Ankerst, Donna P.

Abstract Background: Missing risk factors, whether random or not measured at all, across different hospitals and patients provide challenges, both for the developers of online clinical risk tools and the patients trying to use such tools. This paper provides a development and end-user solution to the commonly encountered limitations of clinical risk tool based decision making due to missing information.Methods: Six state-of-the-art logistic regression approaches accommodating missing data were compared using prostate cancer data from ten North American and European cohorts from the Prostate Biopsy Collaborative Group (PBCG). An additional large European PBCG cohort was withheld for external validation, where calibration-in-the-large (CIL), calibration curves, and area-underneath-the-receiver-operating characteristic curve (AUC) were evaluated. Ten-fold leave-one-cohort-internal validation further validated the optimal missing data approach.Results: Among 12,703 biopsies from 10 training cohorts, 3,597 (28%) had clinically significant prostate cancer, compared to 1,757 of 5,540 (32%) in the external validation cohort. In external validation, the available cases method that pooled individual patient data containing all risk factors input by an end-user had best CIL, under-predicting risks as percentages by 2.9% on average, and obtained an AUC of 75.7%. Imputation had the worst CIL (-13.3%). The available cases method was further validated as optimal in internal cross-validation and thus used for development of an online risk tool. For end-users of the risk tool, two risk factors were mandatory: serum prostate-specific antigen (PSA) and age, and ten were optional: digital rectal exam, prostate volume, prior negative biopsy, 5-alpha-reductase-inhibitor use, prior PSA screen, African ancestry, Hispanic ethnicity, first-degree prostate-, breast-, and second-degree prostate-cancer family history.Conclusion: Developers of clinical risk prediction tools should optimize use of available data and sources even in the presence of high amounts of missing data and offer options for users with missing risk factors.

Purpose Palliation of bone pain can be achieved in men with androgen-independent prostate cancer treated with docetaxel and estramustine (DE) or mitoxantrone and prednisone (MP). While Southwest Oncology Group trial 99-16 demonstrated a survival improvement of DE over MP, the study also was designed to compare the palliation of disease-related symptoms. Methods Pain palliation and global quality of life (QOL) were the two primary patient-reported outcomes. Pain was measured with the Present Pain Intensity scale of the McGill Pain Questionnaire-Short Form. The European Organisation for Research and Treatment of Cancer Core Quality of Life Questionnaire C30 (QLQ-C30) and its Prostate Cancer Module (PR25) measured QOL and symptom status. Pain and analgesic use were measured at random assignment, every cycle for eight cycles, and 1 year from random assignment; the QLQ-C30 and the PR25 were administered at random assignment, before cycle four (week 10) and cycle eight (month 6) and at 1 year. In addition to the primary intent-to-treat, missing at random analysis, sensitivity analyses were performed to assess robustness of global QOL conclusions under alternative informative missing data assumptions. Results Six hundred seventy four eligible patients received DE (n = 338) or MP (n = 336). In an intention-to-treat analysis, median overall survival was 17.5 months for the DE arm and 15.6 months for the MP arm (P = .02). There were no statistically significant differences in pain palliation between the treatment arms. The sensitivity analyses showed a consistent lack of statistically significant global QOL differences for the two arms. Conclusion DE had superior clinical efficacy (overall survival, time-to-progression, and prostate-specific antigen declines) with similar global QOL and pain palliation in the MP arm.