Androgen Deprivation Therapy at Time of Fluorine 18 Fluciclovine PET/CT More Likely to Return a Positive Scan

Prostate cancer is the second most common cancer in men in the United States. It is most likely to develop in men aged >65 years and in non-Hispanic black men.¹ It is estimated that in 2021, 248,530 men will develop prostate cancer and about 34,130 men will die from the disease.¹ However, most men diagnosed with prostate cancer do not die from the disease.¹ Recent research advances and ongoing clinical trials have improved the detection of prostate cancer, which has helped lead to the development of improved therapies.² The US Food and Drug Administration approved fluorine 18 fluciclovine (FACBC), an amino acid analog radiotracer, in 2016 for use in positron emission tomography (PET) in biochemically recurrent prostate cancer after primary therapy has been performed.² In the September 2021 edition of The Journal of Urology, Klaassen and colleagues presented the results of a real-world study of FACBC utilization in 300 patients who received FACBC PET/computed tomography (CT) at the Veterans Affairs (VA) Health System. The study objectives were to determine the impact of prostate-specific antigen (PSA) levels and the use of androgen deprivation therapy (ADT) on FACBC PET/CT positivity rates and patient sociodemographics.

The 300 patients were randomly selected from a total of 830 patients who received FACBC PET/CT from 44 VA sites. They were grouped according to whether they received ADT therapy and by their PSA levels at the time of imaging. Low PSA level was defined as <1 ng/mL and high PSA level was defined as ≥1 ng/mL. When the FACBC PET/CT was evaluated, 33% of patients with a PSA between 0 ng/mL and 0.5 ng/mL were positive, 21% of patients with a PSA >0.5 ng/mL to 1 ng/mL were positive, 54% of patients with a PSA >1 ng/mL to 2 ng/mL were positive, and 66% of patients with a PSA >2 ng/mL were positive. For patients who were treated with ADT, 59% had a positivity rate and 37% of those not treated with ADT had a positivity rate. Positive scans were more likely in white patients compared with black patients (55% positivity for white patients compared with 38% positivity for black patients). When primary treatment was compared, those patients who had radiotherapy were more likely to have a positivity rate than patients treated with radical prostatectomy (55% positivity with radiotherapy compared with 33% positivity with radical prostatectomy).

After multivariable logistic regression analysis, the investigators found that use of ADT, PSA, and race was a predictor as to whether the patient had a positive FACBC PET/CT. Furthermore, patients who were receiving ADT at the time of the FACBC PET/CT had >4 times likelihood of having a positive scan.

References

1. American Cancer Society. Key statistics for prostate cancer. Updated January 12, 2021. www.cancer.org/cancer/prostate-cancer/about/key-statistics.html. Accessed September 20, 2021.
2. Laudicella R, Albano D, Alongi P, et al. ¹⁸F-Facbc in prostate cancer: a systematic review and meta-analysis. Cancers (Basel). 2019;11:1348.
3. Klaassen Z, Gu L, Waller JD, et al. Real-world evidence of 18F-fluciclovine PET/CT utilization for recurrent prostate cancer in the Veterans Affairs Health System. J Urol. 2021;206:e185-185.