Minimally invasive sentinel lymph node mapping of the pig colon with Lymphoseek

Drug formulation and nanomedicine approaches to targeting lymphatic cancer metastases

Lymphatic metastasis plays an important role in cancer progression and prognosis. However, conventional small-molecule chemotherapy drugs inefficiently access the lymphatic system, making the effective eradication of lymphatic metastases difficult without dose-limiting toxicity. Various formulation and nanomedicine-based approaches can be used to significantly enhance the trafficking of small-molecule, peptide and protein drugs toward the lymphatic system to enhance drug exposure at sites of lymphatic cancer growth. However, a number of obstacles exist in translating improved lymphatic exposure into improved chemotherapeutic outcomes. This review highlights the opportunities and challenges inherent in employing formulation and nanomedicinal approaches to improve chemotherapeutic drug activity within the lymphatic system and, importantly, at sites of lymphatic cancer metastasis.

Radiolabelled Polymeric Materials for Imaging and Treatment of Cancer: Quo Vadis?

Owing to their tunable blood circulation time and suitable plasma stability, polymer-based nanomaterials hold a great potential for designing and utilising multifunctional nanocarriers for efficient imaging and effective treatment of cancer. When tagged with appropriate radionuclides, they may allow for specific detection (diagnosis) as well as the destruction of tumours (therapy) or even customization of materials, aiming to both diagnosis and therapy (theranostic approach). This review provides an overview of recent developments of radiolabelled polymeric nanomaterials (natural and synthetic polymers) for molecular imaging of cancer, specifically, applying nuclear techniques such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT). Different approaches to radiolabel polymers are evaluated from the methodical radiochemical point of view. This includes new bifunctional chelating agents (BFCAs) for radiometals as well as novel labelling methods. Special emphasis is given to eligible strategies employed to evade the mononuclear phagocytic system (MPS) in view of efficient targeting. The discussion encompasses promising strategies currently employed as well as emerging possibilities in radionuclide-based cancer therapy. Key issues involved in the clinical translation of radiolabelled polymers and future scopes of this intriguing research field are also discussed.

The inextricable axis of targeted diagnostic imaging and therapy: An immunological natural history approach

In considering the challenges of approaches to clinical imaging, we are faced with choices that sometimes are impacted by rather dogmatic notions about what is a better or worse technology to achieve the most useful diagnostic image for the patient. For example, is PET or SPECT most useful in imaging any particular disease dissemination? The dictatorial approach would be to choose PET, all other matters being equal. But is such a totalitarian attitude toward imaging selection still valid? In the face of new receptor targeted SPECT agents one must consider the remarkable specificity and sensitivity of these agents. (99m)Tc-Tilmanocept is one of the newest of these agents, now approved for guiding sentinel node biopsy (SLNB) in several solid tumors. Tilmanocept has a Kd of 3×10(-11)M, and it specificity for the CD206 receptor is unlike any other agent to date. This coupled with a number of facts, that specific disease-associated macrophages express this receptor (100 to 150 thousand receptors), that the receptor has multiple binding sites for tilmanocept (>2 sites per receptor) and that these receptors are recycled every 15 min to bind more tilmanocept (acting as intracellular "drug compilers" of tilmanocept into non-degraded vesicles), gives serious pause as to how we select our approaches to diagnostic imaging. Clinically, the size of SLNs varies greatly, some, anatomically, below the machine resolution of SPECT. Yet, with tilmanocept targeting, the SLNs are highly visible with macrophages stably accruing adequate (99m)Tc-tilmanocept counting statistics, as high target-to-background ratios can compensate for spatial resolution blurring. Importantly, it may be targeted imaging agents per se, again such as tilmanocept, which may significantly shrink any perceived chasm between the imaging technologies and anchor the diagnostic considerations in the targeting and specificity of the agent rather than any lingering dogma about the hardware as the basis for imaging approaches. Beyond the elements of imaging applications of these agents is their evolution to therapeutic agents as well, and even in the neo-logical realm of theranostics. Characteristics of agents such as tilmanocept that exploit the natural history of diseases with remarkably high specificity are the expectations for the future of patient- and disease-centered diagnosis and therapy.

γ-Tilmanocept, a New Radiopharmaceutical Tracer for Cancer Sentinel Lymph Nodes, Binds to the Mannose Receptor (CD206)

γ-Tilmanocept ((99m)Tc-labeled-tilmanocept or [(99m)Tc]-tilmanocept) is the first mannose-containing, receptor-directed, radiolabeled tracer for the highly sensitive imaging of sentinel lymph nodes in solid tumor staging. To elucidate the mannose-binding receptor that retains tilmanocept in this microenvironment, human macrophages were used that have high expression of the C-type lectin mannose receptor (MR; CD206). Cy3-labeled tilmanocept exhibited high specificity binding to macrophages that was nearly abolished in competitive inhibition experiments. Furthermore, Cy3-tilmanocept binding was markedly reduced on macrophages deficient in the MR by small interfering RNA treatment and was increased on MR-transfected HEK 293 cells. Finally, confocal microscopy revealed colocalization of Cy3-tilmanocept with the macrophage membrane MR and binding of labeled tilmanocept to MR(+) cells (macrophages and/or dendritic cells) in human sentinel lymph node tissues. Together these data provide strong evidence that CD206 is a major binding receptor for γ-tilmanocept. Identification of CD206 as the γ-tilmanocept-binding receptor enables opportunities for designing receptor-targeted advanced imaging agents and therapeutics for cancer and other diseases.

