title: Increased FDG avidity in lymphoid tissue associated with response to combined immune checkpoint blockade.
abstract: BACKGROUND
  Antibodies against programmed death 1 (PD-1) receptor and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) have transformed the systemic treatment of melanoma and many other cancers. Understanding the spectrum of benign findings and atypical response patterns seen in immune checkpoint blockade is important for accurately assessing treatment response as these immunotherapies become more widely used.
  
  
  METHODS
  We report a 63-year-old man with metastatic melanoma successfully treated with combination CTLA-4 and PD-1 blockade (ipilimumab and nivolumab), after non-response to pembrolizumab monotherapy. The initial impression of disease progression, based on cutaneous and PET/CT findings of increased fluoro-2-deoxy-D-glucose (FDG) uptake in benign lymphoid tissue, proved to be erroneous after assiduous review of radiographic imaging and correlative pathology.
  
  
  CONCLUSIONS
  These findings indicate that increased FDG uptake in benign lymphoid tissue seen on PET/CT may be a surrogate marker of immune activation and treatment response. Prospective studies will be invaluable in validating immune-related radiographic findings as a prognostic biomarker of response in cancer patients being treated with immune checkpoint blockade.
authors.affiliation: Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, 1600 Divisadero Street, Box 1770, San Francisco, CA 94115 USA.
authors.forename: Katy K
authors.initials: KK
authors.lastname: Tsai
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California, San Francisco, 505 Parnassus Avenue, San Francisco, CA 94117 USA.
authors.forename: Miguel H
authors.initials: MH
authors.lastname: Pampaloni
authors.affiliation: Department of Dermatology, University of California, San Francisco, 1701 Divisadero Street, San Francisco, CA 94115 USA.
authors.forename: Charity
authors.initials: C
authors.lastname: Hope
authors.affiliation: Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, 1600 Divisadero Street, Box 1770, San Francisco, CA 94115 USA.
authors.forename: Alain P
authors.initials: AP
authors.lastname: Algazi
authors.affiliation: Department of Pathology, University of California, San Francisco, 1600 Divisadero Street, San Francisco, CA 94115 USA.
authors.forename: Britt-Marie
authors.initials: BM
authors.lastname: Ljung
authors.affiliation: Department of Dermatology, University of California, San Francisco, 1701 Divisadero Street, San Francisco, CA 94115 USA.
authors.forename: Laura
authors.initials: L
authors.lastname: Pincus
authors.affiliation: Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, 1600 Divisadero Street, Box 1770, San Francisco, CA 94115 USA.
authors.forename: Adil I
authors.initials: AI
authors.lastname: Daud
keywords: Biomarker; CTLA-4; Immunotherapy; PD-1; PET/CT