Author of

• 12544

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  P3.08 - Poster Session 3 - Radiotherapy (ID 199)

  • Event: WCLC 2013
  • Type: Poster Session
  • Track: Radiation Oncology + Radiotherapy
  • Presentations: 1
  • Moderators:
  • Coordinates: 10/30/2013, 09:30 - 16:30, Exhibit Hall, Ground Level

  • 12563

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    P3.08-019 - Visual assessment of the presence of central photopenia on FDG-PET imaging in non-small cell lung cancer (NSCLC) and its prognostic influence on survival in patients treated with radiotherapy. A subset analysis of TROG 99.05. (ID 2513)

    09:30 - 09:30  |  Author(s): R.A. Cox
    • Abstract

    Background
    Cavitation in NSCLC has anecdotally been associated with worse prognosis and survival. It has been postulated that rapid tumour growth and disordered angiogenesis leads to necrosis, cavitation and central hypoxia, with associated reduction in tumour radiosensitivity. This study investigated central photopenia on FDG-PET imaging (indicating reduced metabolic activity in necrotic areas) as an independent prognostic factor in patients with NSCLC treated by definitive radiotherapy.

    Methods
    Pre-treatment PET images for 172 patients (single institution, enrolled in multicentre prospective observational study TROG 99.05) with pathologically proven stage I-III NSCLC planned for definitive radiotherapy (minimum 50 Gy in 20 fractions) or chemoradiotherapy (93.4%) were independently analysed by two investigators at two time points one month apart. The presence and percent of tumour demonstrating central photopenia were scored using visual assessment. Central photopenia was defined as a non-peripheral volume within the primary tumour with an SUV <40% of the SUVmax. Survival was adjusted for known prognostic factors including performance status, T and N stage.

    Results
    Inter-observer agreement for the presence (Kappa=0.822, p<0.001) and proportion (intraclass correlation coefficient (ICC)=0.913 with 95% CI, 0.862-0.946, p<0.001) of photopenia and were good. Intra-observer reassessment showed fair agreement (Kappa=0.600, p<0.001 and ICC=0.752 with 95% CI, 0.634-0.836, p<0.001). Photopenia, present in 43% of the tumours was associated with larger tumour volumes (mean volume 197.3cm[3 ]vs 56.2cm[3 ]in solid tumours, p<0.001) and weight loss (51% of patients vs 31%, p=0.029). Median survival was shorter in the presence of photopenia but there was no significant difference in overall survival (OS) on univariate (HR=1.25, 95% CI, 0.89-1.77, p=0.200) or multivariate analysis (HR=1.14, 95% CI, 0.80-1.61, p=0.465) after adjusting for stage and performance status. Correlations of OS and the percent of photopenia were not statistically significant. Figure 1

    Conclusion
    The presence and proportion of photopenia on FDG-PET imaging can be reproducibly measured using visual analysis without requiring specialist workstation software. Central photopenia was associated with larger tumours, weight loss, and shorter median survival, but there was no statistically significant effect on overall survival after adjusting for known prognostic factors.