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Planning Study of Dose Escalation with Biodegradable Spacer in Stereotactic Body Radiotherapy for Pancreatic Cancer

Z Feng

Z Feng12*, D Li1 , A Rao2 , E Shin2 , L Su2 , S kim2 , J Wong2 , A Narang2 , J Herman3 , K Ding2 , (1) Shandong Normal University, Jinan, Shandong, (2) Johns Hopkins University, Baltimore, MD, (3) MD Anderson Cancer Center, Houston, TX


SU-I-GPD-T-418 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: Biologically effective dose (BED) greater 70 Gy has been reported to have a superior overall survival in pancreatic cancer treatment. This study aimed to overcome the limited prescription dose caused by the dose constraint of adjacent normal tissues, specifically duodenum when applying dose escalation with stereotactic body radiotherapy (SBRT).

Methods: Three prescriptions, 25 Gy/1f (BED = 84 Gy), 36 Gy/3f (BED = 72 Gy) and 50 Gy/5f (BED = 100 Gy), were selected for this dose-escalation planning study. One cadaver specimen was injected with hydrogel spacer between pancreas and duodenum under endoscopic ultrasound. CT scans from seven previously treated pancreatic cancer patients were selected to simulate hydrogel injection. Dose-escalation SBRT plans were created for CTs before and after actual or simulated hydrogel injection with 15 mm separation. Dose escalation results were evaluated by clinical constraints from our institute and corresponding previous researchers.

Results: Plans of cadaver specimen showed that clinical constraints were all achieved in the three prescriptions with dose escalation. For the simulated results, with 25 Gy/1f prescriptions, D5 of proximal duodenum was significantly decreased from 15.45 Gy to 10.79 Gy. Simulated plans achieved clinical requirement for Dmax(< 23 Gy). However, there was no significant difference observed in D50. As escalation dose increased to 36 Gy/3f, the corresponding clinical requirement (Dmax < 25 Gy) was only satisfied with simulated plan (Dmax = 23.76 Gy). Our analysis also showed separation should be 15 mm (Dmax = 32.30 Gy) at least to meet the clinical requirement of 50 Gy/5f prescription (Dmax < 36.1 Gy).

Conclusion: Biodegradable hydrogel spacer can potentially allow dose escalation to pancreatic tumor without compromising the dose constraint of duodenum in pancreatic cancer SBRT.

Funding Support, Disclosures, and Conflict of Interest: This research was partially funded by the National Natural Science Foundation of China (NO.61471226), Natural Science Foundation for Distinguished Young Scholars of Shandong Province (NO. JQ201516).We also thank the supporting of Taishan scholar project of Shandong Province.

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