Researchers may not realize how badly new cancer drugs make patients feel because physicians don’t always accurately report side effects, suggests a new study. 

The comparison of side effects reported by patients and their physicians in three separate cancer drug trials found that doctors under-reported by up to 75 percent how many patients had six of the most common chemotherapy side effects.

Lacking accurate estimates of side effects makes it difficult for doctors to discuss the benefits versus risks of new cancer drugs with their patients, the study authors say.

“Our findings are consistent with previous research data and confirm that patient reported outcomes have to be integrated into cancer clinical trials because they are very important in defining tolerability of new treatments from the patients’ perspective,” senior study author Dr. Francesco Perrone told Reuters Health in an email.

“Patients should be empowered to directly report subjective side effects and be active in defining the tolerability of anticancer drugs,” said Perrone, director of the Clinical Trials Unit at the National Cancer Institute of Naples, Italy.

For their study in the Journal of Clinical Oncology, Perrone and colleagues reviewed the side effects reported by a total of 1,090 patients from three separate cancer drug trials. One trial was of a secondary treatment for elderly patients with breast cancer and two trials involved new first-line treatments for lung cancer.

Almost 2,500 treatment cycles were included in the analysis. Trial physicians reported and graded their perceptions of patients’ side effects afterwards, and the patients filled out questionnaires following each cycle that assessed the presence and severity of appetite loss, nausea, vomiting, constipation, diarrhea and hair loss.

When the researchers compared reports from doctors and patients, they found physicians had under-reported loss of appetite by about 75 percent, nausea by about 40 percent, vomiting by about 47 percent, constipation by about 70 percent, diarrhea by about 51 percent and hair loss by about 65 percent.

When the study team focused just on severe side effects that patients reported experiencing “very much,” they found physicians under-reported appetite loss by about 50 percent, nausea by about 26 percent, vomiting by about 13 percent, constipation by about 44 percent, diarrhea by about 24 percent and hair loss by about 43 percent.

Perrone said the findings show that physicians should be cautious when reading and interpreting the results of clinical trials, particularly if patient reports of subjective side effects are not included.

The results should also push physicians toward spending more time listening to the patient’s experience of symptoms, he said.

“When I tell somebody what to expect from the side effects standpoint, I really rely on the previously published studies, which are largely based on other clinical investigators reporting out the percentage of things like nausea, pain, hair loss, fatigue and knowing that these side effects may be under-reported, I think is important,” said Dr. Sam Lubner, an oncologist with the University of Wisconsin School of Medicine and Public Health in Madison.

Lubner, who was not involved in the study, said physicians have criteria for assessing subjective complaints like nausea, pain, and anxiety, but it’s often difficult for patients to describe their levels of discomfort.

Lubner said patients should ask for a written list of the possible side effects before they begin treatment.

In addition, patients should keep a diary of their symptoms so they can bring that information to office visits, he said.

“One thing I tell patients, is these are the expected side effects - if you experience these with regularity, write them down and make sure that we talk about them every time and see if they’re getting better or worse,” he said.

Lubner added that it’s important to tell doctors about side effects because they can often be managed and that sometimes just talking about them and knowing what is expected can help.