Researchers at the University of Arkansas have demonstrated the first use of a noninvasive optical technique to determine complex biochemical changes in cancers treated with immunotherapy.

“We show that optical spectroscopy provides sensitive detection of early changes in the biomolecular composition of tumours” said Narasimhan Rajaram, associate professor of biomedical engineering.

“This is important because these changes predict response to immunotherapy with immune checkpoint inhibitors. Thus, our work is the first step in determining whether Raman spectroscopy can identify treatment responders and non-responders early during the course of therapy.”

Immune checkpoints act as brakes on the immune system to ensure that the body’s immune response is proportional to the threat level detected. Immune checkpoint inhibitors effectively remove these brakes and unleash the body’s immune system against cancer cells.

The study, published in Cancer Research, a journal of the American Association for Cancer Research, describes the use of Raman spectroscopy to determine the molecular composition of colon cancer tumours in mice treated with two types of immunotherapy drugs currently used in the clinical treatment of patients.

Raman spectroscopy uses optical fibres to direct near-infrared laser light to biological tissue. The Raman signal scattered from the tissue is especially sensitive to the molecular composition of the tissue.

For this study, the researchers used machine-learning approaches to train hundreds of Raman datasets acquired from colon cancer tumours treated with different immunotherapy drugs. They then tested the data from each tumour against the overall dataset to determine the difference between tumours that had received various types of immunotherapy and tumours that did not receive any therapy.

The Raman technique demonstrated sensitive detection of early changes in the biomolecular composition of tumours and differentiated tumour response to different treatments. Changes picked up by the non-invasive Raman probe were consistent with changes described by detailed tissue analysis, the researchers found.

Unlike other forms of cancer treatment, immunotherapy does not result in an immediate and predictable reduction in tumour size, and there are currently no accurate methods to determine treatment response in patients. Only a small group of patients benefit from immunotherapy, and there are severe side effects associated with specific combinations of immunotherapy.

Source: University of Arkansas