Driving Improvement in Prostate Cancer Radiotherapy Outcomes through a National Quality Assurance Program: Results from a Large UK Academic Center.

Abstract

The UK National Prostate Cancer Audit (NPCA) is a national quality assurance program reporting prostate cancer (PC) outcomes across public sector hospitals. In 2019, NPCA reported a 16% rate of severe late gastrointestinal (GI) toxicity following external beam radiotherapy (EBRT) at our institution from 2016, exceeding the national average of 10%. This prompted a systematic multidisciplinary review of the EBRT process to validate reported toxicity, identify modifiable contributors across the radiotherapy pathway, and assess the impact of subsequent protocol changes. All PC patients receiving radical EBRT at our center in 2016 were retrospectively reviewed. Severe late GI toxicity was defined as Radiation Therapy Oncology Group (RTOG) grade ≥2 toxicity or needing a colonoscope with intervention within two years of radiotherapy. NPCA-identified cases were independently validated using clinical and endoscopy records. Multidisciplinary root cause analysis was performed, incorporating patient, tumor, treatment, dosimetric, rectal anatomy, and treatment verification imaging data. Patients with severe late GI toxicity were compared with a control cohort. Findings informed protocol changes implemented in 2020-2021, impact of which was evaluated by the subsequent NPCA re-audit in 2022. Chi-square, Mann-Whitney, and t-tests were used. p<0.05 was considered statistically significant. Follow-up data were available for 281/290 (96.8%) of 2016 cohort. Severe late GI toxicity was confirmed in 16%. There were no significant associations with patient or tumor characteristics, fractionation, or CTV-PTV margins. Higher rectal mean dose (>45Gy in 37 fractions or >35Gy in 20 fractions) was significantly associated with severe late GI toxicity (p=0.043). 36% of patients with severe late GI toxicity had rectal diameters ≥4.5 cm. We identified potentially correctable setup deviations in 13% of fractions for 3 patients with highest toxicity. Following protocol changes-tighter rectal constraints, enema use, updated verification pathway, reduced CTV-PTV margins-NPCA reported a reduction in severe late GI toxicity to 7.5% in patients treated in 2022. NPCA reporting triggered multidisciplinary EBRT pathway optimization which were followed by substantial reduction in GI toxicity, highlighting the value of national audit programs in improving radiotherapy outcomes.