# Patient- and clinician-reported acute radiation-induced diarrhoea in patients with prostate cancer during curative external radiation therapy: A prospective observational cohort study

## TL;DR

This study shows that patient-reported diarrhoea during prostate cancer radiation therapy is more severe than what clinicians report, highlighting the need for patient input in assessments.

## Contribution

The study demonstrates that patient-reported outcomes better capture the severity of acute radiation-induced diarrhoea than clinician assessments.

## Key findings

- One in four patients experienced Grade 2/3 diarrhoea according to patient reports, but none were classified as such by clinicians.
- There was a significant difference (p < 0.001) between clinician and patient-reported diarrhoea grades over time.
- Patients with higher diarrhoea grades experienced significant weight loss earlier in treatment.

## Abstract

Acute radiation-induced diarrhoea (RID) typically develops from gut mucosa inflammation within 2 weeks of external beam radiation therapy (EBRT) to the pelvis. The Common Terminology Criteria for Adverse Events (CTCAE) commonly assesses RID. In patients with prostate cancer undergoing curative EBRT, acute RID was evaluated using both a clinician-reported outcome (ClinRO)-CTCAE, and a patient-reported (PRO) stool diary.

During 2022–2024, 40 newly diagnosed patients with prostate cancer receiving curative EBRT were enrolled at the Oncology Departments in two centres. CTCAE was assessed at baseline (week 1), at end of EBRT (week 8 or 9), 2 weeks after end of EBRT (week 10 or 11), and 8 weeks after end of EBRT (week 16 or 17). Simultaneously, patients maintained a daily PRO diary from baseline to week 10, and at week 16. Patients’ registration of stool frequency was converted to grades according to the CTCAE criteria.

The clinicians assessed all 40 patients with RID Grade 0/1 using CTCAE, whereas the PRO stool diary showed 29/40 with Grade 0/1, 6/40 with Grade 2, and 5/40 with Grade 3. Grade 2 appeared in week 2 and Grade 3 in week 4. There was a significant difference (p < 0.001) between CTCAE and PRO grades from baseline to week 16 or 17. No correlation was observed between irradiation data and RID Grades 2/3. Significant weight loss differences were noted from baseline to week 8 or 9 between patients with RID Grades 0/1 and those with Grades 2/3.

According to the PRO stool diary, one in four patients with prostate cancer undergoing curative EBRT experienced acute RID Grade 2/3, but none with ClinRO CTCAE. A PRO stool diary effectively monitored the onset, course of acute RID, and body weight changes. The CTCAE does not adequately assess acute RID and needs PRO stool diary supplementation.

Clinicaltrials.gov, NCT05684432. Registered 5 January 2023.

The online version contains supplementary material available at 10.1186/s41687-025-00957-3.

Prostate cancer is the most common cancer in men. Radiation therapy can often cure the patients. Some of them experience diarrhoea with more than 3 watery stools daily. Commonly, the diarrhoea is assessed by the clinician. This study compares patient-reported diarrhoea with the clinician assessment. During treatment and 8 or 9 weeks after, the patients noted the stool frequency and consistency. One in four patients reported acute diarrhoea, which was not captured by the clinician assessment. Therefore, the patients’ reports need to supplement the clinicians’ assessment in diagnosing and preventing acute diarrhoea.

The online version contains supplementary material available at 10.1186/s41687-025-00957-3.