Relationship between progression-free survival and overall survival in patients with advanced non-small cell lung cancer treated with anticancer agents after first-line treatment failure

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.

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.

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.

Clinical significance of post-progression survival in lung cancer

Progression-free survival (PFS) and overall survival (OS) are two common endpoints in cancer trials. OS is usually preferred, because it is reliable, precise, meaningful, and can easily be documented. However, subsequent lines of therapy might confound the effects of first-line treatment on OS. Whether PFS or OS is the more appropriate endpoint in clinical trials of metastatic cancer remains controversial. Previous reports on lung cancer have shown that an increase in PFS does not necessarily result in an increase in OS; however, post-progression survival (PPS) is strongly associated with OS after early-line treatment. The significance of PPS after first and second-line therapy at the individual level in patients with advanced lung cancer has also recently been reported. Findings of previous reports indicate that PPS is highly associated with OS after first and second-line chemotherapy in patients with advanced non-small cell lung cancer and small cell lung cancer, whereas PFS is only moderately associated with OS. Therefore, subsequent treatment after disease progression following early-line treatments may greatly influence OS. This review demonstrates that even in advanced lung cancer, PPS, rather than PFS, has become more strongly associated with OS over the years, potentially because of intensive post-study treatments. As a result of the increasing impact of PPS on OS, a PFS-related advantage does not necessarily indicate an OS-related advantage. Thus, the prolongation of PPS might limit the classical role of OS for assessing true efficacy derived from early-line chemotherapy in future clinical trials.

Association between time to progression and subsequent survival inceritinib-treated patients with advanced ALK-positive non-small-cell lung cancer

OBJECTIVE

Time to progression (TTP) is a surrogate marker of overall survival (OS). However, OS is also dependent on post-progression survival (PPS). This study evaluated the association between TTP and the duration of PPS among adult patients who received ceritinib (Zykadia ¹ ) for the treatment of advanced anaplastic lymphoma kinase positive (ALK+) non-small-cell lung cancer (NSCLC).

RESEARCH DESIGN AND METHODS

A pooled analysis was performed on 181 ASCEND-1 (phase I) and ASCEND-2 (phase II) patients who experienced disease progression while on ceritinib. TTP was assessed on its association with PPS in a Kaplan-Meier analysis and in Cox proportional hazard models, adjusted for clinical covariates.

MAIN OUTCOME MEASURES

Main outcomes measured include TTP, PPS, and OS.

RESULTS

Patients with TTP ≥6 months experienced significantly longer PPS compared to those with TTP <6 months (median: 9.8 vs. 6.5 months, log-rank p-value < .01). When TTP was assessed as a continuous variable, every 3 months of longer TTP was associated with a 21% lower hazard of death following progression (hazard ratio [HR]: 0.79, 95% confidence interval [CI]: 0.63-1.00; adjusted HR: 0.79, 95% CI: 0.64-0.99). This positive association translated into an OS benefit: each 3 months of longer TTP was associated with a lower hazard of death (adjusted HR: 0.46, 95% CI: 0.37-0.58). Median OS was 20.0 months for patients with TTP ≥6 months and was 10.9 months for patients with TTP <6 months.

CONCLUSIONS

A longer duration of TTP after treatment with ceritinib was significantly associated with a longer duration of both PPS and OS.

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.

The value of surrogate endpoints for predicting real-world survival across five cancer types

OBJECTIVE

It is unclear how well different outcome measures in randomized controlled trials (RCTs) perform in predicting real-world cancer survival. We assess the ability of RCT overall survival (OS) and surrogate endpoints - progression-free survival (PFS) and time to progression (TTP) - to predict real-world OS across five cancers.

METHODS

We identified 20 treatments and 31 indications for breast, colorectal, lung, ovarian, and pancreatic cancer that had a phase III RCT reporting median OS and median PFS or TTP. Median real-world OS was determined using a Kaplan-Meier estimator applied to patients in the Surveillance and Epidemiology End Results (SEER)-Medicare database (1991-2010). Performance of RCT OS and PFS/TTP in predicting real-world OS was measured using t-tests, median absolute prediction error, and R(2) from linear regressions.

RESULTS

Among 72,600 SEER-Medicare patients similar to RCT participants, median survival was 5.9 months for trial surrogates, 14.1 months for trial OS, and 13.4 months for real-world OS. For this sample, regression models using clinical trial OS and trial surrogates as independent variables predicted real-world OS significantly better than models using surrogates alone (P = 0.026). Among all real-world patients using sample treatments (N = 309,182), however, adding trial OS did not improve predictive power over predictions based on surrogates alone (P = 0.194). Results were qualitatively similar using median absolute prediction error and R(2) metrics.

CONCLUSIONS

Among the five tumor types investigated, trial OS and surrogates were each independently valuable in predicting real-world OS outcomes for patients similar to trial participants. In broader real-world populations, however, trial OS added little incremental value over surrogates alone.