Immunotherapy is a promising technology for cancer treatment. Essentially, body’s own immune system is taught how to recognize cancer cells and kill them. When other treatments have failed, immunotherapy can still shrink tumours and prolong survival. However, it doesn’t work for everyone – how to predict which patients could benefit from this treatment?
Scientists from the University of Toronto were looking for a way to identify cancer patients who would benefit from immunotherapy the most. And they developed a blood test, which is able to detect changing levels of tumour fragments in the body. This could be an easy, non-invasive and quick way to predict who will benefit from immunotherapy.
The problem of immunotherapy is that it can only help 20-30 % of patients. Clinicians do not know whether it will help when they start the treatment – it is basically just a trial and error. The problem with that approach is that immunotherapy can have severe side effects, even though they are rare. A reliable way to predict its effectiveness would help doctors and patients to make an informed decision whether to go ahead with the treatment or the risk is just not worth it.
Scientists designed a novel study, involving a group of 74 cancer patients and a specific immunotherapy drug. They used a blood test, customized to fit each patient’s tumour profile. Scientists found that within 6-7 weeks they can detect a beneficial response to immunotherapy, because the test showed a decrease in these circulating tumour DNA fragments. Obviously, tiny DNA fragments from tumours are not easy to catch, but the next-generation sequencing technologies already allow detecting and measuring that kind of cellular debris in the bloodstream accurately.
A big part of this approach was personalized testing. Scientists looked at all 20,000 genes in each cancer and refused the one-size-fits-all approach. Instead they designed a personalized blood test for each person. When tumour DNA fragments were reducing, patients had better outcomes and longer survival. If the frequency of those fragments was increasing, the outcomes were sad – knowing that would have allowed cutting immunotherapy short, avoiding causing potential harm.
Dr. Lillian Siu, co-senior author of the study, said: ““Few studies have used a clinical biomarker across different types of cancers. The observation that ctDNA clearance during treatment and its link to long-term survival is novel and provocative, suggesting that this biological marker can have broad clinical impact.”
Immunotherapy is a tremendous innovation, but it still needs perfecting. For now, because it can’t help everyone, we need a way to predict who can benefit from it. An easy blood test would be a perfect way to do it.
Source: University of Toronto