Radiation Oncology, University Medical Center Freiburg, Freiburg, Germany
Eleni Gkika , Sonja Adebahr , Tanja Schimek-Jasch , Rolf Wiehle , Katja Zirlik , Uwe Wittel , Ursula Nestle , Anca Grosu , Thomas B. Brunner
Background: SBRT in pancreatic cancer can be limited by its proximity to critical organs at risk (OAR) of the upper abdomen. In this study we evaluate the toxicity and efficacy of two different treatment approaches. Methods: Patients with recurrent or oligometastatic pancreatic cancer were treated with SBRT. According to the prescription method patients were divided in two cohorts 1 (C1) and 2 (C2). In both groups the planning target volume (PTV) was created through a 4 mm expansion of the internal target volume based on a four dimensional CT. In C2, we created additionally a sub-volume, a simultaneous integrated protection (SIP) PTV in order to reduce the risk of toxicity in critically OAR without reducing the dose to the rest of the PTV. The SIP consisted in the overlap of the PTV with the planning risk volume (PRV) of a specific vulnerable structure to which we prescribed a reduced dose within the specific constraints. Results: Eighteen patients with 23 lesions were included in this analysis. Seven patients were treated for local recurrence or progression, nine for oligometastases (liver, lymph nodes) and two patients were treated for both. Eleven lesions were treated without SIP (C1) and 12 with SIP (C2). The median follow up was 12.8 months. Median overall survival (OS) time for all patients was 11.2 (2.3-42.6) months. The OS rates at 6 and 12 months after SBRT were 87% and 58%, respectively. Freedom from local progression (FFLP) for both cohorts was 93% at 6 months and 67% at 12 months and was not statistically different between the two groups. One patient in C2 (5%) experienced grade 3 acute toxicities (mechanical ileus and gastrointestinal bleeding) during treatment and 1 patient in C1 (5%) experienced a grade 3 late toxicity (gastrointestinal bleeding). Conclusions: We here show outcome data using a novel prescription method for upper abdominal SBRT with a favorable overall toxicity profile . Local control and overall survival after SBRT in this high risk group of patients were good despite of dose sacrifices in small subvolumes in half of the patients where OARs were adjacent to the PTV.
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