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.

Relationship Between Metastasis-free Survival and Overall Survival in Patients With Nonmetastatic Castration-resistant Prostate Cancer

BACKGROUND

Metastasis-free survival (MFS) has been shown to be predictive of overall survival (OS) in hormone-sensitive localized prostate cancer. We evaluated the relationship between MFS and OS in nonmetastatic castration-resistant prostate cancer (nmCRPC).

PATIENTS AND METHODS

A retrospective analysis of 1207 high-risk patients with nmCRPC from the SPARTAN study (clinicaltrials.gov, NCT01946204) was undertaken. Landmark analyses of MFS status at several time points from randomization were performed to minimize guarantee-time bias. Hazard ratio (HR) of death as a function of MFS status was estimated based on a Cox proportional hazards model with 2-sided 95% confidence interval (CI). Estimated HRs were adjusted for stratification factors. Correlation analysis was performed using the Fleischer method.

RESULTS

At all time points, MFS status strongly predicted OS. At landmark time points of 6, 9, and 12 months, risk of death was significantly higher for patients with metastases versus those without (adjusted HR at 6 months = 4.12; 95% CI, 2.60-6.54; P < .0001). MFS was positively correlated with OS based on the Fleischer method (HR, 0.69; 95% CI, 0.69-0.70; P < .0001). Approximately one-half of the variability in OS can be explained by MFS.

CONCLUSION

Metastasis development, regardless of time point, is associated with significantly greater risk of death in men with high-risk nmCRPC; hence, MFS is predictive of OS.

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.

Evolution of randomized controlled trials and surrogacy of progression-free survival in advanced/metastatic urothelial cancer

BACKGROUND

Clinical trials in advanced/metastatic urothelial cancer have been difficult to perform. We review the current characteristics of randomized controlled trials (RCTs) and evaluate whether PFS could be a potential surrogate endpoint for overall survival (OS) in advanced/metastatic urothelial cancer.

METHODS

We identified trials by a systematic review of Medline, Embase, and the Cochrane Central Register of Controlled Trials from inception to April 2017. We included RCTs of patients with locally advanced/metastatic urothelial cancer that involved systemic therapy as an intervention, and those with reported hazards ratios (HRs) and corresponding 95% confidence intervals (CIs) for both OS and PFS, or provided Kaplan-Meier curves from which HRs and 95% CI could be calculated. The correlation coefficient between log of HRs for OS and PFS was calculated using linear regression weighted by sample size.

RESULTS

Forty eight trials that enrolled 7019 patients were included in the review and 24 RCTs were included in the surrogacy analysis. 27(56.3%) of identified 48 RCTs were phase II trials, and the median sample size was 107(range, 30-626) for all RCTs. The correlation coefficient between log HR for PFS and log HR for OS was 0.79 (95% CI, 0.58-0.91). The correlation coefficient increased to 0.87 (95% CI, 0.72-0.94) after excluding the only trial with immune checkpoint inhibitor. Multiple sensitivity analyses did not change the results..aph."/> CONCLUSIONS: PFS is strongly correlated with OS in trials of advanced/metastatic urothelial cancer assessing the treatment benefit of new drugs And PFS warrants further exploration as a surrogate endpoint in clinical trial datasets.

Early chemotherapy discontinuation and mortality in older patients with metastatic bladder cancer: The AGEVIM multicenter cohort study

PURPOSE

Median age for the diagnosis of metastatic bladder cancer (MBC) is 73 years. The feasibility of chemotherapy in older patients is controversial. Our objectives were to assess associations linking age to first line chemotherapy regimen selection, early chemotherapy discontinuation, and 1-year mortality in everyday practice.

MATERIALS AND METHODS

Between 1999 and 2011, 197 consecutive patients aged≥70 years with MBC referred to 4 hospitals were included in the AGEVIM multicenter cohort. At baseline, we recorded performance status (PS); tumor characteristics; the Charlson Comorbidity Index; and plasma creatinine, hemoglobin, and albumin. Early discontinuation data were available for 193 patients, and overall 1-year mortality for 180 patients. We assessed the probabilities of initial cisplatin-based combination chemotherapy (CCC), early discontinuation (≤2 cycles), and 1-year mortality, using multivariate logistic regression and Cox proportional hazards modeling.

