Evaluation of viable dynamic treatment regimes in a sequentially randomized trial of advanced prostate cancer

• Autores: Wang, Lu; Rotnitzky, Andrea Gloria; Lin, Xihong; Millikan, Randall; Thall, Peter
• Año de publicación: 2012
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: CAUSAL INFERENCE; EFFICIENCY; INFORMATIVE DROPOUT; INVERSE PROBABILITY WEIGHTING; MARGINAL STRUCTURAL MODELS; OPTIMAL REGIME; SIMULTANEOUS CONFIDENCE INTERVALS
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

We present new statistical analyses of data arising from a clinical trial designed to compare two-stage dynamic treatment regimes (DTRs) for advanced prostate cancer. The trial protocol mandated that patients be initially randomized among four chemotherapies, and that those who responded poorly be re-randomized to one of the remaining candidate therapies. The primary aim was to compare the DTRs' overall success rates, with success defined by the occurrence of successful responses in each of two consecutive courses of the patient's therapy. Of the 150 study participants, 47 did not complete their therapy as per the algorithm. However, 35 of them did so for reasons that precluded further chemotherapy, that is, toxicity and/or progressive disease. Consequently, rather than comparing the overall success rates of the DTRs in the unrealistic event that these patients had remained on their assigned chemotherapies, we conducted an analysis that compared viable switch rules defined by the per-protocol rules but with the additional provision that patients who developed toxicity or progressive disease switch to a non-prespecified therapeutic or palliative strategy. This modification involved consideration of bivariate per-course outcomes encoding both efficacy and toxicity.We used numerical scores elicited from the trial's principal investigator to quantify the clinical desirability of each bivariate per-course outcome, and defined one endpoint as their average over all courses of treatment. Two other simpler sets of scores as well as log survival time were also used as endpoints. Estimation of each DTR-specific mean score was conducted using inverse probability weighted methods that assumed that missingness in the 12 remaining dropouts was informative but explainable in that it only depended on past recorded data.We conducted additional worst-and best-case analyses to evaluate sensitivity of our findings to extreme departures from the explainable dropout assumption.
Fil: Wang, Lu. University of Michigan; Estados Unidos
Fil: Rotnitzky, Andrea Gloria. Universidad Torcuato Di Tella. Departamento de Economía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina
Fil: Lin, Xihong. Harvard University; Estados Unidos
Fil: Millikan, Randall. University of Texas; Estados Unidos
Fil: Thall, Peter. University of Texas; Estados Unidos