Chrysostomos Kalyvas

Mr. Chrysostomos Kalyvas

orcid

Research Focus & Metrics

Academic Career Length

10Years (2017-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 May 2021 in Lung Cancer
Verified
Journal Article
Open access
Balazs HalmosBalazs Halmos
Balazs Halmos
TBThomas Burke
Thomas Burke
CKChrysostomos Kalyvas
Chrysostomos Kalyvas
KVKristel Vandormael
Kristel Vandormael
AFAndrew Frederickson
Andrew Frederickson
BPBilal Piperdi
Bilal Piperdi
Multiple immunotherapy and chemotherapy combinations are approved for the management of advanced NSCLC which have not been directly compared in randomized clinical trials. This study indirectly compared the effectiveness of pembrolizumab + chemotherapy versus atezolizumab + chemotherapy+/-bevacizumab for previously untreated non-squamous NSCLC patients without EGFR/ALK aberrations. A matching-adjusted indirect comparison (MAIC) was conducted using individual patient data (IPD) from KEYNOTE-021 Cohort G (KN021 G) (pembrolizumab + carboplatin + pemetrexed; N = 59) and KEYNOTE-189 (KN189) (pembrolizumab + pemetrexed + platinum chemotherapy; N = 410) and published aggregate data from IMpower 130 (atezolizumab + carboplatin + nab-paclitaxel; N = 451) and IMpower 150 (atezolizumab + carboplatin + paclitaxel + bevacizumab; N = 356). To adjust for cross-trial differences in baseline characteristics, data from patients randomized to pembrolizumab + chemotherapy in KN021 G/KN189 were reweighted to match the baseline characteristics of patients randomized to atezolizumab + chemotherapy from IMpower 130 or atezolizumab + chemotherapy + bevacizumab from IMpower 150. Outcomes included overall survival (OS), blinded independent review-assessed progression-free survival (PFS) and objective response rate (ORR). OS and PFS follow-up were truncated to the trial with shorter follow-up. Sensitivity analyses were conducted without truncation of follow-up of OS and PFS. After matching for cross-trial differences, the effective sample size of pembrolizumab + chemotherapy was 428 and 389 for the IMpower 130 and IMpower 150 comparisons, respectively. The estimated HRs (95 % CIs) of pembrolizumab + chemotherapy versus atezolizumab + chemotherapy were 0.80 (0.67,0.95) and 0.79 (0.67,0.93) with regard to OS and PFS, respectively. For pembrolizumab + chemotherapy versus atezolizumab + chemotherapy + bevacizumab, the estimated HR (95 % CIs) was 0.86 (0.72,1.03) for OS and 0.81 (0.68,0.96) for PFS. For ORR, the estimated risk ratio (95 % CI) and the risk difference (95 % CI) was 0.9 (0.8,1.1) and -3.5 % (-10.0,3.1) for pembrolizumab + chemotherapy versus atezolizumab + chemotherapy, respectively, and 0.8 (0.7,0.9) and -12.2 % (-19.6,-4.8) for pembrolizumab + chemotherapy versus atezolizumab + chemotherapy + bevacizumab, respectively. Findings were consistent across sensitivity analyses for both outcomes. MAIC results showed a significantly better OS and PFS for pembrolizumab + chemotherapy compared with atezolizumab + chemotherapy and a significantly better PFS for pembrolizumab + chemotherapy compared with atezolizumab + chemotherapy + bevacizumab.

