ESTRO 2023 - Abstract Book

S1079

Digital Posters

ESTRO 2023

Median follow up was 10.1 months (range 9.0-11.3 months). Median overall survival for CRT group was 12.9 months (range 12.7-13.6) and 10.5 months (range 7.8 – 12.0) in patients treated with CRT ad CHT, respectively. The meta-analysis showed a significant advantage in favour of CRT (HR 0.70, 0.59-0.82, 95% CI; p<0.001).

Conclusion This meta-analysis shows a significant advantage of concurrent CRT, in terms of OS, compared to CHT alone.

PO-1347 Prognostic value of neutrophil/lymphocyte count in pancreas patients receiving ablative MR-guided RT

M. Chuong 1 , R. Herrera 1 , M. Rubens 2 , A. Ucar 3 , F. De Zarraga 3 , S. Aparo 3 , S. Joseph 3 , O. Olorunlogbon 4 , M. Hall 1 , G. Estevez 1 , R. Kotecha 1 , A. Kaiser 1 1 Miami Cancer Institute, Radiation Oncology, Miami, USA; 2 Miami Cancer Institute, Office of Clinical Research, Miami, USA; 3 Miami Cancer Institute, Medical Oncology, Miami, USA; 4 Florida International University, Herbert Wertheim College of Medicine, Miami, USA Purpose or Objective Ablative stereotactic MR-guided adaptive radiotherapy (A-SMART) for inoperable pancreatic ductal adenocarcinoma (PDAC) is well-tolerated and may improve OS compared to non-ablative radiotherapy (RT). Biomarkers for identifying patients who benefit from RT dose escalation are lacking. Absolute lymphocyte count (ALC), absolute neutrophil count (ANC), and neutrophil-to-lymphocyte ratio (NLR) may be significant prognostic factors of clinical outcomes in PDAC patients although have not been previously evaluated after A-SMART. Materials and Methods We retrospectively evaluated non-metastatic inoperable PDAC patients who received A-SMART with median prescription dose 50 Gy (range, 40-50) in 5 consecutive fractions (median BED10=100 Gy) on a 0.35T MR-linac using continuous intrafraction cine-MRI, soft tissue tracking, and automatic beam gating at a single institution. All required on-table adaptive replanning to ensure organ-at-risk constraints were met and to secondarily optimize target volume coverage. Univariate (UVA) and multivariate analyses (MVA) were performed including ANC, ALC, and NLR at 4 time points – (TP1) initial PDAC diagnosis, (TP2) just prior to A-SMART, (TP3) 3 months after A-SMART, (TP4) 6 months after A-SMART – to determine associations with freedom from local failure (FFLF), freedom from distant failure (FFDF), progression-free survival (PFS), and overall survival (OS). Results 68 patients with median follow-up 21.5 months (range, 4.8-50.8) from diagnosis were evaluated. Most had locally advanced (72.1%), and otherwise borderline resectable (17.6%) or medically inoperable (10.3%) PDAC. 98.5% had ECOG performance status 0-1. Most had head of pancreas lesions (88.2%). Median greatest tumor dimension was 3.7 cm. 63 (92.6%) patients received induction chemotherapy, usually FOLFIRINOX (n=43; 68.3%) or gemcitabine/nab-paclitaxel (n=16; 25.4%) for a median 4.2 months. Median GTV mean, minimum, and maximum dose were 55.7 Gy, 31.5 Gy, 68 Gy, respectively. Median CA19-9 at TP1, TP2, TP3, and TP4 were 154, 47, 44.5, and 35, respectively. Median ANC were 4.4, 3.4, 3.4, and 3.6, respectively. Median ALC were 1.5, 1.4, 0.9, 1.0, respectively. Median NLR were 3.3, 3.0, 3.5, and 3.2, respectively. Higher OS on MVA was only associated with (a/w) female gender (HR=0.43, 95% CI: 0.22-0.84; p=0.013). ANC median at TP3 was significant on MVA for both worse OS (HR=2.07, 95% CI: 1.03-4.15; p=0.042) and worse FFDF (HR=2.56, 95% CI: 1.17-5.6; p=0.018). Higher NLR at TP3 and lower ALC at TP4 were significantly a/w worse OS on UVA, but not MVA. No factor was significant on MVA for FFLF or PFS. Chemotherapy (type, duration) or RT (dose, volume) factors were not significant on MVA for any clinical outcome. Conclusion Higher ANC within 3 months of A-SMART is a/w OS and FFDF and we plan to establish an optimal ANC cutoff value to guide clinical decision making. Additional studies are needed to more extensively evaluate whether RT-related factors impact clinical outcomes through ANC and/or ALC changes.

PO-1348 Efficacy and safety of image-guided hypofractionated RT for HCC with portal vein tumor thrombosis

S.M. Lee 1 , E.K. Chie 1 , H. Kang 1 , K.S. Kim 1