The Search for Surrogate Endpoints in Trials in Diffuse Large B-Cell Lymphoma: The Surrogate Endpoints for Aggressive Lymphoma Project

Progression-free survival at 24 months (PFS24) and subsequent outcome for patients with diffuse large B-cell lymphoma (DLBCL) enrolled on randomized clinical trials

Background

Patients with diffuse large B-cell lymphoma treated with first-line anthracycline-based immunochemotherapy and remaining in remission at 2 years have excellent outcomes. This study assessed overall survival (OS) stratified by progression-free survival (PFS) at 24 months (PFS24) using individual patient data from patients with DLBCL enrolled in multi-center, international randomized clinical trials as part of the Surrogate Endpoint for Aggressive Lymphoma (SEAL) Collaboration.

Patients and methods

PFS24 was defined as being alive and PFS24 after study entry. OS from PFS24 was defined as time from identified PFS24 status until death due to any cause. OS was compared with each patient's age-, sex-, and country-matched general population using expected survival and standardized mortality ratios (SMRs).

Results

A total of 5853 patients enrolled in trials in the SEAL database received rituximab as part of induction therapy and were included in this analysis. The median age was 62 years (range 18-92), and 56% were greater than 60 years of age. At a median follow-up of 4.4 years, 1337 patients (23%) had disease progression, 1489 (25%) had died, and 5101 had sufficient follow-up to evaluate PFS24. A total of 1423 assessable patients failed to achieve PFS24 with a median OS of 7.2 months (95% CI 6.8-8.1) after progression; 5-year OS after progression was 19% and SMR was 32.1 (95% CI 30.0-34.4). A total of 3678 patients achieved PFS24; SMR after achieving PFS24 was 1.22 (95% CI 1.09-1.37). The observed OS versus expected OS at 3, 5, and 7 years after achieving PFS24 was 93.1% versus 94.4%, 87.6% versus 89.5%, and 80.0% versus 83.7%, respectively.

Conclusion

Patients treated with rituximab containing anthracycline-based immunochemotherapy on clinical trials who are alive without progression at 24 months from the onset of initial therapy have excellent outcomes with survival that is marginally lower but clinically indistinguishable from the age-, sex-, and country-matched background population for 7 years after achieving PFS24.

Dynamic Risk Profiling Using Serial Tumor Biomarkers for Personalized Outcome Prediction

Accurate prediction of long-term outcomes remains a challenge in the care of cancer patients. Due to the difficulty of serial tumor sampling, previous prediction tools have focused on pretreatment factors. However, emerging non-invasive diagnostics have increased opportunities for serial tumor assessments. We describe the Continuous Individualized Risk Index (CIRI), a method to dynamically determine outcome probabilities for individual patients utilizing risk predictors acquired over time. Similar to "win probability" models in other fields, CIRI provides a real-time probability by integrating risk assessments throughout a patient's course. Applying CIRI to patients with diffuse large B cell lymphoma, we demonstrate improved outcome prediction compared to conventional risk models. We demonstrate CIRI's broader utility in analogous models of chronic lymphocytic leukemia and breast adenocarcinoma and perform a proof-of-concept analysis demonstrating how CIRI could be used to develop predictive biomarkers for therapy selection. We envision that dynamic risk assessment will facilitate personalized medicine and enable innovative therapeutic paradigms.

The role of maintenance therapy in patients with diffuse large B cell lymphoma: A systematic review and meta-analysis

Randomized trials of maintenance therapy (MT) in diffuse large B cell lymphoma (DLBCL) are inconclusive regarding its effect on overall survival (OS) and disease control. We aimed to examine the efficacy and safety of MT in this meta-analysis. Systematic review and meta-analysis of randomized controlled trials comparing MT with observation or placebo, in patients with DLBCL, who achieved complete response (CR) or partial response (PR) after first-line chemotherapy with or without rituximab. Primary outcome was OS. Secondary outcomes included relapse rate, disease control (defined as progression-free survival, event-free survival, or disease-free survival, as reported in the original trials), and safety. Our search yielded 14 trials including 5122 patients. Median age of patients was 49 to 70 years. Six trials included rituximab as the MT; three included Interferon alfa; other trials include thalidomide, lenalidomide, cyclophosphamide and prednisone, serine threonine kinase inhibitor enzastaurin, and mTOR inhibitor everolimus. MT did not improve OS compared to observation, OR 0.91, (95% CI 0.78-1.07). Results were the same in a subgroup analysis by the type of maintenance (rituximab vs other). MT did decreased relapse rate, RR 0.76 (95% CI 0.65-0.89) and improved disease control, OR 0.74 (95% CI 0.65-0.84). Disease control was significantly improved in the subgroup of studies evaluating rituximab as maintenance OR 0.61 (95% CI 0.47-0.79) and in the subgroup of R-CHOP induction studies OR 0.77 (95% CI 0.67-0.88). Serious or grade III/IV adverse events including neutropenia and infections were significantly more common in the maintenance arm, RR = 1.69 (95% CI 1.29-2.22). MT in patients with DLBCL achieving CR or PR after induction therapy did not affect OS, yet it decreased relapse rate and improved disease control at the cost of higher infection rate. Our data do not support routine administration of MT in patients with DLBCL.

Progression-Free Survival as a Surrogate End Point for Overall Survival in First-Line Diffuse Large B-Cell Lymphoma: An Individual Patient-Level Analysis of Multiple Randomized Trials (SEAL)

Purpose Overall survival (OS) is the definitive and best-established primary efficacy end point to evaluate diffuse large B-cell lymphoma (DLBCL) therapies, but it requires prolonged follow-up. An earlier end point assessed post-treatment would expedite clinical trial conduct and accelerate patient access to effective new therapies. Our objective was to formally evaluate progression-free survival (PFS) and PFS at 24 months (PFS24) as surrogate end points for OS in first-line DLBCL. Patients and Methods Individual patient data were analyzed from 7,507 patients from 13 multicenter randomized controlled trials of active treatment in previously untreated DLBCL, published after 2002, with sufficient PFS data to predict treatment effects on OS. Trial-level surrogacy examining the correlation of treatment effect estimates of PFS/PFS24 and OS was evaluated using both linear regression ( R²_WLS) and Copula bivariable ( R²_Copula) models. Prespecified criteria for surrogacy required either R²_WLS or R²_Copula ≥ 0.80 and neither < 0.7, with lower-bound 95% CI > 0.60. Results Trial-level surrogacy for PFS was strong ( R²_WLS = 0.83; R²_Copula = 0.85) and met the predefined criteria for surrogacy. At the patient level, PFS strongly correlated with OS. The surrogate threshold effect had a hazard ratio of 0.89. Surrogacy was consistent across comparisons with or without rituximab and with rituximab maintenance trials. Trial-level surrogacy for PFS24 was relatively strong ( R²_WLS = 0.77; R²_Copula = 0.78) but did not meet prespecified criteria. At the patient level, PFS24 significantly correlated with OS. The surrogate threshold effect had an odds ratio of 1.51. Conclusion This large pooled analysis of individual patient data supports PFS as a surrogate end point for OS in future randomized controlled trials evaluating chemoimmunotherapy in DLBCL. Use of this end point may expedite therapeutic development with the intent of bringing novel therapies to this patient population years before OS results are mature.