External validation of predictive models of sexual, urinary, bowel and hormonal function after surgery in prostate cancer subjects

Matthew A Borg; Michael E O'Callaghan; Kim L Moretti; Andrew D Vincent

doi:10.1186/s12894-023-01373-9

External validation of predictive models of sexual, urinary, bowel and hormonal function after surgery in prostate cancer subjects

BMC Urol. 2024 Jan 2;24(1):2. doi: 10.1186/s12894-023-01373-9.

Authors

Matthew A Borg¹, Michael E O'Callaghan^{2

3

4

5}, Kim L Moretti^{3

6

7

8}, Andrew D Vincent⁹

Affiliations

¹ School of Public Health, University of Adelaide, Adelaide, SA, Australia. matthew.borg@adelaide.edu.au.
² Urology Unit, Flinders Medical Centre, Bedford Park, SA, Australia.
³ South Australian Prostate Cancer Clinical Outcomes Collaborative, Adelaide, SA, Australia.
⁴ Flinders Health and Medical Research Institute, Flinders University, Bedford Park, SA, Australia.
⁵ Discipline of Medicine, The University of Adelaide, Adelaide, SA, Australia.
⁶ Discipline of Surgery, The University of Adelaide, Adelaide, SA, Australia.
⁷ Cancer Epidemiology and Population Health Allied Health & Human Performance, University of South Australia, Adelaide, SA, Australia.
⁸ Faculty of Medicine Nursing and Health Sciences, School of Public Health and Preventative Medicine Monash University, Melbourne, Victoria, Australia.
⁹ Freemasons Centre for Male Health & Wellbeing, University of Adelaide, Adelaide, SA, Australia.

Abstract

Background: In 2020, a research group published five linear longitudinal models, predict Expanded Prostate Cancer Index Composite-26 (EPIC-26) scores post-treatment for radical prostatectomy, external beam radiotherapy and active surveillance collectively in US patients with localized prostate cancer.

Methods: Our study externally validates the five prediction models for patient reported outcomes post-surgery for localised prostate cancer. The models' calibration, fit, variance explained and discrimination (concordance-indices) were assessed. Two Australian validation cohorts 1 and 2 years post-prostatectomy were constructed, consisting of 669 and 439 subjects, respectively (750 in total). Patient reported function in five domains post-prostatectomy: sexual, bowel, hormonal, urinary incontinence and other urinary dysfunction (irritation/obstruction). Domain function was assessed using the EPIC-26 questionnaire.

Results: 1 year post-surgery, R² was highest for the sexual domain (35%, SD = 0.02), lower for the bowel (21%, SD = 0.03) and hormone (15%, SD = 0.03) domains, and close to zero for urinary incontinence (1%, SD = 0.01) and irritation/obstruction (- 5%, SD = 0.04). Calibration slopes for these five models were 1.04 (SD = 0.04), 0.84 (SD = 0.06), 0.85 (SD = 0.06), 1.16 (SD = 0.13) and 0.45 (SD = 0.04), respectively. Calibration-in-the-large values were - 2.2 (SD = 0.6), 2.1 (SD = 0.01), 5.1 (SD = 0.1), 9.6 (SD = 0.9) and 4.0 (SD = 0.2), respectively. Concordance-indices were 0.73, 0.70, 0.70, 0.58 and 0.62, respectively (all had SD = 0.01). Mean absolute error and root mean square error were similar across the validation and development cohorts. The validation measures were largely similar at 2 years post-surgery.

Conclusions: The sexual, bowel and hormone domain models validated well and show promise for accurately predicting patient reported outcomes in a non-US surgical population. The urinary domain models validated poorly and may require recalibration or revision.

Keywords: External validation; Patient-reported outcomes; Prostate cancer; Prostatectomy.

MeSH terms

Australia
Hormones
Humans
Male
Prospective Studies
Prostatectomy / adverse effects
Prostatic Neoplasms* / radiotherapy
Quality of Life
Urinary Incontinence* / epidemiology
Urinary Incontinence* / etiology
Urinary Incontinence* / surgery

Substances

Hormones