Magnetic Marking and Intraoperative Detection of Primary Draining Lymph Nodes in High-Risk Prostate Cancer Using Superparamagnetic Iron Oxide Nanoparticles: Additional Diagnostic Value

Influence of lymph node degeneration on metastases in prostate cancer: or why we must look for a needle in a haystack

BACKGROUND

To evaluate the incidence of lymph node degeneration and its association with nodal metastatic pattern in prostate cancer.

METHODS

A retrospective analysis of the submitted lymph node specimen of 390 prostatectomies in 2011 was performed. All lymph nodes were histologically re-evaluated and the degree of lymph node degeneration e.g. lipomatous atrophy, capsular and framework fibrosis, and calcifications as well as the lymph node size were recorded. Lymph node degeneration was compared in the anatomic regions of the pelvis as well as in lymph nodes with and without metastases of prostatic cancer.

RESULTS

Eighty-one of 6026 lymph nodes demonstrated metastases. Complete histologic examination with analysis of a complete cross-section was possible in 5173 lymph nodes including all lymph nodes with metastases. The incidence of lymph node degeneration was different across the various landing sites. Lymph node metastases were primarily detected in less degenerative and therefore more functional lymph nodes. In metastatic versus non-metastatic lymph nodes low lipomatous atrophy was reported in 84.0% versus 66.7% (p = 0.004), capsular fibrosis in 14.8% versus 35.4% (p < 0.001), calcifications in 35.8% versus 46.1% (p = 0.072) and framework fibrosis in 69.8% versus 75.3% (p = 0.53). Metastases were also identified more frequently in larger than in smaller lymph nodes (63.0% vs. 47.5%; p = 0.007).

CONCLUSIONS

Degenerative changes in pelvic lymph nodes are commonly detectable but occur with variable frequency in the various nodal landing sites in the pelvis. The degree of lymph node degeneration of single lymph nodes has a significant influence on whether a lymph node is infiltrated by tumor cells and may harbour metastases.

Magnetometer-Guided Sentinel Lymph Node Dissection in Prostate Cancer: Rate of Lymph Node Involvement Compared with Radioisotope Marking

Simple Summary

Pelvic lymph node dissection is recommended in prostate cancer according to the patients’ individual risk for nodal metastases. Targeted removal of sentinel lymph nodes increases the number of detected lymph node metastases in patients with prostate cancer. We previously established magnetometer-guided sentinel lymph node dissection in patients with prostate cancer to overcome logistical and technical disadvantages associated with the standard radioisotope-guided technique. This retrospective study compared the magnetometer-guided and standard techniques in terms of their ability to detect lymph node metastases. Using the magnetometer-guided technique, more sentinel lymph nodes were detected per patient. The detected rates of lymph node involvement matched the predictions in both techniques equally well. Our findings confirm the reliability of magnetometer-guided sentinel lymph node dissection and highlight the importance of the sentinel technique for detecting lymph node metastases in prostate cancer.

Abstract

Sentinel pelvic lymph node dissection (sPLND) enables the targeted removal of lymph nodes (LNs) bearing the highest metastasis risk. In prostate cancer (PCa), sPLND alone or combined with extended PLND (ePLND) reveals more LN metastases along with detecting sentinel LNs (SLNs) outside the conventional ePLND template. To overcome the disadvantages of radioisotope-guided sPLND in PCa treatment, magnetometer-guided sPLND applying superparamagnetic iron oxide nanoparticles as a tracer was established. This retrospective study compared the nodal staging ability between magnetometer- and radioisotope-guided sPLNDs. We analyzed data of PCa patients undergoing radical prostatectomy and magnetometer- (848 patients, 2015–2021) or radioisotope-guided (2092 patients, 2006–2015) sPLND. To reduce heterogeneity among cohorts, we performed propensity score matching and compared data considering sentinel nomogram-based probabilities for LN involvement (LNI). Magnetometer- and radioisotope-guided sPLNDs had SLN detection rates of 98.12% and 98.09%, respectively; the former detected more SLNs per patient. The LNI rates matched nomogram-based predictions in both techniques equally well. Approximately 7% of LN metastases were detected outside the conventional ePLND template. Thus, we confirmed the reliability of magnetometer-guided sPLND in nodal staging, with results comparable with or better than radioisotope-guided sPLND. Our findings highlight the importance of the sentinel technique for detecting LN metastases in PCa.

