Feasibility of Stereotactic Body Radiation Therapy for Pancreatic Tumors Abutting Organs at Risk Using Magnetic Resonance Guided Adaptive Radiation Therapy.
Alden D'Souza, Kylie H Kang, John E Lattin, Bita Kalaghchi, John S Ginn, Alex T Price, David S Lakomy, Michael R Waters, Joshua P Schiff, Yi Huang, Richard Tsai, Pamela P Samson, Carl J DeSelm, Lauren E Henke, Farnoush Forghani, Xiaodong Zhao, Eric Morris, Geoffrey D Hugo, Tong Zhu, Allen Mo, Eric Laugeman, Hyun Kim
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引用次数: 0
Abstract
Purpose: Stereotactic body radiation therapy (SBRT) has historically been contraindicated in patients with tumors abutting gastrointestinal (GI) organs due to risk of toxicity. Adaptive magnetic resonance (MR) guided SBRT (MRgSBRT) is an increasingly used treatment paradigm to prescribe ablative doses to pancreatic tumors. Here we present our institutional experience of adaptive MRgSBRT for pancreatic tumors abutting or invading GI organs at risk (OARs).
Methods and materials: Forty-eight patients with pancreatic adenocarcinoma tumors abutting or invading GI OARs who received MRgSBRT to 50 Gy in 5 fractions at our institution between 2018-2019 were reviewed. Dosimetric variables were compared pre- and postadaptation to determine adequacy of target coverage, reasons for online adaptation, and resulting changes in GI OAR and constraints.
Results: Patients' mean age was 67 years, 50% female, 63% with ECOG 0-1, and with majority of tumors being locally advanced (52%) and located in the pancreatic head, uncinate process, or neck (92%). Tumors abutted or invaded GI OARs in 100% and 21% of cases, respectively. Of the 240 fractions evaluated, 99% required online adaptation and 77% underwent normalization. The mean PTV_opt (PTV minus a 5mm-expansion of GI OAR contours as the plan optimization structure) receiving prescription dose was 93%. The predicted and adapted critical volume (V36Gy ≤0.5 cc) for OARs were found to be statistically significantly different (P < .001). The duodenum had the highest volume receiving 36 Gy for both preadapted (mean 3.4 cc) and postadapted (mean 0.33 cc) plans. Plans for pancreatic head, uncinate process, or neck tumors frequently exceeded duodenum dose constraints and plans for pancreatic body or tail tumors more often exceeded stomach constraints (P < .001).
Conclusions: Adaptive MR guidance may permit SBRT for pancreatic tumors abutting or invading OARs with minimal toxicity.
期刊介绍：
International Journal of Radiation Oncology • Biology • Physics (IJROBP), known in the field as the Red Journal, publishes original laboratory and clinical investigations related to radiation oncology, radiation biology, medical physics, and both education and health policy as it relates to the field.
This journal has a particular interest in original contributions of the following types: prospective clinical trials, outcomes research, and large database interrogation. In addition, it seeks reports of high-impact innovations in single or combined modality treatment, tumor sensitization, normal tissue protection (including both precision avoidance and pharmacologic means), brachytherapy, particle irradiation, and cancer imaging. Technical advances related to dosimetry and conformal radiation treatment planning are of interest, as are basic science studies investigating tumor physiology and the molecular biology underlying cancer and normal tissue radiation response.
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