Author of

• 11890

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  P2.19 - Poster Session 2 - Imaging (ID 180)

  • Event: WCLC 2013
  • Type: Poster Session
  • Track: Imaging, Staging & Screening
  • Presentations: 1
  • Moderators:
  • Coordinates: 10/29/2013, 09:30 - 16:30, Exhibit Hall, Ground Level

  • 11902

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    P2.19-012 - Inter-method Comparison of 18F-FDG PET Metabolic Response Assessment in Non-small Cell Lung Cancer (ID 2670)

    09:30 - 09:30  |  Author(s): K.K. Wong
    • Abstract

    Background
    This study aimed to: 1) compare qualitative and semi-quantitative assessment of [18]F-fluorodeoxyglucose PET based categorical metabolic response in patients with NSCLC and determine their value for prognosis prediction; 2) investigate the relationship between semi-quantitative assessments of post-treatment change of metabolic activity and survival and explore an optimal cutoff to distinguish a subset of responders with more favorable outcome.

    Methods
    This is a secondary analysis of prospective studies with IRB approval. Enrolled patients with NSCLC underwent PET/CT imaging within 2 weeks prior to (pre-RT PET/CT), at 4 weeks during and after radiation treatment (post-RT PET/CT). Post-RT metabolic therapeutic response was assessed using 1) visual assessment and 2) semi-quantitative measurement based on reduction in tumor FDG uptake; SUVmax normalized to mediastinal blood pool (NSUV-A). Interpretation of PET/CT scans was performed by three nuclear medicine physicians, blinded to clinical information. The three physicians did independent reads of the patients, performing a single read for each patient’s set of PET studies. Kappa coefficient was used to evaluate the agreement between categorical variables. Survival analysis and Cox proportional hazard regression model were adopted to analyze the effect of various response criteria on overall survival (OS) and progression free survival (PFS).

    Results
    Forty-four patients (36 male: 8 female) were eligible for analysis. The median interval between end of RT and post-RT PET/CT scan was 93 days. A poor agreement was observed between visual and semi-quantitative responses (Kappa coefficient = 0.393). Categorical responses were significantly correlated with both OS and PFS independent of employed response assessment criteria (either visual or semi-quantitative, p < 0.001) and patients with complete metabolic response (CMR) obtained the longest survival. As a continuous variable, reduction percentage of NSUV-A showed significant correlations with OS (hazard ratio, HR = 0.980, p < 0.001) and PFS (HR=0.984, p < 0.001). Analysis of OS and PFS consistently recommended NSUV-A reduction of sixty percent (60%) as another discriminative cutoff to distinguish patients with different outcome (p < 0.01).

    Conclusion
    There is a great discrepancy in metabolic response rates between qualitative and semi-quantitative methods. Categorical metabolic response criteria, either from qualitative visual assessment or a semi-quantitative method, demonstrate significant association with overall survival and progression free survival. Visual method offers a simpler approach that provides good information with regard to predicting OS and PFS, while the semi-quantitative method provides ordinal value that correlates with prolonged OS. As a continuum, the numerical percentage reduction in the normalized SUV is positively correlated with longer overall survival, reinforcing the prognostic value of metabolic change on FDG PET/CT. A sixty percent reduction of SUV may be the optimal cutoff for metabolic response to identify subsets of the PMR population with distinct outcomes, pending validation by an independent population.