Management of nodal disease from colon cancer in the laparoscopic era

PURPOSE

In colon cancer (CC), nodal involvement is the main prognostic factor following potentially curative (R0) resection. The purpose of this study was to examine data from the literature to provide an up-to-date analysis of the management of nodal disease with special reference to laparoscopic treatment.

METHODS

MEDLINE and EMBASE databases were searched for potentially eligible studies published in English up to July 15, 2014.

RESULTS

In CC, nodal involvement is a frequent event and represents the main risk of cancer recurrence. Node negative patients recur in 10-30 % of cases most likely due to underdiagnosed or undertreated nodal disease. Extended colonic resections (complete mesocolic excision with central vascular ligation; D3 lymphadenectomy) provides a survival benefit and better local control. Sentinel lymph node mapping in addition to standard surgical resection represents an option for improving staging of clinical node negative patients. Both extended resection and sentinel lymph node mapping are feasible in a laparoscopic setting.

CONCLUSIONS

Both extended colonic resection and sentinel lymph node mapping should play a role in the laparoscopic treatment of CC with the purpose of improving control and staging of nodal disease.

Preclinical evaluation of robotic-assisted sentinel lymph node fluorescence imaging

An ideal substance to provide convenient and accurate targeting for sentinel lymph node (SLN) mapping during robotic-assisted surgery has yet to be found. We used an animal model to determine the ability of the FireFly camera system to detect fluorescent SLNs after administration of a dual-labeled molecular imaging agent.

METHODS

We injected the footpads of New Zealand White rabbits with 1.7 or 8.4 nmol of tilmanocept labeled with (99m)Tc and a near-infrared fluorophore, IRDye800CW. One and 36 h after injection, popliteal lymph nodes, representing the SLNs, were dissected with the assistance of the FireFly camera system, a fluorescence-capable endoscopic imaging system. After excision of the paraaortic lymph nodes, which represented non-SLNs, we assayed all lymph nodes for radioactivity and fluorescence intensity.

RESULTS

Fluorescence within all popliteal lymph nodes was easily detected by the FireFly camera system. Fluorescence within the lymph channel could be imaged during the 1-h studies. When compared with the paraaortic lymph nodes, the popliteal lymph nodes retain greater than 95% of the radioactivity at both 1 and 36 h after injection. At both doses (1.7 and 8.4 nmol), the popliteal nodes had higher (P < 0.050) optical fluorescence intensity than the paraaortic nodes at the 1- and 36-h time points.

CONCLUSION

The FireFly camera system can easily detect tilmanocept labeled with a near-infrared fluorophore at least 36 h after administration. This ability will permit image acquisition and subsequent verification of fluorescence-labeled SLNs during robotic-assisted surgery.

What should we intend for minimally invasive treatment of colorectal cancer?

Non-inferiority of laparoscopic treatment of colorectal cancer (CRC) has been demonstrated in randomized controlled trials although operative and perioperative management varies widely among centers. Literature data in English language published up to April 15, 2014 were analyzed in order to give an up to date analysis that would highlights the key aspects of a modern and factual minimally invasive treatment of CRC. Laparoscopic resection is the first choice treatment of colon cancer. Laparoscopic resection of rectal cancer should be considered an investigational procedure to be performed in high volume centers with special interest in laparoscopy and colorectal surgery. Less invasive approaches should be taken into account with the aim of reducing surgical stress. The adoption of ERAS programs has demonstrated to optimize short-term results. Future research should be directed to prove possible long-term advantages, in terms of overall and disease-free survival, of minimally invasive treatment of CRC.

A phase 2 study of (99m)Tc-tilmanocept in the detection of sentinel lymph nodes in melanoma and breast cancer

BACKGROUND

Several (99m)Tc-labeled agents that are not approved by the U.S. Food and Drug Administration are used for lymphatic mapping. A new low-molecular-weight mannose receptor-based, reticuloendothelial cell-directed, (99m)Tc-labeled lymphatic imaging agent, (99m)Tc-tilmanocept, was used for lymphatic mapping of sentinel lymph nodes (SLNs) from patients with primary breast cancer or melanoma malignancies. This novel molecular species provides the basis for potentially enhanced SLN mapping reliability.

METHODS

In a prospectively planned, open-label phase 2 clinical study, (99m)Tc-tilmanocept was injected into breast cancer and cutaneous melanoma patients before intraoperative lymphatic mapping. Injection technique, preoperative lymphoscintigraphy (LS), and intraoperative lymphatic mapping with a handheld gamma detection probe were performed by investigators per standard practice.

