Review of meta-analyses evaluating surrogate endpoints for overall survival in oncology

Correlation Between Early Time-to-Event Outcomes and Overall Survival in Patients With Locally Advanced Head and Neck Squamous Cell Carcinoma Receiving Definitive Chemoradiation Therapy: Systematic Review and Meta-Analysis

Background

Overall survival (OS) is the most patient-relevant outcome in oncology; however, in early cancers, large sample sizes and extended follow-up durations are needed to detect statistically significant differences in OS between interventions. Use of early time-to-event outcomes as surrogates for OS can help facilitate faster approval of cancer therapies. In locally advanced head and neck squamous cell carcinoma (LA-HNSCC), event-free survival (EFS) was previously evaluated as a surrogate outcome (Michiels 2009) and demonstrated a strong correlation with OS. The current study aimed to further assess the correlation between EFS and OS in LA-HNSCC using an updated systematic literature review (SLR) focusing on patients receiving definitive chemoradiation therapy (CRT).

Methods

An SLR was conducted on May 27, 2021 to identify randomized controlled trials assessing radiotherapy alone or CRT in the target population. Studies assessing CRT and reporting hazard ratios (HRs) or Kaplan-Meier data for OS and EFS were eligible for the analysis. CRT included any systemic treatments administered concurrently or sequentially with radiation therapy. Trial-level EFS/OS correlations were assessed using regression models, and the relationship strength was measured with Pearson correlation coefficient (R). Correlations were assessed across all CRT trials and in trial subsets assessing concurrent CRT, sequential CRT, RT+cisplatin, targeted therapies and intensity-modulated RT. Subgroup analysis was conducted among trials with similar EFS definitions (i.e. EFS including disease progression and/or death as events) and longer length of follow-up (i.e.≥ 5 years).

Results

The SLR identified 149 trials of which 31 were included in the analysis. A strong correlation between EFS and OS was observed in the overall analysis of all CRT trials (R=0.85, 95% confidence interval: 0.72-0.93). Similar results were obtained in the sensitivity analyses of trials assessing concurrent CRT (R=0.88), sequential CRT (R=0.83), RT+cisplatin (R=0.82), targeted therapies (R=0.83) and intensity-modulated RT (R=0.86), as well as in trials with similar EFS definitions (R=0.87), with longer follow-up (R=0.81).

Conclusion

EFS was strongly correlated with OS in this trial-level analysis. Future research using individual patient-level data can further investigate if EFS could be considered a suitable early clinical endpoint for evaluation of CRT regimens in LA-HNSCC patients receiving definitive CRT.

Addition of EGFR inhibitors to standard chemotherapy increases survival of advanced head and neck squamous cell carcinoma patients: a systematic review and meta-analysis

Head and neck squamous cell carcinoma (HNSCC) is among the common tumors associated with high mortality. The aim of our meta-analysis was to determine how additional anti-EGFR (epidermal growth factor receptor) therapy to standard chemotherapy affects the progression-free (PFS) and overall survival (OS) of the patients, besides the most common side effects. We used CENTRAL, MEDLINE and Embase databases until October 26, 2020, and included 13 eligible randomized controlled trials in our systematic research. The pooled hazard ratios (HR) for the main outcomes from the original data were estimated and for the other dichotomous outcomes, odds ratios (ORs) with their 95% confidence intervals (CI) were calculated. Addition of EGFR inhibitors to conventional chemotherapy significantly decreased the death and disease progression (for PFS HR:0.68, 95% CI:0.55-0.81, I² =65.5%, p=0.005) and mortality (for OS HR:0.83, 95% CI:0.72-0.94, I² =42.3%, p=0.076). In the EGFR inhibitor group, we revealed an increased chance of the over Grade 3 skin rashes (OR:4.86; 95% CI:1.52-15.49, I² =2.3%, p=0.407), as well as all Grade skin rashes (OR:18.32, 95% CI:8.07-41.60, I² =56.6 %, p=0.032). Despite their unwanted dermatological side effects, the addition of EGFR inhibitors are recommended to be included in advanced HNSCC therapy.

Systemic Therapy in Recurrent or Metastatic Head and Neck Squamous Cell Carcinoma- A Systematic Review and Meta-Analysis

BACKGROUND

The most effective regimen is unclear for patients with recurrent or metastatic head and neck squamous cell carcinomas (R/M HNSCC). We performed a systematic review and meta-analysis of randomized controlled trials (RCTs) investigating only systemic therapy for R/M HNSCC.

METHODS

This systematic review followed PRISMA and the Cochrane Collaboration Handbook for Systematic Reviews of Interventions. Endpoints included overall survival (OS), progression-free survival (PFS) and overall response rates (ORR).

RESULTS

55 RCTs from 1990-November 2019 qualified for review (n=12132). Only PD-1/PDL-1 inhibitors increased OS in R/M HNSCC platinum-resistant disease against their control (HR = 0·79, 95%CI 0·70-0.90, p<0·001), especially for PD-L1 ≥ 1% expressing tumours (HR = 0·72, 95%CI 0·60-0·86, p<0·001). PFS was prolonged for anti-EGFR agents against methotrexate when used in a second line setting (HR = 0·74, 95 %CI 0·62-0·87, p=0·001), and when cetuximab (HR = 0·60, 95%CI 0·49-0·72, p<0·0001) and panitumumab (HR = 0·76, 95%CI 0·65-0·89, p=0·001) were introduced to platinum-based regimens for first-line treatment.

