ESTRO 2023 - Abstract Book

S1230

Digital Posters

ESTRO 2023

PO-1512 radical chemoradiotherapy to the bladder: review of practice at the Northern Centre for Cancer Care

A. Waton 1 , X. Jiang 1 , R. Chandler 1

1 Northern Centre for Cancer Care, Oncology and haematology, Newcastle upon Tyne, United Kingdom

Purpose or Objective The Royal College of Radiologists recommends the use of a radiosensitiser for patients undergoing radical radiotherapy for muscle invasive bladder cancer (MIBC). Radiosensitisation with mitomycin/5-fluorouracil (BC2001) improves locoregional control of MIBC and a trial using concurrent carbogen and nicotinamide (BCON) demonstrated an improvement in overall survival. An alternative chemoradiation protocol involves weekly gemcitabine and has been shown to be efficacious and tolerable in phase 2 studies. On a previous audit of chemoradiotherapy at the Northern Centre for Cancer Care (NCCC), disappointing rates of radiosensitisation were identified (41%, all patients received mitomycin/5FU). On this basis, weekly gemcitabine (100 mg/m2) was introduced as an option, primarily in less fit patients. We have then reviewed chemoradiotherapy practices. Materials and Methods Retrospective data was collected from patients who underwent radical radiotherapy for MIBC between July 2019 and September 2021 at a large tertiary cancer centre in North-East England (NCCC, Newcastle-upon-Tyne). Those with nodal disease and/or neuroendocrine differentiation were excluded from the analysis. Results Ninety-two patients were identified. Forty-eight (52%) received a concurrent radiosensitiser in the form of mitomycin/5FU (14/48, 29%) or gemcitabine (34/48, 71%). The majority receiving chemoradiotherapy were male (39/48, 81%), had a histological diagnosis of transitional cell carcinoma (41/48, 85%) and were performance status 0/1 (45/48, 94%). Median age 70.5years (range 41-80). Twenty-six percent (9/34) prescribed weekly gemcitabine failed to receive the full course due to side effects. The most common reasons were ALT derangement (2) and bowel toxicity (4). Twenty-nine percent (4/14) of patients receiving mitomycin/5FU failed to receive the complete course of chemotherapy due to side effects. Five (10%; gemcitabine n=4, mitomycin/5FU n=1) patients experienced grade 3 bowel toxicity. Post-treatment cystoscopy reports were available in 34/48 of CRT patients and there was no evidence of local recurrence in 91% (31/34). There was no significant difference in 2-year survival rates between patients receiving gemcitabine or mitomycin/5FU (p=0.23, 95% CI 0.7 – 9.5). Conclusion Since adopting weekly gemcitabine as an alternative radio-sensitiser to mitomycin/5FU, our centre has witnessed an increase in the rate of CRT for the non-surgical management of MIBC. This is despite the period of data collection covering the COVID-19 pandemic. Weekly gemcitabine is the more prevalent radiosensitising agent used in the treatment of MIBC within our centre. Our experiences suggest that weekly gemcitabine is relatively easy to deliver, and it appears to be tolerable and efficacious when compared to mitomycin/5FU. The discontinuation rate of concurrent gemcitabine described above (9/34, 26%) is greater than that described in a phase 2 trial of weekly gemcitabine plus radical radiotherapy, however grade 3 toxicity rates are comparable. Purpose or Objective PSMA PET is being increasingly used in restaging of biochemical recurrence after definitive therapy for prostate cancer. It has also regenerated the debate on the role of elective nodal irradiation (ENI) in localized prostate cancer. The Roach formula estimates the risk of regional lymph node involvement (LNI) based on preoperative PSA and Gleason score. Extension of radiation fields to include pelvic nodes in patients with LNI risk >15% has previously been recommended. More recently the POP-RT trial demonstrated a benefit of whole pelvic radiotherapy (RT) over prostate only RT in patients with Roach LNI risk >20%. We carried out a retrospective review of patients with PSMA PET confirmed pelvic nodal recurrences post-prostatectomy to determine whether they would have met the Roach formula criteria for ENI if they had had primary prostate RT instead of prostatectomy. We also sought to determine whether these nodal recurrences were within standard ENI fields. Materials and Methods We identified patients who underwent PSMA PET imaging at our institution for biochemical failure post-prostatectomy. Within that group, we identified patients with PSMA PET confirmed pelvic nodal recurrences only, who were referred to our institution for consideration of salvage pelvic radiotherapy. Preoperative and postoperative clinical parameters were reviewed. Roach LNI risk was calculated using preoperative data. Results Thirty patients with PSMA PET confirmed pelvic nodal recurrences were identified. Median age at radical prostatectomy was 61 years (range 49-70). Median pre-op PSA was 7.9 ng/ml (range 3.7 – 48). At diagnosis, 50% of patients were clinical stage T3a or T3b and 50% were Gleason 8, 9 or 10. Preoperative staging bone scans and CTs were done in 73% and 50% of patients respectively. At surgery, 40% were Gleason 8, 9 or 10 and 77% were pathologic stage T3a or T3b. Pathologic nodal staging was Nx in 57% of patients, N0 in 30% and N1 in 13%. The median lymph node yield in patients who did have nodes removed was 4 (range 1-16). Margins were positive in 53% of patients. Postoperative PSA was detectable in 83.3%. PO-1513 The Roach formula and elective nodal irradiation for prostate cancer in the era of PSMA PET imaging F. Walkins 1 , G. Rangaswamy 1 , M. Cunningham 1 1 St. Luke's Radiation Oncology Network, Radiation Oncology, Dublin, Ireland