Establishment and validation of a novel predictive model to quantify the risk of bone metastasis in patients with prostate cancer

Background

Patients with prostate cancer (PCa) commonly suffer from bone metastasis during disease progression. This study aims to construct and validate a nomogram to quantify bone metastasis risk in patients with PCa.

Methods

Clinicopathological data of patients diagnosed with PCa between 2010 and 2015 were retrospectively retrieved from the Surveillance, Epidemiology, and End Results (SEER) database. Predictors for bone metastasis were identified by logistic regression analyses to establish a nomogram. The concordance index (c-index) and calibration plots were generated to assess the nomogram’s discrimination, and the area under the receiver operating characteristic curve (AUC) was used to compare the precision of the nomogram with routine staging systems. The nomogram’s clinical performance was evaluated by decision curve analysis (DCA) and clinical impact curves (CIC). Independent prognostic factors were identified by Cox regression analysis.

Results

A total of 168,414 eligible cases were randomly assigned to the training cohort or validation cohort at a ratio of 1:1. The nomogram, which was established based on independent factors, showed good accuracy, with c-indexes of 0.911 in the training set and 0.910 in the validation set. Calibration plots also approached 45 degrees. After other distant metastatic sites were included in the predictive model, the new nomogram displayed superior prediction performance. The AUCs and net benefit of the nomograms were both higher than those of other routine staging systems. Furthermore, bone metastasis prediction points were shown to be a new risk factor for overall survival.

Conclusions

Novel validated nomograms can effectively predict the risk of bone metastasis in patients with PCa and help clinicians improve cancer management.

New Frontiers in Molecular Imaging with Superparamagnetic Iron Oxide Nanoparticles (SPIONs): Efficacy, Toxicity, and Future Applications

Supermagnetic Iron Oxide Nanoparticles (SPIONs) are nanoparticles that have an iron oxide core and a functionalized shell. SPIONs have recently raised much interest in the scientific community, given their exciting potential diagnostic and theragnostic applications. The possibility to modify their surface and the characteristics of their core make SPIONs a specific contrast agent for magnetic resonance imaging but also an intriguing family of tracer for nuclear medicine. An example is 68Ga-radiolabeled bombesin-conjugated to superparamagnetic nanoparticles coated with trimethyl chitosan that is selective for the gastrin-releasing peptide receptors. These receptors are expressed by several human cancer cells such as breast and prostate neoplasia. Since the coating does not interfere with the properties of the molecules bounded to the shell, it has been proposed to link SPIONs with antibodies. SPIONs can be used also to monitor the biodistribution of mesenchymal stromal cells and take place in various applications. The aim of this review of literature is to analyze the diagnostic aspect of SPIONs in magnetic resonance imaging and in nuclear medicine, with a particular focus on sentinel lymph node applications. Moreover, it is taken into account the possible toxicity and the effects on human physiology to determine the SPIONs' safety.

Advanced Nanotechnology Leading the Way to Multimodal Imaging-Guided Precision Surgical Therapy

Surgical resection is the primary and most effective treatment for most patients with solid tumors. However, patients suffer from postoperative recurrence and metastasis. In the past years, emerging nanotechnology has led the way to minimally invasive, precision and intelligent oncological surgery after the rapid development of minimally invasive surgical technology. Advanced nanotechnology in the construction of nanomaterials (NMs) for precision imaging-guided surgery (IGS) as well as surgery-assisted synergistic therapy is summarized, thereby unlocking the advantages of nanotechnology in multimodal IGS-assisted precision synergistic cancer therapy. First, mechanisms and principles of NMs to surgical targets are briefly introduced. Multimodal imaging based on molecular imaging technologies provides a practical method to achieve intraoperative visualization with high resolution and deep tissue penetration. Moreover, multifunctional NMs synergize surgery with adjuvant therapy (e.g., chemotherapy, immunotherapy, phototherapy) to eliminate residual lesions. Finally, key issues in the development of ideal theranostic NMs associated with surgical applications and challenges of clinical transformation are discussed to push forward further development of NMs for multimodal IGS-assisted precision synergistic cancer therapy.