CONCLUSIONS

PD-1/PD-L1 inhibitors may represent the future of R/M HNSCC treatment. However, EGFR inhibitors may still play improve clinical outcomes.

Association Between the Use of Surrogate Measures in Pivotal Trials and Health Technology Assessment Decisions: A Retrospective Analysis of NICE and CADTH Reviews of Cancer Drugs

OBJECTIVE

To assess whether using surrogate versus patient-relevant endpoints in pivotal trials of cancer drugs was associated with health technology assessment recommendations in England (National Institute for Health and Care Excellence [NICE]) and Canada (Canadian Agency for Drugs and Technologies in Health [CADTH]).

METHODS

Cancer drug approvals from 2012 to 2016 were categorized by demonstrating benefit on overall survival (OS), progression-free survival, disease response, or having no comparator. Approvals were analyzed by benefit category and health technology assessment recommendation. The association between benefit (surrogate vs OS) and recommending a drug was examined using descriptive statistics and linear probability models controlling for unmet need, orphan designation, and cost-effectiveness.

RESULTS

Of 42 cancer indications that NICE recommended, 15 (36%) demonstrated OS benefit. Cancer indications with OS benefit were less likely to receive a recommendation from NICE than those without (P = .04). In linear probability models, availability of OS benefit was no longer associated with a recommendation from NICE (P = .32). Cost-effective cancer drugs had a 55.6% (95% CI: 38.9%-72.3%) higher probability of receiving a recommendation from NICE than those that were not. In Canada, 15 of 37 (41%) cancer indications that were recommended showed OS benefit. There was no detectable association between surrogate measures and CADTH recommendations based on descriptive statistics (P = .62) or in linear probability models (P = .73).

CONCLUSION

When cost-effectiveness was considered, pivotal trial endpoints were not associated with NICE recommendations. Pivotal trial endpoints, unmet need, orphan status, and cost-effectiveness did not explain CADTH recommendations.

Endpoint surrogacy in oncological randomized controlled trials with immunotherapies: a systematic review of trial-level and arm-level meta-analyses

Few cancer drugs or their indications achieved survival benefit in subsequent trials during postmarket period after approval based on surrogate endpoints. This causes a concern of using surrogate endpoints instead of overall survival (OS) as the primary endpoint for trial design, implementation and regulation approval. We conducted a systematic review to summarize the findings from published meta-analyses which have evaluated endpoint surrogacy for OS in oncological randomized controlled trials (RCTs) with immunotherapies. After searching articles indexed in PubMed prior to 24 February 2019, we identified a total of 11 meta-analyses for advanced multiple tumors, non-small cell lung cancer (NSCLC), urothelial carcinoma, renal cell carcinoma, melanoma; most (91%; 10/11) focused on immune checkpoint inhibitors. Although the evaluation criteria adopted by these meta-analyses for validating endpoint surrogacy were not consistent (ranging from R² ≥0.60 to R² ≥0.80), the results were consistent. Few studies show an association between OS and progression-free survival (PFS)/objective response rate (ORR) that met the lowest evaluation criteria (R² ≥0.60), based on treatment effects (8%; 2/26 indications) or absolute results from experimental arm (0%; 0/11 indications). However, the association between OS and 1-year survival rate met the lowest criteria based on both the trial-level results (4/4 indications) and the arm-level results (5/5 indications). In lieu of this finding, we are supportive of an alternative endpoint, e.g., 1-year survival rate, rather than the more conventional choices PFS and ORR, as promising surrogate endpoint for OS in immunotherapy RCTs. We encourage further investigation on endpoint surrogacy based on the same or different settings, especially an assessment on survival rate at milestone time (e.g., 1-year), which has been demonstrated valuable for predicting OS in meta-analyses.

Early experiences with PD-1 inhibitor treatment of platinum resistant epithelial ovarian cancer

Objective

In this study, we evaluated the toxicity and clinical efficacy of nivolumab, a programmed cell death protein 1 (PD-1) inhibitor, on patients with platinum resistant ovarian cancer.

Methods

Every second week, 18 patients with platinum resistance ovarian cancer received nivolumab until disease progression occurred. We assessed toxicity, disease control rate, progression free survival (PFS) and overall survival (OS). Radiological response evaluation according to irRECIST was performed every 12th week, while clinical evaluation was done every second week.

Results

The disease control rate was 44% (95% confidence interval [CI]=19–87) as 8 showed stable disease, 6 showed progressive disease and 4 died before the first radiological response evaluation. The median OS was 30 weeks (95% CI=14–42; range, 3–95), and PFS was 15 weeks (95% CI=13–17). The median follow-up time was 30 weeks (range, 3–123). The rate of grade 2–5 adverse events was 28% (5 out of 18). Two patients (11%) developed grade 2 and 3 adverse events, respectively, while no grade 4 events were observed. One patient died from intestinal perforation, believed to be caused by concomitant bevacizumab rather than nivolumab.

