The team from University of Bristol has found that in more than two thirds of cases, patients were not given enough information about the survival benefits of such treatment.
The survival gain for patients receiving palliative chemotherapy treatment tends to be months rather than years.
The researchers looked at 37 cases from a large teaching hospital and a district general hospital in the south west of England, where the consultations with oncologists were digitally recorded with each patient, all of whom had advanced forms of cancer.
Three common cancers were chosen - colorectal, non-small cell lung, and pancreatic cancer.
The team examined the consultation sessions with patients and found there was consistency in informing patients that a cure was not being sought for them, but the amount of information about survival benefit varied considerably.
The information given to patients about survival benefit included: numerical data ("about four weeks"); an idea of timescales ("a few months extra"); vague references ("buy you some time"); or no mention at all.
Only six patients out of 37 were given numerical data about the survival benefits of treatment.
The researchers said that there are concerns that the "intrusiveness of unfavourable numbers", in terms of months left to live, can undermine healthcare relationships and destroy hope.
"Giving comprehensible and appropriate information about survival benefit is extremely difficult. In addition, the reluctance to inform patients of the limited survival gain of palliative chemotherapy may be motivated by a desire to 'protect' patients from bad news," British Medical Journal quoted researchers, as saying.
"However, the reluctance to address these difficulties and sensitivities may be hampering patients' ability to make informed decisions about their future treatment," they added.
The researchers urged that the patients should be given accurate information so they can give informed consent before starting chemotherapy.