ESTRO 2023 - Abstract Book

S1254

Digital Posters

ESTRO 2023

To analyze risk factors for acute and late rectal toxicity during IMRT for prostate cancer. We know from the literature that the position of the rectum at the time of CT treatment planning is probably not fully representative of the position during RT due to inter- or intrafractional variations in rectal filling, intestinal gas, and bladder filling. On the other hand, an empty rectum is recommended during the simulation to avoid introducing a systematic error in the coverage of the PTV. The fact that CT imaging features before and during treatment can predict radiation toxicity and the combination of imaging and clinical / dosimetric features can improve the predictive performance of radiotoxicity modeling. A high rate of acute rectal toxicity is now recognized as being associated with late RT proctopathy. From these premises we decided to empty the rectum constantly and repeatedly every day from simulation to treatment and then analyze the results. Materials and Methods From March 2020 to May 2022. 115 patients received 70-76 Gy in 30-33 fractions in the prostate and seminal vesicles. Each patient was provided with a form explaining how to fill the bladder before treatment and a diet low in fiber and with foods designed to avoid intestinal gas formation was recommended both during the simulation and during the entire treatment. Subsequently, after evaluating the first treated patients, an oral therapy with vegetable charcoal and macrogoal was added. Common Terminology Criteria for Adverse Events version 3.0 was used to classify rectal toxicity. During radiotherapy we measured the displacement of the rectum with respect to the simulation and we evaluated it. Results Two groups of patients both on a fiber-free diet but one on a carbon supplement and macrogoal. Acute rectal toxicity occurred in 6 (20.68%) patients (1 grade 3 others G1) in the diet group, in the supplement group in 1 patient (1.16). Measurement of the irradiated rectum during the control cone beam in patients who performed only diet and bladder filling was predictive of the recorded toxicity, in the other group the irradiated rectum was perfectly adherent to the irradiated rectum at the time of the simulation Conclusion In prostate cancer patients treated with the IMRT schedule, the use of diet and the supplementation of coal and macro lens lowered the incidence and degree of acute rectal toxicity better than diet alone. There were no cases of late toxicity in either group. 1 Department of Oncology, Vejle Hospital, University Hospital of Southern Denmark, Radiotherapy Research Team, Vejle, Denmark; 2 School for Oncology and Developmental Biology, Maastricht University Medical Center, Department of Radiation Oncology (MAASTRO), GROW, Maastricht, The Netherlands; 3 Lillebaelt University Hospital of Southern Denmark, Center for Shared Decision Making, Vejle, Denmark; 4 Department of Oncology, Vejle Hospital, University Hospital of Southern Denmark, Department of Radiotherapy, Vejle, Denmark; 5 IT Department,, Vejle Hospital, University Hospital of Southern Denmark, Clinical IT, Vejle, Denmark; 6 Department of Oncology, Vejle Hospital, University Hospital of Southern Denmark, Department of Oncology, Vejle, Denmark Purpose or Objective Knowledge about the impact of radiotherapy (RT) on patient’s quality of life (QoL) is mandatory to improve future treatments. For this purpose, Common Terminology Criteria for Adverse Events (CTCAE) and Patient Reported Outcome Measures (PROMs) are often used in clinical trials. However, there is also a need for knowledge regarding patients QoL after modern conventional RT especially if this has not been investigated through PROMs earlier. Therefore, we conducted a prospective and longitudinal collection of CTCAE and PROMs for patients receiving standard RT for prostate cancer in our clinic. Materials and Methods In 2015 one radiotherapy nurse, two oncologists and two physicists designed a protocol for prospective registration of adverse effects following either curative RT for T1-T3N0M0 prostate cancer, or salvage RT for biochemical recurrence after radical prostatectomy. The scope was to gather information based on validated questionnaires regarding AE. Hence, CTCAE v4.0 (26 items like diarrhea and rectal bleeding), the Expanded Prostate Cancer Index Composite (EPIC), EORTC QLQ-C30 and a segment of EORTC QLQ-PR25 were set up. The infrastructure was ready for inclusion by October 2017. Oncologists provided patient characteristics (weight, smoking status, tumor classification etc.). At the consultations, CTCAE scores were initially recorded on paper but as staff became more experienced, direct database entry was practiced. The electronic collection of PROMs was done in SurveyXact (Rambøll): The database was programmed to send out links to the patient’s digital mailbox (supplied by the Danish authorities) at predefined dates counting from the last day of RT in advance of each follow-up consultation. The study was observational and clinicians were expected to access the patient’s answers to focus on the most important QoL topics during the consultation. Depending on residence, patients had full or partial appearances as given in Table 1 and they gave consent to registration of CTCAE and PROMs or CTCAE only. Patient inclusion was planned to run for five years with a five year follow up time. Results Enrolment ended in June 2022. Enrolment rate was high, with 403 patients out of 426 eligible patients included. A database audit in 2019 showed a drop in data quality in especially baseline data collection for both CTCAE and PROMs. Table 2 shows the number of patients enrolled and the response rates (RR). The observed RR are higher than the 42%±8.7% reported by Wang et al. for electronic-only format [1]. PO-1546 Systematic registration of CTCAE and PROMs for patients having standard RT for prostate cancer M. Berg 1 , L. Wee 2 , K. Olling 3 , M. Svenson 4 , L. Holberg 5 , H.D. Nissen 1 , L. Fokdal 6 , C.V. Madsen 6