Imaging modalities in synchronous oligometastatic prostate cancer

Abstract

Purpose: Along with a number of other malignancies, the term "oligometastatic" prostate cancer has recently emerged. It represents an attempt to define a subtype of cancer with a limited metastatic load that might perform more favorably than a distinctly disseminated disease, or even one that may be managed in a potentially curative way. Since there is currently a knowledge gap of what imaging modalities should be utilized to classify patients as having this type of tumor, we aimed to shed light on the role of conventional and marker-based imaging in the setting of synchronous oligometastatic prostate cancer as well as summarize the available evidence for its clinical application.

Methods: A literature search on December 15th 2017 was conducted using the Pubmed database.

Results: Functional imaging techniques like ⁶⁸Ga PSMA. ⁶⁸Ga PSMA PET-CT has currently been shown the best detection rates for the assessment of nodal, bone and visceral metastases, especially for smaller lesions at low PSA levels.

Conclusions: Functional imaging helps detect low-burden disease metastatic patients. However, these imaging modalities are not available in every center and thus clinicians may be prone to prescribe systemic treatment rather than referring patients for cytoreductive treatments. We hope that the ongoing prospective trials will help guide clinicians in making a more personalized management of synchronous metastatic patients.

Keywords: Imaging; MRI; Oligometastatic; PET-CT; PSMA; Prostate cancer.

Fig. 1

73-year-old man with a Gleason 4 + 3 PCa pT3 with PSA of 18.2 ng/ml. A whole-body MR examination was performed. Coronal whole body T1-weighted image (a) shows a left iliac bone metastasis (b; magnification; arrows). The bone metastasis (arrows) are evident on whole-body DWI images (c, d). e In the right lung, para-hilar, a 15 mm metastasis was observed (circle)

Fig. 2

53-year-old man with a Gleason 4 + 4 PCa pT3 with PSA of 12.5 ng/ml. Primary staging with bone scan showed no lesions suspicious for bone metastases (a), but because he complained of right shoulder pain a ¹⁸F choline PET-CT was performed. This demonstrated focal tracer uptake in the spina scapulae (b, white arrow), indicating a bone metastase. On the corresponding CT image the scapula was unremarkable. Choline PET-CT may demonstrate bone metastases that are occult on bone scan and CT because it can detect changes in the bone marrow before osteoblastic reaction occurs. Nevertheless, bone scan currently remains the standard imaging modality in the primary staging of PCa

Fig. 3

72-year-old man with biopsy proven PCa Gleason 4 + 3 pT2c and PSA of 6.7 ng/ml. Preoperative staging with imaging revealed two small lymph nodes in the pelvis, along the left common iliac artery (white arrow) and in the presacral fat (white arrowhead). On CT scan they both have a size of 5 mm which is below the morphological threshold to classify them as suspicious, but on ⁶⁸Ga PSMA PET-CT they both showed highly avid tracer uptake, indicative of lymph node metastases. Pelvic lymph node dissection was performed and both lymph nodes proved to be malignant. Preoperative staging with ⁶⁸Ga PSMA PET-CT thus appears to allow for more complete and accurate primary staging of PCa patients compared to standard routine imaging but its role in routine clinical practice is yet to be defined