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Gamma probe-assisted lymph node removal

Prostate cancer metastases in neighbouring lymph nodes are often so small that they cannot be reliably identified using conventional imaging methods such as MRI or CT scans. New methods enable surgeons to identify even small metastases and lymph nodes containing cancer cells more effectively than ever before – and then treat them successfully. This treatment uses a contrast agent that is otherwise harmless to humans and accumulates in tumour tissue, thereby providing radioactive labelling of metastases.

A contrast agent makes the tumour cells visible

PSMA-PET imaging makes use of Prostate-Specific Membrane Antigen (PSMA), a protein that can be found frequently on the surfaces of prostate cancer cells. The contrast agent is a radioligand that binds to the PSMA and acts as a radioactive label on prostate cancer cells. Positron emission tomography (PET) visualises metastases that are emitting radiation. This enables the surgeon to determine the precise location and size of the malignant tissue and optimise their surgical plans accordingly. 

Martini-Klinik

Accompanies you through this topic

Prof. Dr. Tobias Maurer
Faculty member

PSMA-radioguided surgery

Identifying lymph nodes containing tumour cells is not always straightforward during surgery. Scientists have therefore developed PSMA radioligands for intraoperative use. PSMA-radioguided surgery now enables surgeons to measure the radiation in tissue during a procedure using a gamma probe, similar to a Geiger counter. The gamma probe emits signals as it approaches infected tissue. This is an immense aid for surgeons, as it enables them to identify the lymph nodes containing tumour cells and make sure that they are removed.

PSMA-radioguided Surgery Ablauf
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During the operation, the probe emits a fast and clearly audible ticking noise when the surgeon approaches cancerous tissue. The cancer can also be measured after it is removed from the body, as shown in this image: the measuring device indicates 136 “counts” per second – a very high reading.

Martini-Klinik

PSMA-radioguided surgery

The acoustic signal emitted when cancer is identified is clearly audible.

9 seconds

Minimally invasive robotic-assisted PSMA-radioguided surgery

Small gamma probes have now been developed for use in robotic-assisted surgery. The world’s first robotic PSMA-radioguided surgery was performed at the Martini-Klinik in 2018 (using a prototype device). Since 2021, however, we have routinely offered PSMA-radioguided surgery as an option for minimally invasive operations – once again as one of the first centres worldwide to do so.

Who is a candidate for radioguided surgery?

In our experience, patients with the following characteristics are most suitable for this surgery:

  • Good general health, minimal comorbidities
  • Long remaining life expectancy 
  • Findings isolated (as far as possible) in the pelvic region through PSMA-PET/CT
  • Smallest possible increase in PSA level (ideally <2 ng/ml)

However, it is always important to obtain extensive advice by discussing the advantages and disadvantages before deciding on such a procedure, taking into account the patient’s individual circumstances and up-to-date PSMA-PET imaging.   

Summary

This method has been developed recently and its therapeutic potential has yet to be demonstrated conclusively. However, initial studies have shown that patients treated with this method can benefit from lasting reductions in their PSA level. In addition, many patients get by without the need for further treatment for an extended period after the surgery.

If the cancer returns and these metastases are removed at an early stage, this can postpone the need for hormone therapy or radiotherapy. In some cases, it can eliminate the need for follow-up treatment altogether, which is an immense relief for the patients in question. However, this treatment method for recurrent prostate carcinoma is currently still considered experimental and is not included in official guidelines. Although the initial results are very promising, we do not yet have long-term oncological data for PSMA-PET or PSMA-radioguided surgery.

Video

PSMA-radioguided surgery
2016: BR: A new method for treating recurrent prostate cancer that uses specially developed surface markers to localise and remove very small tumours. [German only]

Lymph node removal for prostate cancer
2015: BR: This video report shows how metastasised prostate cancer cells can be localised and removed with precision. [German only]

Media articles

“Als hätte jemand das Licht eingeschaltet”
2021 / Labor Journal: In this interview, Prof. Tobias Maurer explains the PSMA-PET imaging method for metastasised prostate cancer. [German only]

Metastasen-direktive Therapie beim Prostatakrebsrezidiv
2020 / Urologie: PSMA-PET has become increasingly established in recent years as a standard imaging technique in cases of biochemical recurrence. [German only]

Experte im Gespräch: Dr. Tobias Maurer über Prostatakrebs
2019 / Operation Karriere: Dr. Maurer discusses the latest treatment methods, such as PSMA-radioguided surgery, focal treatment and robotic-assisted surgery. [German only]

Rezidivierendes Prostatakarzinom
2019 / Urologische Nachrichten: Biochemical response and treatment-free interval following PSMA-radioguided surgery. Experiences after 198 patients. [German only]

Moin PD Dr. Tobias Maurer
2019 / UKE-Life: In this interview with the UKE patient magazine, Dr. Tobias Maurer discusses the new treatment method he has introduced and why he is so fond of Hamburg. [German only]

Die PSMA-"radioguided surgery" beim Prostatakarzinomrezidiv
2018 / Jatros: In this article, Dr. Tobias Maurer describes how PSMA-radioguided surgery can identify and remove even small metastases. [German only]

How does radioactive labelling help to remove prostate cancer metastases?

Prostate cancer metastases in neighbouring lymph nodes are often so small that they cannot be reliably identified and surgically removed using conventional imaging methods such as MRI or CT scans. PSMA-radioguided surgery relies on radioactive labelling of prostate cancer cells to make them visible in imaging scans and detectable with a gamma probe during surgery.