Diagnostic Accuracy of Magnetometer-Guided Sentinel Lymphadenectomy After Intraprostatic Injection of Superparamagnetic Iron Oxide Nanoparticles in Intermediate- and High-Risk Prostate Cancer Using the Magnetic Activity of Sentinel Nodes

Due to the high morbidity of extended lymph node dissection (eLND) and the low detection rate of limited lymph node dissection (LND), targeted sentinel lymph node dissection (sLND) was implemented in prostate cancer (PCa). Subsequently, nonradioactive sentinel lymph node (SLN) detection using magnetic resonance imaging (MRI) and a magnetometer after intraprostatic injection of superparamagnetic iron oxide nanoparticles (SPIONs) was successfully applied in PCa. To validate the reliability of this approach, considering the magnetic activity of SLNs or whether it is sufficient to dissect only the most active SLNs as shown in other tumor entities for radio-guided sLND, we analyzed magnetometer-guided sLND results in 218 high- and intermediate-risk PCa patients undergoing eLND as a reference standard. Using a sentinel nomogram to predict lymph node invasion (LNI), a risk range was determined up to which LND could be dispensed with or sLND only would be adequate. In total, 3,711 LNs were dissected, and 1,779 SLNs (median, 8) were identified. Among 78 LN-positive patients, there were 264 LN metastases (median, 2). sLND had a 96.79% diagnostic rate, 88.16% sensitivity, 98.59% specificity, 97.1% positive predictive value (PPV), 93.96% negative predictive value (NPV), 4.13% false-negative rate, and 0.92% additional diagnostic value (LN metastases only outside the eLND template). For intermediate-risk patients only, the sensitivity, specificity, PPV, and NPV were 100%. Magnetic activities of SLNs were heterogeneous regardless of metastasis. The accuracy of predicting the presence of metastases for each LN from the proportion of activity was only 57.3% in high- and 65% in intermediate-risk patients. Patients with LNI risk of less than 5% could have been spared LND, as no positive LNs were found in this group. For patients with an LNI risk between 5% and 20%, sLND-only would have been sufficient to detect almost all LN metastases; thus, eLND could be dispensed with in 36% of patients. In conclusion, SPION-guided sLND is a reliable alternative to eLND in intermediate-/high-risk PCa. No conclusions can be drawn from magnetic SLN activity regarding the presence of metastases. LND could be dispensed with according to a nomogram of predicted probability for LNI of 5% without losing any LN-positive patient. Patients with LNI risk between 5% and 20% could be spared eLND by performing sLND.

Enhancement of Magnetic Hyperthermia by Mixing Synthetic Inorganic and Biomimetic Magnetic Nanoparticles

In this work we report on the synthesis and characterization of magnetic nanoparticles of two distinct origins, one inorganic (MNPs) and the other biomimetic (BMNPs), the latter based on a process of bacterial synthesis. Each of these two kinds of particles has its own advantages when used separately with biomedical purposes. Thus, BMNPs present an isoelectric point below neutrality (around pH 4.4), while MNPs show a zero-zeta potential at pH 7, and appear to be excellent agents for magnetic hyperthermia. This means that the biomimetic particles are better suited to be loaded with drug molecules positively charged at neutral pH (notably, doxorubicin, for instance) and releasing it at the acidic tumor environment. In turn, MNPs may provide their transport capabilities under a magnetic field. In this study it is proposed to use a mixture of both kinds of particles at two different concentrations, trying to get the best from each of them. We study which mixture performs better from different points of view, like stability and magnetic hyperthermia response, while keeping suitable drug transport capabilities. This composite system is proposed as a close to ideal drug vehicle with added enhanced hyperthermia response.

