival (PFS) as the primary endpoint in advanced epithelial ovarian, fallopian tube, and primary peritoneal cancer (AEOC) trials may be confounded by the difficulty of radiologic evaluation of disease progression and the potential for discrepancy between investigator and blinded independent central assessments. PFS as assessed by local investigator (INV) was the primary endpoint of AGO-OVAR16, a randomized, double-blind trial of pazopanib maintenance therapy in AEOC. To confirm the robustness of the primary analysis, PFS was also evaluated by blinded independent central review (BICR).

METHODS

Patients with histologically confirmed AEOC (N = 940) were randomized 1:1 to receive pazopanib 800 mg/day or placebo for up to 24 months. Tumor response in the intent-to-treat population was evaluated by CT/MRI every 6 months and analyzed per RECIST 1.0.

RESULTS

Pazopanib prolonged PFS versus placebo by INV (median 17.9 vs 12.3 months; hazard ratio [HR] = 0.766, 95% confidence interval [CI]: 0.643-0.911; P = 0.0021). Results for PFS by BICR were similar (median 15.4 vs 11.8 months; HR = 0.802, 95% CI: 0.678-0.949; P = 0.0084). Progression events were recorded later by INV in 23% of pazopanib-treated patients and 17% of placebo-treated patients. The overall concordance between INV and BICR assessments was 84% and 86% in the pazopanib and placebo arms, respectively.

CONCLUSIONS

By INV and BICR assessments, maintenance therapy with pazopanib in AEOC provided a significantly longer PFS than placebo. The good overall concordance between INV and BICR assessments, as well as HR and P value consistency, supports the reliability of investigator-assessed PFS as the primary endpoint in AGO-OVAR16.

Overview: progression-free survival as an endpoint in clinical trials with solid tumors

Progression-free survival (PFS) is increasingly used as an important and even a primary endpoint in randomized cancer clinical trials in the evaluation of patients with solid tumors for both practical and clinical considerations. Although in its simplest form, PFS is the time from randomization to a predefined endpoint, there are many factors that can influence the exact moment of when disease progression is recorded. In this overview, we review the circumstances that can devalue the use of PFS as a primary endpoint and attempt to provide a pathway for a future desired state when PFS will become not just a secondary alternative to overall survival but rather an endpoint of choice.

The clinical viewpoint: definitions, limitations of RECIST, practical considerations of measurement

In selecting an endpoint in clinical trial design, it is important to consider that the endpoint is both reliably measured and clinically meaningful. As such, overall survival (OS) has traditionally been considered the most clinically relevant and convincing endpoint in clinical trial design as long as it is accompanied by preservation in quality of life. However, progression-free survival (PFS) is increasingly more prominent in clinical trial design because of feasibility issues (smaller sample sizes and shorter follow-up). PFS has the advantage of taking into account not only responsive disease, but stable disease as well, an issue of particular importance in the relapsed and refractory setting in which therapies are often associated with a minimal to nil response but may still confer a survival advantage. Finally, PFS has a significant advantage in molecularly selected populations, in whom OS advantages are difficult to detect due to the effects of crossover. With an understanding of the limitations and biases that are introduced with PFS as a primary endpoint, we believe that PFS is not only a viable but also a necessary alternative to OS in assessing the efficacy of selected novel-targeted therapies in molecularly defined cancer populations. Ultimately, the selection of a clinical trial endpoint should not be based on a one-size-fits all approach; rather, it should be based on the specifics of the therapeutic strategy being tested and the population under study.

Modeling the relationship between progression-free survival and overall survival: the phase II/III trial

The standard phase II trial design has changed dramatically over the past decade. Randomized phase II studies have essentially become the standard phase II design in oncology for a variety of reasons. The use of these designs is motivated by concerns about the use of historical data to determine if a new agent or regimen shows promise of activity. However, randomized phase II designs come with the cost of increased study duration and patient resources. Progression-free survival (PFS) is an important endpoint used in many phase II designs. In many clinical settings, changes in PFS with the introduction of a new treatment may represent true benefit in terms of the gold standard outcome, overall survival (OS). The phase II/III design has been proposed as an approach to shorten the time of discovery of an active regimen. In this article, design considerations for a phase II/III trial are discussed and presented in terms of a model defining the relationship between OS and PFS. The design is also evaluated using 15 phase III trials completed in the Southwest Oncology Group (SWOG) between 1990 and 2005. The model provides a framework to evaluate the validity and properties of using a phase II/III design. In the evaluation of SWOG trials, three of four positive studies would have also proceeded to the final analysis and 10 of 11 negative studies would have stopped at the phase II analysis if a phase II/III design had been used. Through careful consideration and thorough evaluation of design properties, substantial gains could occur using this approach.