A US medical study has suggested guidelines for chemotherapy use in patients with terminal cancer should be revised.

Giving chemotherapy to people with terminal cancer who are near the end of their lives is likely to cause more harm than good, according to a US study.

The findings in the Journal of the American Medical Association (JAMA) Oncology are based on a group of more than 300 patients with metastatic cancer, meaning their tumors had spread from the initial site in the body to other organs, and had become incurable.

About half of the patients were on chemotherapy, which delivers potent chemicals into the body to destroy cancer cells and shrink tumors. Side effects can include weakness, nausea, fatigue, confusion and hair loss.

Most of the patients were men and their average age was 59. They had about four months to live.

The aim of the study was to examine how chemotherapy affected quality of life when the patients were near the end of their lives, particularly regarding their ability to walk, do work and take care of basic needs.

Based on caregivers' assessments of patients' physical and mental distress in their final week of life, researchers found that chemotherapy did not improve quality of life for patients who already had limited mobility.

And for those who were still able to perform basic life functions, chemotherapy made their quality of life worse.

"Not only did chemotherapy not benefit patients regardless of performance status, it appeared most harmful to those patients with good performance status," the study, led by Holly Prigerson of Weill Cornell Medical College and New York Presbyterian Hospital, said.

It suggested "guidelines regarding chemotherapy use in patients with terminal cancer may need to be revised to recognise the potential harm of chemotherapy use in patients with progressive metastatic disease".