The immunotherapy nivolumab is kinder than chemotherapy for people with advanced head and neck cancer - easing many of the negative effects of the disease on patients' quality of life.
Both head and neck cancer and the treatment for it can have a huge impact on patients - affecting their speech, breathing, eating and drinking, facial appearance, and general wellbeing.
All of this can cause substantial psychological, as well as physical, distress.
But patients taking part in a major phase III clinical trial reported that nivolumab helped them maintain a better quality of life for longer.
By contrast, the study - led by researchers at The Institute of Cancer Research, London, and The Royal Marsden NHS Foundation Trust - found that people treated with standard chemotherapies docetaxel, methotrexate or cetuximab reported a decline in quality of life from the start of treatment.
Last year, the clinical trial of 361 patients found that nivolumab - which sparks the immune system into action against cancers - greatly increased survival for people with recurrent or metastatic head and neck cancer.
But the drug was initially rejected by NICE in April this year and is currently under consultation before a final decision is due.
The new results add to the growing body of evidence that immunotherapy can be a smarter, kinder treatment for people with cancer.
In the latest study, 129 patients on the trial filled in questionnaires about their quality of life - covering physical symptoms, mental health and general wellbeing.
The research is published in the journal The Lancet Oncology on Friday and was funded by Bristol-Myers Squibb, with support from the NIHR Biomedical Research Centre at The Royal Marsden and The Institute of Cancer Research (ICR).
While patients on chemotherapy judged their quality of life to be lower at nine and 15 weeks into the trial, patients on nivolumab gave consistently better ratings throughout.
After nine weeks, patients given nivolumab reported that they were doing better than their counterparts on other treatments for a range of symptoms, including pain, sensory problems, appetite loss, tiredness and breathing problems.
After 15 weeks, the list of beneficial effects was even longer, with patients taking nivolumab being less badly affected by nausea, insomnia and weight loss.
Professor Kevin Harrington, Professor of Biological Cancer Therapies at The Institute of Cancer Research, London, and Consultant Clinical Oncologist at The Royal Marsden NHS Foundation Trust, said:
"Head and neck cancer is an extremely debilitating disease, and if it spreads or patients relapse then it's extremely difficult to treat.
"But our research has found that nivolumab really is a game-changing treatment for patients with head and neck cancer. Not only does it extend survival -- we have now shown that patients feel much better in the extra time that the drug grants them.
"When immunotherapies first hit the clinic, there were concerns over side-effects and the fact that they didn't work for everyone. But in only two or three years we have become very good at managing the side-effects they cause, and we are better able to select patients in whom these treatments are most likely to be effective.
"We now need to test if we can move away from resorting to traditional chemotherapies, which come with far too much collateral damage, and see these smarter, kinder therapies used as a first-line treatment to replace chemotherapy altogether."
Professor Paul Workman, chief executive of The Institute of Cancer Research, London, said:
"Creating cancer treatments that can not only extend life but also minimise the impact of the disease on patients' lives is a major aim of researchers worldwide.
"So it's great news that this trial has found that as nivolumab greatly extends life among these patients it also gives marked improvements in quality of life compared with current treatment options.
"I hope that this drug will be now approved very soon for use on the NHS so that this group of patients, who badly need new treatment options, can see the benefit."
Professor David Cunningham, Director of Clinical Research at The Royal Marsden NHS Foundation Trust and Director of the NIHR Biomedical Research Centre at The Royal Marsden and The Institute of Cancer Research, London, said:
"Using the body's own immune system to attack cancer continues to find wider application across the spectrum of cancers we have to treat in the clinic. Head and neck cancer is a particularly challenging disease and these results are an important step in improving outcomes for our patients."