The world of cancer is a fast-paced one, where the disease progresses rapidly, and to catch up with it, the field of cancer therapeutics—treatments, medicines and diagnostics tests—evolve each day. From computer tomography (CT) and Magnetic Resonance Imaging (MRI) scans to biopsies, surgeries and personalised drugs, treating and monitoring cancer today, although easier, is more expensive than ever. At times, cancer patients can build resistance to certain medications, leading to a relapse of the disease. Hence, it is critical to monitor the progression or regression of the illness constantly.

In a recent breakthrough, a team of Indian scientists, working with their collaborators elsewhere, have shown how clusters of circulating tumour cells (CTCs) could help monitor the response to cancer treatments and predict a patient's survival chances. CTCs are nothing but the cancer cells that have sloughed off the tumour and are circulating in the blood.

"Assessing if a treatment is working for a patient is an extremely challenging area," says, Prof Prashant Kumar, Faculty Scientist at the Institute of Bioinformatics, Bangalore, who led the study. In collaboration with his colleague, Mr Ajay Balakrishnan, and Dr Annapoorni Rangarajan from the Indian Institute of Science, they propose a method to quantify clusters of circulating tumour cells in cancer patients during different treatments.

Their study is published in the journal Scientific Reports and is funded by the Department of Biotechnology, Department of Science and Technology, Wellcome Trust-DBT India Alliance, and the Council of Scientific and Industrial Research.

Often, doctors resort to periodic biopsies to monitor cancer. It is an invasive procedure, and most of the time, when the patient reaches the terminal stage, it is not advisable to collect tissue samples through a biopsy. Besides, not every patient can go through surgery, especially when the cancer is in advanced stages. Here is where 'liquid biopsy' comes to the rescue.

In the proposed technique, the researchers used blood from the patient to predict the progression of cancer and the response of the treatment. "This method, called liquid biopsy, or simply a blood test, could be used for cancer diagnosis and treatment monitoring," explains Prof Kumar, who has been studying clusters of circulating tumour cells since 2013. "Here we are not isolating the CTCs or enriching them, but allowing them to grow in a natural microenvironment before testing them."

Based on how the cultured cells look, a doctor can assess whether a patient is responding to the treatment provided to him. Blood samples that contained tight clusters indicate patients who are not responding to the therapy. Thus, the technique can help them determine the best course of treatment.

The researchers, in collaboration with oncologists from the Kidwai Memorial Institute of Oncology, Bengaluru, validated their method by testing it on over 150 blood samples from patients suffering from one of the four cancers – lung, breast, oesophageal or bladder cancer. They found that if the cluster of the tumour cells was tight, there was a higher chance of the patients having cancer. This correlation was found to be true for most of the cancer samples studied. "We have correlated the progress of the treatment as detected using CTCs in a liquid biopsy with methods such as CT scan and MRI, and it has correlated well," says Dr Govind Babu K, Professor of Medical Oncology at Kidwai.

The test takes around a week to show the results and costs a fraction of most present-day tests. It can monitor how cancerous cells in the body would respond to the drugs in real-time. In a country where roughly 12 lakh people succumb to cancer each year, it is incredible how a simple blood test could facilitate a better way to follow up with this disease. As the next course of the study, the researchers plan to apply this method to develop preclinical models to characterise the evolution of the disease better and implement effective therapies.

Editor's Note: This article was edited for a typo. The error is regretted.

This article has been run past the researchers, whose work is covered, to ensure accuracy.