[OA072] Per-voxel cox regression with interaction terms. (August 2018)

• Record Type: Journal Article
• Authors: Green, Andrew; Osorio, Eliana Vasquez; Beasley, William; McWilliam, Alan; van Herk, Marcel
• Is Part Of: Physica medica. Volume 52(2018)Supplement 1
• Page Start: 28
• Publication Date: 2018-08
• Subjects: Medical physics -- Periodicals; Biophysics -- Periodicals; Biophysics -- Periodicals; Imagerie médicale -- Périodiques; Radiothérapie -- Périodiques; Rayons X -- Sécurité -- Mesures -- Périodiques; Physique -- Périodiques; Médecine -- Périodiques; 610.153
• DOI: 10.1016/j.ejmp.2018.06.144
• Languages: English
• ISSNs: 1120-1797

Abstract

Abstract : Purpose: Image based data mining (IBDM) is a novel technique in which dose response relationships are extracted from routine clinical data by relating the dose at each voxel in the planned dose to the eventual outcome for the patient. In IBDM many patients are registered to a reference patient to spatially normalise their dose distributions for analysis, eliminating the need for clinician contours and removing assumptions implicit in DVH based analyses. Recently, IBDM has been used to identify a dose sensitive region in the heart where patients receiving excess dose have poorer overall survival[1] . Methods: In this work, a subset (n = 872) of the cohort of patients in[1] is used, but a more sophisticated IBDM technique is applied. A Cox regression, considering tumour size, age, performance status, dose and a dose-PS interaction is calculated in each voxel of the planned dose distribution. Performance status is binarised using a threshold of PS > = 1 to account for inaccuracy in its determination. This analysis leads to a map of hazard ratio across the reference patient anatomy. Statistical significance is assessed using a permutation test in which only survival labels are permuted. Results: When performing the analysis with an interaction between performance status and dose present in the Cox model, a region is identified in the base of the heart where excess dose is detrimental to survival. This region overlaps with that found by other analyses, and suggests that patients with a performance status of 2 or greater suffer a more profound effect from dose in this region. In the present analysis statistical significance is not reached in any voxel for either the dose, PS or dose-PS interaction. Conclusions: A region in the base of the heart is identified, consistent with other analyses, in which excess dose is related to poorer overall survival, particularly for those patients with poor performance. Statistical significance may be reached by including more data, or modifying the permutation technique.