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

Authors

  • Wu L,

    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
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  • Zhang W,

    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
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  • Kwee S,

    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
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  • Li M,

    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
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  • Peng X,

    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
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  • Xie L,

    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
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  • Lin Z,

    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
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  • Wang H,

    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
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  • Kuang Y

    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
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Abstract

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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