Heterogeneity in Survival with Immune Checkpoint Inhibitors and Its Implications for Survival Extrapolations: A Case Study in Advanced Melanoma.

Background: Survival heterogeneity and limited trial follow-up present challenges for estimating lifetime benefits of oncology therapies. This study used CheckMate 067 (NCT01844505) extended follow-up data to assess the predictive accuracy of standard parametric and flexible models in estimating the long-term overall survival benefit of nivolumab plus ipilimumab (an immune checkpoint inhibitor combination) in advanced melanoma. Methods: Six sets of survival models (standard parametric, piecewise, cubic spline, mixture cure, parametric mixture, and landmark response models) were independently fitted to overall survival data for treatments in CheckMate 067 (nivolumab plus ipilimumab, nivolumab, and ipilimumab) using successive data cuts (28, 40, 52, and 60 mo). Standard parametric models allow survival extrapolation in the absence of a complex hazard. Piecewise and cubic spline models allow additional flexibility in fitting the hazard function. Mixture cure, parametric mixture, and landmark response models provide flexibility by explicitly incorporating survival heterogeneity. Sixty-month follow-up data, external ipilimumab data, and clinical expert opinion were used to evaluate model estimation accuracy. Lifetime survival projections were compared using a 5% discount rate. Results: Standard parametric, piecewise, and cubic spline models underestimated overall survival at 60 mo for the 28-mo data cut. Compared with other models, mixture cure, parametric mixture, and landmark response models provided more accurate long-term overall survival estimates versus external data, higher mean survival benefit over 20 y for the 28-mo data cut, and more consistent 20-y mean overall survival estimates across data cuts. Conclusion: This case study demonstrates that survival models explicitly incorporating survival heterogeneity showed greater accuracy for early data cuts than standard parametric models did, consistent with similar immune checkpoint inhibitor survival validation studies in advanced melanoma. Research is required to assess generalizability to other tumors and disease stages. Highlights: Given that short clinical trial follow-up periods and survival heterogeneity introduce uncertainty in the health technology assessment of oncology therapies, this study evaluated the suitability of conventional parametric survival modeling approaches as compared with more flexible models in the context of immune checkpoint inhibitors that have the potential to provide lasting survival benefits.This study used extended follow-up data from the phase III CheckMate 067 trial (NCT01844505) to assess the predictive accuracy of standard parametric models in comparison with more flexible methods for estimating the long-term survival benefit of the immune checkpoint inhibitor combination of nivolumab plus ipilimumab in advanced melanoma.Mixture cure, parametric mixture, and landmark response models provided more accurate estimates of long-term overall survival versus external data than other models tested.In this case study with immune checkpoint inhibitor therapies in advanced melanoma, extrapolation models that explicitly incorporate differences in cancer survival between observed or latent subgroups showed greater accuracy with both early and later data cuts than other approaches did.

Indirect treatment comparison of nivolumab versus placebo as adjuvant treatment for resected melanoma.

BACKGROUND: Nivolumab (an anti-programmed death-1 antibody) is an adjuvant standard of care for patients with high-risk resected melanoma, although a watch-and-wait strategy remains an option. In the absence of head-to-head evidence, an indirect treatment comparison (ITC) of adjuvant nivolumab versus placebo, the proxy for a watch-and-wait strategy, was conducted in patients with high-risk resected melanoma. METHODS: An ITC using the Bucher method compared nivolumab with placebo using intention-to-treat population data from the phase III CheckMate 238 (nivolumab vs ipilimumab; minimum follow-up, 4 years; NCT02388906) and European Organisation for Research and Treatment of Cancer (EORTC) 18071 (ipilimumab vs placebo; minimum follow-up, ≈4.5 years; NCT00636168) trials. The end-points were recurrence-free survival (RFS), distant metastasis-free survival (DMFS) and overall survival (OS). To account for cross-trial differences in staging and subsequent therapy, additional analyses examined patients with stage IIIB/IIIC disease and adjusted post-recurrence survival in EORTC 18071, respectively. RESULTS: Nivolumab versus placebo was associated with clinically meaningful improvements in RFS (hazard ratio [HR], 0.53; 95% confidence interval [CI], 0.42-0.68) and OS (HR, 0.63; 95% CI, 0.45-0.89). Nivolumab versus placebo was also associated with clinically meaningful improvements in RFS (HR, 0.53; 95% CI, 0.40-0.69), DMFS (HR, 0.62; 95% CI, 0.46-0.83) and OS (HR, 0.67; 95% CI, 0.47-0.97) in patients with stage IIIB/IIIC disease and in OS (HR, 0.65; 95% CI, 0.46-0.92) in the overall population after adjusting post-recurrence survival in EORTC 18071. CONCLUSION: This ITC shows that adjuvant nivolumab provides clinically meaningful improvements in RFS, DMFS and OS versus a watch-and-wait strategy in high-risk resected melanoma.

