Researchers from Dartmouth's Thayer School of Engineering, Geisel School of Medicine and Norris Cotton Cancer Center have helped develop a new method of determining cancer stage and spread that is safer and potentially more accurate than conventional lymph node biopsy. The full technical report is published in the latest issue of Nature Medicine.

The report states, "Lymph node biopsy is employed in many cancer surgeries to identify metastatic disease and to determine cancer stage, yet morbidity and diagnostic delays associated with lymph node biopsy could be avoided if noninvasive imaging of nodal involvement were reliable."

The team presents a new and improved method of noninvasive molecular imaging using a "dual-tracer" technique that corrects the problem of nonspecific uptake of imaging tracers that has made previous attempts at this approach clinically ineffective.

"This work summarizes the development of an imaging method that will allow oncologists to noninvasively detect microscopic levels of cancer spread to the lymphatic system in their patients," says lead author Kenneth Tichauer, engineering professor at Illinois Institute of Technology and former Thayer School post-doc. "Cancer spread [metastasis] is the principal cause of mortality for cancer sufferers, and in an effort to characterize the metastatic potential of a patient’s disease, surgeons often remove tumor draining lymph nodes for analysis during surgical resection of the primary tumor. Such procedures can result in significant morbidity, yet the majority of lymph nodes are found to be free of cancer spread."

"This is a fundamental discovery about cancer imaging that through the use of a radiometric fluorescence signal, we can quantify how many cancer cells are present," says Dartmouth engineering professor Brian Pogue, an author of the report. "Many have tried to use targeted molecular probes to simply ‘detect’ cancer in a lymph node, but all have failed because the variability in the signal is simply too high to be useful. In this work we showed that not only could we detect cancer in the lymph node, but the signal is linearly proportional to the number of cancer cells, with very little noise in the signal. So this measurement technique is very robust and could be translated to human studies easily."

"Medical imaging scientists have been exploring ways of detecting cancer spread to lymph nodes for decades," adds Tichauer. "However, high variability and nonspecific retention of cancer-targeted imaging agents in lymph nodes has resulted in a number of clinical trial failures, and lymph node biopsy remains the standard of care. The novel imaging approach we developed employs co-injection of a cancer-targeted imaging agent with an untargeted imaging agent. The uptake of the untargeted agent is then used to account for variable and nonspecific retention of the targeted agent, ultimately allowing the number of cancer cells present in any lymph node to be estimated. We are excited about the potential of this approach to transform the way lymph node biopsy is carried out and are actively making efforts to translate this work to the clinical stage."