ESTRO 2022 - Abstract Book

S1081

Abstract book

ESTRO 2022

Results 100 (58 BRPC and 42 LAPC) patients with 64 males and median age (Inter Quantile range) of 57 (51-65) years were identified. 69 patients received FOLFIRINOX, and the remaining others gemcitabine-based NACT, with SBRT to a median dose (Inter Quantile range) of 75 (75) Gy (BED Gy10). Overall 36 patients underwent exploration with 26 (72.2%) proceeding with R0 resection where 10 achieved pathological complete response. At a median follow up of 16 months, the DFS, PFS, LFFS and DMFS were 60.5+5, 36.5+5, 54.1+6.3 and 62.6 + 5.7% respectively. The ECOG >1 (HR: 0.02[0.006-0.067]; p<0.001) was the only factor associated with OS, whereas, poor DFS was significantly associated with ECOG >1 (HR: 0.39[0.01-0.15]; p=0.001), local (HR: 6.67[3.31-13.43]; p<0.001) and distant failure (HR: 6.08[2.98-12.42];p<0.001). The overall PFS was significantly associated with post-NACT response (HR: 2.2[0.99-4.92]; p=0.05), local (HR: 4.97[2.72-9.05]; p<0.001) and distant failure (HR: 8.39[4.39-16.05]; p<0.001). Among them, the LFFS was only associated with post NACT response (HR: 7.82 [5.62- 10.02]; p<0.001); while ECOG >1 (HR: 0.38[0.16-0.91]; p=0.03) and local progression (HR: 0.28[0.1-0.80]; p=0.018) were significantly associated with DMFS. Conclusion Local failure remains an important challenge in advanced pancreatic cancers despite standard chemotherapy, SBRT and surgery as feasible. Selecting patients with ECOG <1, good response post-chemotherapy and further dose escalation with SBRT may be helpful in future. 1 Max Super Speciality hospital, Radiation Oncology, Delhi, India; 2 Max Super Specialty Hospital, Radiation oncology, Delhi, India; 3 Max Super Specialty Hospital, radiation oncology, delhi, India Purpose or Objective Surgical resection is the standard of care for Hepatocellular carcinoma (HCC)and liver metastases, however most patients are unable to undergo surgery due to clinical condition or major cost involved. Stereotactic Body Radiotherapy (SBRT) is a non-invasive technique that enables delivery of ablative high doses of radiation with hypo-fractionation. The advantage over conventional fractionation is that high dose delivered per fraction with reduction of dose to normal tissues, due to rapid dose fall off at the periphery of the target. SBRT can achieve local control in accordance with surgery or other local invasive modalities; a trade off exists between dose delivered, local control, gastrointestinal (GI) complications, hematological toxicities and RILD. Our aim is to analyse the dose volume effects to the hematological and GI toxicity, progression of Child Pugh (CP) score and Radiation Induced Liver Disease (RILD). Materials and Methods We retrospectively analysed 50 patients treated from 2011 to 2018. HCC was seen in 46 % and metastatic liver tumors 54 %. CP score and LFT were documented. Motion management techniques used were tumor tracking, abdominal compression, gating and 4DCT to account for the movement of the liver and to create differential planning target volume (PTV) margins as per the technique used. Gross tumor volume (GTV) was contoured after discussing with the liver radiologist. Median GTV Volume was 86 cc (6.8 – 867 cc). Median Normal liver volume was 1251 cc (715 – 2700 cc). Median dose delivered was 48 Gy (35- 54 Gy) and median BED 10 Gy was 85.5 Gy 10 (52.2 Gy 10 to 151.2 Gy 10 ). Median D 700 cc of normal liver was 9.4 Gy. The dose was reduced if the tumor was in proximity to the organs at risk or either the D700 cc was exceeding the normal limit.TG 101 was followed for normal tissue constraints. Results 3 patients lost to follow up. Toxicity analysis and response assessment was by CTCAE V.5 and mRECIST criteria, respectively. CP Score after SBRT No.of patients A to B 15 A to B progression by ≥ 2 5 out of 15 B to A 4 No change 28 On analysis, Non classic RILD was observed in 1 patient. No patient had classic RILD in our study. Abdominal pain was seen in 10 %. Nausea/Vomiting was seen in 32% of our patients with significant association with dose per fraction (p=0.009). Grade 2 -3 hematological toxicities were observed in patients more than 50 years of age and higher dose per fraction (> 8Gy/fraction), not statistically significant (p=0.23). Median local control was 8 months with 1-year local control of 42 %. The median overall survival was 12 months and 1-year survival was 72 %. Conclusion The uniqueness of delivering SBRT liver is that a fixed dose fractionation regimen is not feasible in all patients due to dose volume effects, D700cc, fear of GI toxicities and RILD. Normal liver volume less than 700 cc remains the strict exclusion criteria. SBRT shall provide better local control rates with BED Gy 10 more than 70-80 Gy 10 with acceptable toxicity and no risk of RILD at D700cc < 15-18 Gy. PO-1283 Stereotactic Body Radiotherapy (SBRT) for liver tumors – An analysis of Dose volume effects J. Selvarajan 1 , A.K. Anand 2 , D. Mittal 3 , A.K. Bansal 2 , N. Kumawat 2