Urinary symptoms following external beam radiotherapy of the prostate: Dose–symptom correlates with multiple-event and event-count models

• Published in: Radiotherapy and oncology 2015-11, Vol.117 (2), p.277-282
• Main Authors: Yahya, Noorazrul, Ebert, Martin A, Bulsara, Max, House, Michael J, Kennedy, Angel, Joseph, David J, Denham, James W
• Format: Article
• Language: English
• Subjects: Event-count model; Follow-Up Studies; Hematology, Oncology and Palliative Medicine; Humans; Male; Multiple-event model; Normal tissue complications; Prostate radiotherapy; Prostatic Neoplasms - radiotherapy; Radiotherapy - adverse effects; Radiotherapy Dosage; Urinary Bladder - radiation effects; Urinary Incontinence - etiology; Urinary symptoms
• ISSN: 0167-8140; 1879-0887
• DOI: 10.1016/j.radonc.2015.10.003

Abstract Background and purpose This study aimed to compare urinary dose–symptom correlates after external beam radiotherapy of the prostate using commonly utilised peak-symptom models to multiple-event and event-count models which account for repeated events. Materials and methods Urinary symptoms (dysuria, haematuria, incontinence and frequency) from 754 participants from TROG 03.04-RADAR trial were analysed. Relative (R1–R75 Gy) and absolute (A60–A75 Gy) bladder dose-surface area receiving more than a threshold dose and equivalent uniform dose using exponent a (range: a ∈[1 … 100]) were derived. The dose–symptom correlates were analysed using; peak-symptom (logistic), multiple-event (generalised estimating equation) and event-count (negative binomial regression) models. Results Stronger dose–symptom correlates were found for incontinence and frequency using multiple-event and/or event-count models. For dysuria and haematuria, similar or better relationships were found using peak-symptom models. Dysuria, haematuria and high grade (⩾2) incontinence were associated to high dose (R61–R71 Gy). Frequency and low grade (⩾1) incontinence were associated to low and intermediate dose-surface parameters (R13–R41 Gy). Frequency showed a parallel behaviour ( a = 1) while dysuria, haematuria and incontinence showed a more serial behaviour ( a = 4 to a ⩾ 100). Relative dose-surface showed stronger dose–symptom associations. Conclusions For certain endpoints, the multiple-event and event-count models provide stronger correlates over peak-symptom models. Accounting for multiple events may be advantageous for a more complete understanding of urinary dose–symptom relationships.