Conclusion

This study shows few adverse events, and promising clinical efficacy when using nivolumab for ovarian cancer.

A Systematic Review and Recommendation for Reporting of Surrogate Endpoint Evaluation Using Meta-analyses

Background

Meta-analysis of randomized controlled trials (RCTs) has been widely conducted for the evaluation of surrogate endpoints in oncology, but little attention has been given to the adequacy of reporting and interpretation. This review evaluated the reporting quality of published meta-analyses on surrogacy evaluation and developed recommendations for future reporting.

Methods

We searched PubMed through August 2017 to identify studies that evaluated surrogate endpoints using the meta-analyses of RCTs in oncology. Both individual patient data (IPD) and aggregate data (AD) meta-analyses were included for the review.

Results

Eighty meta-analyses were identified: 22 used IPD and 58 used AD from multiple RCTs. We observed variability and reporting deficiencies in both IPD and AD meta-analyses, especially on reporting of trial selection, endpoint definition, study and patient characteristics for included RCTs, and important statistical methods and results. Based on these findings, we proposed a checklist and recommendations to improve completeness, consistency, and transparency of reports of meta-analytic surrogacy evaluation. We highlighted key aspects of the design and analysis of surrogate endpoints and presented explanations and rationale why these items should be clearly reported in surrogacy evaluation.

Conclusions

Our reporting of surrogate endpoint evaluation using meta-analyses (ReSEEM) guidelines and recommendations will improve the quality in reporting and facilitate the interpretation and reproducibility of meta-analytic surrogacy evaluation. Also, they should help promote greater methodological consistency and could also serve as an evaluation tool in the peer review process for assessing surrogacy research.

Oncologic orphan drugs approved in the EU - do clinical trial data correspond with real-world effectiveness?

BACKGROUND

Evaluation of evidence for efficacy of orphan medicinal products (OMPs) for rare malignancies may be hampered by the use of tumor measurements instead of clinical endpoints. This may cause efficacy data to not always match effectiveness in the real-world. We investigated whether an efficacy-effectiveness gap exists for oncologic OMPs and aimed to identify which factors contribute to it. Also, the magnitude of the clinical efficacy of oncologic OMPs was evaluated.

METHODS

We included all oncologic OMPs authorized in the European Union from 2000 to 2017. Pivotal studies were evaluated by means of the European Society for Medical Oncology - Magnitude of Clinical Benefit Scale (ESMO-MCBS). To estimate real-world effectiveness, a literature search was performed to identify post-marketing studies, of which data on overall survival (OS) were extracted. OS of the new OMP was compared with OS data of standard of care. An OS gain of ≥3 months compared to pre-marketing data was considered clinically relevant.

RESULTS

Twenty OMPs were included, of which 5 were authorized based on OS as a primary endpoint. 10 OMPs had post-marketing data available, of which 40% did not show a clinically relevant OS gain in the real world. All OMPs that were studied with OS as primary endpoint in the pivotal study had a clinically relevant OS gain in the real world. Furthermore, all OMPs that had a high ESMO-MCBS score and post-marketing data available, resulted in a clinically relevant OS gain in the real world.

CONCLUSIONS

Although the sample size is small, our results indicate an efficacy-effectiveness gap for oncologic OMPs exists. Significant changes in PFS do not always lead to an increased OS. The use of PFS may be justified, but validation of surrogate endpoints is needed.

Use of depth of response to predict progression-free survival in relapsed or refractory multiple myeloma: Evaluation of results from 102 clinical trials

Progression-free survival (PFS) is the standard endpoint for demonstration of clinical effectiveness of novel therapies in relapsed or refractory multiple myeloma (RRMM). However, the long evaluation times for PFS limits its usefulness in the development of new therapies. Therefore, the objective of this analysis was to determine the relationship between response rates and median PFS in RRMM. A database was systematically developed from 268 identified RRMM trials reported from 1999 to 2016. Evaluated covariates for the relationship between response rates and PFS included age, sex, drug class(es), and number of drug classes. One-hundred two (102) trials involving 136 cohorts were included in the meta-analysis, representing 13 322 patients in total. Regression analysis using response rates and median PFS indicated that the correlation between very good partial response (VGPR) or better and median PFS was higher (R2  = 0.63) than the separately analyzed correlations between clinical benefit, overall response, or complete response rate and median PFS (R2  = 0.47 - 0.52). Subsequent covariate analysis revealed that treatment with an immunomodulatory imide drug (IMiD) further improved the relationship (R2  = 0.69), with a longer median PFS at a given VGPR or better rate when at least 1 drug treatment was an IMiD. Number of drug classes was not found to alter this relationship. In conclusion, VGPR or better rate can be used to predict the median PFS, with adjustment for the additional PFS provided by an IMiD.

Relapse-Free Survival as a Surrogate for Overall Survival in the Evaluation of Stage II-III Melanoma Adjuvant Therapy

Background

We assessed whether relapse-free survival (RFS; time until recurrence/death) is a valid surrogate for overall survival (OS) among resected stage II-III melanoma patients through a meta-analysis of randomized controlled trials.

