Poster Presentation Clinical Oncology Society of Australia Annual Scientific Meeting 2019

68Ga-prostate-specific membrane antigen (PSMA) PET/CT as a clinical decision-making tool in biochemically recurrent prostate cancer after definitive treatment: an Australian prospective study. (#183)

Amy Davies 1 , Edmond M Kwan 1 2 , John Kourambas 3 , Nicholas Redgrave 3 , Scott Donnellan 3 , Sree Appu 3 , Scott Williams 4 , Andrew Coleman 4 , Marcus Foo 5 , Shakher Ramdave 6 , Arun Azad 7 8
  1. Department of Medical Oncology, Monash Health, Melbourne, VIC, Australia
  2. Department of Medicine, School of Clinical Sciences, Monash University, Melbourne, VIC, Australia
  3. Department of Urology, Monash Health, Melbourne, VIC, Australia
  4. Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, Melbourne, VIC, Australia
  5. GenesisCare, Melbourne, VIC, Australia
  6. Department of Nuclear Medicine & PET, Monash Health, Melbourne, VIC, Australia
  7. Department of Medical Oncology, Peter MacCallum Cancer Centre, Melbourne, VIC, Australia
  8. Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, VIC, Australia

Aims

Prostate-specific membrane antigen (PSMA) PET/CT has emerged as the optimal imaging modality to detect recurrent prostate cancer in patients with biochemical relapse (BCR) following curative intent treatment. However, its impact on clinical decision making in the era of metastasis-directed therapy remains unclear. This study aims to explore the role of PSMA PET/CT on clinical decision making in patients with BCR following definitive therapy.

Methods

We prospectively enrolled 40 patients with BCR to undergo 68Ga-PSMA PET/CT. Baseline clinicopathological factors were obtained and referring clinicians documented their proposed treatment plan both prior to and following imaging. Changes in clinical management were considered to have clinical impact.

Results

68Ga-PSMA PET/CT detected at least one suspicious lesion in 23/40 (58%) patients, with a median PSA level of 0.59ug/L (IQR 0.21-2.31). Positive scans were more frequent at higher PSA levels (p<0.001, Fischer’s exact test). The most common sites of PSMA-avid disease were lymph nodes (61%) and bone (30%). Lymph node involvement was typically pelvic nodes (13/14, 93%). Bone involvement was mostly outside the axial skeleton (5/7, 71%). PSMA PET/CT altered management in 21/40 (53%) patients. Of those planned for watchful waiting, 14/24 (58%) proceeded to a more active management strategy, including salvage radiotherapy (n = 6), stereotactic ablative body radiotherapy (SABR; n = 5), androgen deprivation therapy (n = 2) and salvage surgery (n = 1).

Conclusion

68Ga-PSMA PET/CT altered management strategy in a significant proportion of prostate cancer patients with BCR following definitive therapy. Our data demonstrates a shift from planned watchful waiting to more active treatment in over half patients with a positive 68Ga-PSMA PET/CT. Longer-term follow-up is required to assess the influence of such strategies on clinical outcomes.