Program Information
18F-NaF PET/CT-Directed Dose Escalation in Stereotactic Body Radiotherapy for Spine Oligometastases From Prostate Cancer
L Wu1,3*, W Zhang1 , S Kwee2 , M Li1 , X Peng1 , L Xie1 , Z Lin1 , H Wang3 , Y Kuang3 , (1) Cancer Hospital of Shantou University Medical College, Shantou, Guangdong, China, (2) The Queen's Medical Center, Honolulu, HI, (3) University of Nevada, Las Vegas, Las Vegas, NV
Presentations
SU-C-BRA-1 (Sunday, July 12, 2015) 1:00 PM - 1:55 PM Room: Ballroom A
Purpose: To investigate the technical feasibility of SBRT dose painting using ¹⁸F-NaF positron emission tomography (PET) scans guidance in patients with spine oligometastases from prostate cancer.
Methods: As a proof of concept, six patients with 14 spine oligometastatic lesions from prostate cancer who had ¹⁸F-NaF PET/CT scan prior to treatment were retrospectively included. GTVreg was delineated according to the regular tumor boundary shown on PET and/or CT images; and GTVMATV was contoured based on a net metabolically active tumor volume (MATV) defined by 60% of the SUVmax values on ¹⁸F-NaF PET images. The PTVs (PTVreg and PTVMATV) were defined as respective GTVs (plus involved entire vertebral body for PTVreg) with a 3-mm isotropic expansion margin. Three 1-fraction SBRT plans using VMAT technique along with 10 MV FFF beams (Plan24Gy, Plan24-27Gy, and Plan24-30Gy) were generated for each patient. All plans included a dose of 24 Gy prescribed to PTVreg. The Plan24-27Gy and Plan24-30Gy also included a simultaneous boost dose of 27 Gy or 30 Gy prescribed to the PTVMATV, respectively. The feasibility of 18F-NaF PET-guided SBRT dose escalation was evaluated by its ability to achieve the prescription dose objectives while adhering to organ-at-risk (OAR) dose constraints. The normal tissue complication probabilities (NTCP) calculated by radiological models were also compared between the plans.
Results: In all 33 SBRT plans generated, the planning objectives and dose constraints were met without exception. Plan24-27Gy and Plan24-30Gy had a significantly higher dose in PTVMATV than Plan24Gy (p < 0.05), respectively, while maintaining a similar OAR sparing profile and NTCP values.
Conclusion: Using VMAT with FFF beams to incorporate a simultaneous ¹⁸F-NaF PET-guided radiation boost dose up to 30 Gy into a SBRT plan is technically feasible. The relationship between local control and normal tissue toxicity in SBRT dose painting should be validated in clinical trials.
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