Methods

Individual patient data (IPD) on RFS and OS were collected from 5826 patients enrolled in 11 randomized adjuvant trials comparing interferon (IFN) to observation. In addition, IPD from two studies comparing IFN and vaccination in 989 patients were included. A two-level modeling approach was used for assessing Spearman's patient-level correlation (rho) of RFS and OS and the trial-level coefficient of determination (R²) of the treatment effects on RFS and on OS. The results were validated externally in 13 adjuvant studies without available IPD. We then tested the results on the European Organisation for Research and Treatment of Cancer (EORTC) 18071 double-blind trial comparing ipilimumab 10 mg/kg with placebo, which showed a statistically significant impact of the checkpoint inhibitor on RFS and OS. All statistical tests were two-sided.

Results

With a median follow-up of seven years, 12 of 13 trials showed a consistency between the IFN vs No IFN differences regarding RFS (hazard ratio [HR]RFS = 0.88) and OS (HROS = 0.91), but the small trial, Eastern Cooperative Oncology Group 2696, was an outlier (HRRFS = 0.72 vs HROS = 1.11). Therefore, even if rho was high, R² was low and could not reliably be estimated. Based on the 12 trials, rho remained high (0.89), and the hazard ratios for RFS and OS were strongly correlated (R² = 0.91). The surrogate threshold effect for RFS was estimated to be 0.77. For the EORTC 18071 trial, the hazard ratio for RFS was 0.75, predicting an effect of ipilimumab on OS. This was subsequently confirmed (HROS = 0.72, 95.1% confidence interval = 0.58 to 0.88, P = .001).

Conclusions

In high-risk stage II-III melanoma, RFS appeared to be a valid surrogate end point for OS for adjuvant randomized studies assessing interferon or a checkpoint inhibitor. In future similar adjuvant studies, a hazard ratio for RFS of 0.77 or less would predict a treatment impact on OS.

Model-based meta-analysis of progression-free survival in non-Hodgkin lymphoma patients

BACKGROUND

Non-Hodgkin lymphoma (NHL) is a group of lymphoproliferative malignancies with varying treatment responses and progression-free survival (PFS) times. The objective of this study was to quantify the effect of treatment and patient-population characteristics on PFS in patients with NHL.

METHODS

A database was developed from 513 NHL clinical trials reported from 1993 to 2015. Summary-level PFS was obtained from 112 of these trials, which included 155 cohorts and 11,824 patients. Characteristics evaluated for their impact on PFS included cohort treatment, percentage of patients with each NHL subtype, percentage of patients with different numbers of prior treatments, percentage of subjects previously administered rituximab, performance status, disease stage, median age, and sex distribution.

RESULTS

Rituximab, bendamustine, CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone combination)/CHOP-like, and other nonchemotherapy drugs, aside from bortezomib, prolonged median PFS time 2 to 4-fold. Follicular lymphoma patients had 60% longer median PFS time than mantle cell lymphoma (MCL) patients, while diffuse large B-cell lymphoma patients had a median PFS time that was 25% of MCL patients. Patients who received ≤1 prior treatment had median PFS times > 10-fold longer than patients who received ≥2 prior treatments. The final model predicted the hazard ratio in 75% of the studies within 25% of the observed value and the observed median PFS time of 92% of the studies fell within the predicted 90% confidence intervals.

CONCLUSIONS

The developed PFS model predicts the median PFS time and hazard ratio for specific populations and treatment combinations quantitatively and can potentially be extended to link short-term and long-term clinical outcomes.

Progression-Free Survival and Time to Progression as Real Surrogate End Points for Overall Survival in Advanced Breast Cancer: A Meta-Analysis of 37 Trials

BACKGROUND

Progression-free survival (PFS) and time to progression (TTP) have been reported to correlate with overall survival (OS) in several cancer types. To our knowledge, however, the correlation between them is unclear.

METHODS

A literature-based meta-analysis was performed to assess whether PFS and TTP can be considered reliable surrogate end points for OS in a phase 3 clinical trial of advanced breast cancer (ABC). The median hazard ratios of PFS/TTP and OS were analyzed by determining their nonparametric Spearman rank correlation coefficients (Rs).

RESULTS

A total of 37 trials with 38 treatment arms and 14,966 patients were selected for analysis. The Rs between the median PFS/TTP and OS was 0.405 (95% confidence interval [CI], 0.191-0.582; P = .003), and the correlation coefficient between the hazard ratios of PFS/TTP and OS was 0.555 (95% CI, 0.277-0.748; P = .003). PFS/TTP was closely correlated with OS in the trials of targeted therapy-based treatment (Rs = 0.872; 95% CI, 0.619-0.962; P = .0001) and of PFS/TTP or OS benefit (Rs = 0.753 and Rs = 0.821, respectively) for ABC.

CONCLUSIONS

Both PFS and TTP can be considered valid surrogate end points for OS in the trials of targeted therapy-based treatments and clinical benefits for ABC. Further research is necessary to clarify the surrogacy of PFS/TTP for OS in other trials of targeted therapy-based treatments for ABC.