RESULTS

Among the 193 patients (mean age: 76±4.3y), with 2 metastatic site in median 43.5% received CCC, 36.3% gemcitabine and carboplatin, and 20.2% gemcitabine alone. The probability of CCC decreased with age independently from sex, PS, creatinine clearance, and Charlson Comorbidity Index (P<0.0001), early discontinuation occurred in 24.9% of patients. Factors independently associated with global chemotherapy early discontinuation were age (adjusted odds ratio_{per additional year} = 1.11; 95% CI: 1.02-1.20; P = 0.01) and higher metastatic-site number (adjusted odds ratio_{per additional site} = 1.45; 95% CI: 1.08-1.95; P = 0.01). The number of patients was too small for a robust analysis of factors associated with early chemotherapy discontinuation in each chemotherapy regiment subgroup. Independent predictors of 1-year mortality (median = 9.6 mo) were early discontinuation (adjusted hazard ratio [aHR] = 4.77 [2.85-7.96] when PS<2 and 20.6 [9.43-44.82] when PS≥2; P<0.0001), albumin<35g/l (aHR = 3.06 [1.81-5.17], P = 0.0001), creatinine clearance<30ml/min (aHR = 2.96 [1.45-6.06], P = 0.009), and higher metastatic-site number (aHR = 1.34 [1.14-1.56], P<0.0001).

CONCLUSION

Less than half of older patients with MBC received initial CCC and 25% had≤2 cycles of chemotherapy. Older age was associated with decreased CCC prescription, independently from known contraindications, and with global chemotherapy early discontinuation, but not with 1-year mortality.

The safety and efficacy of single-agent pemetrexed in platinum-resistant advanced urothelial carcinoma: a large single-institution experience

BACKGROUND

Pemetrexed is a commonly used treatment for platinum-resistant advanced urothelial carcinoma (UC) based on objective response rates of 8% and 28% in two small phase II studies. To address the discrepancy in reported response rates and to assess efficacy and toxicity outside of a clinical trial setting, we performed a large retrospective analysis of pemetrexed use at Memorial Sloan Kettering Cancer Center. We also investigated candidate prognostic factors for overall survival in this setting to explore whether the neutrophil-lymphocyte ratio (NLR) had independent prognostic significance.

PATIENTS AND METHODS

Patients receiving pemetrexed for platinum-resistant advanced UC between 2008 and 2013 were identified. The Response Evaluation Criteria in Solid Tumors (RECIST, version 1.1) were used to determine response rate. Kaplan-Meier and Cox regression analyses were used to examine the association of various factors with efficacy and survival outcomes. Hematologic toxicity and laboratory abnormalities were recorded.

RESULTS

One hundred and twenty-nine patients were treated with pemetrexed. The objective response rate was 5% (95% confidence interval: 1%-9%), and the median duration of response was 8 months. Median progression-free survival (PFS) was 2.4 months, and the 6-month PFS rate was 14%. There was no significant difference in response rate by age, Eastern Cooperative Oncology Group (ECOG) performance status, or number of prior therapies. On multivariable analysis, ECOG performance status (p < .01), liver metastases (p = .02), and NLR (p < .01) had independent prognostic significance for overall survival.

CONCLUSION

This 129-patient series is the largest reported data set describing pemetrexed use in advanced UC. Activity was modest, although discovery of molecular biomarkers predictive of response would be valuable to identify the small subset of patients who do gain significant benefit. Overall, the data highlight the urgent need to develop novel therapies for these patients.

Future directions and targeted therapies in bladder cancer

There are substantial unmet needs for patients with metastatic urothelial carcinoma (UC). First-line cisplatin-based chemotherapy regimens yield a median survival of 12 to 15 months and long-term survival in 5% to 15%. Salvage systemic therapy yields a median survival of 6 to 8 months. Hence, the discovery of novel therapeutic targets is of paramount importance. Recent molecular analyses have provided insights regarding molecular tumor tissue alterations on multiple platforms. A multidisciplinary effort using innovative clinical trial designs and exploiting preclinical signals of robust activity guided by predictive biomarkers may provide much needed clinical advances in therapy for advanced UC.