SUO 2018: PSMA-Guided Salvage Lymph Node Dissection

Phoenix, Arizona (UroToday.com) Derya Tilki presented novel PSMA-guided salvage lymph node dissection (sLND) methodology. First, she started by reviewing the impact of biochemical recurrence (BCR) in prostate cancer outcomes.

In their own patient population, BCR occurred in about 20% of men – so 80% of men after definitive therapy never have BCR. This is stratified by pre-operative risk of course, with higher risk patients having higher BCR rates. However, developing BCR does not imply development of recurrence note that only 30% of men with BCR go on to develop clinical recurrence and only 16% die of disease.1 The increasing use of PSMA PET imaging has lead to increased detection of low-volume recurrent disease. This has, in turn, led to more interest in metastasis-directed therapies (MDT).

However, as she notes, the accuracy of PET imaging is not perfect, particularly the older choline and fluoride PET modalities. PSMA PET, however, overcomes many of these deficiencies, and at PSA levels between 1-2, has 90% sensitivity in detecting recurrences. At lower levels, its sensitivity drops off.

Using PSMA PET imaging for sLND has become more common. A recent paper looked at 23 patients with nodal recurrence diagnosed on outside PSMA PET imaging.2 Median PSA at the time was 3.9. Based on this, they removed on average 3 positive LN’s during sPLND – and PSMA PET had pretty good accuracy in predicting side and field of LN. PPV ~70% and NPV ~90%. A systematic review found 27 such institutional series and collated the data. The 2-year BCR-free survival after PSMA-PET based sPLND was between 23-64%.3 Despite BCR-free survival, BCR does occur in the majority of cases. Below is a summary of the PSMA-based sPLND series:

Figure 1

Her last section was on the concept of PSMA-radioguided surgery – which builds on the technology used in breast ALND. Below:

Figure 2

Pre-op IV injection of a technetium labeled PSMA ligand – so it has the specificity as PSMA itself. The surgeons then use a gamma probe intra-operatively to identify the nodes.

In their publication on their series (Knipper et al. Prostate Cancer), they treated 42 consecutive patients with sPLND following PSMA PET. 29 patients had conventional sPLND while 13 had radioguided surgery.

Figure 3

As seen in the waterfall plot, patients undergoing RGS (light blue) had a much better PSA response. They also had a higher median number of positive LN’s removed – though a similar number of PSMA PET lesions on original imaging. Importantly, on ex-vivo analysis, PPV was 100% for metastatic disease.

Obviously prospective studies are required and this is under development. However, this represents a novel technology that may help improve the efficacy of sPLND in this population – which, with the advent of better imaging, will continue to include more and more patients. By potentially sparing systemic therapy, this could have significant impact of patient QOL and hopefully patient outcomes!

Presented By: Derya Tilki, MD, University Medical Center Hamburg and the Martini Klinik Prostate Center

Written by: Thenappan Chandrasekar, MD, Clinical Instructor, Thomas Jefferson University, @tchandra_uromd, @TjuUrology, at the 19th Annual Meeting of the Society of Urologic Oncology (SUO), November 28-30, 2018 – Phoenix, Arizona

References:
1. Van den Broeck T, van den Bergh RCN, Arfi N Prognostic Value of Biochemical Recurrence Following Treatment with Curative Intent for Prostate Cancer: A Systematic Review Eur Urol. 2018 Oct 17. pii: S0302-2838(18)30752-8. doi: 10.1016/j.eururo.2018.10.011, van den Bergh RCN, Arfi N Prognostic Value of Biochemical Recurrence
Following Treatment with Curative Intent for Prostate Cancer: A Systematic Review Eur Urol. 2018 Oct 17. pii: S0302-2838(18)30752-8. doi: 10.1016/j.eururo.2018.10.011
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2. Mandel P, Tilki D, Chun FK, et at, Accuracy of 68Ga-Prostate-specific Membrane Antigen Positron Emission Tomography for the Detection of Lymph Node Metastases Before Salvage Lymphadenectomy. Eur Urol Focus. 2018 Jul 23. pii: S2405-4569(18)30191-3. doi: 10.1016/j.euf.2018.07.025. [Epub ahead of print]

3. Ploussard G, Gandaglia G, Borgmann H, Salvage Lymph Node Dissection for Nodal Recurrent Prostate Cancer: A Systematic Review Eur Urol. 2018 Oct 31. pii: S0302-2838(18)30836-4. doi: 10.1016/j.eururo.2018.10.041. [Epub ahead of print]
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