title: 18F-FDG PET/CT of Non-Small Cell Lung Carcinoma Under Neoadjuvant Chemotherapy: Background-Based Adaptive-Volume Metrics Outperform TLG and MTV in Predicting Histopathologic Response.
abstract: Assessment of tumor response after chemotherapy using (18)F-FDG PET metrics is gaining acceptance. Several studies have suggested that the parameters metabolically active tumor volume (MTV) and total lesion glycolysis (TLG) are superior to SUVmax for measuring tumor burden. However, the measurement of MTV and TLG is still controversial; the most common method uses an absolute threshold of 42% of SUVmax Recently, we implemented a background-adaptive method to determine the background-subtracted lesion activity (BSL) and the background-subtracted volume (BSV). In this study, we investigated the correlation between such PET metrics and histopathologic response in non-small cell lung carcinoma (NSCLC).
  
  
  
  Forty-four NSCLC patients were retrospectively identified. Their PET/CT data on both types of scan before and after neoadjuvant chemotherapy were analyzed regarding SUVmax, MTV, TLG, BSL, and BSV, as well as the relative changes in these parameters. The tumor regression score as an indicator of histopathologic response was scored on hematoxylin- and eosin-stained sections of the surgical specimens using a 4-tiered scale (scores 1-4). The correlation between score and the absolute and relative PET metrics after chemotherapy was analyzed using Spearman rank correlation tests.
  
  
  
  Tumors that demonstrated a good response after neoadjuvant chemotherapy had significantly lower (18)F-FDG activity than nonresponding tumors (scores 3 and 4: SUVmax, 4.2 [range, 1.8-7.9] vs. scores 1 and 2: SUVmax, 8.1 [range, 1.4-40.4]; P = 0.001). The same was found for change in SUVmax and score (P = 0.001). PET volume metrics based on a 42% fixed threshold for SUVmax did not correlate with score (TLG, P = 0.505; MTV, P = 0.386). However, both of the background activity-based PET volume metrics-BSL and BSV-significantly correlated with score (P < 0.001 each).
  
  
  
  PET volume metrics based on background-adaptive methods correlate better with histopathologic tumor regression score in NSCLC patients under neoadjuvant chemotherapy than algorithms and methods using a fixed threshold (42% SUVmax).
authors.affiliation: Department of Nuclear Medicine, University Hospital Zurich, Zurich, Switzerland Department of Radiology, University Hospital Zurich, Zurich, Switzerland irene.burger@usz.ch.
authors.forename: Irene A
authors.initials: IA
authors.lastname: Burger
authors.affiliation: Department of Surgical Pathology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Ruben
authors.initials: R
authors.lastname: Casanova
authors.affiliation: Department of Radiology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Seraina
authors.initials: S
authors.lastname: Steiger
authors.affiliation: Department of Nuclear Medicine, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Lars
authors.initials: L
authors.lastname: Husmann
authors.affiliation: Department of Nuclear Medicine, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Paul
authors.initials: P
authors.lastname: Stolzmann
authors.affiliation: Department of Nuclear Medicine, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Martin W
authors.initials: MW
authors.lastname: Huellner
authors.affiliation: Department of Medical Oncology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Curioni
authors.affiliation: Department of Thoracic Surgery, University Hospital Zurich, Zurich, Switzerland; and.
authors.forename: Sven
authors.initials: S
authors.lastname: Hillinger
authors.affiliation: Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York.
authors.forename: C Ross
authors.initials: CR
authors.lastname: Schmidtlein
authors.affiliation: Department of Surgical Pathology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Alex
authors.initials: A
authors.lastname: Soltermann
mesh_terms: D000328:Adult; D000368:Aged; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology / Q000628:therapy*; D005260:Female; D019788:Fluorodeoxyglucose F18; D006019:Glycolysis; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D000072078:Positron Emission Tomography Computed Tomography; D012189:Retrospective Studies; D016896:Treatment Outcome; D047368:Tumor Burden
chemical_list: D019788:Fluorodeoxyglucose F18
keywords: NSCLC; neoadjuvant therapy; quantification; tumor regression; volume segmentation
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