Impact of Timing on Measurement of Decision Quality and Shared Decision Making: Longitudinal Cohort Study of Breast Cancer Patients.

Purpose.The objective of this study was to examine whether scores of shared decision-making measures differ when collected shortly after (1 month) or long after (1 year) breast cancer surgical treatment decisions. Methods. Longitudinal, multisite survey of breast cancer (BC) patients, with measurements at 1 month and 1 year after surgery at 4 cancer centers. Patients completed the BC Surgery Decision Quality Instrument (used to generate a knowledge score, ratings of goals, and concordance with treatment preferences) and Shared Decision Making (SDM) Process survey at both time points. We tested several hypotheses related to the scores over time, including whether the scores discriminated between sites that did and did not offer formal decision support services. Exploratory analyses examined factors associated with large increases and decreases in scores over time. Results. Across the 4 sites, 229 patients completed both assessments. The mean total knowledge scores (69.2% [SD 16.6%] at 1 month and 69.4% [SD 17.7%] at 1 year, P = 0.86), SDM Process scores (2.7 [SD 1.1] 1 month v. 2.7 [SD 1.2] 1 year, P = 0.68), and the percentage of patients receiving their preferred treatment (92% at 1 month and 92% at 1 year, P = 1.0) were not significantly different over time. The site using formal decision support had significantly higher knowledge and SDM Process scores at 1 month, and only the SDM Process scores remained significantly higher at 1 year. A significant percentage of patients had large changes in their individual knowledge and SDM Process scores, with increases balancing out decreases. Conclusion. For population-level assessments, it is reasonable to survey BC patients up to a year after the decision, greatly increasing feasibility of measurement. For those evaluating decision support interventions, shorter follow-up is more likely to detect an impact on knowledge scores.