Evaluating surrogacy metrics and investigating approval decisions of progression-free survival (PFS) in metastatic renal cell cancer: a systematic review

Surrogate Endpoints as Predictors of Overall Survival in Metastatic Urothelial Cancer: A Trial-level Analysis

Background

Surrogate endpoints (SEs), such as progression-free survival (PFS) and objective response rate (ORR), are frequently used in clinical trials. The relationship between SEs and overall survival (OS) has not been well described in metastatic urothelial cancer (MUC).

Objective

We evaluated trial-level data to assess the relationship between SEs and OS. We hypothesize a moderate surrogacy relationship between both PFS and ORR with OS.

Design setting and participants

We systematically reviewed phase 2/3 trials in MUC with two or more treatment arms, and report PFS and/or ORR, and OS.

Outcome measurements and statistical analysis

Linear regression was performed, and the coefficient of determination (R²) and surrogate threshold effect (STE) estimate were determined between PFS/ORR and OS.

Results and limitations

Of 3791 search results, 59 trials and 62 comparisons met the inclusion criteria. Of the 53 trials that reported PFS, 31 (58%) reported proportional hazard regression for PFS and OS. Linear regression across trials demonstrated an R² of 0.60 between hazard ratio (HR) for PFS (HR^PFS) and HR for OS (HR^OS), and an STE of 0.41. Linear regression of ΔPFS (median PFS in months of the treatment arm - that of the control arm) and ΔOS demonstrated an R² of 0.12 and an STE of 14.1 mo. Thirty trials reported ORRs. Linear regression for ORR^ratio and HR^OS among all trials found an R² of 0.08; an STE of 95% was not reached at any value and ΔORR and HR^OS similarly demonstrated a poor correlation with an R² value of 0.03.

Conclusions

PFS provides only a moderate level of surrogacy for OS; An HR^PFS of ≤0.41 provides 95% confidence of OS improvement. ORR is weakly correlated with OS and should be de-emphasized in MUC clinical trials. When PFS is discussed, proportional hazard regression should be reported.

Patient summary

We examined the relationship between surrogate endpoints, common outcomes in clinical trials, with survival in urothelial cancer trials. Progression-free survival is moderately correlated, while objective response rate had a poor correlation with survival and should be de-emphasized as a primary endpoint.

The value of anticancer drugs - a regulatory view

The high prices of new anticancer drugs and the marginal added benefit perceived by some stakeholders have fuelled a debate on the value of anticancer drugs in the European Union, even though an agreed definition of what constitutes a drug's value does not exist. In this Perspective, we discuss the value of drugs from different viewpoints and objectives of decision makers: for regulators, assessment of the benefit-risk balance of a drug is a cornerstone for approval; payers rely on cost-effectiveness analyses carried out by health technology assessment agencies for reimbursement decisions; for patients, treatment choices are based on personal preferences and attitudes to risk; and clinicians can use several scales (such as the ESMO Magnitude of Clinical Benefit Scale (ESMO-MCBS)) that have been developed as an attempt to measure value objectively. Although a unique definition that fully captures the concept of value is unlikely to emerge, herein we discuss the importance of understanding different perspectives, and how regulators can help to inform different decision makers.

The validity of progression-free survival 2 as a surrogate trial end point for overall survival

BACKGROUND

Overall survival (OS) is the gold-standard end point for oncology trials. However, the availability of multiple therapeutic options after progression and crossover to receive investigational agents confound and delay OS data maturation. Progression-free survival 2 (PFS-2), defined as the time from randomization to progression on first subsequent therapy, has been proposed as a surrogate for OS. Using a meta-analytic approach, the authors aimed to assess the association between OS and PFS-2 and compare this with progression-free survival 1 (PFS-1) and the objective response rate (ORR).

METHODS

An electronic literature search was performed to identify randomized trials of systemic therapies in advanced solid tumors that reported PFS-2 as a prespecified end point. Correlations between OS and PFS-2, OS and PFS-1, and OS and ORR as hazard ratios (HRs) or odds ratios (ORs) were assessed via linear regression weighted by trial size.

