Five key factors may help predict how cancer patients will respond to chemotherapy designed to harness the immune system to fight tumours, medical researchers have said in a study released on Thursday.

They are hoping the five factors could guide chemotherapy decisions and contribute to improved treatment outcomes after immunotherapy which currently leads to positive responses in only 20 per cent to 40 per cent of cancer patients.

“Our results open the door to the possibility of using these five factors to guide clinical practice in the future,” Abel Gonzalez Perez, a research associate and study team member at the Institute of Research in Biomedicine, Barcelona, Spain, told The Telegraph.

The study relates to a type of immunotherapy called checkpoint inhibitors that block proteins that prevent cells of the immune system from killing cancer cells. Despite multiple studies in the past, the underlying factors that might help explain differences in treatment outcomes remain unclear.

“We hope the five factors we’ve identified can be integrated in clinical practice to guide therapeutic decisions,” said Nuria Lopez-Bigas, a researcher at the IRB who led the study. “Our study marks a step in understanding how different characteristics of tumours might influence treatment response.”

The five factors are the counts of mutations in tumours, the counts of anti-cancer immune cells in tumours, the levels of a key growth-related biomarker molecule in the tumours’ microenvironment, exposure to previous chemotherapy, and the tumour’s aggressiveness.

Lopez-Bigas and her colleagues analysed genomic and clinical data from 479 patients who had received checkpoint inhibitors as part of their treatment. They validated their preliminary findings through data from six more sets of a total of 1,479 patients. The six sets of patients had various cancers of the lung, colon and skin.