Abstract 2369: Correlating circulating tumor cells with 18F-FDG positron emission tomography (PET) uptake in patients with treatment naïve non-small cell lung cancer: A pilot study

Abstract

Abstract BACKGROUND: Circulating tumor cells (CTCs) represent disease derived cells identified in the blood of cancer patients with prognostic implications. 18F-2-fluoro-2-deoxyglucose (FDG) PET tumor uptake in non-small cell lung cancer (NSCLC) may be associated with poor prognosis despite therapy since the tracer accumulates in increasing amounts in more aggressive cancers. We therefore set out to investigate whether CTCs correlate with FDG uptake. METHODS: For this multi-center, prospective, observational study patients were consented and underwent phlebotomy into a cell preservative blood collection tube. Samples were shipped at ambient temperature and processed within 36 hours. CTC detection was defined by immunofluorescence (CK, DAPI, CD45) followed by automated morphometric analysis that was validated manually. Patients who underwent surgery or had medical treatment prior to imaging were excluded and only those with biopsy proven NSCLC who had PET images acquired within 4 weeks of CTC sample procurement were eligible. Semi-quantitative values (maximum standardized uptake value [SUVmax]) were extracted from images using a region of interest drawn over the tumor by the interpreting physician. Correlations were calculated by either a Pearson or Spearman-rank test depending on the distribution of the underlying variable. RESULTS: Twenty-six patients with treatment naïve NSCLC underwent phlebotomy for CTCs and had FDG PET imaging done at four medical centers during the pilot phase of this study. Five patients were excluded for further analysis due to pending results or more than 4 weeks from PET imaging to CTC draw. The average age for this cohort was 67 (± 11) years, 13 of 21 patients were male (62%) and 71% were stage I or II NSCLC. Mean tumor size was 3.0 cm (range 1.5-7.5 cm), median SUVmax was 7.4 (IQR 4.4-16.1) and two-thirds of patients had adenocarcinoma. At least one CTC per ml was detected in 81% of patients (17/21), and the median CTC count was 27 per ml (IQR 2.4-59.0) across all samples and histologic types. CTCs appeared to correlate more with tumor size (r=0.42) than with glucose metabolism as measured by SUVmax (r=0.22). CONCLUSION: We have established a multi-center workflow to expeditiously study tumor glucose metabolism using imaging and in-vitro diagnostics. Preliminary data show good sensitivity for a combined immunofluorescent and cytometric CTC detection approach in early-stage disease. CTC count may not correlate well with tumor glucose metabolism in NSCLC but further study is required. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2369. doi:1538-7445.AM2012-2369