RESULTS

Thirty-eight trials were included, and they comprised 19,031 patients across 8 tumor types. PFS-2 displayed a moderate correlation with OS (r = 0.67; 95% confidence interval [CI], 0.08-0.69). Conversely, correlations of ORR (r = 0.12; 95% CI, 0.00-0.13) and PFS-1 (r = 0.21; 95% CI, 0.00-0.33) were poor. The findings for PFS-2 were consistent for subgroup analyses by treatment type (immunotherapy vs nonimmunotherapy: r = 0.67 vs 0.67), survival post progression (<12 vs ≥12 months: r = 0.86 vs 0.79), and percentage not receiving subsequent treatment (<50% vs ≥50%: r = 0.70 vs 0.63).

CONCLUSIONS

Across diverse tumors and therapies, the treatment effect on PFS-2 correlated moderately with the treatment effect on OS. PFS-2 performed consistently better than PFS-1 and ORR, regardless of postprogression treatment and postprogression survival. PFS-2 should be included as a key trial end point in future randomized trials of solid tumors.

Glycated hemoglobin as a surrogate for evaluating the effectiveness of drugs in diabetes mellitus trials: a systematic review and trial-level meta-analysis

OBJECTIVE

The objective of this study was to investigate whether glycated hemoglobin (HbA1c) is a valid surrogate for evaluating the effectiveness of antihyperglycemic drugs in diabetes mellitus (DM) trials.

METHODS

We conducted a systematic review of placebo-controlled randomized clinical trials (RCTs) evaluating the effect of a treatment on HbA1c (mean difference between groups) and clinical outcomes (relative risk of mortality, myocardial infarction, stroke, heart failure, and/or kidney injury) in patients with DM. Then, we investigated the association between treatment effects on HbA1c and clinical outcomes using regression analysis at the trial level. Lastly, we interpreted the correlation coefficients (R) using the cut-off points suggested by the Institute for Quality and Efficiency in Healthcare (IQWiG). HbA1c was considered a valid surrogate if it demonstrated a strong association: lower limit of the 95 percent confidence interval (95 percent CI) of R greater than or equal to .85.

RESULTS

Nineteen RCTs were identified. All studies included adults with type 2 DM. None of the associations evaluated was strong enough to validate HbA1c as a surrogate for any clinical outcome: mortality (R = .34; 95 percent CI -.14 to .69), myocardial infarction (R = .20; -.30 to .61), heart failure (R = .08; -.40 to .53), kidney injury (R = -.04; -.52 to .47), and stroke (R = .81; .54 to .93).

CONCLUSIONS

The evidence from multiple placebo-controlled RCTs does not support the use of HbA1c as a surrogate to measure the effectiveness of antihyperglycemic drugs in DM studies.

LncRNAs specifically overexpressed in endocervical adenocarcinoma are associated with an unfavorable recurrence prognosis and the immune response

Background

Cervical cancer is the fourth most common gynecological tumor in terms of both the incidence and mortality of females worldwide. Cervical squamous cell carcinoma (CSCC) accounts for 70–80% of cervical cancers, and endocervical adenocarcinoma (EAC) accounts for 20–25%. Unlike CSCC, EAC has worse clinical outcomes and prognosis. In this study, we explored the relationship between various types of long noncoding RNAs (lncRNAs) and pathological types of cervical cancer.

Methods

RNA sequencing (RNA-Seq) and clinical data from The Cancer Genome Atlas (TCGA) were used in this study. A single-sample gene set enrichment analysis (ssGSEA) and the ESTIMATE package were used to assess lncRNA activity and immune responses, respectively. RT-qPCR was performed to verify our findings.

Results

We explored the relationship between various types of lncRNAs and pathological types of cervical cancer. A series of long intergenic noncoding RNAs (lincRNAs) and antisense RNAs, which are the major types of lncRNAs, were identified to be specifically expressed in EAC and associated with a poor recurrence prognosis in patients with cervical cancer, suggesting that they might serve as independent prognostic markers of recurrence in patients with cervical cancer. RT-qPCR was performed to verify the 10 EAC-specific lncRNAs in cervical cancer samples we collected. Furthermore, the overexpression of these lncRNAs was positively correlated with EAC pathology levels but negatively correlated with immune responses in the microenvironment of cervical cancer.