4 December 2020 in Cancers
Verified
Journal Article
Open access
PDF file
Balazs HalmosBalazs Halmos
Balazs Halmos
TBThomas Burke
Thomas Burke
CKChrysostomos Kalyvas
Chrysostomos Kalyvas
RIRalph Insinga
Ralph Insinga
KVKristel Vandormael
Kristel Vandormael
BPBilal Piperdi
Bilal Piperdi
Background: In the absence of head-to-head trials, this study indirectly compared the effectiveness of pembrolizumab + chemotherapy vs nivolumab + ipilimumab for the first-line treatment of metastatic stage IV NSCLC patients with PD-L1 tumor proportion score (TPS) ≥1%. Methods: An anchored matching-adjusted indirect comparison (MAIC) was conducted using pooled individual patient data (IPD) from the ITT population in KEYNOTE-021G, KEYNOTE-189 and KEYNOTE-407 (n = 816) and published aggregate data of nivolumab + ipilimumab from CheckMate 227 Part 1A (n = 793). To adjust for cross-trial differences in baseline characteristics, data from KEYNOTE-021G/KEYNOTE-189/KEYNOTE-407 were re-weighted to match the baseline characteristics of CheckMate 227 Part 1A. Outcomes included OS, PFS and ORR. Base case analyses were restricted to patients with PD-L1 TPS ≥1%, with sub-group analyses in PD-L1 TPS ≥50% and 1–49%. Results: The estimated HR (95% CI) of pembrolizumab + chemotherapy vs nivolumab + ipilimumab was 0.80 (0.59,1.09) and 0.53 (0.41,0.68) for OS and PFS, respectively. For ORR, the estimated risk ratio was 1.8 (1.3,2.4) for pembrolizumab + chemotherapy vs nivolumab + ipilimumab and the risk difference was 25.5% (15.0,36.0). PD-L1 TPS ≥50% and 1–49% sub-groups showed an OS HR of 0.89 (0.58,1.36) and 0.68 (0.46,1.01), respectively. Conclusion: These MAIC results suggest that pembrolizumab + chemotherapy leads to a greater clinical benefit vs nivolumab + ipilimumab in patients with PD-L1 TPS ≥1% across multiple endpoints.

5 February 2021 in Research Synthesis Methods
Verified
Journal Article
Open access
PDF file
LSLoukia M. Spineli
Loukia M. Spineli
CKChrysostomos Kalyvas
Chrysostomos Kalyvas
KPKaterina Papadimitropoulou
Katerina Papadimitropoulou
Conducting sensitivity analyses is an integral part of the systematic review process to explore the robustness of results derived from the primary analysis. When the primary analysis results can be sensitive to assumptions concerning a model's parameters (e.g., missingness mechanism to be missing at random), sensitivity analyses become necessary. However, what can be concluded from sensitivity analyses is not always clear. For instance, in a pairwise meta‐analysis (PMA) and network meta‐analysis (NMA), conducting sensitivity analyses usually boils down to examining how ‘similar’ the estimated treatment effects are from different re‐analyses to the primary analysis or placing undue emphasis on the statistical significance. To establish objective decision rules regarding the robustness of the primary analysis results, we propose an intuitive index, which uses the whole distribution of the estimated treatment effects under the primary and alternative re‐analyses. This novel index is compared to an objective threshold to infer the presence or lack of robustness. In the case of missing outcome data, we additionally propose a graph that contrasts the primary analysis results to those of alternative scenarios about the missingness mechanism in the compared arms. When robustness is questioned according to the proposed index, the suggested graph can demystify the scenarios responsible for producing inconsistent results to the primary analysis. The proposed decision framework is immediately applicable to a broad set of sensitivity analyses in PMA and NMA. We illustrate our framework in the context of missing outcome data in both PMA and NMA using published systematic reviews.

30 March 2025 in Statistics in Medicine
Verified
Journal Article
Open access
LSLoukia M. Spineli
Loukia M. Spineli
KPKaterina Papadimitropoulou
Katerina Papadimitropoulou
CKChrysostomos Kalyvas
Chrysostomos Kalyvas
The feasibility of network meta‐analysis depends on several factors, one of which is the validity of the transitivity assumption that posits no systematic differences in the distribution of effect modifiers across treatment comparisons within a connected network. However, evaluating transitivity is complex for relying on epidemiological grounds. Therefore, establishing a methodological framework to evaluate this assumption is challenging. We propose a novel approach, which involves calculating dissimilarities between treatment comparisons based on study‐level aggregate participant and methodological characteristics reported across studies and applying hierarchical clustering to cluster similar comparisons. This approach detects “hot spots” of potential intransitivity in the network, enabling empirical exploration of transitivity and semi‐objective judgments. Our approach quantifies clinical and methodological (non‐statistical) heterogeneity within and between treatment comparisons by computing the dissimilarities across studies in key characteristics acting as effect modifiers. The investigated networks showed varying between‐comparison dissimilarities, indicating variability in the clinical and methodological heterogeneity of the networks. Several pairs of treatment comparisons with “likely concerning” non‐statistical heterogeneity were identified, and some studies were organized into several clusters, suggesting potential intransitivity in the networks. These findings necessitate a closer examination of the evidence base, and such scrutiny becomes pivotal in determining whether concerns about the feasibility of network meta‐analysis are justified. Similar to statistical heterogeneity, heterogeneity in clinical and methodological characteristics of the collected studies should be expected and appropriately assessed. Our proposed approach facilitates the evaluation of transitivity using well‐established methods and can be applied to newly planned and published systematic reviews.

