Madrid, Spain
Onsite/Online

ESTRO 2021

Session Item

Sunday
August 29
16:45 - 17:45
Room 1
Proffered papers 25: Upper GI
Karin Haustermans, Belgium;
Thomas Brunner, Germany
1770
Proffered papers
Clinical
17:25 - 17:35
Long-term outcomes of MR-guided SABR & on-table adaptive replanning for unresectable pancreas cancer
Michael Chuong, USA
OC-0415

Abstract

Long-term outcomes of MR-guided SABR & on-table adaptive replanning for unresectable pancreas cancer
Authors: Michael Chuong(Miami Cancer Institute, Radiation Oncology, Miami, USA), Kathryn Mittauer(Miami Cancer Institute, Radiation Oncology, Miami, USA), Roberto Herrera(Miami Cancer Institute, Radiation Oncology, Miami, USA), Tino Romaguera(Miami Cancer institute, Radiation Oncology, Miami, USA), DIane Alvarez(Miami Cancer Institute, Radiation Oncology, Miami, USA), Rupesh Kotecha(Miami Cancer Institute, Radiation Oncology, Miami, USA), Matthew Hall(Miami Cancer Institute, Radiation Oncology, Miami, USA), Adeel Kaiser(Miami Cancer Institute, Radiation Oncology, Miami, USA), John Bryant(Moffitt Cancer Center, Radiation Oncology, Tampa, USA), James McCulloch(Miami Cancer Institute, Radiation Oncology, Miami, USA), Antonio Ucar(Miami Cancer Institute, Medical Oncology, Miami, USA), Fernando De Zarraga(Miami Cancer Institute, Medical Oncology, Miami, USA), Santiago Aparo(Miami Cancer Institute, Medical Oncology, Miami, USA), Horacio Asbun(Miami Cancer Institute, Surgical Oncology, Miami, USA), Ramon Jimenez(Miami Cancer Institute, Surgical Oncology, Miami, USA), Govindarajan Narayanan(Miami Cancer Institute, Interventional Oncology, Miami, USA), Sarah Joseph(Miami Cancer Institute, Medical Oncology, Miami, USA), Alonso Gutierrez(Miami Cancer Institute, Radiation Oncology, Miami, USA), Muni Rubens(Miami Cancer Institute, Office of Clinical Research, Miami, USA)
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Purpose or Objective

Radiation therapy (RT) dose escalation may improve clinical outcomes for patients with inoperable pancreas cancer (PCa), although can potentially cause severe toxicity due to the proximity of gastrointestinal luminal organs.  A few studies have suggested that significant dose escalation may be safely achieved using magnetic resonance image (MRI) guidance with on-table adaptive replanning although long-term outcomes are not well understood

Material and Methods

A single institution retrospective analysis was performed of 50 consecutive patients with inoperable non-metastatic pancreas adenocarcinoma treated on a 0.35T-MR Linac without fiducial markers from 2018-2020.  Median age was 70 years (range 35-91).  ECOG performance status was mostly 0-1 (94%).  Locally advanced disease was most common (82%), otherwise borderline resectable (8%) or medically inoperable (10%).  Median CA19-9 at diagnosis was 122.2 U/mL (range, 0.9-12,868.6).  Induction chemotherapy (CT) was routine (94%), usually FOLFIRINOX (58%) or gemcitabine/nab-paclitaxel (26%), for a median 4.2 months (range, 0.2-14.5).  Local control (LC) was defined using RECIST 1.1 criteria.  Acute (<3 months from SABR) and late toxicity were assessed as per CTCAE v5 criteria.  Outcomes were assessed from the date of PCa diagnosis.

Results

Median prescribed dose was 50 Gy (range 40-50), median biologically effective dose (BED10) was 100 Gy10.  The median PTV volume was 111.0 cm3 (range 11.3-374.33).  Treatment in breath hold was common (90%).  On-table adaptive replanning was performed for a median 5 fractions (range 1-5) in 96% of patients.  Post-SABR therapy included pancreaticoduodenectomy (14%), irreversible electroporation (10%), and/or CT (52%).  Negative margins were achieved in 6/7 patients who had surgery.  Median follow-up was 18 months (range 7-39 months) from diagnosis.  Median, 1-yr, and 2-yr estimated LC was not reached, 97.8%, and 88.9%, respectively.  Median, 1-yr, and 2-yr estimated progression free survival (PFS) was 16 months, 67.7%, and 25.7%, respectively.  Median, 1-yr, and 2-yr estimated overall survival (OS) was 21 months, 87.9%, and 50%, respectively.  Induction CT duration >3 months was the only predictor of improved PFS (hazard ratio [HR] 0.358; 95% confidence interval [CI] 0.141-0.913; P=0.031) and OS (HR 0.288; 95% CI 0.104-0.799; P=0.017) on multivariate analysis.  Acute and late grade 3+ toxicity rates were 2% and 10%, respectively.

Conclusion

To our knowledge, this is the largest series of 5-fraction MRI-guided stereotactic ablative body radiation therapy (SABR) with on-table adaptive replanning for inoperable PCa.  Our 2-yr estimated OS of 50% is significantly higher compared to historical outcomes of ~20% from CT +/- non-ablative RT.  Additional study is needed to improve our understanding about optimal patient selection, treatment response assessment, and the need for additional therapy after SABR.