Sentinel lymph node imaging in urologic oncology

Lymph node (LN) metastases in urological malignancies correlate with poor oncological outcomes. Accurate LN staging is of great importance since patients can benefit from an optimal staging, accordingly aligned therapy and more radical treatments. Current conventional cross-sectional imaging modalities [e.g., computed tomography (CT) and magnetic resonance imaging (MRI)] are not accurate enough to reliably detect early LN metastases as they rely on size criteria. Radical lymphadenectomy, the surgical removal of regional LNs, is the gold standard of invasive LN staging. The LN dissection is guided by anatomic considerations of lymphatic drainage pathways of the primary tumor. Selection of patients for lymphadenectomy heavily relies on preoperative risk stratification and nomograms and, as a result a considerable number of patients unnecessarily undergo invasive staging with associated morbidity. On the other hand, due to individual variability in lymphatic drainage, LN metastases can occur outside of standard lymphadenectomy templates leading to potential understaging and undertreatment. In theory, metastases from the primary tumor need to pass through the chain of LNs, where the initial node is defined as the sentinel LN. In theory, identifying and removing this LN could lead to accurate assessment of metastatic status. Radiotracers and more recently fluorescent dyes and superparamagnetic iron oxide nanoparticles (SPION) are injected into the primary tumor or peritumoral and the sentinel LNs are identified intraoperatively by a gamma probe, fluorescent camera or a handheld magnetometer. Preoperative imaging [e.g., single-photon emission computed tomography (SPECT)/CT or MRI] after tracer injection can further improve preoperative planning of LN dissection. While sentinel LN biopsy is an accepted and widely used approach in melanoma and breast cancer staging, its use in urological malignancies is still limited. Most data published so far is in penile cancer staging since this cancer has a typical echelon-based lymphatic metastasizing pattern. More recent data is encouraging with low false-negative rates, but its use is limited to centers with high expertise. Current guidelines recommend sentinel LN biopsy as an accepted alternative to modified inguinal lymphadenectomy in patients with pT1G2 disease and non-palpable inguinal LNs. In prostate cancer, a high diagnostic accuracy could be demonstrated for the sentinel approach. Nevertheless, due to lack of data or high false-negative rates in other urological malignancies, sentinel LN biopsy is still considered experimental in other urological malignancies. More high-level evidence and longitudinal data is needed to determine its final value in those malignancies. In this manuscript, we will review sentinel node imaging for urologic malignancies.

Sentinel lymph node dissection in prostate cancer using superparamagnetic particles of iron oxide: early clinical experience

PURPOSE

Superparamagnetic nanoparticles of iron oxide (SPION) were shown to be non-inferior to standard radioisotope tracer in breast cancer and may be used as an alternative to identify sentinel lymph nodes (SLN). The aim of this study was to assess the feasibility of sentinel lymph node dissection (SLND) using SPION in prostate cancer and to evaluate its diagnostic accuracy.

METHODS

Twenty patients with intermediate- and high-risk prostate cancer were prospectively enrolled in 2016. After intraprostatic injection of SPION, SLND using magnetometer was performed the following day. Extended pelvic lymph node dissection (ePLND) was added as a reference standard test. The diagnostic performance of the test were evaluated, as well as the rate of in vivo detected SLN. Surgical times of SLND and ePLND were compared using paired two-sample t test.

RESULTS

In total, 97 SLN were detected with median 5 (IQR 3-7) per patient. Non-diagnostic rate of the procedure was 5%. In total, 19 nodal metastases were found in 5 patients, of which 12 were located in SLN. The sensitivity per patient for the whole cohort was 80% and per node 56%. If only patients with at least one detected SLN were considered, the sensitivity per patient and per node reached 100 and 82%, respectively. A median of 20 LNs (IQR 18-22) were removed by subsequent ePLND. Surgical times of SLND and ePLND differed significantly, with medians of 17 and 39 min, respectively (p < 0.001).

CONCLUSIONS

SLND with SPION is feasible and safe in prostate cancer and the diagnostic accuracy is comparable to the published results of radioguided procedures. In open surgery, SPION may be used as an alternative tracer with its main advantage being the lack of radiation hazard.