1 May 2019 in Journal of Comparative Effectiveness Research
Verified
Journal Article
Open access
VSVibeke Strand
Vibeke Strand
IMIain McInnes
Iain McInnes
PMPhilip Mease
Philip Mease
PNPeter Nash
Peter Nash
HTHoward Thom
Howard Thom
ECErnest Choy
Ernest Choy
Aim:To compare secukinumab with infliximab in biologic-naive patients with psoriatic arthritis using matching-adjusted indirect comparison.Patients & methods:Individual patient baseline data for secukinumab were matched to published aggregate data for infliximab by key baseline characteristics, with matching weights determined by logistic regression, and used to recalculate American College of Rheumatology (ACR) responses for secukinumab, for comparison with infliximab.Results:There were no differences in outcomes between secukinumab and infliximab at weeks 6/8 and 14/16. At weeks 24 and 54/52, ACR 20 responses were higher with secukinumab 150 mg than infliximab. At week 54/52, ACR 20/50 responses were higher for secukinumab 300 mg than infliximab.Conclusion:In the mid to long term, patients receiving secukinumab were more likely to achieve ACR 20/50 responses than those receiving infliximab.

25 February 2019 in Journal of Child Neurology
Verified
Journal Article
Open access
PDF file
PGPatricia Guyot
Patricia Guyot
CKChrysostomos Kalyvas
Chrysostomos Kalyvas
CMCarole Mamane
Carole Mamane
NDNatalya Danchenko
Natalya Danchenko
Background: Botulinum neurotoxins type A (BoNT-As) are used in pediatric lower limb spasticity, which affects more than 2.5 million children worldwide. Botulinum neurotoxins type-A improve active function and delay musculoskeletal complications. The objective of this analysis was to evaluate the efficacy and safety of abobotulinumtoxinA versus other botulinum neurotoxins type A in pediatric spasticity, in the absence of head-to-head evidence. Methods: A systematic literature review was conducted to identify relevant randomized controlled trials. The evidence base was synthesized with Bayesian network meta-analyses. Outcomes analyzed included Modified Ashworth Scale, Tardieu Scale (TS) spasticity grade, and Goal Attainment Scale (standard mean difference only) at 12 weeks postinjection, and adverse events occurring during study periods. Results: Thirty-eight studies were identified, 10 of which met inclusion criteria for quantitative synthesis. On Modified Ashworth Scale, abobotulinumtoxinA 15 U/kg/leg was significantly more efficacious than onabotulinumtoxinA 4 U/kg/leg (–0.99 [–1.34, –0.64]) and onabotulinumtoxinA 4 U/kg/leg+casting (–0.81 [–1.16, –0.46]) and numerically better than onabotulinumtoxinA 8 U/kg (–0.40 [–0.67, –0.14]). AbobotulinumtoxinA 10 U/kg/leg was significantly more efficacious than onabotulinumtoxinA 4 U/kg/leg (±casting). On Goal Attainment Scale, abobotulinumtoxinA 15 U/kg/leg and 10 U/kg/leg were significantly more efficacious than onabotulinumtoxinA 12 U/kg/leg. On Tardieu Scale spasticity grade, abobotulinumtoxinA was comparable to other treatments. AbobotulinumtoxinA demonstrated adverse event rates comparable to all doses of onabotulinumtoxinA. Conclusions: In pediatric lower limb spasticity, abobotulinumtoxinA offered significant or numerical efficacy advantages on tone (Modified Ashworth Scale) and functional outcomes (Goal Attainment Scale), and comparable efficacy on Tardieu Scale spasticity grade. AbobotulinumtoxinA was comparable to onabotulinumtoxinA on tolerability. Results should be interpreted in the context of heterogeneity and sparsity of the evidence base.