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TU‐A‐WAB‐07: Evaluation of Local Therapy Response for Locally Advanced Pancreatic Cancer (LAPC) Using PET/CT
Author(s) -
Yue Y,
Tuli R,
Yang W,
Antonuk A,
Sandler H,
Fraass B
Publication year - 2013
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4815341
Subject(s) - nuclear medicine , medicine , radiation therapy , image registration , radiology , artificial intelligence , computer science , image (mathematics)
Purpose: To quantify local treatment response for pancreatic radiotherapy using PET/CT, and investigate prediction of residual high‐uptake areas using Pre‐radiotherapy scans. Methods: 18FDG‐PET/CT scans were obtained from ten LAPC patients, pre‐RT, 8–12 weeks following treatment (Post‐RT), and at 2 to 4month follow‐up intervals. Four patients received 3 follow‐up scans; others had at least one follow‐up scan. All PET/CT images were registered to the planning CT using object‐specific deformable registration which preserves target volume rigidity while deforming surrounding tissue. Therapy response evaluation is performed by comparing changes in SUVmax and volume pre‐RT and post‐RT. Local response is further evaluated by dividing the volume of interest into 4.8×4.8×4.8mm ^ 3 subvolumes. Each subvolume is characterized with mean uptakes (SUVpre, SUVpost), SUVdiff=SUVpre‐SUVpost, and treatment dose. Local response is evaluated using 3 volumes (VOIs): (1) ITV, (2) volume between PTV and ITV, (3) 3mm expansion around the PTV. For each VOI, the quantified response index is calculated [QR = (#subvolumes with SUVdiff>0)/(#subvolumes)]. A large QR suggests better local control. Subvolumes with SUVdiff<0 are investigated by examining SUVpre and treatment dose. Local response results are correlated to global SUVmax changes, disease volume changes, and clinical radiologist readings. Results: 10 follow‐up scans of 5 patients show strong positive response to treatment, with QRs for all VOIs >0.75 [ITV: 0.97+/−0.07, PTV‐ITV: 0.84+/−0.18, 3mm PTV expansion: 0.76+/−0.29]. Global disease volumes (identified by high‐uptake values) are reduced >70%, global SUVmaxs are reduced more than 50%. Three partial response patients have QR=0.50–0.75 (0.62+/−0.11 for ITV volumes). Two cases (failures) have QR<0.4, with mean 0.26+/−0.06. Conclusion: Quantification of local metabolic response provides a feasible approach for evaluating efficacy of local control of pancreatic cancer treatment. The results can be used to identify persistent and local failure of disease, toward implementing response‐driven adaptive radiotherapy.