Conclusions

These lncRNAs potentially represent new biomarkers for the prediction of the recurrence prognosis and help obtain deeper insights into potential immunotherapeutic approaches for treating cervical cancer.

Surrogate Endpoints in Oncology: Overview of Systematic Reviews and Their Use for Health Decision Making in Mexico

OBJECTIVES

The use of surrogate endpoints (SEs) for cancer drug approval in health systems is common. The objectives of this study were to identify systematic reviews (SRs) that evaluated the correlation of SEs with overall survival (OS) in cancer drugs to analyze the applications of approved cancer drugs with SEs in Mexico and to apply the validation framework proposed by the Institute for Quality and Efficiency in Health Care (IQWiG).

METHODS

An overview of SRs was conducted according to Cochrane Collaboration methodology. Applications for approved cancer drugs with SEs in Mexico were analyzed. The IQWiG validation framework was applied to evaluate the SEs identified in the overview and in the applications in Mexico.

RESULTS

A total of 85 SRs that assessed 192 SEs for different types of cancer were selected. According to the IQWiG model, only 2.5% of the SEs analyzed in the overview and only one of the applications in Mexico could be used as surrogates for OS because the reliability (methodological quality) of the SRs and the strength of the correlation of SEs with OS was mostly low (92%) and low (correlation coefficient r ≤ 0.7; 50.5%), respectively. Of the total number of cancer drugs approved in Mexico, 19.4% used SEs.

CONCLUSIONS

Most SEs for different types of cancer could not be used as surrogates for OS according to the IQWiG model, and their use for the approval of cancer drugs in Mexico is generally not justified.

Overexpression of MUC16 predicts favourable prognosis in MUC16-mutant cervical cancer related to immune response

Cervical cancer (CC) is the fourth ranking gynaecologic tumour in women worldwide, with respect to both incidence and mortality. MUC16 is one of the most frequently mutated genes, which functions as a tumour marker in CC. In the present study, mutation, clinical and RNA-Seq data collected from The Cancer Genome Atlas database were used to investigate the association between MUC16 mutation, immune response and clinical prognosis in CC. mRNA expression levels from the TCGA datasets and the results from the present study demonstrated that MUC16 was overexpressed in CC samples; however, there was no difference between mutant and wild-type CC samples. Furthermore, the results indicated that patients with MUC16-mutant overexpression had a prolonged survival time. In addition, overexpression of MUC16 was associated with immune responses in the microenvironment of MUC16-mutant CC. Immune responses were upregulated in patients with early-stage MUC16-mutant. The results from the present study provided novel biomarkers for potential immunotherapy approaches for CC.

CHALLENGES AND METHODOLOGIES IN USING PROGRESSION FREE SURVIVAL AS A SURROGATE FOR OVERALL SURVIVAL IN ONCOLOGY

OBJECTIVES

A primary outcome in oncology trials is overall survival (OS). However, to estimate OS accurately requires a sufficient number of patients to have died, which may take a long time. If an alternative end point is sufficiently highly correlated with OS, it can be used as a surrogate. Progression-free survival (PFS) is the surrogate most often used in oncology, but does not always satisfy the correlation conditions for surrogacy. We analyze the methodologies used when extrapolating from PFS to OS.

METHODS

Davis et al. previously reviewed the use of surrogate end points in oncology, using papers published between 2001 and 2011. We extend this, reviewing papers published between 2012 and 2016. We also examine the reporting of statistical methods to assess the strength of surrogacy.

RESULTS

The findings from 2012 to 2016 do not differ substantially from those of 2001 to 2011: the same factors are shown to affect the relationship between PFS and OS. The proportion of papers reporting individual patient data (IPD), strongly recommended for full assessment of surrogacy, remains low: 33 percent. A wide range of methods has been used to determine the appropriateness of surrogates. While usually adhering to reporting standards, the standard of scholarship appears sometimes to be questionable and the reporting of results often haphazard.

