Author of

• 20163

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  P1.14 - Radiotherapy (ID 700)

  • Event: WCLC 2017
  • Type: Poster Session with Presenters Present
  • Track: Radiotherapy
  • Presentations: 1
  • Moderators:
  • Coordinates: 10/16/2017, 09:30 - 16:00, Exhibit Hall (Hall B + C)

  • 22783

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    P1.14-016 - Assessing the Feasibility of FLT-PET for Evaluation of Non-Small Cell Lung Cancer (NSCLC) Treated with Stereotactic Body Radiotherapy (SBRT) (ID 8455)

    09:30 - 09:30  |  Author(s): B. Driscoll
    • Abstract

    Background:
    Distinguishing fibrosis from tumor recurrence following lung SBRT remains a clinical challenge since CT has poor sensitivity and specificity for detecting recurrence. 18F-Fluoro-L-thymidine-PET (FLT-PET) uptake correlates with cell proliferation. The purpose of this study is to investigate the feasibility of FLT-PET as an imaging biomarker for lung SBRT response assessment.
    
    Method:
    In this prospective study, three groups were included: 1) newly-diagnosed biopsy-proven NSCLC pre-SBRT, 2) established post-SBRT mass-like fibrosis on serial follow-up CT scans by co-investigators’ consensus, and 3) biopsy-proven locally-recurrent NSCLC after SBRT. Non-gated, helical gated (3D-CT/4D-PET) and phase-matched (4D-CT/4D-PET) FLT-PET images were obtained. Group-1 underwent fluorodeoxyglucose (FDG)-PET scan according to clinical guidelines. FLT uptake was measured by SUV95 and SUV50 (95% and 50% of maximum pixel value plus average background value, respectively), SUV2Dpeak and SUV3Dpeak (1cm diameter circular or spherical around region of interest, respectively), SUVmean and SUVmax. Descriptive statistics were gathered. Kolmogorov–Smirnov test was used to determine normality. Statistical significance was reported using student’s t-test.
    
    Result:
    27 patients were included, with 19 primary tumors (group-1), 12 established fibrosis (group-2) and 1 recurrence (group-3). In group-1, 16 tumors were T1. Group-1, mean FDG-PET SUVmax, SUV95, SUV50, SUV2Dpeak, SUV3Dpeak and SUVmean were 7.40, 5.88, 2.39, 5.59, 6.02 and 2.78, respectively. Mean FLT-PET values for group-1 were 3.43, 2.84, 1.71, 2.9, 2.82 and 1.78, respectively. Group-2 SBRT dose was either 48Gy in 4 fractions (83%) or 60Gy in 8 fractions. Median time from radiation to FLT-PET scan in group-2 was 19.5 months (5.8-83.8mos). The patient in group-3 had SUV50, SUV95, SUV2Dpeak, SUV3Dpeak, SUVmean and SUVmax of 2.27, 3.85, 6.37, 6.05, 2.39 and 7.64, respectively. Mean FLT-PET SUVmax for groups 1 and 2 was significantly different (p=0.03) at 3.42(1.14-7.04) and 2.34(1.23-4.35) respectively. Similarly, mean (range) of SUV50, SUV95 and SUVmean for group-1 was 1.8(0.74-3.43), 2.97(1.03-5.83), 1.87(0.73-3.44), and for group-2 was 1.22(0.81-2.26), 1.85(1.13-3.8) and 1.25(0.83-2.39), respectively (p<0.01, <0.01 and <0.01). There was no statistically-significant difference between SUV2Dpeak and SUV3Dpeak between groups 1 and 2, with a mean of 2.97(0.99-6.30) and 2.91(0.90-6.11) for group-1 and 2.10(1.11-3.91) and 2.03(1.00-3.86) for group-2 (p=0.06 and 0.06), respectively. There was no statistically significant difference between the 3D and 4D image acquisition in group-1. There were no FLT-PET-related toxicities.
    
    Conclusion:
    FLT-PET is feasible in SBRT patients pre- and post-treatment, and may assist in distinguishing fibrosis from recurrent tumor. Further validation studies are needed.