Predicting Real-World Effectiveness of Cancer Therapies Using Overall Survival and Progression-Free Survival from Clinical Trials: Empirical Evidence for the ASCO Value Framework

OBJECTIVES

To measure the relationship between randomized controlled trial (RCT) efficacy and real-world effectiveness for oncology treatments as well as how this relationship varies depending on an RCT's use of surrogate versus overall survival (OS) endpoints.

METHODS

We abstracted treatment efficacy measures from 21 phase III RCTs reporting OS and either progression-free survival or time to progression endpoints in breast, colorectal, lung, ovarian, and pancreatic cancers. For these treatments, we estimated real-world OS as the mortality hazard ratio (RW MHR) among patients meeting RCT inclusion criteria in Surveillance and Epidemiology End Results-Medicare data. The primary outcome variable was real-world OS observed in the Surveillance and Epidemiology End Results-Medicare data. We used a Cox proportional hazard regression model to calibrate the differences between RW MHR and the hazard ratios on the basis of RCTs using either OS (RCT MHR) or progression-free survival/time to progression surrogate (RCT surrogate hazard ratio [SHR]) endpoints.

RESULTS

Treatment arm therapies reduced mortality in RCTs relative to controls (average RCT MHR = 0.85; range 0.56-1.10) and lowered progression (average RCT SHR = 0.73; range 0.43-1.03). Among real-world patients who used either the treatment or the control arm regimens evaluated in the relevant RCT, RW MHRs were 0.6% (95% confidence interval -3.5% to 4.8%) higher than RCT MHRs, and RW MHRs were 15.7% (95% confidence interval 11.0% to 20.5%) higher than RCT SHRs.

CONCLUSIONS

Real-world OS treatment benefits were similar to those observed in RCTs based on OS endpoints, but were 16% less than RCT efficacy estimates based on surrogate endpoints. These results, however, varied by tumor and line of therapy.

Fifth Ovarian Cancer Consensus Conference of the Gynecologic Cancer InterGroup: recurrent disease

This manuscript reports the consensus statements regarding recurrent ovarian cancer (ROC), reached at the fifth Ovarian Cancer Consensus Conference (OCCC), which was held in Tokyo, Japan, in November 2015. Three important questions were identified: (i) What are the subgroups for clinical trials in ROC? The historical definition of using platinum-free interval (PFI) to categorise patients as having platinum-sensitive/resistant disease was replaced by therapy-free interval (TFI). TFI can be broken down into TFIp (PFI), TFInp (non-PFI) and TFIb (biological agent-free interval). Additional criteria to consider include histology, BRCA mutation status, number/type of previous therapies, outcome of prior surgery and patient reported symptoms. (ii) What are the control arms for clinical trials in ROC? When platinum is considered the best option, the control arm should be a platinum-based therapy with or without an anti-angiogenic agent or a poly (ADP-ribose) polymerase (PARP) inhibitor. If platinum is not considered the best option, the control arm could include a non-platinum drug, either as single agent or in combination. (iii) What are the endpoints for clinical trials in ROC? Overall survival (OS) is the preferred endpoint for patient cohorts with an expected median OS < or = 12 months. Progression-free survival (PFS) is an alternative, and it is the preferred endpoint when the expected median OS is > 12 months. However, PFS alone should not be the only endpoint and must be supported by additional endpoints including pre-defined patient reported outcomes (PROs), time to second subsequent therapy (TSST), or time until definitive deterioration of quality of life (TUDD).

Objective response rate is a possible surrogate endpoint for survival in patients with advanced, recurrent ovarian cancer

OBJECTIVE

Evaluate literature to assess response rate as a surrogate endpoint of survival in ovarian cancer (OC).

METHODS

Systematic review consistent with PRISMA criteria, identified randomized, controlled trials reporting overall survival (OS), progression-free survival (PFS), and objective response rate (ORR) in recurrent OC. MEDLINE® and Embase® searches (year 2000-March 23, 2015) were augmented by bibliographic screening. Proposed surrogate measures (independent variables) were ORR and disease control rate. True clinical outcomes (dependent variables) were median OS and PFS. Analyses were performed on unweighted and weighted data using correlation analysis, linear regression, and surrogate threshold effect (STE). Smaller STE indicates greater predictive precision with magnitude of STE dependent on variance of prediction.

RESULTS

Thirty-nine studies were included for review, representing 9223 platinum-sensitive and resistant patients. Objective response rate (r=0.82; P<0.001) was a better predictor than disease control rate (r=0.58; P<0.001) and strongly correlated with PFS (r=0.85; P<0.0001). Weighted-regression analysis demonstrated that for each 10% increase in ORR, PFS increased by 1.20months and OS by 2.83months. Regression analysis of treatment effects (odds ratio of response, hazard ratio of survival) suggests that a 10% increase in odds ratio of ORR would result in 2.5% reduction in the hazard ratio of OS. Based on weighted data, STE indicated that an ORR of ≥1% is needed to achieve nonzero OS benefit.

CONCLUSION

This systematic review supports ORR as a possible surrogate clinical trial endpoint for OS in recurrent OC with at least second-line therapy.

