Prognostic Evaluation of Metastatic Castration Resistant Prostate Cancer and Neuroendocrine Prostate Cancer with [(68)Ga]Ga DOTATATE PET-CT

SIMPLE SUMMARY: Prostate cancer is the most common cancer in men and, along with the aggressive neuroendocrine variant of prostate cancer, is known to express high levels of the somatostatin receptor. This study explored the feasibility of using the somatostatin binding radiopharmaceutical, [(68)Ga]Ga-DOTATATE PET/CT, to identify metastatic lesions in 17 men with known metastatic castrate resistant prostate cancer or neuroendocrine prostate cancer. All patients demonstrated [(68)Ga]Ga-DOTATATE avid lesions corresponding to sites of disease as identified by CT. Additionally, we retrospectively correlated the degree of [(68)Ga]Ga-DOTATATE to treatment response and found that men with marked [(68)Ga]Ga-DOTATATE uptake in their metastatic deposits had significantly worse outcomes compared to those with moderate or mild [(68)Ga]Ga-DOTATATE uptake. Conversely, men with only mild [(68)Ga]Ga-DOTATATE uptake in their metastatic deposits had a favorable prognostic outcome. ABSTRACT: Objectives: Prostate cancer is well known to express high levels of somatostatin receptors and preliminary data suggests that PET imaging with the somatostatin analog, [(68)Ga]Ga-DOTATATE, may allow for whole body staging of patients with metastatic castration resistant prostate cancer (mCRPC) and neuroendocrine prostate cancer (NePC). This study explores the utility of [(68)Ga]Ga-DOTATATE PET-CT to identify metastatic deposits in men with mCRPC and NePC and prognosticate disease progression. Methods: [(68)Ga]Ga-DOTATATE PET-CT was performed in 17 patients with mCRPC and of those, 2/17 had NePC. A semiquantitative analysis with standardized uptake values (SUV) (e.g., SUVmax, SUVmean) was performed for each metastatic lesion and reference background tissues. [(68)Ga]Ga-DOTATATE uptake in metastatic deposits was further classified as: mild (less than liver), moderate (up to liver average), or marked (greater than liver). Serial prostate-specific antigen measurements and patient survival were followed up to 3 years after PET imaging to assess response to standard of care treatment. Results: All patients had at least one metastatic lesion with identifiable [(68)Ga]Ga-DOTATATE uptake. Marked [(68)Ga]Ga-DOTATATE uptake was found in 7/17 patients, including both NePC patients, and all were non-responders to systemic therapy and died within the follow up period, with a mean time to death of 8.1 months. Three patients had mild [(68)Ga]Ga-DOTATATE uptake, and all were responders to systemic therapy and were alive 36 months after [(68)Ga]Ga-DOTATATE imaging. Conclusions: [(68)Ga]Ga-DOTATATE is able to identify mCRPC and NePC metastatic deposits, and lesions with [(68)Ga]Ga-DOTATATE uptake > liver may portend poor outcomes in patients with mCRPC.