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ASCO 2019 Annual Meeting

ASCO 2019: Uses for PSMA Diagnostics and Therapeutic Approaches in Localized Disease: A Urologist's Perspective

Chicago, IL (UroToday.com) Robert Evan Reiter, MD, gave a Urologist’s perspective on the use of PSMA in localized prostate cancer at ASCO 2019. He began his presentation stating the importance of imaging in all stages of prostate cancer (Figure 1).

Figure 1 – Role of imaging in the various stages of prostate cancer

ASCO2019_role_of_imaging.png

The performance of PSMA-PET in biochemical recurrence is correlated to the PSA level. The higher the level of PSA, the higher positivity of the PSMA-PET scan (Figure 2).1 Examining the data from a UCLA-UCSF study,2 the distribution of lesions in men with biochemical recurrence is shown in Figure 3, demonstrating the increased detection rate of PSMA-PET with rising PSA, and showing that most lesions occur in multiple regions and not in the prostate bed (Figure 3).

Figure 2 – Correlation of PSMA-PET positivity to PSA values:

ASCO2019_PSA_values.png

Figure 3 – UCLA-UCSF study showing the distribution of lesion in men with biochemical recurrence:

ASCO2019_UCLA-UCSF.png

There is a plethora of data showing that there is between 29% to 76% management change after using PSMA-PET imaging in patients with biochemical recurrence.3-7 These include decreased use of salvage radiotherapy to the prostate bed, increased use of salvage node dissection, stereotactic radiotherapy, and androgen deprivation therapy (ADT).

Usage of PSMA-PET has raised some important questions that need to be answered. These include:

  1. Whether prostate bed only lesion permit omitting of node-irradiation?
  2. Does the detection of nodes outside the usual radiation fields lead to enhanced radiation delivery that makes a difference in outcome?
  3. Does salvage lymphadenectomy or stereotactic body radiation therapy improve meaningful outcomes for regional or oligometastatic disease?
  4. Should salvage radiation be delayed until there is a detectable disease?
In men with high-risk prostate cancer PSMA-PET should be able to provide us data on whether surgery should or should not be performed if the lymph nodes demonstrate uptake, and whether a pelvic lymph node dissection could be omitted if the PSMA is node-negative. Other important questions to answer include whether we should perform surgical resection or stereotactic body radiation therapy at sites of PSMA positivity, or surgical resection followed by radiotherapy to metastatic sites. Lastly, and probably most importantly, it is not clear if anything should be changed at all, and whether it is better we continue to do as we did before the introduction of PSMA-PET. As Dr. Reiter calls it: “Was ignorance bliss?”

Dr. Reiter concluded his presentation and stated that PSMA-PET is sensitive and specific for local recurrence and regional/distant metastasis in the setting of biochemical recurrence. It is not a perfect imaging test, and still misses many sites, smaller than 5 mm. Its sensitivity is only 30%-40% of high-risk disease. However, it is considerably better than conventional imaging used so far for high-risk disease.

To date, imaging has not changed management, but new technology raises new clinical management dilemmas, and we still need to decipher how PSMA-PET should alter management in specific conditions, and most importantly, whether it improves disease outcomes at all.

Presented by: Robert Evan Reiter, MD, Urology Surgery, Complex General Surgical Oncology, Institute of Urologic Oncology, University of California Los Angeles, Los Angeles, California, United States

Written by: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto, Princess Margaret Cancer Centre @GoldbergHanan at the 2019 ASCO Annual Meeting #ASCO19, May 31-June 4, 2019, Chicago, IL USA

References:
  1. Perera et al. "Sensitivity, Specificity, and Predictors of Positive 68Ga-Prostate-specific Membrane Antigen Positron Emission Tomography in Advanced Prostate Cancer: A Systematic Review and Meta-analysis." European Urology. 2016. doi: 10.1016/j.eururo.2016.06.021.
  2. Fendler et al. "Assessment of 68Ga-PSMA-11 PET Accuracy in Localizing Recurrent Prostate Cancer: A Prospective Single-Arm Clinical Trial."JAMA Oncology. 2019. doi:10.1001/jamaoncol.2019.0096.
  3. Van Leeuwen et al. "(68) Ga-PSMA has a high detection rate of prostate cancer recurrence outside the prostatic fossa in patients being considered for salvage radiation treatment." BJU InternationaI. 2016. doi: 10.1111/bju.13397.
  4. Calais et al. "Potential impact of 68Ga-PSMA-11 PET/CT on prostate cancer definitive radiation therapy planning." The Journal of Nuclear Medicine. 2018. doi: 10.2967/jnumed.118.209387.
  5. Han et al. "Impact of 68Ga-PSMA PET on the Management of Patients with Prostate Cancer: A Systematic Review and Meta-analysis." European Urology. 2018. doi: 10.1016/j.eururo.2018.03.030.
  6. Bianchi et al. BJUI 2018
  7. Albisinni et al. "Impact of 68Ga-PSMA PET on the Management of Patients with Prostate Cancer: A Systematic Review and Meta-analysis." BJU International. 2018. doi: 10.1016/j.eururo.2018.03.030.