Validation of surrogate endpoints in advanced solid tumors: systematic review of statistical methods, results, and implications for policy makers

OBJECTIVES

Licensing of, and coverage decisions on, new therapies should rely on evidence from patient-relevant endpoints such as overall survival (OS). Nevertheless, evidence from surrogate endpoints may also be useful, as it may not only expedite the regulatory approval of new therapies but also inform coverage decisions. It is, therefore, essential that candidate surrogate endpoints be properly validated. However, there is no consensus on statistical methods for such validation and on how the evidence thus derived should be applied by policy makers.

METHODS

We review current statistical approaches to surrogate-endpoint validation based on meta-analysis in various advanced-tumor settings. We assessed the suitability of two surrogates (progression-free survival [PFS] and time-to-progression [TTP]) using three current validation frameworks: Elston and Taylor's framework, the German Institute of Quality and Efficiency in Health Care's (IQWiG) framework and the Biomarker-Surrogacy Evaluation Schema (BSES3).

RESULTS

A wide variety of statistical methods have been used to assess surrogacy. The strength of the association between the two surrogates and OS was generally low. The level of evidence (observation-level versus treatment-level) available varied considerably by cancer type, by evaluation tools and was not always consistent even within one specific cancer type.

CONCLUSIONS

Not in all solid tumors the treatment-level association between PFS or TTP and OS has been investigated. According to IQWiG's framework, only PFS achieved acceptable evidence of surrogacy in metastatic colorectal and ovarian cancer treated with cytotoxic agents. Our study emphasizes the challenges of surrogate-endpoint validation and the importance of building consensus on the development of evaluation frameworks.

Kernel machine score test for pathway analysis in the presence of semi-competing risks

In cancer studies, patients often experience two different types of events: a non-terminal event such as recurrence or metastasis, and a terminal event such as cancer-specific death. Identifying pathways and networks of genes associated with one or both of these events is an important step in understanding disease development and targeting new biological processes for potential intervention. These correlated outcomes are commonly dealt with by modeling progression-free survival, where the event time is the minimum between the times of recurrence and death. However, identifying pathways only associated with progression-free survival may miss out on pathways that affect time to recurrence but not death, or vice versa. We propose a combined testing procedure for a pathway's association with both the cause-specific hazard of recurrence and the marginal hazard of death. The dependency between the two outcomes is accounted for through perturbation resampling to approximate the test's null distribution, without any further assumption on the nature of the dependency. Even complex non-linear relationships between pathways and disease progression or death can be uncovered thanks to a flexible kernel machine framework. The superior statistical power of our approach is demonstrated in numerical studies and in a gene expression study of breast cancer.

Evaluation of a cloud-based local-read paradigm for imaging evaluations in oncology clinical trials for lung cancer

Background

Although tumor response evaluated with radiological imaging is frequently used as a primary endpoint in clinical trials, it is difficult to obtain precise results because of inter- and intra-observer differences.

Purpose

To evaluate usefulness of a cloud-based local-read paradigm implementing software solutions that standardize imaging evaluations among international investigator sites for clinical trials of lung cancer.

Material and Methods

Two studies were performed: KUMO I and KUMO I Extension. KUMO I was a pilot study aiming at demonstrating the feasibility of cloud implementation and identifying issues regarding variability of evaluations among sites. Chest CT scans at three time-points from baseline to progression, from 10 patients with lung cancer who were treated with EGFR tyrosine kinase inhibitors, were evaluated independently by two oncologists (Japan) and one radiologist (France), through a cloud-based software solution. The KUMO I Extension was performed based on the results of KUMO I.

Results

KUMO I showed discordance rates of 40% for target lesion selection, 70% for overall response at the first time-point, and 60% for overall response at the second time-point. Since the main reason for the discordance was differences in the selection of target lesions, KUMO I Extension added a cloud-based quality control service to achieve a consensus on the selection of target lesions, resulting in an improved rate of agreement of response evaluations.

Conclusion

The study shows the feasibility of imaging evaluations at investigator sites, based on cloud services for clinical studies involving multiple international sites. This system offers a step forward in standardizing evaluations of images among widely dispersed sites.

Efficacy and Safety Assessment of the Addition of Bevacizumab to Adjuvant Therapy Agents in Cancer Patients: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

AIM

To evaluate the efficacy and safety of bevacizumab in the adjuvant cancer therapy setting within different subset of patients.