CONCLUSIONS

Standards of analysis and reporting PFS to OS surrogate studies should be improved by increasing the rigor of statistical reporting and by agreeing to a minimum set of reporting guidelines. Moreover, the use of IPD to assess surrogacy should increase.

Serum urate as surrogate endpoint for flares in people with gout: A systematic review and meta-regression analysis

OBJECTIVES

The primary efficacy outcome in trials of urate lowering therapy (ULT) for gout is serum urate (SU). The aim of this study was to examine the strength of the relationship between SU and patient-important outcomes to determine whether SU is an adequate surrogate endpoint for clinical trials.

METHODS

Multiple databases through October 2017 were searched. Randomized controlled trials comparing any ULT in people with gout with any control or placebo, ≥three months duration were included. Open label extension (OLE) trial data were included in secondary analyses. Standardized data elements were extracted independently by two reviewers.

RESULTS

Ten RCTs and 3 OLE studies were identified. From the RCTs (maximum duration 24 months) meta-regression did not reveal an association between the relative risk of a gout flare and the difference in proportions of individuals with SU < 6mg/dL (P = 0.47; R2 = 8%). In a post hoc analysis, the ratio of the time in months at which the proportion of individuals having a flare was reported/time in months at which the proportion of individuals with SU < 6mg/dL was reported was calculated and studies where the ratio was <2 were excluded. Using the remaining 6 studies there was an association between proportion of individuals achieving SU < 6mg/dL and gout flares (over patient years). Duration of ULT was inversely associated with the proportion of patients experiencing a flare. Study duration and variability in reporting of outcomes limited the analysis. Observational studies supported the trend of fewer flares in those with lower SU.

CONCLUSIONS

Based on aggregate clinical trial-level data an association between SU and gout flare could not be confirmed. However, based on observational ecological study design data-including longer duration extension studies-SU < 6mg/dL was associated with reduced gout flares.

Impact of targeted therapies in metastatic renal cell carcinoma on patient-reported outcomes: Methodology of clinical trials and clinical benefit

BACKGROUND

Molecular targeted therapies have improved progression-free survival (PFS) without translating systematically into overall survival (OS) for patients with metastatic renal cell carcinoma (mRCC). In this population, patient-reported outcomes (PROs) have become a significant outcome. We evaluated the methodological quality of the assessment of PROs in randomized controlled trials (RCTs) and the clinical benefit of the different treatments including survival and quality of life (QoL).

METHODS

A systematic review identified RCTs published between January 2005 and July 2014. They were evaluated according to 11 items derived from the 2013 CONSORT PROs reporting guidelines. Survival outcomes and PROs main results were analyzed and the magnitude of clinical benefit was assessed with the European Society for Medical Oncology Magnitude of Clinical Benefit Scale (ESMO-MCBS).

RESULTS

12 RCTs were included with a total of 22 publications. The mean CONSORT score for all items was 4.5 on an 11-point scale. No publication reported the power of the PROs analysis and only one reported a PRO hypothesis. 50% of studies did not interpret PROs in relation to clinical outcomes and only 18% discussed specific limitations of PROs and their implications for generalizability. By adding the QoL criterion to PFS, 4 trials (36.4%) obtained a high level of proven clinical benefit according to the ESMO-MCBS.

CONCLUSION

The methodology for assessing PROs in mRCC is not optimal. Efforts should focus on defining PROs endpoint and increasing the quality of reporting of QoL. New-generation therapies in mRCC should demonstrate a gain not only in survival but also in QoL to be included in the therapeutic arsenal.

Using serum urate as a validated surrogate end point for flares in patients with gout: protocol for a systematic review and meta-regression analysis

INTRODUCTION

Gout is the most common inflammatory arthritis in men over 40 years of age. Long-term urate-lowering therapy is considered a key strategy for effective gout management. The primary outcome measure for efficacy in clinical trials of urate-lowering therapy is serum urate levels, effectively acting as a surrogate for patient-centred outcomes such as frequency of gout attacks or pain. Yet it is not clearly demonstrated that the strength of the relationship between serum urate and clinically relevant outcomes is sufficiently strong for serum urate to be considered an adequate surrogate. Our objective is to investigate the strength of the relationship between changes in serum urate in randomised controlled trials and changes in clinically relevant outcomes according to the 'Biomarker-Surrogacy Evaluation Schema version 3' (BSES3), documenting the validity of selected instruments by applying the 'OMERACT Filter 2.0'.

