January 23, 2006
Magnetic Nanoparticles Improve Diagnosis of Metastasis
One of the critical factors that determines the course of cancer therapy is whether there are metastases in given patients' lymph nodes. Today, however, there are few methods short of a full surgical biopsy to accurately determine if cancer has spread to the lymph nodes. And while researchers are developing a variety of non-invasive imaging techniques using magnetic resonance imaging (MRI), positron emission tomography (PET) and ultrasound, for finding lymph node involvements, the jury is still out on how well these techniques perform compared to surgical biopsy.
One promising MRI-based method uses biodegradable iron oxide nanoparticles, coated with a sticky sugar polymer known as dextran, that accumulates specifically in metastatic lymph nodes. Several dozen studies, most involving 50 or fewer cancer patients, have suggested that this agent, known as ferumoxtran-10, can identify those patients with metastatic lymph nodes and which lymph nodes are affected. But the small number of patients examined in each separate study has left physicians questioning the value of this technique.
Now, a combined analysis of 19 of these studies, involving a total of 631 patients, shows conclusively that ferumoxtran-10 MRI is a sensitive, specific and safe method of detecting lymph-node metastases in a wide variety of cancers. A team of oncologists in the United Kingdom, led by Paris P. Tekkis, M.D., of St. Mary’s Hospital in London, published the results of its meta-analysis in the journal Lancet Oncology.
The investigators combed the literature for all studies conducted using ferumoxtran-10 to detect metastasis, and then selected only the studies that compared MRI results with those obtained via surgical biopsy on the same patients. The researchers further narrowed their selection of studies by eliminating multiple studies conducted by a single group of researchers because of the possibility that these studies would not have each involved a unique set of patients — counting the same patients twice in a meta-analysis would introduce bias in the final results.
This study is detailed in a paper titled, “Diagnostic precision of nanoparticle-enhanced MRI for lymph-node metastases: a meta-analysis.” Investigators from Queen Mary’s School of Medicine and Dentistry and St. Mary’s Hospital, both in London, UK, participated in this study. An abstract is available through PubMed.