METHODS & DESIGN/ RESULTS

PubMed, EMBASE, Cochrane and Clinical trials.gov databases were searched for English language studies of randomized controlled trials comparing bevacizumab and adjuvant therapy with adjuvant therapy alone published from January 1966 to 7th of May 2014. Progression free survival, overall survival, overall response rate, safety and quality of life were analyzed using random- or fixed-effects models according to the PRISMA guidelines. We obtained data from 44 randomized controlled trials (30,828 patients). Combining bevacizumab with different adjuvant therapies resulted in significant improvement of progression free survival (log hazard ratio, 0.87; 95% confidence interval (CI), 0.84-0.89), overall survival (log hazard ratio, 0.96; 95% CI, 0.94-0.98) and overall response rate (relative risk, 1.46; 95% CI: 1.33-1.59) compared to adjuvant therapy alone in all studied tumor types. In subgroup analyses, there were no interactions of bevacizumab with baseline characteristics on progression free survival and overall survival, while overall response rate was influenced by tumor type and bevacizumab dose (p-value: 0.02). Although bevacizumab use resulted in additional expected adverse drug reactions except anemia and fatigue, it was not associated with a significant decline in quality of life. There was a trend towards a higher risk of several side effects in patients treated by high-dose bevacizumab compared to the low-dose e.g. all grade proteinuria (9.24; 95% CI: 6.60-12.94 vs. 2.64; 95% CI: 1.29-5.40).

CONCLUSIONS

Combining bevacizumab with different adjuvant therapies provides a survival benefit across all major subsets of patients, including by tumor type, type of adjuvant therapy, and duration and dose of bevacizumab therapy. Though bevacizumab was associated with increased risks of some adverse drug reactions such as hypertension and bleeding, anemia and fatigue were improved by the addition of bevacizumab.

Relationship between progression-free survival and overall survival in chronic lymphocytic leukemia: a literature-based analysis

BACKGROUND

The endpoints of progression-free survival (pfs) and time-to-progression (ttp) are frequently used to evaluate the clinical benefit of anticancer drugs. However, the surrogacy of those endpoints for overall survival (os) is not validated in all cancer settings. In the present study, we used a trial-based approach to assess the relationship between median pfs or ttp and median os in chronic lymphocytic leukemia (cll).

METHODS

The pico (population, interventions, comparators, outcomes) method was used to conduct a systematic review of the literature. The population consisted of patients with cll; the interventions and comparators were standard therapies for cll; and the outcomes were median pfs, ttp, and os. Two independent reviewers screened titles, abstracts, and full papers for eligibility and then extracted data from selected studies. Correlation coefficients were calculated to assess the relationship between median pfs or ttp and median os. Subgroup correlation analyses were also conducted according to the characteristics of the selected studies (such as line of treatment and type of treatment under investigation).

RESULTS

Of the 1263 potentially relevant articles identified during the literature search, twenty-three were included. On average, median pfs or ttp was 16.0 months (standard deviation: 12.4 months) and median os was 43.5 months (standard deviation: 31.2 months). Results of the correlation analysis indicated that median pfs or ttp is highly correlated with median os (Spearman correlation coefficient: 0.813; p ≤ 0.001). A significant correlation between median pfs or ttp and median os was observed in second- and subsequent-line therapies, but not in the first-line setting.

CONCLUSIONS

Our study demonstrates a strong correlation between median pfs or ttp and median os in previously treated cll, which reinforce the hypothesis that pfs and ttp could be adequate surrogate endpoints for os in this cancer setting.

Which Metrics Are Appropriate to Describe the Value of New Cancer Therapies?

Patients with certain cancers are treated with curative intent, but for others the results are less favorable and different therapeutic approaches are needed. Early data suggest that new therapies, which modulate immune responses to cancers, may have potential for long-term survival in a proportion of cases. Therefore, it is timely to consider whether metrics generally used to describe the medical value of therapies for patients with common solid tumors remain appropriate for therapies with curative potential. Literature reviews were conducted to define how various stakeholders describe cure in oncology and to identify the endpoints used in clinical trials for selected solid tumors. The results showed that “cure” is described using various terms that can be divided broadly into lack of disease progression, eradication of cancerous cells, and survival. The review of trial endpoints showed frequent use of median overall survival (OS) and progression- and response-related endpoints. Because these endpoints were mainly described in the context of chemotherapies that are not generally curative, they may not adequately capture outcomes of new therapeutic modalities with potential for long-term survival. More appropriate endpoints may include mean OS, cure fraction, and OS rate at landmark time points.

Clinically meaningful end points in the evolving treatment paradigm for radioactive iodine-refractory differentiated thyroid cancer

Radioactive iodine (RAI) is often used post-operatively for treatment of differentiated thyroid cancer (DTC), but many patients develop RAI-refractory disease. Patients with RAI-refractory DTC may be asymptomatic and stable for long periods of time, so identifying tumors that are no longer likely to respond to RAI treatment and determining when to transition to systemic therapy are critical issues for optimal patient care. The purpose of this paper is to review and assess the end points used in studies of RAI-refractory DTC in relation to the issues facing clinicians in transitioning patients to systemic therapy. Our goals are to provide a framework to help evaluate whether study results are clinically meaningful in guiding treatment decisions and to make recommendations to better define these end points for RAI-refractory DTC.

Outcomes and endpoints in trials of cancer treatment: the past, present, and future

Cancer treatment should allow patients to live better or longer lives, and ideally, both. Trial endpoints should show clinically meaningful improvements in patient survival or quality of life. Alternative endpoints such as progression-free survival, disease-free survival, and objective response rate have been used to identify benefit earlier, but their true validity as surrogate endpoints is controversial. In this Review we discuss the measurement, assessment, and benefits and limitations of trial endpoints in use for cancer treatment. Many stakeholders are affected, including regulatory agencies, industry partners, clinicians, and most importantly, patients. In an accompanying Review, reflections from individual stakeholders are incorporated into a discussion of what the future holds for clinical trial endpoints and design.

