ESTRO 2023 - Abstract Book

S1121

Digital Posters

ESTRO 2023

At a median follow-up of 3 (range 3-12) months, no in-field local progression occurred. Median Progression Free Survival was 7 months (Fig.2). No Grade ≥ 3 treatment-related toxicity was reported. At the time of analysis 2 patients died, 4 experienced out-of-field disease progression, while the remaining patients reported stable disease. Among progressive patients who continued active treatment, metastasis-directed SBRT was performed in 2 cases while one patient resumed systemic therapy.

Conclusion In patients with LAPC, robotic SBRT using a 50 Gy in 5 fractions schedule was feasible in the majority of patients, with no reported high-grade treatment-related toxicity and no local failure events.

Poster (Digital): Lower GI

PO-1392 Neoadjuvant short-course RT or chemoradiation plus consolidation chemotherapy for rectal cancer

S.F. Lee 1,2 , P.L. Yip 2 , B.A. Vellayappan 1 , H.J. Mamon 3 , F.A. Lee 2

1 National University Cancer Institute, Radiation Oncology, Singapore, Singapore; 2 Tuen Mun Hospital, Clinical Oncology, Hong Kong, Hong Kong (SAR) China; 3 Brigham and Women’s Hospital / Dana Farber Cancer Institute, Radiation Oncology, Boston, USA Purpose or Objective Evidence comparing pre-operative short-course radiotherapy (SCRT) versus neoadjuvant chemoradiation (NCRT), both followed by consolidation chemotherapy before radical rectal surgery is limited. We performed a retrospective cohort study to compare the two treatment strategies in terms of treatment response, survival outcomes, and toxicity. Materials and Methods We identified locally advanced rectal cancer (cT3–4 and/or N+) who received SCRT or NCRT with consolidation chemotherapy followed by total mesorectal excision between 2013 and 2021. We evaluated the cause-specific cumulative incidence of disease-related treatment failure , locoregional recurrence, distant metastases, and overall survival by using flexible parametric competing risk analysis and Kaplan-Meier methods as appropriate and adjusting for treatment regimens, and clinicopathological factors. Treatment response including pathological complete response (pCR), and tumor downstaging, and toxicity were reported. Results We analyzed 144 patients in which 115 (80%) underwent curative rectal surgery. 42 (76%) patients in the NCRT and 45 (75%) in the SCRT group had sphincter preserving surgery . pCR was achieved in 10 (18%) and 7 (12%) patients in NCRT and SCRT