Poster Presentation Clinical Oncology Society of Australia Annual Scientific Meeting 2023

FAPI-CUP - A prospective cohort study of patients with Cancer of Unknown Primary (CUP) to evaluate a novel radiotracer, fibroblast activated protein (FAPI) targeting cancer-associated fibroblasts to improve primary site detection. (#515)

Tharani Sivakumaran 1 2 , Tim Akhurst 3 , Grace Kong 3 , Anthony Cardin 1 3 , Su-Faye Lee 3 , Prasangi Pelpola 3 , Peter Roselt 3 , Ian M Collins 4 , Mark Warren 5 , Hui Li Wong 1 2 , David Bowtell 1 6 , Penelope Schofield 6 7 , Richard Tothill 8 9 , Rodney Hicks 10 11 , Linda Mileshkin 1 2
  1. Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, VIC, Australia
  2. Medical Oncology, Peter MacCallum Cancer Centre, Melbourne, VIC, Australia
  3. Cancer Imaging , Peter MacCallum Cancer Centre, Melbourne, VIC, Australia
  4. South West Healthcare, Warrnambool, VIC, Australia
  5. Department of Medical Oncology, Bendigo Health, Melbourne, VIC, Australia
  6. Peter MacCallum Cancer Centre, Melbourne, VIC, Australia
  7. Department of Psychological Sciences, Swinburne University of Technology, Melbourne, VIC, Australia
  8. University of Melbourne Centre for Cancer Research, University of Melbourne, Melbourne, VIC, Australia
  9. Department of Clinical Pathology, University of Melbourne, Melbourne, VIC, Australia
  10. Melbourne Theranostic Innovation Centre, Melbourne, VIC, Australia
  11. The University of Melbourne Department of Medicine, St Vincent’s Hospital, , Melbourne, VIC, Australia

Background

Cancer of unknown primary (CUP) represents a heterogeneous group of metastatic tumours for which standardised diagnostic work-up fails to identify the tissue of origin at diagnosis. Despite improvement in conventional diagnostic processes the primary site is only identified ante mortem in < 30% of CUP patients. 18F-FDG-PET/CT aids in CUP patient management and identification of putative primary site however has limited sensitivity for detecting cancers with high stromal content, as in CUP. Fibroblast activation protein (FAP) is a type  II transmembrane serine protease and highly expressed by cancer-associated fibroblasts abundant in desmoplastic tumours, such as CUP. 68Ga-FAPI-46 is a promising FAP-targeting PET tracer in multiple solid cancers but has not been directly compared to FDG-PET in CUP.

 

Aims

We aim to determine if the novel PET tracer (68Ga-FAPI-46) detects more primary sites compared with 18F-FDG-PET/CT and CT scans in CUP patients and if there is an association with FAPI avidity and response to treatment.

 

Methods

The FAPI-CUP study is a prospective cohort study currently recruiting CUP patients across three sites in Victoria. Key inclusion criteria are 1) patients considered CUP after preliminary diagnostic work-up, pathological review and gender appropriate tests; 2) adequate haematologic and organ function to commence systemic treatment; 3) not commenced current line of systemic treatment (exception palliative radiotherapy for symptom control); 4) ECOG 0-2 and life expectancy > 3months. 5) up to 1 prior line of systemic treatment. Patients undergo imaging with CT chest/abdomen/pelvis, 18F-FDG-PET/CT and 68Ga-FAPI-PET/CT scan which are reviewed at a multidisciplinary meeting and results are relayed back to the treating clinician. Patients start systemic treatment and have follow-up as part of standard of care with information regarding survival outcome and further lines of treatment collected at 3 monthly intervals for a total of 12 months. Clinical trial information: NCT05263700.