Online adaptive radiotherapy: Assessment of planning technique and its impact on longitudinal plan quality robustness in pancreatic cancer

Kathryn E Mittauer; Sreenija Yarlagadda; John M Bryant; Nema Bassiri; Tino Romaguera; Andres G Gomez; Robert Herrera; Rupesh Kotecha; Minesh P Mehta; Alonso N Gutierrez; Michael D Chuong

doi:10.1016/j.radonc.2023.109869

Online adaptive radiotherapy: Assessment of planning technique and its impact on longitudinal plan quality robustness in pancreatic cancer

Radiother Oncol. 2023 Nov:188:109869. doi: 10.1016/j.radonc.2023.109869. Epub 2023 Aug 31.

Authors

Affiliations

¹ Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL 33176, USA; Herbert Wertheim College of Medicine, Florida International University, Miami, FL 33199, USA. Electronic address: kathrynm@baptisthealth.net.
² Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL 33176, USA. Electronic address: sreenija.yarlagadda@baptisthealth.net.
³ Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL 33176, USA; Herbert Wertheim College of Medicine, Florida International University, Miami, FL 33199, USA. Electronic address: john.bryant@moffitt.org.
⁴ Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL 33176, USA; Herbert Wertheim College of Medicine, Florida International University, Miami, FL 33199, USA. Electronic address: nema.bassirigharb@baptisthealth.net.
⁵ Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL 33176, USA; Herbert Wertheim College of Medicine, Florida International University, Miami, FL 33199, USA. Electronic address: AntinogenesR@baptisthealth.net.
⁶ Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL 33176, USA. Electronic address: AndresGome@baptisthealth.net.
⁷ Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL 33176, USA. Electronic address: RobertoHerr@baptisthealth.net.
⁸ Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL 33176, USA; Herbert Wertheim College of Medicine, Florida International University, Miami, FL 33199, USA. Electronic address: RupeshK@baptisthealth.net.
⁹ Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL 33176, USA; Herbert Wertheim College of Medicine, Florida International University, Miami, FL 33199, USA. Electronic address: MineshM@baptisthealth.net.
¹⁰ Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL 33176, USA; Herbert Wertheim College of Medicine, Florida International University, Miami, FL 33199, USA. Electronic address: AlonsoG@baptisthealth.net.
¹¹ Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL 33176, USA; Herbert Wertheim College of Medicine, Florida International University, Miami, FL 33199, USA. Electronic address: MichaelChu@baptisthealth.net.

PMID: 37657726
DOI: 10.1016/j.radonc.2023.109869

Abstract

Background and purpose: Planning on a static dataset that reflects the simulation day anatomy is routine for SBRT. We hypothesize the quality of on-table adaptive plans is similar to the baseline plan when delivering stereotactic MR-guided adaptive radiotherapy (SMART) for pancreatic cancer (PCa).

Materials and methods: Sixty-seven inoperable PCa patients were prescribed 50 Gy/5-fraction SMART. Baseline planning included: 3-5 mm gastrointestinal (GI) PRV, 50 Gy optimization target (PTV_opt) based on GI PRV, conformality rings, and contracted GTV to guide the hotspot. For each adaptation, GI anatomy was re-contoured, followed by re-optimization. Plan quality was evaluated for target coverage (TC = PTV_opt V_100%/volume), PTV D_90% and D_80%, homogeneity index (HI = PTV_opt D_2%/D_98%), prescription isodose/target volume (PITV), low-dose conformity (D_2cm = maximum dose at 2 cm from PTV_opt/Rx dose), and gradient index (R_50%=50% Rx isodose volume/PTV_opt volume).A novel global planning metric, termed the Pancreas Adaptive Radiotherapy Score (PARTS), was developed and implemented based on GI OAR sparing, PTV/GTV coverage, and conformality. Adaptive robustness (baseline to fraction 1) and stability (difference between two fractions with highest GI PRV variation) were quantified.

Results: OAR constraints were met on all baseline (n = 67) and adaptive (n = 318) plans. Coverage for baseline/adaptive plans was mean ± SD at 44.9 ± 5.8 Gy/44.3 ± 5.5 Gy (PTV D_80%), 50.1 ± 4.2 Gy/49.1 ± 4.7 Gy (PTV_opt D_80%), and 80%±18%/74%±18% (TC), respectively. Mean homogeneity and conformality for baseline/adaptive plans were 0.87 ± 0.25/0.81 ± 0.30 (PITV), 3.81 ± 1.87/3.87 ± 2.0 (R_50%), 1.53 ± 0.23/1.55 ± 0.23 (HI), and 58%±7%/59%±7% (D_2cm), respectively. PARTS was found to be a sensitive metric due to its additive influence of geometry changes on PARTS' sub-metrics. There were no statistical differences (p > 0.05) for stability, except for PARTS (p = 0.04, median difference -0.6%). Statistical differences for robustness when significant were small for most metrics (<2.0% median). Median adaptive re-optimizations were 2.

Conclusion: We describe a 5-fraction ablative SMART planning approach for PCa that is robust and stable during on-table adaption, due to gradients controlled by a GI PRV technique and the use of rings. These findings are noteworthy given that daily interfraction anatomic GI OAR differences are routine, thus necessitating on-table adaptation. This work supports feasibility towards utilizing a patient-independent, template on-table adaptive approach.

Keywords: MR-guided radiotherapy; Online adaptive radiotherapy; Pancreatic radiotherapy; SBRT.