Enrollment and eligibility data about obese patients with cancer are severely underreported in randomized clinical trials (RCT), according to a study published in the Annals of Oncology.1

Obesity is a well-known risk factor for many types of cancer and may negatively affect treatment decisions and outcomes. There is concern that randomized obesity-related cancer trials underrepresent obese patients, which may affect the generalizability of findings.

For this systematic review, the authors evaluated 76 RCTs of 10 obesity-related cancer types: postmenopausal breast, colon/rectum, endometrial, esophageal, gall bladder, kidney, hepatic, pancreatic, ovarian, and thyroid. By examining the reporting trial articles, protocols, and registration records, the authors investigated if any eligibility criteria that limited obese patient enrollment were reported, what proportion of study patients were obese, and whether subgroup analyses of obese patients were conducted.

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Publically available eligibility information about obese patients was found for just 6.6% (5) of the included RCTs, and the proportion of obese patients could be estimated only for 12% (9) of the RCTs. Only 1 RCT performed a subgroup analysis for obese patients.

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Of unpublished studies, 41% (31) reported the eligibility data of obese patients, though it was unclear whether the other 59% considered obese patients eligible — and what proportion of patients were obese. 

The median proportion of obese patients was 18%, as observed over 22 RCTs.

The authors concluded that “articles reporting RCT results provide scant information about the eligibility of obese patients and the number of obese patients actually enrolled. Transparency in participant information is needed to understand participation of obese people in cancer clinical trials and applicability of results to obese patients with cancer.”


  1. Pestine E, Stokes A, Trinquart L. Representation of obese participants in obesity-related cancer randomized trials. Ann Oncol. 2018 Apr 20. doi: 10.1093/annonc/mdy138 [Epub ahead of print]