RESULTS

Seventy-eight patients underwent (99m)Tc-tilmanocept injection and were evaluated (47 melanoma, 31 breast cancer). For those whom LS was performed (55 patients, 70.5%), a (99m)Tc-tilmanocept hot spot was identified in 94.5% of LS patients before surgery. Intraoperatively, (99m)Tc-tilmanocept identified at least one regional SLN in 75 (96.2%) of 78 patients: 46 (97.9%) of 47 in melanoma and 29 (93.5%) of 31 in breast cancer cases. Tissue specificity of (99m)Tc-tilmanocept for lymph nodes was 100%, displaying 95.1% mapping sensitivity by localizing in 173 of 182 nodes removed during surgery. The overall proportion of (99m)Tc-tilmanocept-identified nodes that contained metastatic disease was 13.7%. Five procedure-related serious adverse events occurred, none related to (99m)Tc-tilmanocept.

CONCLUSIONS

Our results demonstrate the safety and efficacy of (99m)Tc-tilmanocept for use in intraoperative lymphatic mapping. The high intraoperative localization and lymph node specificity of (99m)Tc-tilmanocept and the identification of metastatic disease within the nodes suggest SLNs are effectively identified by this novel mannose receptor-targeted molecule.

Sentinel lymph node mapping of breast cancer via intradermal administration of Lymphoseek

Lymphoseek is a molecular imaging agent specifically designed for sentinel lymph node (SLN) mapping. We conducted a Phase I trial which measured the injection site clearance and SLN accumulation after a single intra dermal injection of Lymphoseek or [99mTc]sulfur colloid protocol. Ten patients with breast cancer participated in this study. Five patients received an intradermal administration of 1.0 nmol of 99mTc-labeled Lymphoseek and five patients received an intradermal administration of filtered [99mTc]sulfur colloid (fTcSC). Lymphoseek exhibited a significantly (P<.001) faster injection site clearance than fTcSC. The mean Lymphoseek clearance half-time was 2.61+/-0.72 h compared to 24.1+/-17.7 h for fTcSC. The mean SLN uptake of Lymphoseek (1.1+/-.5%) and fTcSC (2.5+/-4.9%) was statistically equivalent (P=.28). When an intra dermal injection was employed, Lymphoseek demonstrated faster injection site clearance than fTcSC.

Lymphoseek: a molecular imaging agent for melanoma sentinel lymph node mapping

BACKGROUND

Lymphoseek is a molecular imaging agent specifically designed for sentinel lymph node mapping. We conducted a phase I clinical trial in which Lymphoseek was compared with filtered [(99m)Tc]sulfur colloid (fTcSC) for melanoma sentinel lymph node detection.

METHODS

Twenty-four patients (33-81 years) with melanoma participated in this study. Four groups of six patients received an intradermal administration (.5 mCi) of 1.0, 5.0, or 10.0 nmol of (99m)Tc-labeled Lymphoseek or filtered [(99m)Tc]sulfur colloid. The injection site clearance was monitored by nuclear imaging for 3 hours. Lymph nodes obtained by gamma-guided biopsy (4.0-8.7 hours after injection) were assayed for radioactivity. Clinical chemistry values were monitored (before injection, before surgery, and 4 and 24 hours), and whole-body scans were acquired at 1 and 12 hours after injection.

RESULTS

Lymphoseek exhibited a significantly (P < .001) faster injection site clearance at all dose levels. The mean Lymphoseek clearance half-time was 2.17 +/- .96 hours (n = 18) compared with 14.7 +/- 6.3 hours for fTcSC (n = 6). The mean sentinel lymph node uptakes of Lymphoseek (.73% +/- .94%) and fTcSC (.85% +/- 1.19%) were statistically equivalent (P = .68). Lymphoseek exhibited a lower mean number of sentinel lymph nodes per basin (1.6) than fTcSC (1.9). No adverse events were observed, nor were any clinically significant alterations in laboratory parameters. Radiation absorbed doses were lower than filtered [(99m)Tc]sulfur colloid.

CONCLUSIONS

The molecular imaging agent Lymphoseek demonstrated faster injection site clearance and equivalent primary sentinel node uptake when compared with filtered [(99m)Tc]sulfur colloid.

Molecular targeting of the lymphovascular system for imaging and therapy

Progress toward targeting cancer cells is a multi-disciplinary endeavor. In addition to the surgical and oncology specialties, radiologists collaborate with mathematicians, computer scientists, and physicists, in a constant effort to incrementally improve upon the current imaging modalities. Recently, radiologists have formed collaborations with molecular biologists and chemists in order to develop molecular agents that target cancer cells via receptor-substrate or specific physiochemical interactions. In this review, we summarize selected efforts toward molecular targeting of the lymphovascular system. Standard imaging modalities, positron emission tomography, single photon emission tomography, and ultrasound, are reviewed as well as, the targeted introduction of substances for endolymphatic therapy. We also review the current status of sentinel lymph node mapping with radiocolloids and the application of molecular targeting for the development of a radiopharmaceutical specifically designed for sentinel lymph node mapping.