ESTRO 2020 Abstract Book

S228 ESTRO 2020

Digestive Oncology, Brussels, Belgium ; 7 CHU St-Pierre, Gastroenterology, Brussels, Belgium

Purpose or Objective The optimal treatment sequence for localized pancreatic ductal adenocarcinoma (PDAC) remains controversial. The stereotactic body radiotherapy (SBRT) technique has the advantages of limiting interruption of systemic treatments and increasing the biological equivalent dose delivered potentially leading to improved local control, resection rates and overall survival (OS). We report here the preliminary results of our neoadjuvant treatment strategy including mFOLFIRINOX followed by SBRT with simultaneous integrated boost (SIB) at the tumor-vessels interfaces (TVI). Material and Methods From August 2017, all patients diagnosed with high-risk resectable (HR-R), borderline (BR), or locally advanced (LA) PDAC - according to the criteria defined by the National Comprehensive Cancer Network (NCCN) - were prospectively included. Induction by mFOLFIRINOX alone or followed by gemcitabine/nab-paclitaxel (G/NabP) if no response or intolerance was delivered for an average of 7 cycles. After a radiological assessment showing no progression, SBRT was delivered (35Gy in 5 sessions) with a TVI-SIB up to 50Gy. Patients with partial, complete response (CR) or stable disease were explored for oncologic resection 4 to 6 weeks after SBRT. Acute toxicities (≤ 6 months) were graded according to CTCAE v.4. Results Twenty-seven patients with localized PDAC - 1 HR-R, 9 BR, 17 LA - received either mFOLFIRINOX only (85%) or followed by G/NabP (15%). The median age at diagnosis was 60.5 years (P25 52 - P75 70) and the median follow-up is currently 11.5 months (P25 7 - P75 14.5). After radiological assessment, 3 patients developed metastases, 1 presented a CR and surgery was directly performed, 2 were not candidates for SBRT due to the failure of fiducials insertion and 21 received SIB-SBRT (78%). Of these 21 patients, 4 became metastatic at the pre-surgical assessment (19%), 4 were inoperable due to portal cavernoma or initial contraindication to general anesthesia (19%) and 13 patients (62%; 1HR-R, 5 BR, 7 LA) were explored. Resection was not performed in 4 patients due to per-operative discovery of liver metastases (n=2/13) or non-reconstructible vascular invasion (n=2/13). The R0 resection rates >0.1mm and ≥1mm are respectively 78% (n=7/9) and 44% (n= 4/9). The 6 months OS and progression free survival rates are respectively 100% and 70% for the entire cohort. To date, the 1-year OS for patients with sufficient follow-up who received the complete neoadjuvant sequence with SBRT is 91% (n=10/11) versus 81% for the entire cohort (n=13/16). Acute toxicity is minimal, with most patients experiencing fatigue (grade≤2: 90%) and flare-up epigastric pain (grade 1: 52%). No acute grade ≥3 gastrointestinal toxicity has been reported. Conclusion These preliminary results indicate that the integration of SIB-SBRT following multi-agent induction chemotherapy is feasible for the neoadjuvant treatment of localized PDAC. Our first analyses show favorable R0 resection rate, acute toxicity profile and 1-year OS in selected patients.

Conclusion In line with previous animal studies (1), radiotherapy can cause a decrease in right-ventricle systolic function already 6 weeks after treatment. In CLARIFY we will continue to characterise the incidence and clinical impact of radiation induced signs of PH. This could facilitate the future development of prevention and treatment strategies to ameliorate the consequences of cardiopulmonary toxicity in terms of quality of life and survival of these patients. (1) Ghobadi, G. et al. Thorax 67, 334–341 (2012). PD-0420 Induction by mFOLFIRINOX followed by SIB- SBRT for the neoadjuvant treatment of pancreatic cancer. C. Bouchart 1 , J. Engelholm 2 , M.A. Bali 2 , J. Closset 3 , J. Navez 3 , P. Loi 3 , Y. Gökburun 4 , T. De Grez 4 , A. Hendlisz 5 , L. Mans 6 , P. Eisendrath 7 , D. Van Gestel 1 , L. Moretti 1 , J. Van Laethem 6 1 Institut Jules Bordet ULB, Radiotherapy, Brussels, Belgium ; 2 Institut Jules Bordet ULB, Radiology, Brussels, Belgium ; 3 Erasme Hospital, Gastrointestinal Surgery, Brussels, Belgium ; 4 CHR Namur, Gastroenterology and digestive oncology, Namur, Belgium ; 5 Institut Jules Bordet ULB, Digestive oncology, Brussels, Belgium ; 6 Erasme Hospital, Gastroenterology- Hepatology and