Comparative efficacy and safety of adjuvant nivolumab versus other treatments in adults with resected melanoma: a systematic literature review and network meta-analysis.

BACKGROUND: Immune checkpoint inhibitors and targeted therapies are approved for adjuvant treatment of patients with resected melanoma; however, they have not been compared in randomized controlled trials (RCTs). We compared the efficacy and safety of adjuvant nivolumab with other approved treatments using available evidence from RCTs in a Bayesian network meta-analysis (NMA). METHODS: A systematic literature review was conducted through May 2019 to identify relevant RCTs evaluating approved adjuvant treatments. Outcomes of interest included recurrence-free survival (RFS)/disease-free survival (DFS), distant metastasis-free survival (DMFS), all-cause grade 3/4 adverse events (AEs), discontinuations, and discontinuations due to AEs. Time-to-event outcomes (RFS/DFS and DMFS) were analyzed both assuming that hazard ratios (HRs) are constant over time and that they vary. RESULTS: Of 26 identified RCTs, 19 were included in the NMA following a feasibility assessment. Based on HRs for RFS/DFS, the risk of recurrence with nivolumab was similar to that of pembrolizumab and lower than that of ipilimumab 3 mg/kg, ipilimumab 10 mg/kg, or interferon. Risk of recurrence with nivolumab was similar to that of dabrafenib plus trametinib at 12 months, however, was lower beyond 12 months (HR [95% credible interval] at 24 months, 0.46 [0.27-0.78]; at 36 months, 0.28 [0.14-0.59]). Based on HRs for DMFS, the risk of developing distant metastases was lower with nivolumab than with ipilimumab 10 mg/kg or interferon and was similar to dabrafenib plus trametinib. CONCLUSION: Adjuvant therapy with nivolumab provides an effective treatment option with a promising risk-benefit profile.

Cost-Utility Analysis of Nivolumab in Adjuvant Treatment of Melanoma in France.

INTRODUCTION: The aim of the current study is to estimate the cost-effectiveness of adjuvant treatment with nivolumab relative to clinically relevant comparators in adult patients with melanoma with lymph node involvement or metastatic disease who have undergone complete resection from a French societal perspective. METHODS: The comparators were observation, low-dose interferon and pembrolizumab. A subgroup analysis was carried out in patients with BRAF mutation, adding dabrafenib plus trametinib. A three-state partitioned survival model was developed to project costs and health benefits over a 20-year time horizon. Extrapolation for recurrence-free survival (RFS) and overall survival (OS) was carried out using spline-based models. Because of the immaturity of OS data in pivotal trials for nivolumab and pembrolizumab, a predictive model of OS treatment effect based on RFS effect was developed using a correlation equation. Health state utilities and adverse events disutilities were derived from the CheckMate 238 trial and literature. Costs were estimated in 2019 euros. The model's primary outcome was efficiency frontier. Deterministic and probabilistic sensitivity analyses were conducted to assess the robustness of results. RESULTS: Observation, low-dose interferon and nivolumab were on the efficiency frontier. The incremental cost-utility ratio of nivolumab versus low-dose interferon (closest therapy on the efficiency frontier) was €37,886/quality-adjusted life year (QALY). Probabilistic sensitivity analysis reported an 80% probability of nivolumab being a cost-effective strategy for a willingness-to-pay threshold of €52,000/QALY. In the subgroup with BRAF mutation, the efficiency frontier was not changed by the addition of dabrafenib plus trametinib. CONCLUSIONS: Nivolumab is a cost-effective strategy as adjuvant treatment in adult patients with surgically resected melanoma in France.

