Accuracy of Lymph Node Imaging in Prostate Cancer: PSMA PET-CT and Nano-MRI

Overview

Following curative intended therapy in prostate cancer patients, a high proportion of patients (approx. 25%) relapse with local and/or distant recurrence. The metastasis of a lymph node (LN) in a patient with prostate cancer means that the disease has become systemic with the increased risk of disease progression. Therefore the ability to detect the presence of LN metastasis is important in terms of disease prognosis and treatment options. In the past, patients with LN metastasis have had poor prognoses due to the scarcity of accurate staging techniques and toxic treatment regimens such as radiotherapy. For those patients with a medium to high risk of having LN metastasis, the current procedure is a bilateral pelvic lymph node dissection (PLND). This is the standard procedure prior to curative treatment with either radical prostatectomy or radiation therapy. However, the procedure is not optimal due to the frequent inability to remove all positive lymph nodes within the dissection area. 41% of metastatic LN disease is not found, due to these LN being outside the routine surgery field. As a result, some urologists will perform an extended lymphadenectomy (e-PLND), which leads to extended operating times and the risk of complications. Also, therapy of LN metastases has limitations: more than 50% of metastatic LN are outside the routine (RTOG-CTV) radiation field. Thus the effect of standard LN radiotherapy is limited. Currently used imaging techniques such as CT and conventional MRI are also not sensitive enough to detect prostate cancer metastases due to the small size of the nodes (\< 8mm). In this study, patients that undergo a pelvic lymph node dissection will be undergoing a 68Ga PSMA PET-CT and a nano-MRI prior to surgery. The results of the PSMA PET-CT and the nano-MRI will be validated using the pathology results of the (PLND).