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A Dose Predication Model for Duodenum Sparing in Pancreatic Cancer with Biodegradable Hydrogel Spacer

Z Feng

Z Feng1,2*, D Li1 , Z Cheng2 , A Rao2 , E Shin2 , J Moore2 , L Su2 , S kim2 , J Wong2 , A Narang2 , J Herman3 , T McNutt2 , K Ding2 , (1) Shandong Normal University, Jinan, Shandong, (2) Johns Hopkins University, Baltimore, Maryland, (3) MD Anderson Cancer Center, Houston, TX,


SU-K-FS1-1 (Sunday, July 30, 2017) 4:00 PM - 6:00 PM Room: Four Seasons 1

Purpose: By using the overlap-volume-histogram (OVH), we propose a prediction model as a means to guide the hydrogel injection and predict the required hydrogel spacing to achieve clinical constraints.

Methods: 232 patients with pancreatic cancer treated with 33 Gy in 5 fractions were analyzed. According to the clinic constraints for the duodenum, La9 and La3, the GTV-expanded-2 mm expansion distance at which 9 cc and 3 cc absolute volumes of the duodenum overlaps, were calculated using OVH. Da9 and Da3 of duodenum were analyzed based on dose volume histogram, defined as the dose received by volumes of 9 cc and 3 cc of the duodenum. Prediction models were established by linear regression between Lax and Dax. Two cadaver specimens, with hydrogel injection, were involved in this study to assess the accuracy of pre- and post- dose prediction. Furthermore, CT scans from 6 patients with pancreatic cancer were used to verify predicted hydrogel spacing.

Results: The correlation analysis showed the significant correlation between Lax and Dax (r2 = 0.5146 and 0.5118 for La3-Da3 and La9-Da9, respectively). According to the clinical requirement for duodenum in our institution (V15 < 9cc, V20 < 3cc), two thresholds were obtained for predicting required hydrogel spacing (La3 > 7mm and La9 > 13 mm). The planning doses of duodenum from pre- and post- hydrogel injection CTs of cadaver specimens were within in the prediction range. By applying the required hydrogel spacing predicted from our model, pre- and post- hydrogel injection were simulated in CTs from 6 patients. The planning doses of Da3 and Da9 were also in corresponding predicted ranges.

Conclusion: Our prediction model can accurately predict duodenum planning dose based on OVH. By applying the predicted duodenum dose and required hydrogel spacing, the injection can be guided to improve efficacy.

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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