Oligometastatic prostate cancer (OMPC) is a special clinical state with a tumour biology that is presumed to be more indolent than polymetastatic disease. It is potentially curable with metastasis-directed ablative therapies. In this joint session, a panel of experts will discuss new approaches to OMPC and show the collaborative work done by the ESR and the European Organisation for Research and Treatment of Cancer (EORTC).
Prostate cancer is the second most frequent malignancy in men worldwide. Although much progress has been made in prostate cancer research in the past decade, the disease remains a significant cause of morbidity and mortality in men. Most prostate cancer-associated deaths are due to metastatic disease, whereby lymph nodes adjacent to primary tumours are often the first site of metastases, followed by metastases of the bones, and less often, usually in more advanced stages of the disease, metastases of the liver and lungs. OMPC, generally defined by the presence of five or fewer metastatic sites on imaging, is one of the clinical states within the spectrum of the natural history of prostate cancer, representing a transitional state between localised and widespread metastatic disease.
Recently, it has been proposed that men with oligometastases may have a more indolent course and that outcome may be further improved with metastasis-directed local ablative therapy. “Patients with OMPC often have controllable symptoms, and cures are possible. Technical improvements in surgery and radiotherapy have introduced the option of metastasis-directed ablative therapies as an adjunct or alternative to standard-of-care systemic therapies,” said Prof. Nandita M. deSouza, lead academic radiologist at the Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, Sutton, UK, who will chair today’s session together with Prof. Frédéric E. Lecouvet, from the Department of Radiology and Medical Imaging at the University Hospital St. Luc, Brussels, Belgium.
Several clinical trials and registries are investigating the benefit of these therapeutic approaches across several cancer sites. “This requires that patients are correctly included and followed with appropriate imaging, as the correct recognition of OMPC is heavily dependent on imaging,” she noted, highlighting the partnership between the ESR and EORTC in this regard. “The EORTC includes many radiation and medical oncologists and a large statistics unit dedicated to delivering multicentre trials in oncology. Within the imaging group of the EORTC, there are not only radiologists, but also many active nuclear medicine physicians, so there are active links to the European Association of Nuclear Medicine (EANM). By joining with this community, we can bring imaging biomarkers into clinical trials as both primary and exploratory endpoints. The involvement of radiologists in clinical trials research will help to achieve quality standards across imaging platforms.”
A number of imaging modalities may be used for the detection of OMPC. These include conventional imaging (CT and 99mTc bone scans), whole-body MRI and dedicated positron emission tomography (PET) scans, which offer the ability to evaluate tumour metabolism and can be performed with different radionuclides (e.g. 18F, 11C and 68GA) and tracers, including 1-amino-3-fluorocyclobutane-1-carboxylic acid, prostate-specific membrane antigen (PSMA), 18-Choline, 18F-fluorodeoxyglucose (18F-FDG) and 18F-NaFluorine.
“Imaging requirements for recognising OMPC vary with metastatic location and the timing of measurement in relation to previous treatment,” said deSouza. “At each point in the disease cycle – diagnosis, response assessment and follow-up – imaging must be tailored to the clinical question and considered in the context of prior treatment. The differential use of whole-body approaches such as 18F-FDG-PET/CT, diffusion-weighted MRI, 18F-Choline-PET/CT and 68Ga-prostate specific membrane antigen-PET/CT require rationalisation depending on clinical risk assessment.”
In terms of the evidence base for imaging modalities in prostate cancer, 68Ga-PSMA seems to be most accurate, although whole-body MRI and choline PET/CT may be used depending on clinical circumstance, according to deSouza. “Optimal standardised imaging approaches will enable OMPC trials to document patterns of disease progression and outcomes of treatment. Quality-assured and quality-controlled imaging data included in large databases will establish a large and high-quality imaging warehouse for future research,” she said.
Another expert providing guidance in today’s session is Dr. Daniela Oprea-Lager, from the Department of Radiology and Nuclear Medicine at the University Medical Center Amsterdam, the Netherlands, who also emphasised the importance of the correct recognition of OMPC and precise tumour delineation in order to offer patients optimal management strategies based on their risk of further recurrence or progression.
“At each point, the imaging needs to accurately determine the location and extent, and ideally quantify the character of the metastases, so that treatment response can be assessed,” she said. In prostate cancer, recognition of OMPC enables local metastasis directed therapies. “These therapies potentially shorten or postpone the use of systemic treatment and can delay further metastatic progression, and thus increase overall survival,” she added.
Oprea-Lager also shared her thoughts on hybrid imaging modalities and different therapeutic approaches, including stereotactic body radiation therapy (SBRT), a high-dose external beam radiotherapy that can be performed non-invasively and in an ambulatory setting.
“The introduction of hybrid imaging modalities such as radiolabelled PSMA PET/CT offers the possibility of detecting lesions with high PSMA expression at relatively low PSA levels. For these lesions, local therapy might represent an attractive treatment paradigm. Emerging evidence suggests that treatment of single metastases with SBRT, which has been associated with low levels of toxicity in patients with prostate cancer irradiated for bone or lymph node metastases, might prolong progression-free survival (PFS) and allows the start of Androgen Deprivation Therapy (ADT) to be deferred, thereby delaying the related side effects.”
Besides SBRT, therapy with 177Lu-PSMA radioligand therapy (RLT) using inhibitors of PSMA is a novel therapeutic option in patients with prostate cancer. “This therapy has been evaluated especially in metastatic castration-resistant prostate cancer and has been proven to be well tolerated and effective. However, the role of RLT in patients with oligometastatic disease, in the hormone-sensitive setting, has not been investigated yet,” said Oprea-Lager.
Please note that for pre-recorded sessions published during the ECR Highlight Weeks, there will be no chairpersons. However, we still wanted to keep Professor deSouza’s interview and statements for the article as she initially gave them, when she was supposed to chair this session.
Joint Session of the ESR and the EORTC
Advanced imaging for stratifying treatment in oligometastatic prostate cancer
- Prostate cancer: managing the oligometastatic patient
Martin Spahn; Zurich/CH - Whole-body MRI: is it ready for prime time to detect oligometastatic prostate cancer
Frederik de Keyzer; Leuven/BE - Molecular imaging for directing and delivering therapy in oligometastatic prostate cancer
Daniela Oprea-Lager; Amsterdam/NL
FURTHER READING
Johnston EW, Latifoltojar A, Sidhu HS et al (2019) Multiparametric whole-body 3.0-T MRI in newly diagnosed intermediate- and high-risk prostate cancer: diagnostic accuracy and interobserver agreement for nodal and metastatic staging. Eur Radiol. 29(6):3159-3169: european-radiology.org/5813
Napoli A, Scipione R, Anzidei M, Bazzocchi A, Dababou S, Catalano C (2017) MR-guided high intensity focused ultrasound (MRgFUS) for the treatment of oligometastatic prostate cancer bone disease. ECR 2017 / C-2966: myESR.org/172966
Vyas M, Sharma S (2019) Comparative analysis of 68Ga,18F and 99mTc labelled with Prostate Specific Membrane Antigen (PSMA). ECR 2019 / C-1104: myESR.org/191104