SU‐C‐BRA‐01: 18F‐NaF PET/CT‐Directed Dose Escalation in Stereotactic Body Radiotherapy for Spine Oligometastases From Prostate Cancer

• Published in: Medical physics (Lancaster) Vol. 42; no. 6Part2; p. 3195
• Main Authors: Wu, L, Zhang, W, Kwee, S, Li, M, Peng, X, Xie, L, Lin, Z, Wang, H, Kuang, Y
• Format: Journal Article
• Language: English
• Published: United States American Association of Physicists in Medicine 01-06-2015
• Subjects: 60 APPLIED LIFE SCIENCES; ANIMAL TISSUES; Cancer; Computed tomography; COMPUTERIZED TOMOGRAPHY; Dosimetry; FLUORINE 18; NEOPLASMS; POSITRON COMPUTED TOMOGRAPHY; Positron emission tomography; PROSTATE; RADIATION DOSES; RADIOTHERAPY; SODIUM FLUORIDES; Tissues; VERTEBRAE
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1118/1.4923811

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.