Indirect treatment comparison of nivolumab versus placebo for the adjuvant treatment of melanoma.

INTRODUCTION: Until recently, adjuvant treatment options for stage III and IV resectable melanoma have been limited. Patients were often managed through routine surveillance. The phase III randomised controlled trial (RCT) CheckMate 238 (238) demonstrated the safety and efficacy of nivolumab as an adjuvant treatment for melanoma in patients with stage IIIB/C or IV disease (American Joint Committee on Cancer [AJCC], 7th edition) versus ipilimumab. The study objective was to estimate the relative efficacy, safety and health-related quality of life (HRQoL) between nivolumab and routine surveillance. METHODS: Indirect treatment comparisons (ITCs) of nivolumab versus placebo were constructed using data from 238 and EORTC 18071. EORTC 18071 is a phase III RCT comparing ipilimumab with placebo in patients with resected stage IIIA-IIIC melanoma (AJCC, 6th edition). ITCs were performed using the Bucher comparison method and patient-level data for efficacy, safety and HRQoL. RESULTS: For the efficacy outcomes, nivolumab performed significantly better than placebo for recurrence-free survival (hazard ratio [HR]: 0.53 [95% confidence interval {CI}: 0.41, 0.68]) and distant metastases-free survival (HR: 0.59 [95% CI: 0.44, 0.78]). Safety ITCs indicated that patients receiving nivolumab had a greater hazard of experiencing an adverse event (AE) and AEs leading to treatment discontinuation, whereas there was a non-significant increased hazard of experiencing a serious AE. HRQoL ITCs showed comparable time to deterioration in 14 of the 15 QLQ-C30 domains; only the dyspnoea domain significantly favoured placebo. CONCLUSION: Nivolumab was associated with significantly improved efficacy outcomes versus placebo, whereas maintaining patient's overall HRQoL. Across the different analysis and populations, there was a high level of consistency in the effect size.

Modelling Survival of Patients Treated with Adjuvant Nivolumab Who Have Melanoma with Lymph Node Involvement or Metastatic Disease After Complete Resection.

INTRODUCTION: Nivolumab demonstrated significant recurrence-free survival (RFS) gains versus ipilimumab in the CheckMate-238 trial, whereas the CA184-029 trial showed superior RFS gains for ipilimumab versus placebo. No head-to-head trial data were available to compare the efficacy of nivolumab to that of observation, so indirect treatment comparisons were required. Additionally, overall survival (OS) data were not available from CheckMate-238, and the clinical pathway for melanoma has changed significantly over the last decade. Four modelling options were developed using different methods and evidence sources to estimate OS and the impact of nivolumab on predicted life-years in the adjuvant setting; however, this article focuses on two primary methods. METHODS: RFS for nivolumab and observation were informed by a patient-level data meta-regression. The first model was a partitioned survival model, where the parametric OS curve for observation was derived from CA184-029 and nivolumab OS was based on a surrogacy relationship between RFS and OS specific to adjuvant melanoma. The other option used a state-transition model to estimate post-recurrence survival using different data sources. RESULTS: The modelling options estimated different OS for both nivolumab and observation but demonstrated at least a 32% increase in life-years gained for nivolumab versus observation. CONCLUSION: This analysis demonstrated the difficulties in modelling within the adjuvant setting. Each model produced different survival projections, showing the need to explore different techniques to address the extent of uncertainty. This also highlighted the importance of understanding the impact of RFS in the long term in a setting where the aim of treatment is to remain disease free.