Bjarke Mortensen

Background: 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. Methods: 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. Results: 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. Conclusion: 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. Trial registration: Clinicaltrials.gov, NCT05684432. Registered 5 January 2023.

Background: Rectal bleeding is a well-known adverse event following pelvic external beam radiotherapy (EBRT) for prostate cancer. This study investigates risk factors for rectal bleeding and validate our current rectal dose constraints in a real-world setting. Material and methods: This prospective study includes 248 prostate cancer patients who received EBRT between 2017-2022. EBRT consisted of 56 Gy/39 fractions to the prostate, elective lymph nodes, and seminal vesicles with an integrated boost of 78 Gy to the prostate alone (≤T3a) or to the prostate and seminal vesicles (T3b). Rectal dose constraints were V50 Gy ≤50%, V70 Gy ≤20%, and V74 Gy ≤12%. Rectal bleeding was recorded at baseline and regularly duringfollow-up and included staff reported morbidity and patient reported outcome measures. Risk factors were evaluated in multivariate cox regression analysis. Results: Median follow-up was 18 months (range 1-61 months). Sixteen percent (CI:11%;22%) of patients reported rectal bleeding as “rarely”, 4%(CI:2%;8%) “about half the time”, 0% “usually”, and 2%(CI:0%;4%) “always”. Five percent reported rectal bleeding as bothersome. It was possible to comply with current rectal dose constraint (V74 Gy ≤12%) in 99.6% of all patients. Body mass index (BMI) (BMI:25-29.9, HR:0.54(CI:0.30;0.98), p=.044 or BMI>29.9, HR:0.40(CI:0.20;0.79), p=0.008)) were predictors for rectal bleeding. Interpretation: Patient-reported rectal bleeding is common after prostate cancer radiotherapy. High BMI was a protective factor against rectal bleeding. No correlation was observed between rectal dose-volume constraints and the occurrence of rectal bleeding, suggesting that a rectal high-dose constraint of V74 Gy ≤12% is an adequate threshold to minimize patient-reported rectal bleeding.