METHODS AND ANALYSIS

A systematic review described in terms of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) reporting guidelines will identify all relevant studies. Standardised data elements will be extracted from each study by 2 independent reviewers and disagreements are resolved by discussion. The data will be analysed by meta-regression of the between-arm differences in the change in serum urate level (independent variable) from baseline to 3 months (or 6 and 12 months if 3-month values are not available) against flare rate, tophus size and number and pain at the final study visit (dependent variables).

ETHICS AND DISSEMINATION

This study will not require specific ethics approval since it is based on analysis of published (aggregated) data. The intended audience will include healthcare researchers, policymakers and clinicians. Results of the study will be disseminated by peer-reviewed publications.

TRIAL REGISTRATION NUMBER

CRD42016026991.

Strength of Validation for Surrogate End Points Used in the US Food and Drug Administration's Approval of Oncology Drugs

OBJECTIVE

To determine the strength of the surrogate-survival correlation for cancer drug approvals based on a surrogate.

PARTICIPANTS AND METHODS

We performed a retrospective study of the US Food and Drug Administration (FDA) database, with focused searches of MEDLINE and Google Scholar. Among cancer drugs approved based on a surrogate end point, we examined previous publications assessing the strength of the surrogate-survival correlation. Specifically, we identified the percentage of surrogate approvals lacking any formal analysis of the strength of the surrogate-survival correlation, and when conducted, the strength of such correlations.

RESULTS

Between January 1, 2009, and December 31, 2014, the FDA approved marketing applications for 55 indications based on a surrogate, of which 25 were accelerated approvals and 30 were traditional approvals. We could not find any formal analyses of the strength of the surrogate-survival correlation in 14 out of 25 accelerated approvals (56%) and 11 out of 30 traditional approvals (37%). For accelerated approvals, just 4 approvals (16%) were made where a level 1 analysis (the most robust way to validate a surrogate) had been performed, with all 4 studies reporting low correlation (r≤0.7). For traditional approvals, a level 1 analysis had been performed for 15 approvals (50%): 8 (53%) reported low correlation (r≤0.7), 4 (27%) medium correlation (r>0.7 to r<0.85), and 3 (20%) high correlation (r≥0.85) with survival.

CONCLUSIONS

The use of surrogate end points for drug approval often lacks formal empirical verification of the strength of the surrogate-survival association.

Correlations of survival with progression-free survival, response rate, and disease control rate in advanced biliary tract cancer: a meta-analysis of randomised trials of first-line chemotherapy

BACKGROUND

The need to promote novel drug development for advanced biliary tract cancer (ABTC) has emphasised the importance of determining whether various efficacy end points can act as surrogates for overall survival (OS).

METHODS

We conducted a literature search of randomised trials of first-line chemotherapy for ABTC and investigated correlations between efficacy end points and OS using weighted linear regression analysis. The ratios of the median OS, median progression-free survival (PFS), response rate, and disease control rate in each trial were used to summarise treatment effects. The surrogate threshold effect (STE), which was the minimum treatment effect on PFS required to predict a non-zero treatment effect on OS, was calculated.

RESULTS

Seventeen randomised trials with 36 treatment arms were identified, and a sample size of 2148 patients with 19 paired arms was analysed. The strongest correlation between all evaluated efficacy end points was observed between median OS and median PFS ratios (r(2)=0.66). In trials with gemcitabine-containing therapies and targeted agents, the r(2)-values were 0.78. The STE was estimated at 0.83 for all trials and 0.81 for trials with gemcitabine-containing therapies, and was not calculated for trials with targeted agents.

CONCLUSIONS

The median PFS ratio correlated well with the median OS ratio, and may be useful for planning a clinical trial for novel drug development.