Progression-free survival as a potential surrogate for overall survival in metastatic breast cancer

Background

Progression-free survival (PFS) and time to progression (TTP) are frequently used to establish the clinical efficacy of anti-cancer drugs. However, the surrogacy of PFS/TTP for overall survival (OS) remains a matter of uncertainty in metastatic breast cancer (mBC). This study assessed the relationship between PFS/TTP and OS in mBC using a trial-based approach.

Methods

We conducted a systematic literature review according to the PICO method: ‘Population’ consisted of women with mBC; ‘Interventions’ and ‘Comparators’ were standard treatments for mBC or best supportive care; ‘Outcomes’ of interest were median PFS/TTP and OS. We first performed a correlation analysis between median PFS/TTP and OS, and then conducted subgroup analyses to explore possible reasons for heterogeneity. Then, we assessed the relationship between the treatment effect on PFS/TTP and OS. The treatment effect on PFS/TTP and OS was quantified by the absolute difference of median values. We also conducted linear regression analysis to predict the effects of a new anti-cancer drug on OS on the basis of its effects on PFS/TTP.

Results

A total of 5,041 studies were identified, and 144 fulfilled the eligibility criteria. There was a statistically significant relationship between median PFS/TTP and OS across included trials (r=0.428; P<0.01). Correlation coefficient for the treatment effect on PFS/TTP and OS was estimated at 0.427 (P<0.01). The obtained linear regression equation was ΔOS =−0.088 (95% confidence interval [CI] −1.347–1.172) + 1.753 (95% CI 1.307–2.198) × ΔPFS (R²=0.86).

Conclusion

Results of this study indicate a significant association between PFS/TTP and OS in mBC, which may justify the use of PFS/TTP in the approval for commercialization and reimbursement of new anti-cancer drugs in this cancer setting.

Assessment of progression-free survival as a surrogate end-point for overall survival in patients with metastatic renal cell carcinoma

BACKGROUND

To determine suitability of progression-free survival (PFS) as a surrogate end-point for overall survival (OS), we evaluated the relationship between PFS and OS in 750 treatment-naïve metastatic renal cell carcinoma (mRCC) patients who received sunitinib or interferon-alpha (IFN-α) in a phase III study.

METHODS

The relationship between PFS and post-progression survival (PPS; the difference between PFS and OS) was studied, which correctly removes inherent dependencies between PFS and OS, to properly estimate whether and to what extent PFS can serve as a surrogate for OS. A Weibull parametric model to failure time data was fit to determine whether longer PFS was significantly and meaningfully predictive of longer PPS. In a sensitivity analysis by Kaplan-Meier non-parametric method, PPS curves for three approximately equal numbered groups of patients categorised by PFS were compared by log-rank test.

RESULTS

In the Weibull parametric model, longer PFS was significantly predictive of longer PPS (P<0.001). The model also allowed prediction of estimated median PPS duration from actual PFS times. In the Kaplan-Meier (non-parametric) analysis, incrementally longer PFS was also associated with longer PPS, and the PPS curves for the three PFS groups were significantly different (P<0.0001).

CONCLUSIONS

A positive relationship was found between PFS and PPS duration in individual mRCC patients randomised to first-line treatment with sunitinib or IFN-α. These results indicate that PFS can act as a surrogate end-point for OS in the first-line mRCC setting and provide clinical researchers with a potentially useful approach to estimate median PPS based on PFS.

Assessing response to treatment in non--small-cell lung cancer: role of tumor volume evaluated by computed tomography

INTRODUCTION

We set out to investigate whether volumetric tumor measurements allow for a prediction of treatment response, as measured by patient survival, in patients with advanced non-small-cell lung cancer (NSCLC).

MATERIALS AND METHODS

Patients with nonresectable NSCLC (stage III or IV, n = 100) who were repeatedly evaluated for treatment response by computed tomography (CT) were included in a Health Insurance Portability and Accountability Act (HIPAA)-compliant retrospective study. Tumor response was measured by comparing tumor volumes over time. Patient survival was compared with Response Evaluation Criteria in Solid Tumors (RECIST) using Kaplan-Meier survival statistics and Cox regression analysis.

RESULTS

The median overall patient survival was 553 days (standard error, 146 days); for patients with stage III NSCLC, it was 822 days, and for patients with stage IV disease, 479 days. The survival differences were not statistically significant (P = .09). According to RECIST, 5 patients demonstrated complete response, 39 partial response, 44 stable disease, and 12 progressive disease. Patient survival was not significantly associated with RECIST class, the change of the sum of tumor diameters (P = .98), nor the change of the sum of volumetric tumor dimensions (P = .17).

CONCLUSION

In a group of 100 patients with advanced-stage NSCLC, neither volumetric CT measurements of changes in tumor size nor RECIST class significantly predicted patient survival. This observation suggests that size response may not be a sufficiently precise surrogate marker of success to steer treatment decisions in individual patients.