ESTRO 2023 - Abstract Book

S209

Saturday 13 May

ESTRO 2023

treatment), after surgery and during follow-up (FU: 6 months, 1, 2 and 3 years) by using the EORTC QLQ-C30 and colorectal module CR29. ClinicalTrials.gov identifier: NCT02363374. Results Available questionnaires at baseline were 84.6% (n=132) in group A vs. 87.3% (n=131) in group B, 83.0% (n=93) vs. 77.5% (n=79) at 1 year, 76.5% (n=78) vs. 78.9% (n=71) at 2 years, and 67.4% (n=60) vs. 71.8% (n=56) at 3 years. The EORTC summary score was stable in both groups (range 0 to 100): baseline: group A mean 82.2 (SEM +/- 1.2) and group B 82.1 (SEM +/- 1.4); at 3 years: group A 78.6 (SEM +/- 1.9) and group B 76.9 (SEM +/- 2.1). Nausea/vomiting was more pronounced at the end of induction CT in comparison to baseline (group A: 19.1 vs. 2.4 at baseline). Urinary frequency showed poorer patient reported outcome right after CRT (group B: 47.8 vs. 33.6 at baseline). One week before surgery and at all following time- points, no clinically relevant differences (more than 10 points) between groups were found in QoL domains. In both arms role and body function declined and did not fully recover during FU (difference from baseline to 3 years of 10-15 points). Conclusion Overall QoL showed no clinically relevant difference between the two sequences of total neoadjuvant treatment at any time-point. As expected reported nausea/vomiting was worse at the end of induction CT as measured in group A and urinary urge was more pronounced right after radiotherapy as measured in group B. In both arms certain dimensions of QoL showed permanent, moderate deterioration during FU. OC-0274 Trend in overall survival after treatment failure in patients with locally advanced rectal cancer M. Diefenhardt 1,2 , M. Fleischmann 1 , D. Martin 1,3 , R. Hofheinz 4 , C. Rödel 1,3,2 , E. Fokas 1,3,2 1 Frankfurt University Hospital, Department of Radiotherapy and Oncology, 60596 Frankfurt am Main, Germany; 2 Frankfurt Cancer Institute, 60596 Frankfurt am Main, Germany; 3 German Cancer Research Center (DKFZ), Heidelberg, German Cancer Consortium (DKTK), Partner Site Frankfurt am Main, 60596 Frankfurt am Main, Germany; 4 Department of Medical Oncology, University Hospital Mannheim, 68135 Mannheim, Germany Purpose or Objective Intensified neoadjuvant treatment improves disease-free survival in patients with locally advanced rectal cancer, but recurrence or distant metastases still occur in one of four patients. We analysed the probability of treatment failure after curative treatment and the overall survival after treatment failure within three clinical phase II/III trials. Materials and Methods Data from 1935 patients from the CAO/ARO/AIO-94, CAO/ARO/AIO-04, and CAO/ARO/AIO-12 trial were pooled. Occurrence of R2 resection, local recurrence or metachronous distant metastases were defined as treatment failure event. The log- rank test was used to calculate the difference in overall survival after treatment failure. The percentage of treatment failure according to ypTNM classification or trial was calculated by dividing the number of DFS events and the number of patients at risk within the specific period. The t-Test was used to calculate the difference between time to treatment failure and clinical trial, respectively ypTNM classification and Pearson correlation was used to estimate correlation between overall survival and disease-free survival. Results 498 of 1935 patients endured a treatment failure. Median time to treatment failure was significantly longer in the CAO/ARO/AIO-94 trial (18months) compared to the CAO/ARO/AIO-94 (14 months) and the CAO/ARO/AIO-12 trial (14.5 months, P<0.001). Pearson’s correlation coefficient between OS and DFS changed from 0.92 [CAO/ARO/AIO-94], 0.80 [CAO/ARO/AIO-04] to 0.74 [CAO/ARO/AIO-12] but remained highly significant. Overall survival after treatment failure significantly improved over the last three decades. 3-years survival was 32.0% in the CAO/ARO/AIO-94, 42.8% in the CAO/ARO/AIO-04 and 74.3% in the CAO/ARO/AIO-12 trial (P<0.001) (1year: 66%, 79%, 90%). Probability of treatment failure decreases with time but 9.5% of all treatment failures in the CAO/ARO/AIO-94 occurred after 60 months. Distant metastases account for the highest proportion of treatment failure while proportion of local recurrence slightly increase after 48 months. Post-surgical ypTNM classification did not only correlated with risk of treatment failure (0 to 12 months period: ypT0: 1.1%; ypT+:8.0% and ypN+:19.8%) but treatment failure in patients with pCR occurred significantly later (26 months) than in patients with postsurgical positive node status (12 months, P<0.035). Conclusion The improved overall survival after treatment failure in patients with locally advanced rectal cancer treated with neoadjuvant chemoradiotherapy should encourage us to perform structured follow-up and motivate patients to participate. The longer time to treatment failure in patients with pathologic complete remission should be considered in follow-up concepts in the context of organ preservation. Further clinical trials to analyse different treatment options for patients with metachronous metastases or local recurrence are needed to optimize treatment both in terms of survival but also in terms of maintaining quality of life. OC-0275 Timing of surgery after short course radiotherapy for rectal cancer: real-world evidence M. Verweij 1 , J. Franzen 1 , H. van Grevenstein 2 , L. Verkooijen 1 , M. Intven 1 1 University Medical Centre Utrecht, Radiotherapy, Utrecht, The Netherlands; 2 University Medical Centre Utrecht, Surgery, Utrecht, The Netherlands Purpose or Objective Short course radiotherapy (SCRT, 25Gy in 5 fractions) followed by total mesorectal excision (TME) is the standard treatment of intermediate risk rectal cancer (T1-3(without involvement of the mesorectal fascia (MRF-))N1M0 and T3cd(MRF-)N0-1M0) in the Netherlands. A prolonged interval between SCRT and TME (4-8 weeks, SCRT-delay) resulted in a lower postoperative complication rate and a higher pathological complete response (pCR) rate than SCRT and surgery within a week (SCRT- direct surgery) in the randomized Stockholm III trial. The current study sought to confirm these associations in nationwide real-world data of Dutch rectal cancer patients. Materials and Methods Patients with intermediate risk rectal cancer treated with either SCRT-delay (4-12 weeks) or SCRT-direct surgery in 2018- 2021 were selected from the nationwide Dutch ColoRectal Audit. The primary outcome was the general 90-day postoperative complication rate. Secondary outcomes included 90-day postoperative reintervention, ICU admittance, mortality, anastomotic leakage and pathological complete response (pCR). Baseline differences between groups were