Publications by authors named "Michael A Webster-Clark"
Prompt versus Delayed Triple Therapy in COPD: Solutions to Time-Related Biases in Observational Studies.
Int J Chron Obstruct Pulmon Dis
July 2025
Background: Recent observational studies have reported that prompt initiation of single-inhaler triple therapy after a COPD exacerbation is more effective than delayed initiation. We show that their study design, by "peeking into the future" to define the timing of treatment initiation, introduces time-related biases, particularly protopathic bias. These biases can be avoided using the "cloning" approach to emulate a randomized trial approach.
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- The article addresses the challenge of applying treatment effect estimates from randomized trials to real-world clinical settings, due to effect measure modification.* -
- It presents a practical roadmap and four visual tools to aid researchers in selecting variables for models that extend trial effects, specifically using adjuvant chemotherapy for colon cancer as an example.* -
- The visualizations help identify modifiers, assess overlap between populations, and guide model specification, ultimately enhancing the validity of treatment effect extensions to clinical practice.*
Effectiveness of adjuvant FOLFOX vs 5FU/LV in adults over age 65 with stage II and III colon cancer using a novel hybrid approach.
Pharmacoepidemiol Drug Saf
December 2020
Purpose: Estimates of cancer therapy effects can differ in clinical trials and clinical practice, partly due to underrepresentation of certain patient subgroups in trials. We utilize a hybrid approach, combining clinical trial and real-world data, to estimate the comparative effectiveness of two adjuvant chemotherapy regimens for colon cancer.
Methods: We identified patients aged 66 and older enrolled in the Multicenter International Study of Oxaliplatin/5FU-LV in the Adjuvant Treatment of Colon Cancer.
Background: Methods developed to estimate intervention effects in external target populations assume that all important effect measure modifiers have been identified and appropriately modeled. Propensity score-based diagnostics can be used to assess the plausibility of these assumptions for weighting methods.
Methods: We demonstrate the use of these diagnostics when assessing the transportability of treatment effects from the standard of care for metastatic colorectal cancer control arm in a phase III trial (HORIZON III) to a target population of 1,942 Medicare beneficiaries age 65+ years.